HomeMy WebLinkAboutAPA1069>#...~United Statesft~-A~~'De~artment ofl~ii Agnculture
".~Forest Service
Pacific Northwest
Forest and Range
Experiment Station
Research Paper
PNW·307
July 1983
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SO
11
.A45614
no.307
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Classification,~~
Description,and
Dynamics of Plant
Communities After
Fire in the Taiga of
Interior Alaska
M.Joan Foote
.NPS
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Author
M.JOAN FOOTE is a biologist at the 'nstituteARLI"
of Northern Forestry,Pacific Northwest For-U
est and Range Experi ment Station,Fairbank*laska Resources
Alaska 9970 I.Library &InfonnatlOn ServIces
Anchorage,A.laska
Abstract
Foote,M.Joan.Classification,description,
and dynamics of plant communities after
fire in the taiga of interior Alaska.Res.
Pap.PNW-307.Portland,OR:U.S.Depart-
ment of Agriculture,Forest Service,Pacific
Northwest Forest and Range Experiment
Station;1983.108 p.
One hundred thirty forest stands ranging in
age from I month postfire to 200 years were
sampled and described by successional series
(white spruce and black spruce)and by devel-
opm ental stage (newly burned,moss-herb,tall
shrub-sapling,dense tree,hardwood,and
spruce).Patterns of change in the two succes-
sional series are described.In addition,12
mature forest communities are described in
quantitative and qualitative terms.
Keywords:Communities (plant),classification
(plant communities),fire {-plant ecology,
taiga,Alaska (interior).
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One hundred thirty forest stands in the taiga
were sampled after fire.They ranged in age
from I month postfire to 200 years and were
located mostly along the road system in inte-
rior Alaska south of the Yukon River.Each
stand was at least 2 hectares in size,homoge-
neous in composition,and representative of
the surrounding vegetatio n.
Each area was described in quantitative and
qualitative terms,using inventory procedures
adapted from Oh m ann and Ream (1971).The
communities were grouped by site type (white
spruce and black spruce)and six developm ental
stages:(I)newly burned,(2)moss-herb,(3)
talI shrub-sapling,(4)dense tree,(5)hardwood
(or hardwood-spruce),and (6)spruce.Stands
50-200 years old were aggregated;12 mature
forest co mm unity types were then identified
and described,using data collected in this
study.These are:
I.Populus tremuloides/Viburnum edule/
Li nnaea b oreali s
2.Betula papyrifera/Viburnum edule
3.Betula papyrifera/Alnus crispa/
Calamagrostis canadensis
4.Picea glauca/Viburnum edule/
Equisetum arvense/Hylocomium splendens
5.Picea glauca/Rosa acicularis/Equisetum
sylvaticum/Hylocomium splendens
6.Populus balsamifera/Oplopanax horridus
7.Populus tremuloides-Picea mariana/
Cornus canadensis
8.Picea mariana-Betula papyrifera/
Vaccinium uliginosum-Ledum groenlandicu m
9.Pi cea m ari ana/Vaccinium uliginosum-
Ledum groenlandicum/Pleurozium schreberi
10.Picea mariana/feathermoss-lichen
II.Picea mariana-Po glauca/Betula
gl andulosa/I iche n
12.Picea mariana/Sphagnum spp.-Cladina spp.
The community types are named by their dom-
inant species.Slashes separate vegetation
strata-trees,tall shrub,low shrub,and/or
forest floor.Hyphens between plant names
indicate codominance within a strata.Types
1-4 occur on upland white spruce sites,types 5
and 6 on bottomland white spruce sites,types
7-10 on mesic black spruce sites,type II near
timberline,and type 12 on moist black spruce
sites.This list is not exhaustive.Other forest
community types exist but were not encoun-
tered in this study.The mature vegetation
community types described are included in a
vegetation classification system proposed for
Alaska (Vi ereck and Dyrness 1980).
Succession is described separately for white
spruce and black spruce sites,using data
obtained in this study,first statistically by
developmental stage,then dynamically by
patterns of change that span all stages of both
successional series.The successional series
are also compared.
Contents Tables
2
Introduction
Obj ectives
Table I-I-lumber of fires and area burned per
year in interior Alaska,1940-79
i.
I
t
,'K'
3 The Study Are a
7 Methods
8 Results and Discussion
9 Mature Forest Com munity Types
10 White Spruce Sites
28 Blac k Spruce Sites
4~Forest Succession
51 Stages on White Spruce Sites
69 Patterns of Change on White Spruce
Sites
74 Stages on Mesic Black Spruce Sites
93 Patterns of Change on Mesic Black
Spruce Sites
99 Comparison of Patterns of Change
101 Me tri c Equiv al ents
101 Literature Cited
105 Appendix
105 Scientific and Common Names of
Plants
Table 2-Some mature forest com munity types
in the taiga of interior Alaska
Table 3-lmportant plant species and litter
components of the Populus tremuloides/
Viburnum edule/Li nnaea borealis com m unity
type (Type I)of interior Alaska
Table 4-lmportant plant species and litter
components of the Betula papyrifera/Viburnum
edule community type (Type 2)of interior
Alaska
Table 5-lmportant plant species and litter
components of the Betula papyrifera/Alnus
crispa/Calamagrostis canadensis com munity
type (Type 3)of interior Alaska
Table 6-lmportant plant species and litter
components of the Picea glauca/Viburnum
edule/£quisetum arvense/Hylocom ium
~dens com munity type (Type ~)of interior
Alaska
Table 7-lmportant plant species and litter
components of the Picea glauca/Rosa
acicularis/iqu isetum syl va ticumTHYi'Ocom i um
splendens com munity type (Type 5)of interior
Alaska
.Jf
Table 8-lmportant plant species and litter
components of the Populus balsamifera/
Oplopanax horridus community type (Type 6)
of interior Alaska
Table 9-lmportant plant species and litter
components of the Populus tremuloides-Picea
mari ana/Cornus canadensis com munity type
(Type 7)of interior Alaska
Table 10--lmportant plant species and litter
components of the Picea mariana-Betula
papyrif era/Vacci ni um uli gi nosum-Ledum
groenlandicum com m unity type (Type 8)of
interior Alaska
Table II-Important plant species and litter
components of the Picea mariana/Vaccinium
uliginosum-Ledum groenlandicum /PI euro zium
schreberi com munity type (Type 9)of interior
Alaska
Table 12-lmportant plant species and litter
components of the Picea mariana/
featnermoss-lichen com munity type (Type 10)
of interior Alaska
Table 13:'-Important plant species and litter
components of the Picea mariana-Picea
glauca/Betula glandiJ"iOS'a/lichen community
type (Type I I)of interior Alaska
Table 14-lmportant plant species and litter
components of the Picea mariana/Sphagnum
spp.-Cladina spp.com munitytype (Type 12)of
interior Alaska
Table IS-I..)uantitative description of the
newly burned stage of plant succession on
white spruce sites in the taiga of interior
Alaska,by dominant plant species and litter
,component
Table 16--Q'uantitative description of the
moss-herb stage of plant succession on white
spruce sites in tile taiga of interior Alaska,by
dominant plant species and litter component
Table 17-Quantitative description of the tall
shrub-sapling stage of plant succession on
white spruce sites in the taiga of interior
Alaska,by dominant plant species and litter
component
Table 18-Quantitative description of the
dense tree stage of plant succession on white
spruce sites in the taiga of interior Alaska,by
dominant plant species and litter component
Table I ~-Quantitative description of the
hardwood stage of plant succession on white
spruce sites in the taiga of interior Alaska,by
dominant plant species and litter component
Table 2v-Quantitative description of the
spruce stage of plant succession on white
spruce sites in the taiga of interior Alaska,by
dominant plant species and litter component
Table 21-Sum rn ary of the quantitative
descriptions of the 6 stages of plant succession
on white spruce sites in the taiga of interior
Alaska
Table 22-Quantitative description of the
newly burned stage of plant succession on
mesic black spruce sites in the taiga of
interior Alaska,by dominant plant species and
litter component
Table 23-Quantitative description of the
moss-herb stage of plant succession on mesic
blacK spruce sites in the taiga of interior
Alaska,by dominant plant species and litter
component
Table 24-Quantitative description of the tall
shrub-sapling stage of plant succession on
mesic black spruce sites in the taiga of
interior Alaska,by dominant plant species and
litter component
Table 2S-Quantitative description of the
dense tree stage of plant succession on mesic
black spruce sites in the taiga of interior
Alaska,by dominant plant species and litter
component
Table 26-Quantitative description of the
mixed hardwood-spruce stage of plant
succession on mesic black spruce sites in the
taiga of interior Alaska,by dominant plant
species and litter component
Table 27-Quantitative description of the
spruce stage of plant succession on mesic
black spruce sites in the taiga of interior
Alaska,by dominant plant species and litter
component
Table 28-Summary of the quantitative
descriptions of the 6 stages of plant succession
on mesic black spruce sites in the taiga of
interior Alaska
I'
i
I
Introduction
Wildfire is an integral part of the taiga in
Alaska.Wildfires caused by lightning or hu-
man activities burn 1.4 thousand to 2 million
ha each yearJJ (Barney 1971 b).Reoccurring
fires encourage fire resistant species such as
black spruce~and fast growing species such
as quaking aspen and paper birch (lutz 1956).
Since the 1950 1s,people have attempted to
prevent wildfires and reduce the acreage
burned.Fire suppression activities may pro-
tect houses,towns,and important resources
like commercial timber;however,they may
also scar the landscape,encourage erosion,
and set back vegetation development even
more than fire itself.Poorly designed and
pi aced fire lines can increase gully erosion,
surface subsidence,and stream siltation.This
is especially true if large vehicles are used in
areas of ice-rich permafrost (Deleonardis
1971,Lotspeich and Mueller 1971).
Furthermore,if all fires were controlled,other
problems would occur.The landscape would
become less diverse.Young stands of trees
would be rare.Quaking aspen or white spruce
would occur on the very warm and well-
drained sites,whereas black spruce and bog
would occur elsewhere.Paper birch would be
less plentiful,and balsam poplar would grow
only on flood plains adjacent to rivers (Neiland
and Viereck 1977,Viereck 1973).Animals that
are dependent on any stages of succession
except the oldest would become rare or disap-
pear,and predators of these animals would
become rare or move elsewhere.
JJFire data on file at the State Office,Bu-
reau of land Management,U.S.Department of
the Interior,Anchorage,Alaska.
YScientific names for species are given in the
appendix.
Fire has many uses.Aboriginal man used it
for warmth,cooking,hunting,signaling,and
insect control (lutz 1959).Homestead~rs and
miners use it to clear land and thaw frozen
ground.Fire can be used in Alaska to regulate
fuel accumulation on the forest floor,to dis-
pose of timber harvest slash,and to manipu-
late wildlife habitat.It can also be used to
help prepare seedbeds for regeneration or to
convert a stand from one species to another.
Personnel on the Chugach National Forest and
the Kenai National Moose Range currently use
controlled fire to manipulate moose habitat.
Many land managers are actively seeking in-
formation on fire effects and the potential use
of controlled fire.Interest in and concern for
quality land management is high and increasing
because of changing patterns of land owner-
ship.Whether land managers are preserving
natural vegetation or manipulating it for spe-
cial uses,they must define the role fire will
play in their management plans.
Understanding the effects of fire in Alaska be-
gan with the work of Harold Lutz in the early
1950's (Lutz 1956)and has evolved in a slow,
discontinuous manner.In 1971,the Alaska
Forest Fire Council and the Society of Ameri-
can Foresters sponsored a symposium,"Fire in
the northern environment"(Slaughter and
others 1971),which summarized the current
status of research and managemen..t related to
fire in Alaska and parts of northern Canada.
Vi ereck (1973)reviewed most of the current
and early work on fire effects in the taiga of
Alaska and northwest Canada.Kelsall and
others (1977)and Viereck and Schandelmeier
(1980)expanded and updated the review by
Vi ere ck.The interested reader can refer to
these papers for a more detailed discussion of
fire effects in Alaska.
Field studies on the effects of fire began at
the Institute of Northern Forestry in 1971 with
a series of studies designed to document the
immediate and long-term effects of the 1971
v/ickersham fire on forest ecosystems.A ser-
ies of experimental fires in 1976 and again in
1978 adjacent to the Wickersham fire area
were analyzed to provide information on fire
behavior as well as prefire and immediate
postfire data.Two papers (Vi ereck and
Dyrness 1979,and Viereck and others 1979)
summarize work undertaken in and around the
area of the Wickersham fire from 1971 to
1976.Additional work on post fire seed ger-
mination and revegetation (Clautice 1974),on
small mammals (West 1971,1979)and on
moose and snowshoe hare browse (Wolff 1977,
1978)was also done in this study area.
This paper reports the first phase of some re-
search that began in the Wickersham fire area
and expanded to other areas in the Alaska
interior.The project was funded by the U.S.
Department of the Interior,Bureau of Land
Management;National Science Foundation;
and USDA Forest Service.
2
Objectives
This study has two obj ectives:to qualitatively
and quantitatively describe plant com munities
or forest types in the taiga,and to order these
com.munity types into successional patterns for
whi te spruce and black spruce sites.
The study is being undertaken in three phases.
Phase I,reported here,focuses on the classifi-
cation of the different com munities found and
the description of the community typesl!4/lt
does not describe or statistically predict the
composition of each type.Phases 2 and 3 will
increase both the number of community types
and the number of replications studied.
~A community is real in the landscape.A
com munity type is theoretical.
4/This paper is an expansion of a portion of
the following report.Foote,M.Joan.Classi-
fication,description and dynamics of plant
communities following fire in the taiga of in-
terior Alaska.Final report for the Bureau of
Land Management,211 p.,1976.On file at
tne Institute of Northern Forestry,Fairbanks,
Alaska.
The Study Area
Taiga,or northern boreal forest,covers 43
million ha (Vi ereck 1973)to 60 million ha2!in
Alaska.It is bounded on the north by the
Brooks Range,on the west by maritime tun.dra,
on the south by maritime forest,and on the
east by the Canadian taiga.Within this area,
forests are bounded at higher elevations by al-
pine tundra,ice,and snow and at lower eleva-
tions by lakes and muskeg.
The study area of phase I consisted of linear
strips 5-10 km wide along the road system in
interior Alaska south of the Yukon River and a
few remote locations elsewhere where aerial
access was provided.Most of the study area
was in the western p.Jrtion of the Tanana River
valley and adjacent highlands (fig.I).Phases
2 and 3 of the study will expand the area to
the road system north of the Yukon River,to
the Tanana River flood plain southwest of
fairbanks,and to more remote portions of the
taiga.
The climate of the taiga is continental and
characterized by extreme temperatures,low
precipitation and light surface winds (Searby
1968).Variations over short distances are
considerable,and departures from the mean
are common.U.S.Weather Bureau records for
Fairbanks typify the climate of the study area.
The average annual temperature is -3.5°C;
extremes are _51°and 38°C.The mean maxi-
mum and minimum temperatures for summer
are 22°and 3.8°C and for winter are _2.7°and
-30°C,respectively.The average annual total
precipitation is 28 cm.The annual snowfall
averages 178 cm and remains from mid-
October to mid-May.Solar input averages 531
langleys in June and 6 langleys in December;
the form er reflects the 24-hour-long sunlit
days of sum mer whereas the latter reflects
the short,8-hour sunlit periods in winter.The
~J oint Federal-State Land Use Planning
Com mission for Alaska.Ecosystem area fig-
ures computed for the 1980 Renewable Re-
sources Planning Act field effort,1976.On
file at the Institute of Northern Forestry,
Fairbanks,Alaska.
frost-free growing season lasts from m id-J une
to early August.The total growing season,
based on a degre e day of 4.4°C,is about 1,900
hours long (Selkregg 1976,p.43-44).The cu-
mulative sum of daily mean temperatures for
the growing season,using a degree day base of
6°C,is 940°C (Funsch 1964).~
The taiga of AI aska,according to Thorn-
thwaite1s (1931)evapotranspiration classifica-
tion system,has a potential evapotranspiration
of 356-457 mm,and the climate can be de-
scribed as semiarid,with little or no surplus
rainfall and with temperature efficiency nor-
m al to warm m icrotherm al (P a tric and Black
1968).Trigg (1971),using index values of
effective precipitation and temperature,cate-
gorized interior Alaska as hot-arid to warm-
dry,or as an area of high fire frequency.
The geology of interior Alaska varies from
Precambrian rocks to Pleistocene loess.Bed-
rock in the Fairbanks Hills,including the area
around Fairbanks and Wickersham Dome,is
weathered Precambrian micaceous schist of
the Birch Creek formation (Viereck and Dyr-
ness 1979)under a layer of Pleistocene loess.
To the north and east of the Fairbanks Hills
the bedrock is a mixture of metamorphic,
sedimentary,and volcanic rocks of Paleozoic
age ('vJahrhaftig 1965).The loess layer varies
from 0 cm on the hilltops to over 60 m around
Fairbanks (Pewe 1968).Some loess has been
washed down from the hills to th-6 valley bot-
toms where it forms deposits of bedded to
massive silt rich in organic debris (Pewe 1975).
6/A degree day,used to describe the growing
season more precisely,is a day when the mean
temperature is above a certain threshold
(Selkregg used 4.4°C;Funsch,6°C).
3
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Cleary
.aSummit•
1......
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Haystack Mtn,
•
Wickersham
aDome ••
Ester
a Dome
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.el .f \Q..,R\~..J -~
cnataniKa ...;-.,.,....'1}.
/""'.~.--',....'
Bonanza
Creek
:Experimental
Forest
.a__---','-..J
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a Murphy
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\0'",/x\,,,,Q •.-'
\1'1'3-'".ra.::~=-------;:-------;_:::.~''-._.-"Legend"',,'\~~~~Taiga
"'"•1-9 stands
(J Stands surveyed
::.in successive years
J 5 miles I
Figure I.-Location of study
areas in the Alaskan taiga.
4
Soils of the taiga tend to be poorly developed
Inceptisols,undeveloped Entisols,or Histosols
(Rieger and others 1979).Ochrepts or well-
drained Inceptisols (soils that have only small
amounts of organic material in the upper few
centimeters)occur on hills where permafrost
is nonexistent or deep.Wet Inceptisols or
Aquepts (soils with thin to thick layers of
mostly undecomposed organic material)occur
in poorly drained areas where ice-rich perma-
frost is shallow to deep.Flood plains,outwash
plains,and seepage areas may have exposed
wet mineral soils or Entisols.These are most-
ly Aquents or Fluvents,depending on whether
the water table is shallow or deep.Histosol
soils,like Fibrists,are deep organic soils
mostly of undecomposed sphagnum or peat.
These occur in depressions or in moist areas of
long standing.Permafrost mayor may not be
present,but ice does remain until late in the
growing season.
Permafrost is common on north-facing slopes
or valley bottoms which receive little solar
radiation (Brown and Pewe 1973).This frozen
layer underlies an active soil layer which
freezes and thaws each year during the warm
period.Perm afrost influences plant growth
because it impedes the downward penetration
of roots and keeps the active soil layer cool.
This,in turn,slows down litter decomposition
and cell growth.The frozen layer also pre-
vents percolation;accumulated water may
counteract the effect of low rainfall and en-
hance growth or,as in most areas,impede tree
growth and result in the development of mus-
keg,bogs,and ponds.
..,
•
Topography,ground surfaces,and plant Jover
are potential interceptors of solar radiation.
Hills,soils high in silts,clays or peat,moss
mats,and tree canopies tend to decrease the
effect of incoming solar radiation.Thus soils
on north-facing slopes,soils under moss mats
or dense vegetation canopies,and soils which
are high in silts,clays,or peat are usually cool
and underlain by permafrost.South slopes,
coarse-grained sediments,bare rock surfaces,
moss-free surfaces,and tre eless surfaces
which absorb incoming solar radiation tend to
be warmer and free of permafrost (Selkregg
1976,p.100).
Fires,both natural and human caused,can
occur in interior Alaska between April I and
September 30,but most occur in May,june,or
july.Probability indexes of fire occurrence
(buildup index)reach peak values from june to
early july (Barney 1967).This is when tem-
peratures are highest,nighttime cooling is
minimal,humidities are lowest,there are long
periods with little or no precipitation,and
lightning storms are frequent..
Fires burn extensive area each year.Before
fire suppression-1893 to 1939--Lutz (1953)
estimated 405 000 ha burned annually.
Barney's (1971 a,b)more recent estimate is
0.6-1.0 million ha per year.For the time of
active fire suppression-1940 to 1979--the
area burned averaged 201 700 to 502400 ha
per year,based on 10-year intervlls (table I).
Two trends are apparent from the data in
table I:the total area,burned each year is
decreasing,and the total number of fires
reported has increased each decade.These
trends probably reflect improvements in fire
contro I and detection.
5
Table I-Number of fires and area burned per year in interior Alaska,1940-79
1940-49 1950-59 1960-69 1970-79
i~umber of fires and
area.burned per year
Amount Percent A mount Percent Amount Percent Amount Percent
Number Number Number Number
Fires per year:
Muman caused 93.8 82 183.9 71 152.7 64 130.2 42
Lightning caused 20.0 18 74.5 29 85.3 36 180.5 58
Total fires 113.8 100 258.4 100 238.0 100 310.7 100
Thousand Thousand Thousand Thousand
hectares hectares hectares hectares
Area burned per year:
Human caused 88.4 20 63.3 25 3.8 2
Lightning caused 344.2 80 194.4 75 197.9 98
Total area burned 502.4 100 432.6 100 257.7 100 201.7 100
- =No data.
Sources:(a)Fire data on file at the State Office,Bureau of Land Management,U.S.Department of the
Interior,Anchorage,Alaska.(b)Barney (1971 b).
Fires in interior Alaska occur primarily on
tundra,bog,and noncom mercial forest lands
(Viereck 1973).Barney (197Ia)and Viereck
(1975)give the following breakdown by cover
type,based on 5 years of data:treeless (in-
cludes tundra,bog,and grassland)43 percent;
conifer forest (primarily black spruce)36 per-
cent;conifer-broadleaf forest 14 percent;
broadleaf (aspen,birch,and cottonwood)
2 percent;and other (high brush)5 percent.
Barney (1971 a)further states that less than
0.5 percent of the burned forested land could
be classified as potential com m ercial forest
land or land capable of producing 1.4 m 3 of
wood per hectare per year.
6
Human impact on the forests has varied and
early impacts have been masked by those
which came later.Trees are harvested mostly
for local timber and fuel needs as the land is
cleared for settlements,roads,power trans-
mission lines,pipelines,and farm s.F ires are
associated with these activities.The presence
of num erous 50-and 80-year-old forest stands
reflects increases in human activities during
the early 1900's and the mid-I920's.
Methods
Stands were selected to represent variations in
(I)mature forest community type,(2)stage of
forest development,and (3)range of fire ef-
fects.Stands considered for selection were
limited to those that were homogeneous in na-
ture,at least 2 ha in area,and representative
of the surrounding vegetation and topography.
Eighteen burns of known age and numerous
burns of unknown age were visited.The burns
of known age dated from the following fires:
Porcupine (1950),Badger Road (1958),Chena
Dom e (1958),Healy (1958),Chena Hot Spri ngs
Road (I 957:-58},Murphy Dome (1958),Good-
paster (1958),Standard (1966),Harding Lake
(1966),Hess Creek (1966),Cement Creek
(1966),Steese-Chena Hot Springs Road Junc-
tion (1968),Manley (1969),Wickersham (1971),
Ganes Creek (1971),Nixon Flats (1971),
Grenac Road (1977),and Parks Highway (1977).
Som e burned stands were revisited annually or
intermittently to monitor vegetation develop-
ment.
Each stand selected was studied using a grid of
usually 20 points that were approximately
20 m apart and organized along the long axis
of the stand.At each point a nest of three
plots was used to collect:(I)visual estimates
of canopy cover,(2)stem counts by diam eter
class,(3)seedling counts,(4)tree d.b.h.(diam-
eter at breast height),and (5)distance to plot
center.A l-m 2 plot was used to estimate
cover for cryptogams,herbs,low shrubs,ex-
posed ground surface,and litter categories.A
4-m 2 plot was used to estimate cover,and to
count stems for tall shrubs and seedling trees
(Ohmann and Ream 1971);and a point-
centered quarter plotless method (Cottam and
Curtis 1956)was used to count and measure
live sapling,live adult,and standing dead
trees.Depths of litter,organic soil,and depth
to permafrost were measured adjacent to but
outside the l-m 2 plots.Each permafrost
measurement was dated.In addition,15 trees
were bored,fire-scarred trees were sectioned,
and 2-5 photos were taken of both the general
stand and the small l-m 2 plots.
The following data were then summarized for
each stand:(I)m eail percent cover for all
plant species,ground surface and litter cate-
gories,and vegetation layers (moss,lichen,
herb,low shrub,tall shrub,and tree),(2)aver-
age density per hectare for tree seedling,tree,
and tall shrub species,(3)average basal area
per hectare for each tree species,(4)average
d.b.h.for trees and saplings,(5)distribution of
trees and saplings by I-cm d.b.h.classes,(6)
stand age based on annual ring counts,(7)
thickness of the surface organic layer,(8)
depth to permafrost and date,and (9)mean
frequency of plant species encountered in
sample plots.Stand photographs were labeled
and filed.
Si mi lar stands were identified and grouped
with the aid of a computerized clustering sys-
tem.The technique used in the system is a
polythetic -agglom erative num erical classifica-
tion which,based on within-group dispersion
using standard distance,pairs most similar
stands or stand-groups in successive cycles to
produce a hierarchy of stand relationships
(Orloci 1967).The number of stan~groups
recognized from this technique depends on the
level of hierarchy that is found to be meaning-
ful.For this study,stand groupings were used
if they subjectively represented:(I)previously
defined plant community types (Lutz 1956,
Viereck 1973),(2)tentatively defined plant
com munity types (Viereck and Dyrness 1980),
or (3)were visually discrete units .JIof the land-
scape but not previously identified.
The clusteri ng program required use of a re-
duced species list (see appendix).To make the
selection as obj ective and quantitative as pos-
sible,the computer program SCREEN was em-
ployed (Grigal and Ohmann 1975).SCREEN
ranks the species in the data set on six differ-
ent criteri a:(I)frequency,with those species
found in the most plots ranking highest,(2)
arithmetic mean of the frequency of each
species over all stands,(3)the ratio between
7
Results and Discussion
Table 2-Sorne mature forest com munity types
in the taiga of interior Alaska
One hundred thirty stands,ranging in age
from I month postfire to 200 years,were
located and sampled (see fig.I).Forty-seven
older ones (50-200 years old)were aggregated
into most-similar groupings.Twelve of these
groups appeared to reflect well-developed,
mature com m unities and were the basis of the
mature community types described in this pa-
per (table 2).The 12 groups also appeared to
reflect two site types that formed the basis of
the developmental stages described later in
this pap er.
Name of mature forest
com munity type
Populus tremuloides/Viburnum edule/
Linnaea borealis
Betula papyrifera/Viburnum edule
Betula papyrifera/Alnus crispa/
Calamagrostis ca~is
Picea glauca/Viburnum edule/
Equisetum arvense/Hylocomium
splendens
Picea glauca/Rosa acicularisl
Equisetum syTVitTcum/Hylocomium
splendens
Populus balsamifera/Oplopanax
horridus
Populus tremuloides-Picea mariana/
C or nus ca na dens is
Picea mariana-Betula papyrifera/
Vaccinium uliginosum-Ledum
groenlandicum
Picea mariana/Vaccinium uliginosum-
Ledum groenlandicum/Pleurozium
schreberi
P icea mariana/fe ath er moss-Ii ch en
Picea mariana-Picea glauca/Betula
,gl andulosa/lichen
Picea mariana/Sphagnum spp.-
Cladina spp.
9
7
2
3
8
5
4
6
12
10
II
Type
number
Additional community types exist.Some are
reported in the literature (Neiland and Viereck
1977,Viereck and Dyrness 1980),others have
yet to be defined and described.
the computed standard devi ation of observa-
tions for each species and the one predicted on
the basis of the mean,(4)information based on
data recording presence and absence,(5)the
relative contributions made by each species in
the calculation of interstand distanc e,and (6)
the absolute weighting of each species along
the first five principal component axes.This
last step results in a ranked list of species.
The 59 species to be used in subsequent analy-
ses were selected from those ranking highest
on this list,with one exception.In an effort
to have each vegetational stratum well repre-
sented,some species which fell in the middle
of the master lists but high when only their
own stratum was considered were included in
the reduced species list.
The resulting stand groupings are the com mu-
nity or forest types described in this paper.
These types,called community types through-
out this paper,represent actual small seg-
ments of the taiga landscape.They cannot,in
a statistical sense,predict what would occur
throughout the entire taiga.They can,how-
ever,give a first approximation of the species
composition one would expect to find in each
of the com m unity types studied.
Taxonomy follows Viereck and Little (1972)
for woody plants,Hulten (1968)for herbaceous
plants,Worley and Watuski (1970)for mosses,
and Hale and Culberson (1970)for lichens.
Com mon names for plant species follow Vi er-
eck and Little (1972),Hulten (1968),Kelsey
and Dayton (1942),and Welsh (I974).Difficult
identifications of species were determined by
Alan Batten,David Murray,and Barbara Mur-
ray of the University of Alaska herbarium.
Voucher plant specimens were collected and
were deposited in the University of Alaska
herbarium.
8
Figure 2 portrays the general relationship be-
tween stands,stand groups,com munity types,
and site types.
Many taxa were found in all com munity types.
Differences were in amounts of cover,fre-
quency,and density rather than distinct
changes in species composition.A mature
forest community type gets its name from the
plant species which best describes it.Species
The revegetation process is continuous.In this
study,however,it is divided into six stages
representing developmental phases in plant
succession.This paper discusses each stage in
terms of its place in secondary succession on
white spruce or mesic black spruce sites.Each
stage is named by its dominant vegetation;age
limits are suggested.
A mature forest community is the most stable
phase of development attained by a tree spe-
cies.It may be,but is not always,synonymous
with the end of succession.As defined in this
work,maturity occurs when the stand is domi-
nated by trees and the species com plex has
more or less stabilized.The mature character
of a forest community is first apparent when
the trees are at least 50 years old.Changes
that occur thereafter reflect the age and mat-
uration of individual plants;i.e.,trees age,
grow larger in diameter,and die.Some ma-
ture forest com munities are relat~vely self-
perpetuating;others convert to other forest
types.In interior Alaska most communities
are terminated by fire.The oldest stands are
limited to isolated locations or those protected
from fire by topography or wetness.For ex-
ample,river islands are isolated,and bogs and
sphagnum-rich,north-facing slopes are usually
too wet to sustain fire.But even in such pro-
tected locations,no trees older than 300 years
have been disc overed.
that occur in different strata are separat~d by
slashes;species that share the same stratum
are separated by hyphens.For example,in the
Picea mariana-Picea glauca/Betula glandulosa/
lichen community type (table 2,type II),P.
mariana and!:glauca share dominance inthe
tree stratum,B.glandulosa dominates the tall
shrub stratum;-and lichens are important on
the forest floor.
Mature Forest Communities
Black spruce
site type
Figure 2.-Stylized dendrogram
of stands,stand groups,mature
community types,and site types.
Vertical lines depict individual
stands or groups of similar
stands.Connecti ng hori zontal
lines indicate the degree of sim-
ilarity of stands or stand groups;
tne lower the within-group dis-
persion,the more similar the
stands or stand groups.The
lower dashed line identifies the
12 stand groups used to form the
12 mature com m unity types.
The Lipper dashed line identifies
the two stand clusters denoting
the two site types.
Aggregation of stands
White spru e------------------
site type
~100
(,)
Gi.e
co
'iii
Gic.
.!!!
'tl
C.:::>om
Ic:c
:5"i
Gl
III
Cll
Gi><
9
White Spruce Sites
White spruce sites occur on flood plains and
river terraces along river margins,on slopes
with southern exposures within 8 km of the
major river valleys,or near timberline.These
sites are generally warm and covered with
well-drained Inceptisols and Entisols.Seasonal
frost in the soil begins melting in May and is
mostly gone by late June.Permafrost is rare
and,when present,seldom within 10 m of the
surface.
The vegetation is dominated by trees,but tall
shrubs,herbs,and sometimes moss are also
prominent.Quaking aspen,paper birch,bal-
sam poplar,white spruce,prickly rose,high
bushcranberry,field horsetail,and sometimes
the feathermoss Hylocomium splendens grow
well on white spruce sites.The trees occur in
both pure and mixed stands and with the other
ve getation produce the com m unity or fore st
types that occur on white spruce sites.Six of
these forest types will be discussed (table 2,
types 1-6).Of the six,four (types 1-4)are
fo und on upl and s lopes and two (types 5-6)are
found on flood plains near rivers.Other
com munity types exist on white spruce sites
but have not yet been described quantitatively.
10
I.Populus tremuloides/Viburnum edule/
Linnaea boreale community type
Mature stands of this type are characterized
by a closed canopy of quaking aspen (Populus
tremuloides)trees,an almost continuous tall
shrub layer of prickly rose and high bushcran-
berry (Viburnum edule),and twin-flower
(Linnaea borealis)on the forest floor (fig.3).
Figure 3.-A Populus tremu-
(oides/Viburnum edule/Linnaea
borealis com munity.Quaking
aspen in this stand (no.259)are
70 years old.
Quaking aspen grows on south-facing slopes up
to an elevation of 610 m (Gregory and Haack
1965).These slopes vary in grade between
7 and 40 percent and are covered bya 5-to
10-cm surface hori.zon of organic material
that overlies a mantle of loess 0.1-70 m deep.
Quaking aspen trees grow on the warmest for-
est sites in interior Alaska.Snow melts early
in the spring.The seasonal frost retreats to a
minimum depth of 80 cm by late June and is
entirely gone by August.Soils on these sites
can become extremely dry.Wherever quaking
aspen occurs.Populus tremuloides/Viburnum
edule/Linnaea boreale communities may also
occur.
This study found the flora in communities of
this type to be moderately diverse;each stand
studied possessed 3(}-38 plant species.Species
with frequencies averaging 40 percent or more
(that is.species occurring on 40 percent or
more of the sample plots)are listed in table 3.
No species is unique to this com munity type.
Species such as quaking aspen.high bushcran-
berry.twin-flower.and Labrador lousewort.
however.appear to prefer these warm.well-
drained forest sites.Bebb willow.which
occurs widely in seral com munities.remains a
component of only this com munity type.and
even here it is not common.
Communities of this type are mature when the
quaking aspen reach 50-80 years of age.At
that time the tree canopy is continuous.Data
from this study show that tree densities aver-
age 1.200 trees/ha,diameters range from 3-to
35-cm d.b.h.but average 17 cm.and heights
range from 17 to 26 m.Paper birch.white
spruce.and balsam poplar also occur but are
infrequent.Inovermature stands 130 years
old.the canopy is open.tree density has
decre ased to 700 trees/ha,and diam eters in-
creased to more than 40-cm d.b.h.and average
32.8 c m.
>:;;
Prickly rose and high bushcranberry form an
almost continuous tall shrub layer 1-'"1.5 m tall
in both mature and overmature stands.Mean
frequencies for both species range between 85
and 100 percent.Two additional tall shrubs.
American green alder and Bebb willow.occur
occasionally or at frequencies of less than 30
percent.
The low shrub layer is composed of patches
of twin-flower and sometimes mountain-
cranberry.The former.with a mean frequen-
cy of 65 percent.is common;the latter.with a
frequency of 0-40 percent.is occasional.
The herb layer is composed of scattered
plants.It is dominated by field horsetail.
bunchberry.and fireweed.Reedgrass is only
slightly less important.The following species
were present in most of the stands studied:
tall bluebell.one-sided wintergreen.liveried
wintergreen.bluntleaved sandwort.Geocaulon
lividum.and northern bedstraw.Herbs tend to
be less com mon and less extensive in the over--
mature stands;however.this may not be so
with northern bedstraw.Geocauk>n lividum.
and bluntleaved sandwort.
Mosses.when present.grow on the basal trunks
and exposed roots of quaking aspen or occa-
sionally in small patches on the forest floor.
Lichens.primarily Cladonia spp .•occur but
never in large amounts.Leaf litter covers
most of the forest floor to a derlth of 1-2 cm.
II
Table 3-lmportant plant species and litter components of the Populus tremuloides/Viburnum edule/Linnaea borealis community
type (Type I)of interior Alaska
Mature stands Jj Overmature stands §
Species and
litter component
Cover y Density.!!D.b.h.~Frequency ~Cover ~Density.!!D.b.h.~Frequency ~
Percent Stems/ha Cm Percent Percent Stems/ha Cm Percent
Tree layer:
Populus tremuloides-
Mature trees 1,200 15-19 100 700 32.8 100
Saplings 0 0 500 100
Seedlings 1,700 16 8,800 SO
Tall shrub layer:
Rosa acicularis 30,000 92 28,000 100
Viburnum edule 40,000 87 213,000 100
Low shrub layer:
Li nnae a b ore a lis 9 65 3 90
Herb layer:
Calamagrostis spp.I 78 0 0
Cornus canadensis 9 90 7/20
Epilobium angustifolium 3 85 -3 60
Equisetum arvense 10 78 0 0
Galium boreale 7/23 2 70
Geocaulon lividum 7/7 4 40
Moehringia lateriflora Ii 20 I 50
Litter component:
Leaves and twigs 93 100 94 100
Dead wood and
fallen logs 6 93 II 100
--~._.------_.._-
''-i:,,;;,''i<,'<'~'''!f~;,\flj'''l;~''':t'~{(;:':'
lJ Number of mature stands sampled:3;age:50-70 years;number of species found:31-38;depth of organic layer:10 cm.
2/The percent of area shaded by the canopy of a given species or litter cOl1)ponent.It is based on the equation:Cover =I (mean
stand cover value for a species).;-total number of stands sampled.The values given are rounded to the nearest whole number.
3/The computed or counted number of stems occurring in a given area.It is based on the equation:Density =I (mean stand density
value for a species)+total number of stands sampled.The values given above 200 are rounded to the nearest 100;the values below
100 are rounded to the nearest whole number.
if D.b.h.is the diameter of a tree at breast height.The mean stand d.b.h.value for a species is given;when more than I stand was
sampled,the range of mean values is given.
~The percent of plots in which a given species occurs.It is based on the equation:Frequency =I (mean stand frequency value for
a species)-7-total number of stands sampled.The values given are rounded to the n,earest whole number.
§j Number of overmature stands sampled:I;age:130 years;number of species found:22;depth of organic layer:8 cm.
7/Less than 0.5 percent.
."'>ft,
Stands in this com munity type may be able to
maintain themselves through several gener-
ations because young aspen frequently out-
number young stems of other species.Occa-
sionally local patches of dense paper birch
seedlings develop,but there is no evidence
that these survive for long.White spruce
eventually invades,and if no fire occurs,this
quaking aspen community will evolve into a
white spruce community.If·fire occurs,
quaking aspen will probably replace itself.
14
The Populus tremuloides/Viburnum edule/
Linnaea borealis community type is one of
several quaking aspen types.This type and the
closed Populus tremuloides/Viburnum edule/
Linnaea borealis type (Viereck and Dyrness
1980)are based on the aspen/Viburnum/
twin-flower type of Foote (see footnote 4).It
is a component of the more general aspen type
(Buckley and Libby 1957,Hutchison 1968,Lutz
1956,Neiland and Viereck 1977,and Viereck
and Little 1972).On vegetation maps with
sc ales of I :2,500,000 and I :7,500,000,it is in-
cluded in the upland spruce-hardwood forest
type (J oint Federal-State Land Use Planning
Commission forAlaska 1973),the spruce-birch
forest type (Kuchler 1966),and the moderately
high,mixed evergreen and deciduous forest
type (Spetzman 1963).Other aspen types are
discussed in Neiland and Viereck (1977)and
Viereck and Dyrness (1980).
2.detula papyrifera/Viburnum edule com-
munity type
Mature stands of this type are characterized
by dominance of paper birch (Betula papyrif-
era)trees,an extensive tall shrub layer of
prickly rose and high bushcranberry (Viburnum
edule),and an open herb layer of field horse-
tail (fig.4).
Figure 4.-A Betula papyrifera/
Viburnum edule com munity.
Paper birch in this stand (no.
122)are 60 years old.
Paper birch grows on east-and west-facing
slopes at elevations below 610 m.Slopes vary
in grade between 7 and 40 percent and have a
10-to IS-em surface horizon of organic mate-
ri al on top of loess.
Sites supporting paper birch are not as warm
as those supporting quaking aspen.In the
paper birch stands snow stays until early May,
and the seasonal frost leaves more slowly.In
late June the ground thaws to a minimum
depth of only 50 cm;however,by August the
frost layer is gone.
The flora of thi s com m unity type was found to
be sparse;the stands studied averaged 23-28
sp ec i es--eons ider ab Iy fewer th an the num b er
found in the Populus tremuloides/Viburnum
edule/Linnaea borealis community type.Spe-
cies with mean frequencies of 40 percent or
more are listed in table 4.
15
0\Table 4-lmportant plant species and litter components of the Betula papyrifera/Viburnum edule community type (Type 2)of interior
Alaska
JJ Number of mature stands sampled:2;age:60-100 years;number of species found:23;depth of organic layer:13 em.
2/The percent of area shaded by the canopy of a given species or litter component.It is based on the equation:Cover =I (mean
stand cover value for a species);-total number of stands sampled.The values given are rounded to the nearest whole number.
3/The computed or counted number of stems occurring in a given area.It is based on the equation:Density =I (mean stand density
value for a species).;.total number of stands sampled.The values given above 200 are rounded to the nearest 100;the values below
100 are rounded to the nearest whole number.
4/D.b.h.is the diameter of a tree at breast height.The mean stand d.b.h.value for a species is given;when more than I stand was
sampled,the range of mean values is given.
5/The percent of plots in which a given species occurs.It is based on the equation:Frequency =I (mean stand frequency value foraspecies)';'total number of stands sampled.The values given are rounded to the nearest whole number.
2J Number of overmature stands sampled:I;age:140 years;number of species found:28;depth of organic layer:13 em.
!..!Less than 0.5 percent.
Stands of the Betula papyrifera/Viburnu m
edule communities are mature when the paper
birch reach 60-90 years of.age.At that tim e
the tree canopy is closed.Tree densities aver-
age about 800 stems/ha,diameters range from
2.5 to 48-cm d.b.h.but average 21 cm,and
heights range from 12 to 24 m.In overmature
stands,which are com mon,the mean tree den-
sity has decreased to 200 stems/ha,and diam-
eters of the larger trees range from 15.7-to
68.3-c m d.b.h.Gregory and Haack (1965)
found that trees more than 4o-cm d.b.h.are
usually defective.White spruce trees occur
but in fewer numbers.Saplings of both white
spruce and paper birch may occur in small
numbers;seedlings are rare.
A tall shrub layer reaches 1-1.5 m in height,
and a shorter herb layer occurs beneath the
trees.Prickly rose is ubiqui.tous,high bush-
cranberry is com mon,and clum ps of Am erican
green alder occur occasionally.Field horsetail
and leaf litter dominate the forest floor.
Scattered throughout tile stands are other herb
species such as bunchberry,bluntleafed sand-
wort,reedgrass,and fireweed ;low shrub
species such as twin-flower;and feathermoss
species such as P·I eurozium schreberi and Hy-
locomium splendens.The amount of reedgrass
and Pleurozium schreberi increases with stand
age.Leaf litter forms a continuous layer 2-3
cm thick.Occasional rotting logs and short
hollow snags,mostly of paper birch,are found
on tite forest floor.
This com munity type appears to be composed
of even-aged stands.The white spruce and
paper birch most likely started from seed
before heavy leaf litter developed.Gregory
(1966)found that heavy leaf litter falling in
mature paper birch stands prevents the estab-
lishment and survival of young white spruce
seedlings.Regeneration of paper birch within
mature stands is mostly limited to stem
suckers,which sometimes ring the base of old
trees.Eventually,however,the slower grow-
ing white spruce will replace the defective
over mature paper birch in the tree canopy,
and the com munity will succeed to an open
white spruce type.
The Betula papyrifera/Viburnum edule com-
munity type and the closed type of the sam e
name (Viereck and Dyrness 1980)are based on
the birch/Viburnum type of Foote (see foot-
note 4).The open Betula papyrifera/Viburnum
edule/Calamagrostis type (Viereck and Dyrness
1980)may be closely related.In any case,it is
a component of the more general birch,paper
birch,or white birch types (Buckley and Libby
1957,Hutchison 1968,Lutz 1956,Neiland and
Viereck 1977,and Viereck and Little 1972).
On vegetation maps with scales of 1:2,500,000
and 1:7,500,000,it is one component of the
even more generalized types:upland spruce-
hardwood forest (Joint Federal-State Land Use
Planning Com mission for Alaska 1973),spruce-
birch forest (Kiichler 1966),and moderately
high,mixed evergreen and deciduous forest
(Spetzman 1963).Additional paper birch types
are discussed by Neiland and Viereck (1977)
and Viereck and Dyrness (1980).
3.Betula papyrifera/Alnus crispa/Calama-
grostis canadensis com munity type
Mature stands of this type are characterized
by a closed canopy of paper birch (Betula
papyrifera)trees and extensive patches of tall
American green alder (Alnus crispa)(fig.5).
Stands typifying this com munity type occur
on east-and west-facing slopes below 610 m.
Slopes vary in grade between 10 and 30 per-
cent,and a 10-to 15-cm surface horizon of
organic material overlies a thin mantle of
loess.Soil temperatures appear to be cooler
than on the south-facing slopes-at least the
seasonal frost retreats a little more slowly.
By late June seasonal ground frost melts to a
depth of 30 cm-20 cm less than in the Betula
papyrifera/Viburnum edule type.By August it
is probably gone.
The flora found in stands of this com munity
type are composed of 22-34 species.No taxa
are unique to this type.American green alder
flourishes;and Labrador-tea,twin-flower,and
regeneration of black spruce may occur.On
the other hand,this is the only type found on
white spruce sites that lacks high bushcran-
berry and where prickly rose,though present,
is not common.Table 5 lists the most import-
ant plant species found in this com munity type.
The mature stands are 50-130 years old and
average about 600 trees/ha;less than 1 per-
cent of these are white spruce.Regeneration
is sparse (15 sapl ings/ha)and is mostly white
spruce or black spruce,although some paper
birch does occur.Beneath the trees,Ameri-
can green alder commonly forms a tall shrub
layer 2-4 m in height averaging 4,000-5,000
stems/ha.
The forest floor is dominated by intermittent
patches of low shrubs like mountai n-cranberry
and twin-flower;herbs like reedgrass;mosses
like Hylocomium splendens,Polytrichum spp.,
and Dicranum spp.;and a continuous layer of
litter.Small quantities of the following
species also occur:fireweed,ground cedar,
bunchberry,Pleurozium schreberi,and
C I ad 0 nia sp p.
Figure 5.-A Betula papyrifera/
Alnus crispa/Calamagrostis
canadensis community.Paper
birch in this stand (no.172)are
140 years old.
In the absence of fire,stands of this type will
succeed to open Picea glauca,~.mariana,or
m ixed ~.gl auca-~.m ari ana types.
The Betula papyrifera/Alnus crispa/Calama-
grostis canadensis com munity type is synony-
mous with the closed deciduous type of the
same name (Buckley and Libby !..957,Lutz
1956,Viereck 1975,and Viereck and Dyrness
1980).It is a co m pone nt of th e gener a I birch
type (HutChison 1968,Neiland and Viereck
197~,and Viereck and Little 1972).On vege-
tation maps with scales of I :2,500,000 and
1:7,500,000 it is one component of the even
more generalized types:upland spruce-
hardwood forest (Joint Federal-State Land Use
Planning Com mission for Alaska 1973),spruce-
birch forest (Kuchler 1966),and the moderate-
ly high,mixed evergreen and deciduous forest
type (Spetzman 1963).
19
Percent Stems/ha COl Percent
Cover ~Density'.!.../D.b.h.~Frequency ~
Mature stands y
600 16.2-21.0 100
1,000 5.9-16.6 5
15 40
4,800 40
3 55
3 50
2 42
92 100
7 100
~D.b.h.is the diameter of a tree at breast height.The mean stand d.b.h.
value for a species is given;when more than 1 stand was sampled,the range of
mean values is given.
3/The computed or counted number of stems occurring in a given area.It is
based on the equation:Density =I (mean stand density value for a species).;.
total number of stands sampled.The values given above 200 are rounded to
the nearest IOU;the values below 100 are rounded to the nearest whole
number.
Picea mariana-
-saplings
Litter component:
Leaves and twigs
i)ead wood and
fallen logs
Mosses:
Hylocomium splendens
Polytrichum spp.
Herb layer:
Calamagrostis spp.
T all shrub layer:
Alnus crispa
Picea glauca-
-seedlings
2/The percent of area shaded by the canopy of a given species or litter
component.It is based on the equation:Cover =I (mean stand cover value
for a species)7-total number of stands sampled.The values given are rounded
to the nearest whole number.
Table 5-lmportant plant species and litter components of the Betula
papyrifera/Alnus crispa/Calamagrostis canadensis community type (Type 3)of
interior Alaska
Species and
litter component
J.J Number of stands sampled:2;age:50-130 years;number of species found:
22-34;depth of organic layer:12-13 em.
Tree layer:
Betula papyrifera-
Mature trees
20
5/The percent of plots in which a given species occurs.It is based on the
equation:Frequency =I (mean stand frequency value for a species).;.total
number of stands sampled.The values given are rounded to the nearest whole
number.
4.Picea glauca/Viburnum edule/Equisetum
arvense/rlylocomium splendens community
type
Mature stands of this type are characterized
by a closed canopy of white spruce (Picea
glauca)trees,an extensive tall shrub layer of
prickly rose and high bushcranberry (Viburnum
edule),and an extensive cover of field horse-
tail (Equisetum arvense)and the feathermoss
rlylocomium splendens (fig.6).
Stands typifying this community type occur on
many south-facing slopes that vary in grade
between 7 and 40 percent.They are most
com mon at lower elevations,those below
610 m and on south-faci ng slopes associated
with the larger river systems.The soil on
these slopes consists of an 8-to IS-em surface
horizon of organic r.laterial over a deeper
mantle of loess.The soil is not much different
from that found on sites where quaking aspen
and paper birch occur.Soil on these sites,
however,is a little cooler than in most hard-
wood stands because the presence of a 10-to
IS-em thick moss layer insulates the ground
from incoming solar radiation.Frost leaves
the ground more slowly but is gone by August.
By late june the soil has thawed to a minimum
depth of 40 em.
The flora in stands of this com munity type is
composed of about 32 species.All species
occurring in hardwood stands also occur in
stands of this type but in different quantities.
Table 6 lists the more important plant species
found in this com munity type.
,Jhen the trees are 100-200 years old,the
community is somewhat open and dominated
by large white spruce trees.Data from this
study show that tree densities average SOO
stems/ha,diameters are 12-to 35-cm d.b.h.,
and heights are 20-30 m.Farr (1967)found
the same characteristics for ISo-year-old
white spruce.Both white spruce and paper
Figure 6.-A Picea glauca/
Viburnum edule/Equisetum
arvense/Hylocomium splendens
community.White spruce trees
in this stand (no.312)are 120
years old.
birCh occur in the understory.Hardwood snags
and decaying logs occur on the forest floor.
Prickly rose and high bushcranberry,both
I-I.S m tall,form a well-developed tall shrub
layer above which occasional clu.lmps of Amer-
ican green alder extend 3-4 m tall.The forest
floor is carpeted with an almost continuous
layer of Hylocomium splendens 20-2S em deep,
occasional patches of twin-flower and
Geocaulon lividum,and a scattering of field
horsetail.Leaf litter occurs but is rapidly
incorporated into the moss layer.
21
Percent Stems/ha Cm Percent
Cover 2/Density'}j D.b.h.4/Frequency ~
Mature stands Y
40 21.0-24.0 25
6 30
700 10
500 27.3-30.6 100
20 100
1,600 25
12,300 70
7,600 40
4 80
4 55
60 90
5 25
25 95
15 60
~The percent of plots in which a given species occurs.It is based on the
equation:Frequency =r (mean stand frequency value for a species)7-total
number of sta.nds sampled.The values given are rounded to the nearest whole
number.
~D.b.h.is the diameter of a tree at breast height.The mean stand d.b.h.
value for a species is given;when more than I stand was sampled,the range of
mean values is given.
3/The computed or counted number of stems occurring in a given area.It is
based on the equation:Density =r (mean stand density value for a species)f
total number of stands sampled.The values given above 200 are rounded to
the nearest 100;the values below 100 are rounded to the nearest whole
number.
2/The percent of area shaded by the canopy of a given species or litter
component.It is based on the equation:Cover =r (mean stand cover value
for a species)f total number of stands sampled.The values given are rounded
to the nearest whole number.
Tall shrub layer:
Rosa acicularis
VibUl-num edule
Litter component:
Leaves and twigs
I>ead wood and
fallen log..
j';1 osses:
Hylocomium splendens
Pleurozium schreberi
Herb layer:'
l::quisetum arvense
Geocaulon lividum
Tree layer:
Betula papyrifera~
ldature trees
Saplings
Seedlings
Table 6--lmportant plant species and litter components of the Picea
glauca/Viburnu m edul e/E qui setu m arvense/Hylocom iu m splendenscom m unity
type (Type 4)of interior Alaska
Species and
litter component
Picea glauca-
Mature trees
Saplings
Seedlings
I/l'llumber of stands sampled:2;age:150-200 years;number of species
found:31-33;depth of organic layer:12 em.
22
Many of these white spruce stands appear to
have developed from the Populus tremuloides
and Betula papyrifera com munity types al-
ready discussed.Some pure white spruce
stands establish themselves immediately after
fire,but thi s is not com m on.The establish-
ment of white spruce depends on the presence
of exposed mineral soil,viable seed,and ade-
quate shade for young seedlings.None of
these requirements are assured when white
spruc e st ands are burned or 0 th erw i se di s-
turbed (Zasada 1972).Stands of this type may
slowly replace themselves or become open
mixed white spruce-paper birch stands since
both species occur in the understory.The
existing trees are all younger than 300 years in
age,however,and most show no sign of inter-
nal rotting so we do not know what happens in
the next generation of com munities of this
type.
The Picea glauca/Viburnum edule/Equisetum
arvense/Hylocomium splendens community
type is synonymous with the closed Picea
glauca/Viburnum edule/Equisetum arvense
type (Viereck and Dyrness 1980;also see
footnote 4).It is a major component of the
more general white spruce or white spruce/
feathermoss types (Buckley and Libby 1957,
Hutchison 1968,Lutz 1956,Neiland and
Viereck 1977;Viereck 1970,1975;and Viereck
and Little 1972).On vegetation maps with
scales of I :2,500,000 and I :7,500,000,it is an
important component of the following types:
upland spruce-hardwood forest (Joint Federal-
State Land Use Planning Commission for
Alaska 1973),spruce-birch forest (Kuchler
1966),and the high,evergreen spruce forest
(Spetzman 1963).
Figure 7.-A Picea glauca/Rosa
aci cu I ari s/E qlJTSetij m syl vat"iCiJm /
Hylocomiurn splendens commu-
nity.White spruce trees in this
stand (no.134)are 110 years old.
5.Picea glauca/Rosa acicularis/Equisetum
syl vatic u m/HylocomTUm spl endens com munity
type
Mature stands of this type are characterized
by a closed canopy of white spruce (Picea
glauca)trees,an extensive tall shrub layer of
prickly rose (Rosa acicularis),an almost con-
tinuous mat of feathermoss (primarily Hylo-
comium splendens),and extensive areas of
woodland horsetail (Equisetum sylvaticum)on
the forest floor (fig.7).
23
Stands typifying this com munity type occur on
flood plain islands or within one-half mile of
active river channels.Periodic flooding of
these sites causes the soil profiles to be strati-
fied;layers of organic matter alternate with
layers of silt,both overlying alluvial sand and
gravel (Zasada 1972).In spring,soils thaw
more slowly than on their upland counterparts.
By late June the minimum depth of thaw is 30
cm-IO cm shallower than the depth of thaw
on upland sites.By mid-July the soil on both
upland and flood plain sites is completely free
of seasonal frost (Viereck 1970).Flood plain
site.s are created,maintained,and destroyed
by the deposition and erosion activities of
meandering river channels.Water channels
also help protect these areas from wildfire.
The flora in communities of this type is com-
posed of about 30 species.No taxa are unique
to these sites;however,the following reach
their best development on these sites:white
spruce,balsam poplar,prickly rose,thinleaf
alder,twin-flower,and the feathermoss
Rhytidiadelphus triquetrus.Data on the more
important species are given in table 7.Stands
of thi s com m unity type are the most produc-
tive in interior Alaska;they contain up to 60
m 3 /ha of wood (Hutchison 1968,Viereck and
Little 1972).
In mature stands 120-200 years old,the tree
canopy is composed of mostly white spruce;
however,balsam poplar and paper birch occur
occasionally.Quaking aspen trees rarely grow
on the flood plain.In these stands,tree den-
sities average 500 stems/ha and di.ameters
average 26.1-33.5-cm d.b.h.with the larger
trees occurring in the older stands.
24
Beneath the trees,tall shrubs,low shrubs,
herbs,and mosses are common.Prickly rose
2-3 m tall is everywhere and probably a good
indicator of the productiveness of the sites!..!
Hi gh bushcranberry occurs but is less abundant
than on upland sites;it appears to decrease as
stand age increases.Hylocomium splendens
blankets the forest floor,although other
feathermosses,Pleurozium schreberi and
Rhytidiadelphus triquetrus,are intermixed,as
are patches of twi n-flower,woodland
horsetail,Geocaulon lividum,one-sided
wintergreen,and Iiverleaf wintergreen.
If these sites are left undisturbed-not burned
or undercut by the stream-and remain close
to the active river channe I,they will probably
maintain themselves.If the active river chan-
nel moves away from the area,however,per-
iodic flooding will become less frequent,
allowi ng the moss layer to accumulate and
thicken.When this happens,these permafrost-
free areas will stagnate;they will slowly be
invaded by black spruce,bog,and perm afrost
(Vi ere ck 1970).
The Picea glauca/Rosa acicularis/Equisetum
sylvaticum/Hylocomium splendens community
type has been variously named:Picea glauca/
Li nnaea borealis/Equisetum sylvaticum
(Viereck and Dyrness 1980;also see footnote
4),white spruce/rose/feathermoss (Neiland
and Viereck 1977),and Picea glauca/feather-
moss (Buckley and Libby 1957;Viereck 1970,
1975;Viereck and Dyrness 1980).On vegeta-
tion maps with scales of I :2,500,000 and
I :7,500,000,it is called bottom land spruce-
poplar forest type (joint Federal-State Land
Use Planning Com mission for Alaska 1973),
upland black spurce-white spruce forest type
(Kuchler 1966),and high,evergreen spruce
forest type (Spetzman 1963).
2!Personal communication with Francis
Herman,Institute of Northern Forestry,Fair-
banks,Alaska.
Table 7-lmportant plant species and litter components of the p'icea
glaucal J{osa aci cularisl E quisetum syl vaticuml Hylocom ium spleilde"i1S
com munity type (Type 5)of interior Alaska
Mature stands )j t"Species and
litter component
Cover ~Density ~D.b.h.41 Frequency ~
Perce nt Stemslha Cm Percent
Tree layer:
Picea glauca-
Mature trees 500 26;1-33.5 100
Seedlings 1,800 30
Tall shrub layer:
J{osa acicularis 16,000 82
Viburnum edule 2,600 40
Low shrub layer:
Linnaea borealis II 90
Herb layer:
Equisetum sylvaticum 3 85
\3eocaulon lividum 2 65
1v1 osses:
Hylocomium splendens 60 95
Pleurozium schreberi 5 30
Litter component:
Leaves and twigs 25 98
Dead wood and
fallen logs 19 100
)j Number of stands sampled:2;age:120-200 years;number of species
found:30;depth of organic layer:5 cm.
21 The percent of area shaded by the canopy of a given species or litter ""
component.It is based on the equation:Cover =1:(mean stand cover value
for a species)';'total number of stands sampled.The values given are rounded
to the nearest whole number.
~I The computed or counted number of stems occurring in a given area.It is
based on the equation:Density =1:(mean stand density value for a species)';'
total number of stands sampled.The values given above 200 are rounded to
the nearest 100;the values below 100 are rounded to the nearest whole
number.
41 D.b.h.is the diameter of a tree at.breast height.The mean stand d.b.h.
value for a species is given;when more than I stand was sampled,the range of
mean values is given.
51 The percent of plots in which a given species occurs.It is based onthe
-;quation:Frequency =1:(mean stand frequency value for a species)';'total
number of stands sampl ed.The values given are rounded to the nearest whole
number.
25
Figure 8.-A Populus balsam-
ifera/Oplopanax horridus com-
munity.Balsam poplar trees in
tni s stand (no.202)are 200 years
old.
26
6.Populus balsamifera/Oplopanax horridus
com munity type
Mature stands of this type are characterized
by a closed canopy of mostly balsam poplar
(Populus balsamiferCi)trees,extensive patches
of devilsclub (Oplopanax horridus),and a scat-
teri ng of shade tolerant herbs and ferns (fig.8).
Stands typifying this com munity type are
restricted to flood plains on the south side of
the Alaska Range.They are especially well
developed near Talkeetna in the Susitna and
Chulitna River valleys.
Soils on these sites are moist silt loams.
Flooding is periodic,at least on the lower
terraces.An organic layer 9-10 c m thick is
striated with silt layers and overlies coarse
sands and gravels of river origin.Snow usually
remains on the ground until late May;conse-
quently,soil temperatures are slow to warm
and the seasonal soil frost is slow to melt.
The flora found in stands of this community
type consists of about 24 species.No taxa are
unique to these sites;however,species such as
balsam poplar,devilsclub,clasping twisted-
stalk,and spinulose shield-fern thrive.Table 8
lists the more important species of this com-
munity type.
Data from this study for stands 200 years old
show an average of 140 trees/ha,a density low
for hardwood types.These trees are large,
however;balsam poplar average 35 m in height
and 65.6-cm d.b.h.,but trees up to 87-cm
d.b.h.were measured.White spruce,the sam e
age are smaller,only 32-cm d.b.h.and account
for one-third of the tree density.Understory
tree regeneration is lacking.
Table 8-lmportant plant species and litter components of the Populus
balsamifera/Oplopanax horridus com munity type (Type 6)of interior Alaska
Mature stands !!
Species and f"
litter component
Cover y Density ~D.b.h.if Frequency ~
Percent Stems/ha Cm Percent
Tree layer:
Picea glauca-
~ure trees 40 32.0 60
Populus balsamifera-
Mature trees 100 65.6 95
Tall shrub layer:
Opl opa nax horri dus 24,100 100
Herb layer:
Dryopteris dilatata 10 35
Equisetum arvense 5 95
Galium triflorum I 70
Pyrola asarifolia 5 30
Streptopus ampl exifolius 7 85
Litter component:
Leaves and twigs 94 100
Dead wood and .
fallen logs 3 70
JJ l'I1umber of stands sampled:I;age:200 years;number of species found:24;
depth of organic layer:9 em.
Y The percent of area shaded by the canopy of a given species or litter
component.It is based on the equation:Cover =L (mean stand cover value
for a species)';'total number of stands sampled.The values given are rounded
to the nearest whole number.
3/The computed or counted numb.er of stems occurring in a given area.It is
based on the equation:Density =L (mean stand density value for a species)7
total number of stands sampled.The values given above 200 are rounded to
the nearest 100;the values below 100 are rounded to the nearest whole
number.
4/D.b.h.is the diameter of a tree at breast height.The mean stand d.b.h.
value for a species is given;when more than I stand was sampled,the range of
mean values is given.
~The percent of plots in which a given species occurs.Itis based on the
equation:Frequency =L (mean stand frequency value for a species)';'total
num ber of stands sampled.The values given are rounded to the nearest whole
number.
27
Other vegetation occurs beneath the trees.
Devilsclub grows 1-2 m in height and domi-
nates the tall shrub layer,but patches of
thinleaf alder may extend even higher,and
high bushcranberry and prickly rose occur in
openings.The low shrub and herb layers are
discontinuous.Currants (Ribes spp.),which
sometime grow at the base of trees,are the
only low shrub species found;spinulose shield-
fern and clasping twisted-stalk are the most
extensive of the herb species.
Regeneration of this community type is little
understood.The balsam poplar will probably
die first.Many already have rotten centers
(Zasada and others 1981).Open white spruce
stands will remain for awhile;however,the
lack of understory regeneration of any tree
species in today1s stands does not aid in spec-
ulations for the future.North of the Alaska
Range,white spruce almost always succeeds
balsam poplar on flood plains.
The Populus balsamifera/Oplopanax horridus
com munity type is probably a south-central
Alaska version of the more general Populus
balsamiferal Alnus tenuifolia/Calam agrostis
canadensis type mentioned or discussed by
Buckley and Libby (1957),Hettinger and Janz
(1974),Lutz (1956),Neiland and Viereck
(1977),Viereck (1970,1975),and Viereck and
Dyrness (1980).On vegetation maps with
scales of I :2,500,000 and 1:7,500,000,this
com munity type is included in the following
types:bottomland spruce-poplar forest (Joint
Federal-State Land Use Planning Commission
for Alaska 1973),spruce-birch forest (Kuchler
1966),and high evergreen spruce forest
(Spetzman 1963).
28
Black Spruce Sites
Black spruce sites occur in areas of poor drain-
age,on north-facing slopes within 8 km of ma-
jor rivers,or on upland slopes of all exposures
more distant from rivers where white spruce is
absent.These sites are usually cool,and per-
mafrost is com mono Soils tend to be wet In-
ceptisols.The soil thaws to a depth of 20-90
cm every summer and,in general,the thicker
the moss layer,the .nore shallow the perma-
frost layer.
The vegetation is dominated by trees,but low
shrubs,mosses,and sometimes lichens are also
prominent.Black spruce,quaking aspen,paper
birch,Alaska larch,mountain-cranberry,bog
blueberry,the mosses Pleurozium schreberi
and Sphagnum spp.,and lichens Cladina spp.
and CI adonia spp.grow prominently on black
spruce sites.Occasionally white spruce is also
found.Together they produce the num erous
forest types that occur on black spruce sites.
Six of these forest types will be described
(tabl e 2,types 7-12).Of the six,four (types
7-10)tend to occur on mesic upland slopes,
one (type II)occurs on cool,mesic to moist
timberline sites,and one (type 12)occurs on
cool,moist valley bottoms and north-facing
sites.The types can intermix to a degree,
except for quaking aspen,which is limited to
warm,well-drained sites.These six mature
com munity types occur extensively throughout
the Alaska taiga but do not preclude the exist-
ence of other community types;for example,
the black spruce-American larch community
type which is not discussed in this paper.
7.Populus tremuloides-Picea mariana/Cornus
canadensis community type
f~ature stands of this type are characterized
by a closed canopy dominated by quaking aspen
(Populus tremuloides);black spruce (Picea
mariana)grows in the understory.Low shrubs,
e sp ec i ally mount ain-c r anberry and bunch ber ry
(Cornus canadensis),dominate on the forest
floor (fig.9).
Stands typifying this com munity type occur on
warm,well-drained black spruce sites;i.e.,on
slopes with southerly exposures or on slightly
raised,better drained areas on upland valley
floors.The organic layer is shallow,about
12 em,and overlies loess,bedrock,or river
alluvium.By late June the seasonal soil frost
melts to a depth of 50-60 em,and by August,
when the seasonal frost is gone,pockets of
permafrost may occur 65 em or more below
the s urfac e.
The flora found in communities of this type is
moderately rich;31-36 species were present in
each of the stands studied.No taxa are unique
to this community type.Species such as quak-
ing aspen,high bushcranberry,twin-flower,
bearoerry,and fireweed occur more abundant-
ly in communities of this type than in com-
munities of Picea mariana types.The flora in
com munities of this type does even better in
quaking aspen com munities growing on white
spruce sites.Table 9 gives information about
the species that occur most frequently.
The quaking aspen and black spruce trees in
this com munity type reach maturity when they
are 60-70 years old.Data from the study show
that tree densities average 1,500 stems/ha for
quaking aspen and 400 stems/ha for black
spruce.Diameters average 12.9-to 13.9-c m
d.b.h.for quaking aspen and 6.1-to 6.6-cm
d.b.h.for black spruce.Heights average lO-
IS m for quaking aspen and 4-12 m for black
spruce.
Figure 9.-A Populus tremu-
loid es-Pi ce-a mariana/Cornus
canadefiSfS(;om minity.Quaking
aspen trees in this stand (no.176)
are 50 years old.
Beneath the trees an intermittent tall shrub
layer is dominated by prickly rose 0.5-1 m
tall;however,clumps of American green alder
or l3ebb willow 2-4 m tall occur occasionally.
Low shrubs of mountain-cranberry,bog blue-
berry,and Labrador-tea along with feather-
mosses Hylocomium splendens and Pleurozium
sch reb eri,and the herbs bunchb erry,reed-
grass,and tall bluebell cover the forest floor.
Except in the clumps of moss,the extensive
litter layer and rotting quaking aspen logs are
visible on the forest floor.
29
w Table 9--lmportant plant species and litter components of the Populus tremuloides-Picea mariana/Cornus canadensis community type0
(Type 7)of interior Alaska
Mature stands II Overmature stands 2J
Species and
litter component
Cover 21 Density ~D.b.h.il Frequency'!J Cover y Density ~D.b.h.41 Frequency'!J
Percent Stems/ha Cm Percent Percent Stems/ha Cm Percent
Tree layer:
Picea mariana-
~ture trees 400 6.1-6.6 55 2,000 6.1-7.2 100
Saplings 40 90 60 95
Seedlings 9,400 60 14,300 75
Populus tremuloides-
Mature trees 1,500 12.9-13.9 95 25 23.9 10
Seedli ngs 2,000 30
Tall shrub layer:
Rosa acicularis 3,600 45 4,400 90
Low shrub layer:
Vaccinium uliginosum 3 55 12 85
Vaccinium vitis-idaea 15 80 5 95
Herb layer:
Calamagrostis spp.I 60 70
Cornus canadensis 6 95 38
Mosses:
Hylocomium splendens 7 45 54 85
Pleurozium schreberi 3 30 16 40
Lichen:
Peltigera canina JJ 5 4 60
Litter component:
Leaves and twi gs 85 100 28 100
Dead wood and
fallen logs 6 85 4 65
II Number of mature stands sampled:2;age:65-70 years;number of species found:31-36j depth oforganic layer:10-15 cmj depth
of active thaw layer:60 cmand over.
21 The percent of area shaded by the canopy of a given species or litter component.It is based on the equation:Cover =I (mean
stand cover value for a species)-:-total number of stands sampled.The values given are rounded to the nearest whole number.
II The computed or counted number of stems occurring in a given area.It is based onthe equation:Density =I (mean stand density
value for a species)t total number of stands sampled.The values givenabove200are rounded to the nearest I OOj the values below
100 are rounded to the nearest whole number..
41 D.b.h.is the diameter of a tree at breast height.The mean stand d.b.h.value for a species is givenj when more than I stand was
sampled,the range of mean values is given.
51 The percent of plots in which Ii given species occurs.It is based on the equation:Frequen~y=I·(mean stand frequency value foraspecies)';'totalnu.mber of stands sampled.The values given are rounded to the nearest whole number.
61 Number of overmaturestands sampled:2;age:65-120 yearsj number of species ·found:Hj depth of organic layer:13-17 cm;
depth of active thaw layer:45-90 cm and over.
JJ Less than 0.5 percent.
As stands in this com munity type age,the
quaking aspen trees die,fall,and decay,
whereas the amount of feathermoss increases
(see table 9).Soon little evidence is left of
the quaking aspen,and the community evolves
into one in the Picea mariana/feathermoss
com munity type.If a fire burns a stand in the
Populus tremuroides-Picea mariana/Cornus
canadensis com munity type,the stand be-
comes self-perpetuating.Quaking aspen and
low shrubs develop from root suckers and
black spruce from seeds,but the faster grow-
ing quaking aspen soon dominate again.
The Populus tremuloides-Picea marianal
Cornus canadensis com munity types have been
variously named.This name was first used by
Foote (see footnote 4)and later by Viereck and
Dyrness (1980).Neiland and Viereck (1977)
mention it as part of the aspen type.Most
authors consider i~part of the more general
closed spruce-hardwood forest type (Neiland
and Viereck 1977,Viereck and Dyrness 1980,
Viereck and Little 1972).On vegetation maps
with scales of 1:2,500,000 and 1:7,500,000,it
is a component of the followi ng types:upland
spruce-hardwood (Joint Federal-State Land
Use Planning Com mission for Alaska 1973),
spruce-birch (Kuchler 1966),and moderately
high,mixed evergreen and deciduous forest
(Spetzman 1963).
32
Figure 10.-A Picea mariana-
Betula papyrifera/Vaccinium
uliginosu m-L ed um groenlandi cu m
community.Black spruce and
paper birch trees in this stand
(no.11':J)are 80-100 years old.
8.Picea mariana-Betula papyriferal
Vaccinium uliginosum-Ledum groenlandicum
com munity type
Mature stands of this type are characterized
by a closed canopy of black spruce (Picea
m ari ana)and paper birch (Betula pa~ra);a
discontinuous understory of low shrubs,mostly
mountain-cranberry,Labrador-tea (Ledum
groenlandicum),and bog blueberry (Vaccinium
uliginosum);and a developing cover of feather-
mosses,mostly Pleurozium schreberi,on the
forest floor (fig.10).
Stands typifying this community type can be
found wherever mesic black spruce sites occur;
i.e.,on slopes of all aspects or on valley bot-'
toms where a modest amount of drainage oc-
curs.Permafrost mayor may not be present.
By July the ground thaws to a maximum depth
of 50 cm.These sites,therefore,may have
slightly cooler soil temperatures than sites
where the Populus tremuloides-Picea mariana!
Cornus canadensis com munity type occurs.
The flora found in com munities of this type is
fairly diverse;it contains 32-34 species.There
are nO'species unique to the com mun-ity type.
Instead,th"e flora is a mixture of taxa;some
represent species that do very well on warm,
well-drained sites and others do very well on
cooler,moderately drained sites.As the com-
munity reaches overmaturity,the number of
species drops to 23-25 per stand.Table 10
gives information on the species occurring
most frequently.
h'hen trees in stands of this community type
are 40-70 years old,black spruce average 900
trees/ha,6.9-8.7-cm d.b.h.and 2-17 m in
height.Saplings,and especially seedlings,are
numerous.Paper birch,on the other hand,are
larger (up to 18.3-cm d.b.h.),fewer in number
(only 300 trees/hal,about the same height,but
with little reproduction.By the time tl:lese
stands are 120 years old,they are overm ature.
Most of the paper birch die,leaving behind
black spruce trees 11.4-to 14.8-cm d.b.h.
Beneath these trees,there mayor may not be
a tall shrub layer but a low shrub layer is al-
ways there.When present,the tall shrub layer
consists of prickly rose and American green
alder.Both these species continue to do well
in overmature stands.The low shrub layer is
always represented bymountain-cra.I1berry,
bog blueberry,and Labrador,...tea,and insome
stands alsocby crowberry.
f
The forest floor is mainly covered by a devel-
oping blanket of feathermoss in which patches
of herbs and lichens may occur.The feather-
moss Pleurozium schrC'beri dominate"s in
70-year-old stands,where it covers'35 percent
of the area,whereas Pleurozium scl'treberi and
Hylocomium splendens share dominance in
I 20-year-old s~ands,where they cover 54 an~
20 percent of the fores't floor.Heros mayor.
may not be present;however,reedgrass occurs
in most stands.Soil lichens (Cladonia s·pp.)
occur but are not abundant.Fallen logs,most-
ly of paper birch,decay ra,pidly leaving holfow
bark cylindersto be overgrown by feathermoss.
In the absence of fire,com mlJnities of this
type slowly lose their paper birch element;
their black spruce component then becomes
pure and the com munity type changes to one
of the Picea mariana types.With the help of
fire,~tands in this com munity type maintain
themselves.S'ince fires reburn most areas on
a cycle of less than 100 years,stands of this
community type are both common and
extensive.
The Picea marlana-Betula papyrifera/Vac-
cinium lJliginosum-Ledum groenlandicLilTiCom-
m unity type is one of the closed spruce-birch
types (Vi ereck and Dyrness 1980)and is prob-:-
ably synonymous with their Pi cea mari ana-
Betula papyrifera/Ledu.m type.On vegetation
maps with scales of I :2,500,000 and
1:7,500,000,it is a component 9f the following
types:upl and spruce-hardwood forest,and
lowland spruce-hardwood forest (Joint
Federal-State Land Use Planning Commission
for Alaska 1973);spruce-birch forest,and
black spruce forest (Kuchler 1966);and mod-
erately high,mixed evergreen and deciduous.
forest,and low,mixed evergreen and decid-.
uous forest (Spetzman 1963).
33
II Number of mature stands sampled:3;age:40-70 years;number of species found:32-34;depth of organic layer:16-18 cm;depth
of active thaw layer:45 cm,July.
21 The percent of area shaded by the canopy of a given species or litter component.It is based on the equation:Cover =I (mean
stand cover value for a species)~total number of stands sampled.The values given are rounded to the nearest whole number.
~The computed or counted number of stems occurring in a given area.It is based ~n the equation:Density =.1 (mean stand density
value for a species)~total number of stands sampled.The values given above 200 are rounded to the nearest 100;the values below
100 are rounded to the nearest whole number..
41 D.b.h.is the diameter of a tree at breast height.The meanstand d.b.h.value for a species is given;when more than I stand was
sampled,the range of mean values is given.
~The percent of plots in which a given species occurs.It is based on the equation:Frequency =I (mean stand frequency value for
a species)+total number of stands sampled.The values given are rounded to the nearest whole number.
~Number of overmature stands sampled:2;age:100-120 years;number of species found:23-25;depth of organic lay~r:13-14 cm;
depth of active thaw layer:50 cm,July.
Figure I I.-A Picea mariana/
Vaccinium uligTll()SUm-Ledum
groenl andi cu m/P Ie urozi urn
sChreberi community.Black
spruce trees in this stand
(no.175)are 50 years old.
36
9.Picea mariana/Vaccinium uliginosum-
L ediJ'"ffigro en I and ic u m/Pie urozium s ch reb eri
com munity type
Mature stands of this type are characterized
by dense black spruce (Picea mariana)with an
understory of low shrubs and moss.Labrador-
tea (Ledum groenlandicum),mountain-
cranberry,and bog blueberry (Vaccinium
uliginosum)dominate the low shrub layer;the
featherrnosses Pleurozium schreberi and
Hylocomium splendens dominate the moss
I ayer (fig.I I).
Stands typifying this com munity type may be
found on all mesic black spruce sites;i.e.,on
both slopes and valley bottoms whenever the
soil is not too wet.Usually a 5-to 25-cm-
thick surface horizon of organic material
overlies a layer of loess,stony residual soil,or
valley alluvium.Ice-rich permafrost is gen-
erally present.The surface soil is kept cool
and moist by the permafrost below and the
moss insulation above.Surface soil tempera-
tures increase throughout the sum mer;the soil
thaws to a depth of 30 cm by late June and to
50 cm by August.
The flora found in communities of this type is
composed of 28-35 species.No taxa are
unique to the com munity type,and some spe-
cies are absent.Hardwoods and lichens,dis-
tinctive of other Picea mariana types,are
essentially under-represented in this commu-
nity type.Table II gives information on the
species occurring most frequently.
Vol hen the trees are 40-60 years old,the vege-
tation in communities of this type is estab-
lished.Data from this study show that trees--
mostly black spruce-average 1,200 to 3,700
stems/ha,4.3-to 5.6-cm d.b.h.,and 3-9 m
tall.Older black spruce trees occur alone or
in stringers.Some have fire scars showing
they date to a preburn era.Smaller saplings,
seedlings,and layerings are also numerous.
Beneath the trees,shrubs-mainly Labrador-
tea,bog blueberry,mountain-cranberry,and
prickly rose-form a discontinuous layer that
grows to I m in height.Mosses cover the
ground to a depth of 20 em in most areas but
up to 100 em where mounds of Sphagnum spp.
occur.American green alder and resin birch
(Betula glandulosa)are sometimes common.
PI eurozium schreberi covers about one-half of
the forest floor,but other mosses-Hylocomi-
um splendens,Polytrichum spp.,and Sphagnum
spp.-are important.Lichens,primarily Cla-
dina rangiferina,and herbs-mostly reedgrass,
cloudberry,and woodland horsetail-are lightly
scattered throughout the moss layer.
Stands dominated by tr~es older than 100 years
in age occur,but usually as stringers or islands
within younger stands.Most of these areas
also have a second age class of trees that is
younger than 100 years suggesting that they
have been lightly disturbed or otherwise in-
fluenced by the disturbances occurring around
them.In any event,these older stands are
similar to the younger stands but show the in-
fluence of time;the trees are larger in diam-
eter (17-cm d.b.h.),less dense (averaging 2,000
stems/hal,and slightly taller (II m).Low
shrubs and Sphagnum spp.moss cover more
area,whereas tail shrubs cover less area.In
addition,the feathermoss layer,which is con-
tinuous in both young and old stands,is
thicker.Black spruce seedlings occur,but re-
production is pri mari Iy by layeri ng.It appears
that in the absence of fire,stands of this com-
munity type will maintain themselves;how-
ever,most stands burn before they are 100
years old.When fire occurs,root systems and
seeds in cones are generally not consumed by
fire,so stands are quick to recover.
The Picea mariana/Vaccinium uliginosum-
Ledum groenlandicum/Pleurozium schreberi
com munity type has been variously named:
Picea mariana/Vaccinium/feathermoss (Lutz
1956;Viereck 1975,1979;Viereck and Dyrness
1980);Picea mariana/Ledum groenlandicum/
EquiseiliiliSYlvaticum (see footnote 4);and·
open,low-growing spruce (Vi ereck and Little
1972).On vegetation maps with scales of
1:2,500,000 and I :7,500,000,it is a component
of the following types:upland and lowland
spruce-hardwood forest (Joint Federal-State
Land Use Planning CommissiolJ for Alaska
1973),black spruce forest (Kuchler 1966),and
both the moderately high and the low,mixed
evergreen and deciduous forests (Spetzman
1963).
37
lJ,)Table II-Important plant species and litter components of the Picea mariana/Vaccinium uliginosum-Ledum00
groenlandicum/Pleurozium schreberi community type (Type 9}of interior Alaska
Mature stands JJ Overmature stands ~
Species and
litter component
Cover 2/Density'}j D.b.h.if Frequency ~/Cover y Density ~/D.b.h.if Frequency ~/
Percent Stems/ha Cm Percent Percent Stems/ha Cm Percent
Tree layer:
Picea mariana-
Mature trees 2,700 4.3-5.6 100 2,000 17.0 100
Sapl i ngs 1,800 100 600 100
Seedlings 15,300 90 9,600 \85
Low shrub layer:
Empetrum nigrum 6 65
Ledum groenlandi cum 8 80 17 95
Vaccinium uliginosum II 90 7 95
Vaccinium vitis-idaea 15 100 20 100
Herb layer:
Calamagrostis spp.2 80 I 40
Equisetum sylvaticum I 25 9 90
Rubus chamaemorus 2 35 7 90
Mosses:
Hylocomium splendens 5 50 42 90
P leurozium schreberi 47 95 24 85
Polytrichum spp.15 60 6 75
Sphagnum spp.12 31 21 75
Lichens:
Cladina arbuscula 1 10 2 60
Cladina rangiferina 4 40 3 55
Litter component:
Leaves and twigs 12 100 9 100
Dead wood and
fallen logs 5 90 80
1/Number of mature stands sampled:5;age:40-70 years;number of species found:28-35;depth of organic layer:18-21 cm;depth
of active thaw layer:35-50 cm.
2/The percent of area shaded by the canopy of a given species or litter component.It is based on the equation:Cover =I (mean
stand cover value for a species)':;'total number of stands sampled.The values given are rounded to the nearest whole number.
3/The computed or counted number of stems occurring in a given area.It is based on the equation:Density =I (mean stand density
value fora species)';'total number of stands sampled.The values given above 200 are rounded to the nearest 100;the values below
100 are rounded to the nearest whole number.
4/O.b.h.is the diameter of a tree at breast height.The mean stand d.b.h.value for a species is given;when 11l0re than I stand was
sampled,the range of mean valJes is given.
5/The percent of plots in which a given species occurs.It is based on the equation:Frequency =I (mean stand frequency value foraspecies);'total number of stands sampled.The values given are rounded to the nearest whole number.
6/Number of overmature stands sampled:I;age:80-170 years;number of species found:29;depth of organic layer:18 cm;depth
of active thaw layer:50 cm.
Figure 12.-A Picea mariana/
feathermoss-lichen community.
This stand (no.490)is 60 years
old.
40
10.Picea mariana/feathermoss-lichen com----munity type
In mature stands of this type,Iichen-
dominated openings separate the black spruce
(Picea mariana)trees,which frequently occur
in small,dense clumps.Low shrubs,mosses
(primarily the feathermoss Pleurozium schreb-
eri),and lichens grow beneath the trees and
extend into the openings (fig.12).
Stands typifying this community type occur
wherever black spruce sites are found;i.e.,on
slopes of all aspects and gradients and on val-
ley bottoms.A surface horizon of organic
material overlies loess,weathered bedrock,or
valley alluvium.The depth of the organic
layer varies from 5 cm in the lichen-dominated
openings to 20 c m in the moss and tree-
dominated areas.Permafrost mayor may not
be present.Snow disappears from the tree
bases and sunny openings first and is usually
gone by late May.Soils continue to warm
throughout the summer,and by August,sea-
sonal soil frost is gone.During dry periods,
the lichens become dessicated and brittle.
The flora of this com munity type include 29-38
species,making it moderately diverse to rich.
No taxa is unique to this type,but it is the li-
chen element that makes this community type
distinctive.Table 12 gives information about
the species which occur most frequently.
When the black spruce trees are 40-70 years
old,they average 2,900 stems/ha,4.3-to
6.2-cm d.b.h.,and 2-9 m tall.Black spruce
saplings average 2,000 stems/ha and seedlings
another 12,000 stems/ha.Despite these den-
sities,which are many times those of the
closed-canopied stands already discussed,
stands in this com munity type have an inter-
mittent overstory canopy.Clumping of trees
withi n the stand and the narrow,triangular
form of black spruce together create the open
canopy.
Beneath the trees is the same vegetation as
occurs in the Picea mariana/Vaccinium uligi-
nosum-Ledum groenlandicum/PI euroziu~
schreberi type plus numerous lichens.
Nephroma arcticum forms extensive patches,
especially in forest openings.Other lichens,
pri mari Iy CI adina rangiferi na,~.arbuscula,
Peltigera aphthosa,and Cetraria islandica,
occur both in openings and beneath the trees.
Together,the lichens cover 20 percent of the
forest floor.Moss covers most of the forest
floor;however,Sphagnum spp.,if present,
occur in very small patches.
Black spruce regeneration,both seed Ii ngs and
layerings,occurs in sufficient quantities
(12,000 stems/hal to retain the forest canopy.
The lichen patches show little evidence of
being invaded by spruce.So in the absence of
fire,stands of this com munity type will suc-
ceed themselves as long as the lichens survive.
It is uncertain how long that is.The oldest
stand located was 70 years old.The lichens
dry out almost as fast as the humidity of the
air drops,making them highly flammable.
Perhaps fire prevents stands of this commu-
nity type from aging.Or perhaps the moss
mat thickens as the stand ages,as it does in
the Picea mariana/Vaccinium uliginosum-
Ledum groenlandicum/Pleurozium schreberi
community type,and the mosses simply over-
top and kill the lichens.More study is needed.
The Picea mariana/feathermoss-Iichen com-
munity type has been called Picea mariana/
lichen (see footnote 4)and open Picea
mari ana/feathermoss-CI adonia (Vi ere ck 1975,
1979;Vi ereck and Dyrness 1980).The wood-
land Picea mariana/Cladonia type (Viereck
1975,Viereck and Dyrness 1980)is closely
re lated.It is certainly a component of the
more general types:black spruce (Lutz 1956),
muskeg (Buckley and Libby 1957),and open,
low-growing spruce (Viereck and Little 1972).
On vegetaton maps with scales of 1:2,500,000
and 1:7,500,000,it is included in the following
types:upland and lowland spr"uce-hardwood
forest (Joint Federal-State Land Use Planning
Commission for Alaska 1973),black spruce and
spruce-birch forest (Kuchler 1966),and both
the moderately high and the low,mixed ever-
green and deciduous forests (Spetzman 1963).
..
41
42
Table 12-lmportant plant species and litter components of the Picea
mariana/hathermoss-lichen community type (Type 10)of interior Alaska
Mature stands Y
Species and
litter component
Cover y Density ~D.b.h.~Frequency ~
Percent Stemslha Cm Percent
Tree layer:
Picea mariana-
Mature trees 2,900 4.3-6.2 100
Sapli ngs 2,000 100
Seedlings 12,000 90
Low shrub layer:
Ledum groenlandicum 6 80
Vaccinium uliginosum 8 70
Vaccinium vitis-idaea II 100
Herb layer:
Calamagrostis sp p.40
Geocaulon Iividum 45
Mosses:
Dicranum spp.3 60
Hylocomium splendens II 50
Pleurozium schreberi 46 95
Polytrichum spp.5 70
Lichens:
Cetraria islandica I 50
Clad ina arbuscula 3 38
Cladina rangiferina 7 60
Nephroma articum 4 30
Peltigera aphthosa 3 60
Litter component:
Leaves and twigs 13 95
Dead wood and
fallen logs 8 85
II Number of stands sampled:6;age:40-70 years;number of species found:
29-38;depth of organic layer:12-18 cm;depth of active thaw layer:54-99
cm and over.
y The percent of area shaded by the canopy of a given species or litter
component.It is based on the equation:Cover =I (mean stand cover value
for a species)';'total number of stands sampled.The values given are rounded
to the nearest whole number.
31 The computed or counted number of stems occurring in a given area.It is
based on the equation:Density =I (mean stand density value for a species).;.
total number of stands sampled.The values given above 200 are rounded to
the nearest 100;the values below 100 are rounded to the nearest whole
number.
~D.b.h.is the diameter of a tree at breast height.The mean stand d.b.h.
value for a species is given;when more than I stand was sampled,the range of
mean values is given.
~The percent of plots in which a given species occurs.It is based on the
equation:Frequency =I (mean stand frequency value for a species).;.total
number of stands sampled.The values given are rounded to the nearest whole
number.
II.Pi cea mariana-Picea glauca/Betula
glandulosa/lichen community type
Stands of this type are usually woodlands.
Interspersed with the trees are numerous tall
shrubs;low shrubs,mosses,and lichens cover
the ground surface (fig.13).
Stands typifying this com munity type occur on
east-or west-facing slopes above 700 m or
near timberline.These slopes are cool and dry
to mesic.A thin surface layer of organic
material 0-3 cm thick overlies stony soils and
shallow bedrock.
The flora of these communities is a diverse
mixture of taxa found on white spruc e,black
spruce,or alpine sites.No species are unique;
however,resin birch (Betula glandulosa),the
hybrid birch (Betula glandulosa X B.papyrif-
era),and lichens do particularly wei I.Table 13
gives information on the most com mon species
found in this com munity type.
The timberline forest stands sampled were of
mixed age.Trees 55 years old were mixed in
approximately equal numbers with trees 110
and 195 years old.The canopy in this commu-
nity is open,averaging 400 trees/ha,and com-
posed of a mixture of white spruce (Picea
glauca)and black spruce (Picea mar~
Sometimes there is more white than black
spruce,at other times the reverse is true.
Younger trees of both species exist,but they
seem to be primarily black spruce.These
stand 3-7 m tall and range from 7.6-to
10.9-cm d.b.h.;however,trees 32-cm d.b.h.
are present occasionally.
Figure 13.-A Picea mariana-
Picea glauca/tietiJi'a glandulosa/
lichen com munity.Spruce trees
in this stand (no.244)are 130
years old.
Beneath the trees,resin birch,which grows to
a height of 1.2 m,forms an alrrtost continuous
tall shrub layer.Clumps of hybrid birch and
grayleaf wi Ilow occasionally stand above the
resin birch with prickly rose sparsely scattered
below.
43
Mature stands II
Table 13--lmportant plant species and litter components of the Picea
mariana-Picea glauca/Betula glandulosa/lichen community type (Type II)of
interior Alaska
44
Species and
litter component
Tree layer:
P iceagl auca-
Mature trees
Saplings
Seedlings
Picea m ariana-
Mature trees
Saplings
Seedlings
Tall shrub layer:
Betula glandulosa
Rosa acicul aris
Low shrub layer:
E mpetrum nigrum
Ledum groenlandicum
Vaccinium uliginosum
Vaccinium vitis-idaea
Herb layer:
Calamagrostis spp.
Mosses:
Aulacom nium palustre
Dicranum spp.
Hylocomium splendens
Pleurozium schreberi
Polytrichum spp.
See footnotes at end of table.
Cover 21
Percent
4
5
23
24
2
3
6
12
23
5
Density ~
Stem s/ha
140
50
400
260
75
1,400
19,800
1,500
D.b.h.~Frequency ~
Cm Percent
8.5-10.9 60
75
10
7.6-9.5 90
100
30
70
30
40
60
100
100
60
40
50
55
70
90
Table 13-lmportant plant species and litter components of th~Picea_
mariana-Picea glauca/Betula glandulosa/lichen commu'nity}ype ("{ype II)of
interior Alaska (continued)
Mature sf~nds.!J
Species and
litter component
Cover 2/Density3/D.b.h.4/Frequency ~J
Per_cent Stems/ha Cm Percent
.~.~;.
Lichens:
Cetraria cucullata
Cetraria islandica
C etrari ari chardsoni i
Cladina arbuscula
Cladina rangiferina
Cladonia gracilis
P eltigera apilthosa
Peltigera cani na
Litter component:
Leaves and twigs
Dead wood and
fallen logs
4
2
2
8
4
I
5
5
26
15
85
75
40
80
85
40
70
65
100
100
.!J Number of stands sampled:2;age:55-100;195 years;number of species
found:38-53;depth of organic layer:1-2 cm;depth of active thaw layer:no
data;ground too rocky to probe.
2/The percent of area shaded by the canopy of a given species or litter--~
component.It is based on the equation:Cover =L (mean stand cover value
for a species)~total number of stands sampled.The values given are rounded
to the nearest whole number.
3/The computed or counted number of stems occurring in a given area.It is
based on the equation:Density =L (mean stand density value for a species).;-
total number of stands sampled.The values given above 200 are rounded to
tile ne.arest 100;the values below 100 are rounded 'to the nearest whole'
number.
4/D.b.h.is the diameter of a tree at breast height.The mean stand d.b.h.
value for a species is given;when more than I stand was sampled,the range of
mean values is given.
5/The percent of plots in which a given species occurs.It is based on the
equation:Frequency =L (mean stand frequency value for a species)-r,total
number of stands sampled.The values given are rounded to the nearest whole
number.
45
III
Be neath the shrubs are a well-developed low
shrub layer and an extensive lichen layer.
Herbs and mosses occur but are scattered.
Mountain-cranberry and bog blueberry,the
two species found on all black spruce sites,
continue to dominate the low shrubs although
Labrador-tea,crowberry,and beauverd spire a
occur.No single lichen species dominates;
however the following lichens were present in
all the stands studied:Cetraria cucullata,C.
islandica,C.richardsonii,Cladina arbuscula-'C.rangiferina,Cladonia gracilis,Peltigera
aphthosa,and P.canina.The herb and moss
species that com monly intermix with the more
dominant vegetation on the forest floor in-
clude reedgrass,the feathermosses Pleurozium
schreberi and Hylocomium splendens,Poly-
trichum spp.,Dicranum spp.,and Aulacomnium
palustre.
Stands of this community type appear able to
maintain themselves.The 50-to 100-year
break in tree age classes suggests that fires
occur every 50-70 years.The presence of
older trees and young white spruce suggests
that the burns are not severe or that they
leave numerous unburned islands in which the
white spruce,mosses,and lichens survive.
The Picea mariana-Picea glauca/Betula
glandulosa/lichen tYl'e is synonymous with the
woodland Picea glauca-Picea mariana/lichen
type (Viereck and Dyrness 1980;also see foot-
note 4)and related to the open Picea mariana-
Picea glauca/Betula glandulosa type (Viereck
1979,Vi ere ck and Dyrness 1980).On vegeta-
tion maps with scales of I :2,500,000 and
I :7,500,000,it is a component of the following
types:upl and spruc e-hardwood forest (J oint
Federal-State Land Use Planning Commission
for Alaska 1973),-spruce-birch'forest (Kuchler
1966),and moderately high,mixed evergreen
and deciduous forest (Spetzman 1963).
46
Figure 14.-A Picea mariana/
Sphagnum spp:::cTadina spp.
community.Trees in this stand
(no.208)are 65 years old.
12.Picea mariana/Sphagnum spp.-Cladina spp.
com munity type
Stands of this type are characterized by wood-
lands or open forests in which black spruce
(Picea mariana)dominates the tree canopy;
and mosses,especially Sphagnum spp.,low
shrubs,and lichens dominate the forest floor
(fig.14).Thaw ponds mayor may not be
present.
Stands typifying this com munity type occur on
valley bottoms or on north-facing slopes;where
ice-rich permafrost is present and a perched
water table is com mono A surface horizon of
organic materi al 0.3 m to over I m thick,
overlies loess or valley alluvium.Soils on
these sites are cool and moist.Surface soils
melt to a depth of 30 em by late June and
60 em by August.Excess~ater from melting
frozen soil and precipitation collects in low
depressions and thaw ponds or is absorbed by
the mounds of Sphagnum spp.which,have very
high water-holding capacities.The permafrost
layer prevents the downw'ard movement of
water.
The flora found on these sites can tolerate the
cool,moist conditions.Species such as tussock
cottongrass,leatherleaf,some sedges,and bog
cranberry need the moisture,whereas Sphag-
num spp.,narrow-I eaf Labrador-tea,dwarf
arctic birch,diamondleaf willow,crowberry,
and cloudberry can tolerate both the coolness
and the moisture.Because Sphagnum spp.
have the capacity to absorb and retain water,
they help create sites where these species
thrive.Table 14 gives information on the spe-
cies with mean frequencies of 50 percent or
more.
In 60-to I 30-year-old stands,the black spruce
trees are 2.5-to 10.0-cm d.b.h.,2-7 m tall,
and average 100-600 stems/ha.Older trees
have the larger diameters.Saplings average
300 stems/ha and seedlings 8,900 stems/ha.
Sites With.the most moisture have ~hefewest
trees.Alaska larch ma.y occur but is not com-
mon.The forest floor is covered with low
shrubs and mosses,although herbs and lichens
are com mono Mountain-cranberry,narrow-
leaf Labrador-tea,bog blueberry,dwarf arctic
birch,and crowberryinterm ix in varying
amounts to form the extensive low shrubJayer.
Sphagnum spp.,with an average cover of 50
percent,'is the most important moss,but both
Pleurozium schreberi andPolytrichum spp.can
'be com mono Herbs such as cloudberry,sedges,
and tussock cottongrass are com mon to all or
most stands of this corn munity type.Lichens,
especially Cladina rangiferina and C.arbus-
,cula,grow intermixed with the moss.Litter
and rotting logs are quickly incorporated into
the moss layer.
Thaw ponds may form where the moss insu-
lating layer is broken by uprooting of trees or
soil heavings.Ponds continue to grow in size
until the unprotected permafrost melts or the
water table drops.In time the ponds fill in or
become covered with enough floating vegeta-
tion to onct:again support shrubs and trees.
Stands of this com munity type burn at least
superficially.When this happens,the vegeta-
tion reestablishes itself from root suckers,un-
burned seeds in situ or fro'm numerous patches
left untouched by fire.
The Picea mariana/Sphagnum spp.-Cladina
spp.com munity type has been variously
named:open Picea mariana/Sphagnum-
Cladonia (Neiland and Viereck 1977,Viereck
and Dyrness 1980),and black spruce/narrow-
leaf Labrador-tea/Sphagnum spp.(see foot-
note 4).It is also a component of the more
general types:black spruce (Lutz 1956),
muskeg (Buckley and Libby 19~7),and open,
low-growing spruce (Vi ereck and Little 1972).
,Onvegetatiop maps with scales of 1:2,500,000
and 1:7,500,000,itis a component of the fol-
lowing types:lowland spruce-hardwood forest
(Joint Federal-State Land Use Planning Com-
mission for AlaskaI973),black spruce forest
and muskeg types (Kuchler 1966),and low,
mixed evergreen and deciduous forest (Spetz-
man 1963).",
47
Table 14-lmportant plant species and litter components of the Picea
mariana/Sphagnum spp.-Cladina spp.com munity type (Type 12)of interior
Alaska
Mature stands 1J
Species and
litter component
Cover ~Density H D.b.h.~Frequency J.!
Percent 5tems/ha Cm Percent
Tree layer:
Picea mariana-
fA a ture tre es 300 5.8-8.1 100
Sapli ngs 300 100
Seedlings 8,900 85
Low shrub layer:
Betula nana 5 80
£mpetrum nigrum 7 65
Ledum decumbens II 65
Vaccinium oxycoccus 2 55
Vaccinium uliginosum 0 95
Vaccinium vitis-idaea 9 100
t1erb layer:
Carex spp.12 80
Rubus chamaemorus 7 100
Mosses:
Pleurozium schreberi 22 70
Polytrichum spp.9 75
Sphagnum spp.SO 85
Lichens:
Cladina arbuscula 4 60
Cladina rangiferina 4 60
Litter component:
Leaves and twigs 13 100
Dead wood and
fallen logs 3 45
1/Number of stands sampled:3:age:60-130 years:number of species found:
28-36:depth of organic layer:20-30 cm and over:depth of active thaw layer:
30-120 cm and over.
2/The percent of area shaded by the canopy of a given species or litter
compOnent.It is based on the equation:Cover =I (mean stand cover value
for a species)-:-total number of stands sampled.The values given are rounded
to the nearest whole num·ber.
3/The computed or counted number of stems occurring in a given area.It is
based on the equation:Density =I (mean stand density value for a species)';'
total number of stands sampled.The values given above 200 are rounded to
the nearest 100;the values below 100 are rounded to the nearest whole
number.
4/D.b.h.is the diameter of a tree at breast height.The mean stand d.b.h.
value for a species is given:when more than I stand was sampled,the range of
mean values is given.
5/The percent of plots in which a given species occurs.It is based on the
equation:Frequency =I (mean stand frequency value for a species)-:-total
numoer of stands sampled.The values given are rounded to the nearest whole
number.
Forest Succession
To understand succession,one must first un-
derstand fire.Fires vary in size,type,rate
and dire ction of spread,intensity,and dura-
tion.Surface fires consume fuel on the forest
floor including bases of trees.Crown fires
sweep from treetop to treetop and may never
reach the ground.Fire can travel up or down
tree bole's causing a ground fire to become a
crown fire and vice versa.Fire can be sta-
tionary or move rapidly ahead,change direc-
tion or even reverse itself without warning,
and can jump to new areas ahead of or behind
the main center of flame activity.Because of
this,fire burns across the landscape in an ir-
regular and uneven manner.The burned sur-
face mayor may not be essentially the same
as the pre burned surface.The depth to which
organic material is consumed is hi ghly vari-
able.Sometimes organic matter is left,and
sometimes mineral soil is exposed.
Fire likewise leaves the vegetation it touches
in a variety of conditions:unburned,scorched,
charred,partially killed,or completely con-
sumed.In general,a severe and long-lasting
fire burns more organic matter (including live
vegetation),produces more ash,and exposes
more mineral soil.Ground surfaces and most
snags are left black with carbon,and plant
growth is term inated,at least temporari lye
Succession after fire in forest ecosystems in
interior Alaska is complex and related to site,
fire,climate,the type and age of vegetation
present before fire,and the plant species
available for sprouting or invasion after fire.
Bl ack spruce stands return to black spruce,
and white spruce stands eventually return to
whi te spruce.Each site,however,is unique
both in its rate of change and composition of
sp ecies.
This study identified six developmental stages
in the revegetation process:(I)newly burned,
(2)moss~herb,(3)tall shrub-sapling,(4)dense
tree,(5)hardwood or mixed hardwood-spruce,
and (6)spruce.
f
I.-The newly burned stage lasts from the
time of fire until the area is again dominated
by living plants.It can be as short as I month
in areas where burns are light or as long as 3-4
years where burns are severe and few plants
are available for reinvasion.
Soon after fire,however,things begin to
happen.With the next rain charcoal and ash
start to mix with the organic and mineral soil
layers.The reappearance of plants may be
rapid or slow;it is limited by:(a)the presence
of underground plant parts with the capacity
to sprout,(b)the availability of spores and
seed,(c)the presence of suitable seedbed,and
(d)favorable climatic and weather conditions.
Usually within 2-3 weeks after fire,green
plants become visible.The first to appear are
shoots at the bases of snags and above buried
roots or underground stems which were not
killed by the fire.These shoots are soon foI-
lowed by protonema of mosses,young thalli of
liverworts,and seedlings of vascular plants,
especially on areas of exposed mineral s?il.As
the vegetation becomes increasingly promi-
nent,the newly burned stage phoases into the
moss-herb stage.
2.-The moss-herb stage is characterized by
moss,herbs,seedli ngs of trees and shrubs,and
newly fallen litter.It can begin as early as 3
months after fire or as late as 3 years after
fire.It will last 3-10 years,or until the shrubs
and trees overtop the herb layeJ.
The first 3-6 years is a time of plant estab-
lishment,when seedbeds are most receptive to
seed germ ination and seedling growth.There-
after,accumulating litter and developing plant
cover make seedbeds less available to new
seed,and competition between plants usually
favors larger plants over you'nger,smaller
seedlings.The established mix of mosses,
liverworts,herbs,shrubs,and trees continues
to grow in height,canopy cover,and mass,and
the species that reproduce vegetatively do so.
Rapidly the herb canopy closes.Eventually
the taller shrubs and trees will overtop the
lower growing plants and the next stage,the
tall shrub-sapling stage,will arrive.
49
This successional trend can be altered in sev-
eral ways.If seedlings of trees and shrub
species are not established,the area will
stagnate in the moss-herb stage.Or if the
young trees and shrubs are heavily impacted
by animals,species can be exterminated,
leaving the moss-herb stage intact.Animals
and birds can selectively exhaust the seeds,
shoots,or stems of preferred species.Grassy
areas within a forest may represent areas
where tree and shrub seedlings never became
established or failed to survive.
3.--lf succession continues,the tall shrub-
sapling stage develops.This stage is charac-
terized by 1.4-to 7-m tall shrubs and/or
saplings.It develops sometime within 3-30
years after fire and lasts about 20 years.Fast
growing sucker shoots reach breast height
(1.4 m)in 3 years,fast growing seedlings in
5-10 years,and slow growing seedlings in
10-30 years.
As this stage develops,the shrub-sapling can-
opy gradually closes and leaf litter accumu-
lates on the forest floor;however,before the
canopy closes,the herb layer,developed in the
previous stage,continues to expand.After the
canopy closes,the herb layer,in general,
wanes.
In time,the saplings grow into trees and over-
top the shrubs.\then this happens,the tall
shrub-sapling stage grades into the dense tree
stage.
Many stands of the tall shrub-sapling stage are
utilized extensively by moose and snowshoe
hares for browse,especially in winter,and for
shelter.They prefer young,small-diameter
stems of quaking aspen,certain willow species,
Alaska larch,and paper birch but will browse
other species.Snowshoe hares can reach twigs
60 cm above the snow line;moose can reach
hi gher.
50
Moderate browsing at this stage appears to
stimulate shrub productivity (Wolff 1978).
Sustained intensive browsing,as on the Kenai
Peninsula,perpetuates the shrub stage.On
the 20-year-old Kenai Lake burn,the tall
shrubs and trees are clipped by moose each
winter at a height of 50-100 cm above the
ground,and each sum m er the plants send up
new shoots;in the adjacent moose exclosure,
plants of the same postfire age are more than
6 m tall.The more com mon pattern is for
browsing to continue only until the shrubs have
grown too tailor the stems too large in diam-
eter for the animals,to reach directly or by
bending them.This usually happens within
15-20 years after fire.This temporary impact
does not stop succession.
4.-The dense tree stage is reached when trees
are at least 2.5-cm d.b.h.,4-8 m tall,and
overtop the shrubs.This stage is first attained
15-40 years after fire,depending on growth
patterns of tree species.Quaki ng aspen re-
quires 15-30 years,paper birch 20-30 years
(Gregory and Haack 1965),and white spruce
15-30 years (Farr 1967).Black spruce grows
even more slowly.As it continues to develop,
the faster growing trees become dominant,the
slower growing trees the subdominates,and
the unsuccessful die.Stands of this stage are
usually dense.
The dense tree stage is transitional,between
the early stages dominated by herbs and shrubs
and the later stages dominated by trees.
Species characteristic of earlier stages-
Ceratodon purpureus,Marchantia polymorpha,
fireweed,and most willows-have disappeared,
some entirely,whiJe species characteristic of
later successional stages-Pleurozium schreb-
eri,and alder-are increasing,sometimes
rapidly.Other important changes are also
occurring.Cladonia spp.and Cladina spp.
have appeared in important amounts.The
understory vegetation is restricted for the
most part to shade-tolerant species that can
grow beneath the now-closed tree canopy.
And fuels,both dead and living,occur in suf-
ficient quantities to make stands in this devel-
opmental stage very flam mabIe.In fact,it is
not uncom monfor stands in the dense tree
stage to be destroyed or at least impacted by
fire.When fire occurs,forward succession is
terminated and the successional process starts
over.If fire does not occur,this stage contin-
ues until the hardwood trees are mature and
the next,or hardwood stage,has arrived.If no
hardwoods are present,however,the dense
tree stage passes directly into the spruce
stage.
5.-The hardwood stage is characterized by
well-developed hardwoods such as quaking
aspen,paper birch,and balsam poplar in either
pure or mixed stands.Spruce may occur as
understory,subdom inant,codom inant,or oc-
casionally as the dominant tree.Stands of this
stage are composed of 50-to I 50-year-old
trees.The stage continues until the hardwood
tre es die.Quaking aspen are the shortest
lived,many dying at 70-80 years of age,paper
birch live 120-150 years,and balsam popla'r
120-200 years.
Beneath the trees,various combinations of
shrubs,herbs,and mosses exist.Species which
tend to increase in cover and/or density as the
stand ages do well,whereas opportunistic spe-
cies are locally abundant to rare.As the stage
advances,spruce and moss become more im-
portant.Lichens are less com mon than in the
pre vi ous stage.
The larger the hardwood component,the more
fire resistant the stands are;however,all will
burn.In fact,many stands burn before the
trees are 100 years old.Succession then starts
anew.If stands do not burn,they continue to
age and eventually develop into the next stage,
the spruce stage.
6.-The spruce stage is characteri zed by
closed-to open-canopied stands of spruce in
which occasional hardwoods may remain.Most
of the stands are 100-200 years old.The un-'
derstory is a mixture of tall shrubs,low shrubs,
herbs,mosses,and lichens.Feathermosses
reach their best development in this stage.
This is the oldest stage and occurs,jn int~rior
Alaska wheredisturl;)ance,such as fire,has...
been minimal tonon~",is'tent.,Since fire bUqlS
extensive areas each year,few areashav'ees-
caped its impact during the last 300 years.
Thus,stands representing the old,pure spruce
stands are less num ~ro\.is than those represent-
ing the younger stages.
The maximum duration of this stage is aca-
demic,since the oldest spruce trees known in
interior Alaska are just under 300 years old
(see footnote 5).Enough reproduction exists
within most stands to maintain this stage,
however,until fire or other disturbances de-
stroy them.
This is the general pattern of postfire suc-
cessio n.Next are exam pies of what each
developmental stage can look like,first on
white spruce sites,and then on mesic black
spruce sites.Sample size is small,however,
and generalizations for the entire taiga are
not impl ied.
Stages on White Spruce Sites
I.-The newly burned stage (o-I year after
fire)is a time of initial impact and recovery.
Ground fires consume or damage vegetation
throughout most of the burned areas.Crown
fires·are less com mona Burned sites are domi-
nated by standing dead trees and an expanse of
charre.d ground and ash.Except.-in unburned
pockets,the preburn ground vegetation has
been killed and mostly consumed.Trees that
have been stem....scorched frequently retain
their green leaves.It is initially difficult to
determine whether they are dead or alive;
most will die.
Within weeks of the fire,growing vegetation is
again apparent.The first to be visible are neW
shoots of prickly rose,high bushcranberry,and
willow,which occur near the remains of
burned shrubs.Sucker s.hoots of quaking aspen,
and seedlings of fireweed,quaking aspen,and
paper birch soon follow.White spruce seed-
lings rarely appear.
51
Figure 15.-Newly burned stage
on white spruce sites.This stand
(BC 4L-4H)is 2 weeks postfire in
age.Light colored areas on the
forest floor are ash in places
where the burn was severe.Ad-
jacent areas with young sucker
shoots and forest litter are
places where tne burn was less
severe.
White spruce trees in interior Alaska produce
viable seed crops on an irregular basis.Abun-
dant seed is produced once every 10 years
(Zasada and Vi ereck 1970).Small quantities of
seed may be produced locally in intervening
years.If seeds reach recently burned ground,
seedlings will develop.More often,white
spruce seed is not available so the species is
absent from the burned area.
Figure 15 and tables 15 and 21,p.56 and 68,
show what occurred on sampled sites in the
newly burned stage.Quaking aspen,prickly
ro se,hi gh bushcranberry,and fire weed
occurred in all stands.Paper birch,willow,
American red raspberry,field horsetail,reed-
grass,and northern bedstraw occurred in most
stands but in lesser amounts.
52
By the end of the first growing season,the
shoots were 2-50 cm tall and the seedlings
1-10 cm in height.Tall shrubs and tree seed-
lings,including suckers,averaged the follow-
i~g densities:prickly rose 45,462 stems/ha;
high bushcranberry 37,562;quaking aspen
28,312;paper birch 1,688;willow 5,250;and
American red raspberry 562.The leading
herb,fireweed,covered 7 percent of the area.
There were small amounts of new litter on the
forest floor.Thus vegetation began to cover
areas that were initially charred ground and
the next,or moss-herb,stage was near.
2.-The moss-herb stage (1-5 years after fire)
is a time of continued introduction and ex-
pansion of species.In addition to the species
found in the newly burned stage,others were
also found:Bebb willow,twin-flower,
mountain-cranberry,tall bluebell,bluntleaved
sandwort,Ceratodon purpureus,Polytrichum
spp.,and Marchantia polymorpha (fig.16;
tables 16 and 21,p.58 and 68).
Four years after the fire,the vegetation was
dominated by the oldest species (quaking as-
pen,prickly rose,various willows,and fire-
weed),one additional species (Ceratodon
purpureus),and litter.Quaking aspen and
paper birch each averaged about 30,000
stems/ha (both sucker shoots and seedlings)
and were 1-2 m tall.Tall shrubs averaged
9,969 stems/ha for prickly rose;6,906 for high
bushcranberry;and 2,547 for willow (mostly
Bebb willow).Herbs,on the average,covered
30 percent of the ground;one species,fire-
weed,accounted for 14 percent or almost
half.Mosses,on the average,covered 30
percent of the area;one species,Ceratodon
purpureus,accounted for most (16 percent).
This rapidly expanding moss forms extensive
patches,especially in areas of exposed mineral
soil.Deadfall litter covered,on the average,
62 percent of the area.As the litter accumu-
lates,it forms an ever-thickening layer of
organic material in various stages of decom-
position.The layer in this stage averaged
3 cm in depth.
3.-The tall shrub-sapling stage (3-30 years
after fire)is a period of domination by tall
shrubs and/or sap1in6s in the overstory,and
herbs,tree seedlings,and litter below
(fig.17).The vegetation continues from the
moss-herb stage.Introduction of new species
may continue for a short time but essentially
stops by the end of this stage.Mosses and
lichens exist but are not important compo-
nents.
Fifteen years after the fire (a mean age for
this stage),the overstory saplings (mostly
quaking aspen)averaged 3,256 stems/ha;wil-
lows (mostly Bebb a,ld grayleaf)21,737;and
other tall shrubs (mostly prickly rose and high
bushcranberry in equal amounts)75,889 (tables
17 and 21,p.60 and 68).The saplings and
willows were 2-5 cm tall and the prickly rose
and high bushcranberry 1-2 m tall.In the un-
derstory,seedlings and sucker shoots (mostly
quaking aspen)averaged 31,792 stems/ha;
herbs (mostly fireweed,reedgrass,and field
horsetail)covered on the average,45 percent
of the area;and low shrubs (no dominating
species)6 percent.On the forest floor,litter
(mostly deadfall leaves)averaged 90-percent
cover;mosses (mostly Ceratodon purpureus)
8 percent;while lichens (mostly Peltigera
spp.)averaged 2 percent.The organic layer
averaged 8 cm in depth.The plants grow
taller as the organic layer grows thicker.With
time the saplings will overtop the shrubs and
become trees and the next stage will arrive.
Figure 17.-Tall shrub-sapling
stage on white spruce sites.
This 3-year-old community has
26,000 quaking aspen saplings
and 67,000 tall shrub stems per
hectare.
Figure 16.-Moss-herb stage on
white spruce sites.The site of
thi s I-year-old com munity had
been severely to moderately
burned.Fireweed and field
horsetail dominate on the se-
verely burned areas;those her~s
plus quaking aspen seedlings
dominate areas moderately
bur ned.
53
Figure 18.-Dense tree stage on
white spruce sites.This stand
(no.150)has 1,645 trees/ha.
4.-The dense tree stage (26 to 45 years after
fire)is a period of dominance by young trees
in the overstory,and hi gh bushcranberry,
pri ck Iy ros e,t wi n-fl 0 w er,m ountai n-cranb er ry,
Labrador-tea,and litter below (fig.18).Cla-
donia spp.(lichens),never very extensive-:are
best developed at this time,and feather-
mosses,especially Pleurozium schreberi,are
now established.Willows,herbs,and seral
mosses are no longer important components.
Dominant trees in sampled stands averaged 36
years in age.Overstory trees (mostly paper
birch and quaking aspen)averaged 2,319
stems/ha,8.4-to I I.I-c m d.b.h.,and 6-10 m
tall (tables 18 and 21,p.62 and 68).Under-
story tall shrubs (mostly high bushcranberry
and prickly rose)averaged 16,075,willows
(mostly Bebb)800,and seedlings (mostly
hardwoods)1,650 stems/ha.Low shrubs and
54
herbs (no dominant species)covered,on the
average,14 and 10 percent,respectively,of
the forest floor.Leaf Ii tter was found 0 n 93
percent of the ground;mosses,mostly Pleuro-
zium schreberi and Polytrichum spp.,on 14
percent;while lichens (Cladonia spp.and
Peltigera spp.in equal amounts)occurred on
2 percent of the ground.The organic layer
remained about 8 cm thick.
As these stands age,the dense trees will un-
dergo self-thinning and the surviving trees will
increase in height and diameter.The next
stage,the hardwood stage,is near.
5.-The hardwood stage (46-150 years after
fire)is characterized by well-developed stands
of quaking aspen,paper birch,or mixtures of
hardwood and hardwood-white spruce (see figs.
3,4,and 5).High bushcranberry,prickly rose,
twin-flower,and field horsetail dominate the
understory,while leaf litter and Hylocomium
splendens dominate the forest floor.Willows,
mosses,and lichens are not important compo-
nents.Paper birch trees tend to outlive quak-
ing aspen trees by 30 to 50 years.Towards the
end of this stage,the stands are mostly paper
birch and/or mixtures of paper birch and white
spruce.
The stands studied in this stage averaged 87
years in age.Of the 909 trees/ha,one-half
were quaking aspen,one-third paper birch,and
one-sixth white spruc e (tables 19 and 211 p.
64 and 68).The dominant trees averaged
18.5-to 20.8-cm d.b.h.and 17-26 m in height.
Of the 58,170 stems/ha of tall shrub,65 per-
cent were high bushcranberry,30 percent
prickly rose,and 4 percent American green
alder.Low shrubs covered,on the average,
7 percent of the area and were half twin-
flower and one-half mountain-cranberry and
Labrador-tea.Herbs covered 7 percent of the
ground.Field horsetail,the most abundant
herb,accounted for half this amount.Hylo-
comium splendens formed 6 percent or half
the total moss cover.Leaf litter covered,on
the average,86 percent of the area,while the
organic layer averaged II cm in depth.Nu-
merous tree seedlings were found,especially
on mineral soil exposed by uprooted and fallen
trees.Most of these (20,761 per hectare)were
paper birch.There was little evidence,how-
ever,these seedlings would survive for long.
This stage will end as the hardwood trees stag-
nate and die,leaving the codominant and/or
understory white spruce to form the overstory
canopy.
6.--The spruce stage (150-300+years after
fire)occurs after the shorter lived plants have
failed to replace themselves (see figs.6 and 7).
The overstory canopy of white spruce is open
to closed.A few hardwood trees,relics of an
earli er stage,may occur in the beginning years
but eventually die.Prickly rose and high bush-
cranberry usually dominate the tall shrub lay-
er,though they may be entirely displaced by
thickets of American green alder.Twin-
flower and field horsetail dominate the un-
derstory.Hylocomium splendens blankets the
forest floor,coveri ng litter,fallen logs,and
slow growing vegetation.Willows are absent
and lichens are present only in minimal
amounts.This stage will develop earli er than
150 years after fire if the hardwoods die when
younger or if no hardwoods are present in the
dense tre e stage.
As stands in the spruce stage age,three
changes occur:(I)the trees increase in diam-
eter but stagnate in height,(2)the moss layer
increases in extent and depth,and (3)Ameri-
can green alder appears to increase in density.
,.
The stands studied averaged 170 years in age.
Trees (mostly white spruce)averaged 566
stems/ha,19.I-cm d.b.h.,and 30 m in height
(tables 20 and 21,p.66 and 68).The 21,781
stems/ha of tall shrubs were 65 percent prick-
ly rose,23 percent high bushcranberry,and 12
percent American green alder.Twin-flower
covered 6 percent of the area and accounted
for most of the low shrub layer.Field horse-
tail covered 4 percent of the area,while Geo-
caul on I ividum covered 3 percent.Together
they accounted for 70 percent of the herb lay-
er.In the moss layer,Hylocomium splendens
covered,on the average,61 percent and
Pleurozium schreberi,5 percent.Litter was
visible on 26 percent of the ground,and the
litter-organic layer averaged 12 cm in depth.
No one knows how long this stage might last in
interior Alaska.The oldest known trees are
300 years old.Many of these are still healthy
and free of center rot.At current rates,fire,
I andcleari ng,and logging will term inate or
impact most of these white spruce stands in
the near future.
Tables 15-20 are grouped together on p.56-67
to aid the reader in following the succession of
common species on white spruce sites through
the six developmental stages.A summary
appears in table 21,p.68.
55
Table l5-Quantitative description of the newly burned stage of plant succession on white spruce sites in the taiga of
interior Alaska,by dominant plant species and litter component if
Tree layer:
Betula papyrifera-
Mature trees JJ (14)(16)(69)(86)
Saplings 0 0 0 0
Seedlings 12 25 1,688 3,375
Picea glauca-
Mature trees (19)(38)(225)(450)
Saplings 0 0 0 0
Seedlings 0 0 0 0
Populus balsamifera-
Mature trees (15)(~O)(294)(589)
Saplings 2 5 2 4
Seedlings 0 0 0 0
Populus tremuloides-
Mature trees (59)(42)(377)(389)
Saplings 0 0 0 0
Seedlings 55 33 28,312 47,551
Tall shrub layer:
Alnus crlspa 8/0 0 0 0
""ROs"aac Icul arls 88 25 45,562 23,740
Rubus idaeus 10 14 562 966
Salix arbusculoides 0 0 0 0
Salix bebbiana 0 0 0 0
~glauca 0 0 0 0
Other Salix spp.15 17 5,250 5,990
Viburnum edule 78 22 37,562 37,220
Low shrub layer:
Ledum groenlandicum 0 0 0 0
Li nnaea borealis 2 5 9/9/
Vaccinium vitis-idaea 0 0
-0 -0
Herb layer:
Calamagrostis spp.22 29 1 I
Cornus canadensis 20 23 9/9/
Epiloblum angustlfolium 80 40 -7 -5
Equisetum arvense 10/20 40 I 2
Equisetum scirpoides 0 0 0 0
Galium boreale 65 40 I 1
Geocaulon lividum 0 0 0 0
Lycopodium annotinum II/2 5 9/9/
Mertensia paniculata 28 22 9/9/
Moehringia lateriflora 0 0 <>-0
Pyrola asarifolia 12/0 0 0 0
Pyrola secunda 0 0 0 0
See footnotes at end of table.
Quantitative description of the newly burned stage
Standard
deviation
D.b.h.M
C entl meters
Mean
(6.7) (3.8)
(8.2)(0)
2.0 0
(17.5)(0)
(18.8)(6.3)
Standard
deviation
Density ~
Stems/ha
Mean
Standard
deviation
Cover ~
Mean
Standard
deviation
Frequency ~
Mean
------ -----Percent ------- ----
Species and litter
component y
56
Table 15-Quantitative description of the newly burned stage of plant succession on white spruce sites in the taiga of
interior Alaska,by dominant plant species and litter component!!(continued)
Quantitative description oJ the newly burned stage
Species and litter
component Y Frequency ~Cover ~Density ~D.ll.h.~
Mean
Standard
deviation Mean
Standard
deviation Mean
Standard
deviation Mean
Standard
deviation
- - - - - - - - - - -Percent - - - - - - - - ---
Mosses:
\Ceratodon purpureus 0 0 0 0
~Dicranum spp.0 0 0 0
'!J Orepanocladus uncinatus 0 0 0 0
Hyloconlium splendens 0 0 0 0
Marchantia polymorpha 0 0 0 0
Pleurozium schreberi 0 0 0 O·
Polytrichum spp.0 0 0 0
Lichens:
Cladonia spp.J]j 0 0 0 0
Peltigera spp.0 0 0 0
Litter component:
Charred ma teri al 100 0 96 4
t.ea ves and t wi gs 100 0 15 8
Dead wood and
fa lien logs 100 0 8
Stemslha Centimeters
II Number of stands sampled:4;age:mean 6 months after fire (standard deviation 7);number of species found:mean
i"2 (standard deviation 3);depth of organic layer:no data available.
21 Only species with a frequency of at least 30 percent in at least I stand are listed in tables 15-20.Not all of those
species occur in every stage of succession;all are listed for each stage,however,to enhance comparison·of their
development.
~The percent of plots in which a given species occurs.It is based on the equation:Frequency =I (mean stand
frequency value for a species)';'total number of stands sampled.Values have been rounded to the nearest whole number.
41 The percent of area shaded by tile canopy of a given species or litter component.It is based on the equation:Cover
';-I (mean stand cover value for a species)-:-total number of stands sampled.Values have been rounded to the nearest
whole nu mber.
~The computed or counted number of stems occurring in a given area.It is based on the equation:Ollnsity =I (mean
stand density value for a species)-;.total number of stands sampled.Values have been rounded to the nearest whole
number.
61 D.b.h.is the diameter of a tree at breast height.The values given are for trees 2.5 em in d.b.h.or larger and are
based on the equation:O.b.h.=I (mean d.b.h.values for a species in a stand)';'total number of stands sampled.
!J Numbers in parentheses indicate the number of trees that originated before the fire.
~Includes Alnus tenuifolia from river-bottom sites.
Jj Less than 0.5 percent.
J!Y Includes Equisetum pratense.
lY Includes Lycopodium clavatum.
J.E Includes Pyrola chlorantha.
J]j Includes Cladina spp.
57
,
Table l6-'-Quantitativedescription of the moss-herb stage of plant succession on white spruce sites in the taiga of interior
Alaska,by dominant plant species and litter component Y
Tree layer:
Betula papyrifera-
Mature trees JJ (26)(37)(126)(309)
Saplings I 2 8/8/
Seedlings 34 42 32,969 75,635
Picea glauca-
Mature trees (I)(2)(2)(4)
Sapl i ngs 0 0 0 0
Seedl ings 4 12 109 309
P opu Ius balsamifera-
Mature trees (I)(4)(3)(8)
Saplings 10 28 5 14
"Seedlings I 2 31 58
P opu Ius tremuloides-
l-.1ature trees (25)(35)(71)(174)
Saplings 61 51 2,41"2 4,194
Seedlings 78 27 30,000 .29,509
Tall shrub layer:
Alnus cri spa 9/2 5 109 309.
Rosa acicularls 40 37 9,969 19,305
Rubus idaeus 4 10 359 967
Salix arbusculoides 0 0 0 0
Salix bebbiana 28 34 2,109 1,952
Salix glauca 0 0 0 0
Other Salix spp.rJ 17 438 785
Viburnum .edule 21 38 6,906 18,018
Low shrub layer:
Ledum groenlandicum 2 4 2 3
Linnaea borealis 26 33 2 4
Vaccinium vitis-idaea 20 35 2 4-----
Herb layer:
Calamagrostis spp..37 36 4 8
Cornus canadensis'12 32 1 3
Epilobium angustifolium 91 19 14 15
Equisetum arvense 10/32 43 4 8
Equisetum scirpoides 26 43 I 2
Galium boreale 8 21 8/I
Geocaulon lividum 4 7 8/8/
Lycopodium annotinum )Jj 7 9 -I -3
Mertensia paniculata 12 15 8/8/
Moeh ri ngi al at eri flora 21 34 -I -I
Pyrola asarifolia 12/0 0 0 0
Pyrola secunda 18 35 I 2
See footnotes at end of table.
Quantitative description of the moss-herb stage
Standard
deviation
D.h.h.~
Centi meters
(7.5)(0)
Mean
(15.7)(0)
,0.8 0
(12.7)(8.5)
0.9 0.4
(11.3)(7.6)
0.1 " 0
Standard
deviation
Stems/ha
Density ~
Mean
Standard
de viation
Cover ~
Mean
Standard
deviation
Frequency H
Mean
-----------Percent -----------
Species and litter
component ~
S8
TableJ6-Quantitative description of the moss-herb stage of plant succession on white spruce sites in the taiga of interior
Alaska,by dominant plant species and litter component!J (continued)
Quantitative description of the moss-herb stage
Species and litter
component ~Frequency y Cover ~Density ~D.h-h.~
Mean
Standard
deviation
Standard
Mean·deviation Mean
Standard
deviation Mean
Standard
deviation
Mosses:
Ceratodon purpureus
Dicranum spp.
Drepanocladus uncina tus
Hylocomium splendens
Marchantia polymorpha
Pleurozium schreberi
P olytri chumspp.
Lichens:
Cladonia spp.13/
Peltigera spp.-
Litter component:
Charred material
Leaves and twigs
Dead wood and
fallen logs
-.---------.-Percent -""---------
76 36 16 16
0 0 0 0
7 14 8/8/
5 9 8/8/
15 21 -I -2
13 24 8/8/
54 38 -4 -6
6 12 8/ 8/
23 39 -2 -3
42 46 15 29
75 46 62 40
84 35 7 4
Ste ms/ha Centi meters
1/Number of stands sampled:8;age:mean 4 years after fire (standard deviation 2);number of species found:mean 20
(Standard deviation 6);depth of organic layer:mean 3 em (standard deviation I).
2/Only species with a frequency of at least 30 percent in at least I stand are listed in tableslS-20.Not all of those
species occur in every stage of success.ion;all are listed for each stage,however,to enhance comparison of their
development.
3/The percent of plots in which a given species occurs.It is based on the equation:Frequency =I (mean stand
frequency value for a species)-:-total number of stands sampled.Values have been rounded to the nearest whole number.
4/The percent of area shaded by tne canopy of a given species or litter component.It is based on the equation:Cover
;;-I (mean stand cover value for a species)7 total number of stands sam pled.Values have been rounded to the nearest
whole number.
Jr
5/The computed or counted number of stems occurring in a given area.It is based on the equation:Density =I (mean
stand density,value for a species)~total number of stands sam pled.Values have been rounded to the nearest whole
number.
6/D.b.h.is tne diameter of a tree at breast height.The values given are for trees 2.5 em in d.b.h.or larger and are
based on the equation:D.b.h.=I (mean d.b.h.values for a species in a stand)-:-total number of stands sampled.
]J Numbers In parentheses indicate the number of trees that originated before the fire.
~Less than 0.5 percent.
'!J Includes Alnus tenuifolia from river-bottom sites.
~Includes Equisetum pratense.
!!J Includes Lycopodium clavatum.
lE Includes Pyrola chlorantha.
QJ Includes Cladina spp.
Table l7--Quantitative description of the tall shrub-sapling stage of plant succession on white spruce sites in the taiga of
interior Alaska,by dominant plant species and litter component ~
Tree layer:
Betula papyrifera-
Mature trees 33 33 27 37
Saplings 51 44 109 143
Seedlings 28 23 4,250 4,058
Picea glauca-
""Mature trees 10 22 8 16
Saplings 12 26 28 48
Seedlings 38 38 4,583 6,096
Populus balsamifera-
Mature trees 7 20 5 13
Sapl i ngs 12 19 116 279
Seedlings 13 24 3,486 9,678
P opu Ius tremuloides-
Mature trees 43 45 83 174
Sapl i ngs 55 46 3,003 7,001
Seedlings 48 46 19,194 30,210
Tall shrubs:
Alnus crispa 71 9 II 958 1,248
Rosa acicul <iris 60 39 38,222 61,931
Rubus idaeus 19 35 3,403 6,708
Salix arbusculoides .19 30 1,903 3,805.
Salix bebbiana 24 38 11,028 21,873
Sal ix gl au ca 27 37 7,306 12,866
Other Salix spp.7 II 1,500 3,057
Viburnum edule 30 38 33,222 59,051
Low shrubs:
Ledum groenlandicum 3 8 81 81
Linnaea borealis 22 24 -I -2
Vaccinium vitis-idaea 12 30 ~I
Herbs:
Calamagrostis spp.64 16 8 8
Cornus canadensis 31 44 12 22
Epilobium angustifolium 80 26 7 9
Equisetum arvense 91 57 36 5 6
Equisetum scirpoides 28 34 2 4
Galium boreale 31 40 4 7
Geocaulon lividum 9 20 81 81
Lycopodium annotinum 101 I 3 81 81
Mertensia paniculata 24 20 -I -I
Moehringia lateriflora 17 15 81 I
Pyrola asarifolia III 6 10 81 81
Pyrol a secunda 14 17 !J !f
See footnotes at end of table.
Quantitative description of the tall shrub-sapling
1.9
0.4
0.2
0.1
0.4
0.2
0.6
0.5
Standard
deviation
D.b.h.§J
Centimeters
5.2
1.4
3.4
0.9
3.7
1.2
4.1
1.6
Mean
Standard
deviation
Density ~
Stems/ha
Mean
Standard
deviation
Cover ~
Mean
Standard
·deviation
Frequency!.!
Mean
--...,.--------Percent -----------
Species and litter
component ~
60
Table 17--Quantitative description of the tall shrub-sapling stage of plant succession on white spruce sites in the taiga of
interior Alaska,by dominant plant species and litter component y (continued)
Quantitative description af the tall shrub-sapling
Species and litter
component y Frequency ~Cover ~Density ~D.bfh.~
Mean
Standard
deviation Mean
Standard
deviation Mean
Standard
deviation Mean
Standard
deviation
-----------Percent -----------
Mosses:
Ceratodon purpureus 60 31 6 7
Dicranum spp.0 0 0 0
Drepanocladus uncinatus 6 13 8/8/
Hylocomium splendens 4 8 8/8I
Marchantia polymorpha 0 0 -0 -0
Pleurozium schreberi 8 II 8/8/
Polytrichum spp.8 16 -I -I
Li chens:
Cladonia spp.~9 12 8/8/
Peltigera spp.33 36 -4 -8
Litter component:
Charred material 7 16 I I
Leaves and twigs 99 2 81 19
Dead wood and
fallen logs 87 17 8 4
Stems/ha Centimeters
1/Number of stands sampled:9;age:mean 15 years'after fire (standard deviation 8);number of species found:mean
30 (standard deviation 11);depth of organic layer:mean 8 cm (standard deviation 6).
2/Only species with a frequency of at least 30 percent in at least I stand are listed in tables 15-20.Not.all of those
species occur in every stage of succession;all are listed for each stage,however,to enhance comparison of their
development.
3/The percent of plots in which a given species occurs.It is based on the equation:Frequency =I (mean stand
frequency value for a species).;.total number of stands sampled.Values have been rounded to the nearest whole number.
4/The percent of area shaded by the canopy of a given species or litter component.It is based on the equation:Cover
=-I (mean stand cover value for a species)';'total number of stands sampled.Values have been rounded to the nearest
whole nu mber.
....
5/The computed or counted number of stems occurring in a given area.It is based on the equation:Density =I (mean
stand density value for a species).;.total number of stands sampled.Values have been rounded to the nearest whole
number.
6/O.b.h.is the diameter of a tree at breast height.The values given are for trees 2.5 cm in d.b.h.or larger and are
based on the equation:D.b.h.=I (mean d.b.h.values for a species in a stand)';'total number of stands sampled.
!J Includes Alnus tenuifolia from river-bottom sites.
~Less than 0.5 percent.
"y Includes,Equisetum pratense.
lEi Includes Lycopodium clavatum.
ill Includes Pyro la chlorantha.
~Includes Cladina spp.
61
Table I~uantitative description of the dense tree stage of plant succession on white spruce sites in the taiga of
interior Alaska,by dominant plant species and litter component!!
Tree layer:
Betula papyrifera-
~ure trees 84 16 1,337 810
Saplings 62 21 41 66
Seedlings 9 7 650 1,044
Picea glauca-
~uretrees 22 33 238 454
Saplings 26 29 9 9
Seedlings 4 4 100 104
Populus balsamifera-
,.1 a ture tre es 0 0 0 0
Sapl i ngs 0 0 0 0
Seedlings 2 3 200 381
Populus tremuloides-
Mature trees 44 36 718 1,027
Saplings 10 17 2 4
Se ed lings II 15 675 1,088
Tall shrubs:
Alnus crispa 7/7 10 700 962
Rosa acicularls 57 30 5,975 3,542
Rubus idaeus 8 15 225 437
Salix arbusculoides 0 0 0 0
Salix bebbiana 13 18 800 1,304
Salix glauca 0 0 0 0
Other Salix spp.20 0 25 56
Viburnum edule 36 33 9,175 8,825
Low shrubs:
Ledum groenlandicum 22 31 3 3
Linnaea borealis 43 29 3 4
Vaccinium vitis-idaea 27 42 4 7
Herbs:
Calamagrostis spp.52 31 3 5
Cornus canadensis 35 32 1 I
Epilobium angustifolium 38 34 I 2
Equisetum arvense 8/41 44 2 3
Equisetum scirpoides 14 26 9/ 9/
Galium boreale 12 17 9/9/
Geocaulon Iividum 0 0 -0 -0
Lycopodium annotinum 10/5 9 9/I
Mertensia paniculata 12 18 9/9/
Moehringia lateriflora 17 23 9/9/
Pyrola asarifolia II/0 0 -0 -0
Pyrola secunda 2 3 2.!2.!
See footnotes at end of table.
Quantitative description of the dense tree stage
2.2
0.5
2.2
0.1
4.4
0.3
Standard
deviation
D.b.h.~
Centimeters
8.8
1.5
8.4
1.8
Mean
1 1.1
1.9
Standard
deviation
Density ~
Stems/ha
Mean
Standard
deviation
Cover ~
Mean
Standard
deviation
Fre qu enc y 'if
Mean
-----------Percent -----------
Species and litter
component ~
62
Table 18-Quantitative description of the dense tree stage of plant succession on white spruce sites in the taiga of
interior Alaska,by dominant plant species and litter component J.J (continued)
Quantitative description of the dense tree stage
Species and litter
component ~Fre quency '}j Cover ~Density ~
,
D.b.h.~
Mean
Standard
deviation Mean
Standard
deviation Mean
Standard
deviation Mean
Standard
deviation
-----------Percent -----------Stemslha Centimeters
Mosses:
Ceratodon purpureus 8 II
Dicranum spp.16 13
Drepanocladus uncinatus 19 25
Hylocomium splendens 7 10
Marchantia polymorpha 0 0
Pleurozium schreberi 48 20
Polytrichum spp.34 32
Lichens:
Cladonia spp.~32 30
Peltigera spp.13 14
Litter component:
Cnarre d ma teri al I 2
Leaves and twi gs 100 0
Dead wood and
fa lien logs 69 19
91
88
5
II Number of stands sampled:5;age:mean 36 years lifter fire (standard deviation 7);number of species found:mean
i9 (standard deviation 4);depth of organic layer:mean 8 cm (standard deviation 3).
21 Only species with a frequency of at least 30 percent in at least I stand are listed in tables 15-20.Notooall of those
species occur in every stage of succession;all are listed for each stage,however,~to enhance comparison of their
development.
31 The percent of plots in which a given species occurs.It is based on the equation:Frequency =I (mean stand
frequency value for a species)';'total number of stands sampled.Values have been rounded to the nearest whole number.
41 The percent of area shaded by the canopy of a given species or litter component.It is based on the equation:Cover
=-I (mean stand cover value tor a species)';'total number of stands sampled.Values have been rounded to the nearest
whole number.
:it
51 The computed or counted number of stems occurring in a given area.It is based on the equation:Density =I (mean
stand density value for a species):-total number of stands sampled.Values have been rounded to the nearest whole
number.
61 D.b.h.is the diameter of a tree at breast height.The values given are for trees 2.5 cm in d.b.h.or larger and are
based on the equation:D.b.h.=I (mean d.b.h.values for a species in a stand)';'total number of stands sampled.
!J Includes Alnus tenuifolia from river-bottom sites.
~Includes Equisetum pratense.
~Less than 0.5 percent.
J!Y Includes Lycopodium clavatum.
!l!Includes Pyrola chlorantha.
gj Includes Cladina spp.
63
Table 19-Quantitative description of the hardwood stage of plant succession on white spruce sites in the taiga of
interior Alaska,by dominant plant species and litter component!!
Tree la yer:
Betula papyrifera-
Mature trees 56 45 317 342
Saplings 8 15 3 3
Seedlings 6 II 20,761 67,867
Picea glauca-
~iUi:etrees 26 29 102 200
Saplings 15 28 6 9
5e edl ings 2 5 227 578
Populus balsamifera-
Mature trees I 3 3 10
Saplings 0 0 0 0
Seedlings I 3 57 188
Populus tremuloides-
Ma ture tre es 46 51 483 582
Saplings 9 30 44 147
Seedlings II 16 1,443 2,658
Tall shrubs:
Alnus crispa 7/16 16 2,443 3,231
Rosa acicularls 75 36 17,727 16,148
Rubus idaeus 0 0 0 0
Salix arbusculoides 4 12 272 904
Salix bebbiana 6 14 375 835
Sal ix gl auca 0 0 0 0
Other Salix spp.0 0 0 0
Viburnum edule 55 50 38,000 61,253
Low shrubs:
Ledum groenlandicum 7 10 I I
Linnaea borealis 47 29 3 6
Vaccinium vitis-idaea 21 29 2 4
Herbs:
Calamagrostis spp.45 34 I 2
Cornus canadensis 55 38 3 4
Epilobium angustifolium 50 40 3 4
Equisetum arvense 8/51 42 10 13
Equisetum scirpoides 0 0 0 0
Galium boreale 16 28 I I
Geocaulonlividum 6 12 9/9/
Lycopodium annotinum 10/6 14 9/-I
Mertensia paniculata 13 20 9/1
Moenringia lateriflora 20 18 9/9/
Pyrola asarifolia 11/9 II 9/9/
Pyrola secunda 9 14 "if "if
See footnotes at end of table.
Quantitative description of the hardwood stage
Standard
deviation
D.b.h.~
Centimeters
Mean
18.6 7.2
1.4 0.6
20.8 6.5
0.4 0
17.5 10.0
18.5 7.8
2.0 0.4
Standard
deviation
Stems/ha
Density ~
Mean
Standard
deviation
Cover ~
Mean
Standard
deviation
Frequency ~
Mean
-----------Percent -----------
Species and litter
component ~
64
Table 19-Quantitative description of the hardwood stage of plant succession on white spruce sites in the taiga of
interior Alaska,by dominant plant species and litter component y(continued)'
Quantitative description of the hardwood stage
Species and litter
component Y Frequency ~Cover ~Density ~
Mean
Standard
deviation Mean
Standard
deviation Mean
Standard
deviation Mean
Standard
deviation
-----------Percent -----------
Mosses:
Cera todon purpure us 3 6 9/9/
Dicranum spp.7 0 9/9/
Drepanocladus uncinatus 16 18 9/9/
Hylocomium splendens 21 29 -6 18
Marchantia polymorpha 0 0 0 0
Pleurozium schreberi 24 24 2 4
Polytrichum spp.II 20 I 2
Li chens:
Cladonia spp.m 12 19 9/I
P eltigera spp.4 10 FJ 2J
Litter component:
Charred material I 3 9/9/
Leaves and twigs 99 4 86 -5
Dead wood and
fallen logs 77 24 6 4
Ste ms/ha Centi meters
1/Number of stands sampled:II;age:mean 87 yeal'S after fire (standard deviation 38);number of species found:mean
24 (standard deviation 5);depth of organic layer:mean II em (standard deviation 3).
2/Only species with a frequency of at least 30 percent in at least I stand are listed in tables 15-20.Not all of those
species occur in every stage of succession;all are listed for each stage,however,to enhance comparison~f their
development.
3/The percent of plots in which a given species occurs.It is based on the equation:Frequency =1:(mean stand
frequency value for a species)-;total number of stands sampled.Values have been rounded to the nearest whole number.
4/The percent of area shaded by the canopy of a given species or litter component.It is based on the equation:Cover
=-1:(mean stand cover value for a species)';'total number of stands sampled.Values have been rounded to the nearest
whole number.
5/The computed or counted number of stems occurring in a given area.It is based on the equation:Deasity =r (mean
stand density value for a species)';total number of stands sampled.Values have been rounded to the nearest whole
number.
6/D.b.h.is the diameter of a tree at breast height.The values given are for trees 2.5 em in d.b.h.or larger and are
based on the equation:D.b.h.=1:(mean d.b.h.values for a species in a stand)';'total number of stands sampled.
!J Includes Alnus tenuifolia from river-bottom sites.
!!Includes Equisetum pratense.
~Less than 0.5 percent.
lEi Includes Lycopodium clavatum.
ill Includes Pyrola chlorantha.
~Includes Cladina spp.
65
Table 2o-Quantitative description of the spruce stage of plant succession on white spruce sites in the taiga of interior
Alaska,by dominant plant species and litter component]j
Tree layer:
Betula papyrifera-
Mature trees 25 24 40 39
Saplings 20 17 6 4
Seedlings 5 10 375 750
Picea glauca-
~ure trees 100 0 512 22
Sapl i ngs 26 46 10 18
Seedlings 29 6 1,719 493
Populus balsamifera-
Mature tre es 2 5 7 14
Sapl i ngs 9 12 2 3
Seedlings 0 0 0 0
Populus tremuloides-
Mature trees 4 5 7 10
Saplings I 2 7/I
Seedlings 6 10 562 1,043
Tall shrubs:
Alnus crispa !!12 10 2,594 4,137
Ros a acicul aris 76 18 14,125 4,071
Rubus idaeus 0 0 0 0
Salix arbusculoides·0 0 0 0
Salix bebbiana 0 0 0 0
Salix glauca 0 0 0 0
Other Salix spp.0 0 0 0
Viburnum edule 39 15 5,062 5,508
Low shrubs:
Ledum groenlandicum 0 0 0 0
Linnaea borealis 52 45 6 5
Vaccinium vi tis-idae a II 22 I 2----
Herbs:
Calamagrostis spp.20 19 I 7/
Cornus canadensis 15 20 1 -I
Epilobium angustifolium 14 21 7/7/
Equisetum arvense 9/84 5 -4 -2
Equisetum scirpoides 0 0 0 0
Galium boreale 20 24 7/7/
Geocaulon lividum 60 13 3 -2
Lycopodium annotinum 10/0 0 0 0
Mertensia paniculata 19 16 7/7/
Moehringia lateriflora II 13 7/7/
Pyrola asarifolia III 32 26 -I 7/
Pyrola secunda 26 27 I -I
See footnotes at end of table.
Quantitative description of the spruce stage
Standard
deviation
D.b.h.~
Mean
Centimeters
19.1 6.1
1.1 0.6
29.4 3.3
0.8 0.2
28.8 2.7
0.8 0
34.1 0.4
1.4 0.3
Standard
deviation
Stems/ha
Density ~
Mean
Standard
deviation
Cover ~
Mean
Standard
deviation
Frequency ~
Mean
- - - - - - - - - - -Perc ent - - - - - - - - ---
Species and litter
component ~
66
Table 2o-Quantitative description of the spruce stage of plant succession on white spruce sites in the taiga of interior
Alaska,by dominant plant species and litter component Jj (continued)
Quantitative description of the spruce stage
Species and litter
component Y FrequencY!J Cover ~Density ~D.bfh.~
Mean
Standard
deviation Mean
Standard
deviation Mean
Standard
deviation Mean
Standard
deviation
-----------Percent -----------
Mosses:
Ceratodon purpureus 2 3 7{7{
Dicranum spp.8 9 7{7{
Drepanocladus uncinatus 4 2 7t 7{
Hylocomium splendens 91 6 61 10
Marchantia polymorpha 0 0 0 0
Pleurozium schreberi 34 18 5 4
P olytri chumspp.2 5 ?J ?J
Lichens:
Cladonia spp.rfj 24 19 7{7{
Peltigera spp.21 10 -I -I
Litter component:
Charred material 0 0 0 0
Leaves and twigs 98 5 26 II
Dead wood and
fallen logs 78 23 16 4
Ste ms{ha Centimeters
I{Number of stands sampled:4;age:mean 170 years after fire (standard deviation 70);number of species found:mean
30 (standard deviation I);depth of organic layer:mean 12 em (standard deviation I).
2{Only species with a frequency of at least 30 percent in at least I stand are listed in tables 15-20.Not all of those
species occur in every stage of succession;all are listed for each stage,however,to enhance comparison o"f their
development.
3{The percent of plots in which a given species occurs.It is based on the equation:Frequency =I (mean stand
frequency value for a species)';'total number of stands sampled.Values have been rounded to the nearest whole number.
4{The percent of area shaded by the canopy of a given species or litter component.It is based on the equation:Cover
~I (mean stand cover value for a species)';total number of stands sampled.Values have been rounded to the nearest
whole nu mber.
5{The computed or counted number of stems occurring in a given area.It is based on the equation:Den~ty =I (mean
stand density value for a species)';'total number of stands sampled.Values have been rounded to the nearest whole
number.
6{D.b.h.is the diameter of a tree at breast height.The values given are for trees 2.5 em in d.b.h.or larger and are
based on the equation:D.b.h.=I (mean d.b.h.values for a species in a stand)';total number of stands sampled.
'!J Less than 0.5 percent.
~Includes Alnus tenuifolia from river-bottom sites.
Y Includes Equisetum pratense.
].2j Includes Lycopodium clavatum.
ill Includes Pyrola chlorantha.
rfj Includes Cladina spp.
67
~Table 21-Sum mary of the quantitative descriptions of the 6 stages of plant succession on white spruce sites In the taiga of Interior Alaska!!
Tall shrub-
Newly burned stage Moss-herb stage sapling stage Dense tree stage Hardwood stage Spruce stage
Item
Standard Standard Standard Standard Standard Standard
Mean deviation Mean deviation Mean deviation Mean deviation Mean deviation Mean deviation
Stand age,years 0.5 0.6 4 2 15 8 36 7 87 38 170 70
Plant species found,number y 12 3 20 6 30 1I 29 4 24 5 30 I
Depth of organic layer,centimeters NA NA 3 1 8 6 8 3 II 3 12 I
Numberof stems per hectare
Density:!!~
Tree layer-
Mature tre es ~(966)(730)(202)(372)124 193 2,319 1,598 909 405 566 26
Sapll ngs 2 4 2,417 4,191 3,256 6,966 52 70 55 144 18 21
Seedlings 30,000 46,558 63,203 70,929 31,792 32,908 1,650 2,536 22,488 68,100 2,656 2,095
Tall shrub layer-
Salix spp.5,250 5,990 2,547 1,939 21,737 29,203 825 1,310 648 1,136 0 0
Other tall shrubs 83,688 57,134 17,344 36,848 75,889 122,141 16,075 11,228 58,170 70,976 21,781 6,708
Percent
Cover:4/6/
Low Shrubs 7/7/7 7 6 10 14 15 7 8 7 6
Herbs T3 To 30 25 45 33 10 6 21 15 iO 4
Mosses 0 0 22 19 8 10 14 10 II 24 69 12
Lichens 0 0 2 3 4 8 2 2 I I 2 I
Litter components 118 9 83 26 90 18 93 7 92 25 42 13
NA =not available.
11 Number of stands sampled:newly burned,4;moss-herb,8;tall shrub-sapling,9;dense tree,5;hardwood,II;spruce,4.
y Also Includes the 3 stages of tree development:mature tree,sapling,and seedling.When present,each stage of a species Is counted as J.
!!The computed or counted number of stems occurring In a given area.
~Totals may be off because of rounding and because data listed were only for the species occurring most frequently.
~Numbers In parentheses Indicate the number of trees that originated before the fire.
Y The percent of area shaded by the canopy of a given plant layer or litter component.
!J Less tllan 0.5 percent.
Patterns of Change
on White Spruce Sites
Although each developmental stage can be
described individually,together they form pat-
terns that change through time.Figure 19 il-
lustrates the changes;each graph in the figure
is limited to one stratum.
Trees start in great numbers as seedlings and
suckers.Most of them will die,but some do
become sapli ngs and then trees (fig.19A).
Seedlings (and sapiings)are most numerous in
the mos,s-herb stag~,are least numerous in the
dense tre e and spruce stages,but are always
present (fig.19B).Quaking aspen and paper
birch dominate throughout.Saplings peak in
the tall shrub-sapli ng stage;beginning with the
dense tree stage,they are present only in
minimal amounts (fig.19C).Trees peak in the
dense tree stage and decline thereafter (fig.
19D).Hardwoods dominate the dense tree and
hardwood stages,and spruce dominates the.
spruce stage.
Willows first appear as sucker shoots and seed-
lings in the newly burned stage,hold their own
in the moss-herb stage,and attain their max-
imum growth and numbers in the tall shrub-
sapling stage (fig.19E).After that,they
decline rapidly and completely disappear
sometime in the hardwood stage.Littletree
and Bebb are the last to die out.Bebb and
grayleaf appear,from the study data,to be
the most common of the willow species.
The non-willow tall shrubs show a more com-
plex pattern (fig.19F).Am erican green alder
appears by the end of the moss-herb stage and
increases continuously,reaching its greatest
density,only 2,600 stems/ha,in the spruce
stage.P ri ckly rose and high bushcranberry are
always present.Sometimes one is more dense,
sometimes the other.Numbers of both are
high in the newly burned,tall shrub-sapling,
and hardwood stages;however,each successive
peak is slightly lower.This may be caused by
stand differences orit may be successful es-
tablishment and then opportunism.More study
is required to distinguish which is the case.
I,
Low shrubs appear early,are always present,
and reach a peak in area covered during the
hardwood stage (fig.19G).Within this pat-
tern,however,two trends are apparent:(I)
Twin-flower is established by the end of the
moss-herb stage and increases thereafter to
become the primary low shrub species in the
spruce stage;and (2)mountain-cranberry and
Labrador-tea peak primarily in the dense tree
stage and decline thereafter.Other species
occur too sporadically to show trends.
The herb layer begins to d.evelop immediately
after fire,increases steadily in tota,lcover,
peaks early in the tall shrub stage~and
decli nes thereafter but never disappears
(fig.19H).Not all herb species,ho'wever,
follow this pattern.Som e,such as Geocaulon'
Iividum,occur in small amounts through the
dense treestage and increase in the spruce
stage.Others,such as fire weed,appear early;
reach their peak in the moss-herb stage,and
decrease thereafter.Still otheJ;s,incl~ding
most herb species,are always present in vary-
ing amounts but develop their greatest cover
early in the tall shrub-sapling stale.Of these,
field horsetail,reedgrass,and bunchberry ac-
count for most of the coverage.
Mosses peak twice,first a small peakin the
moss-herb stage and then a larger peak in the
spruce stage (fig.191).Within this trend three
patterns are apparent.(I)Feathermosses,
especially Hylocomium splenden~appear by
t~e end of the tall shrub stage,startexpandi ng
in t~e dense tree stage,and blanket the ground
in tile spruce stage.Of the featliermosses,
Pleurozium schreberi is most extensive in the
dense tree stage.In the later hardwood stage,
HylQcomium splendens is more extensive.(2)
Ceratodon purpureus and Marchantia poly-
morpha cover extensive are'as early in suc-
cession,peak in the moss-herb stage,and
essentially disappear by the ,beginning of the
dense tree stage.(3)Still others,such as
Polytrichum spp.,tend to be more extensive in
the younger stages but are always present and
may be locally abundant at any time.
69
Spruce
(150-300)
Hardwood
-.....-,-Trees
----Saplings
_.-.-Seedlings
---Betula papyri/era
•••...Picea glauca
_.-.-Populus tremuloides
- - -Other species
--Betula papyri/era
and Picea glauca
_·_·-Populus tremuloides
---'- -Other species
liverworts;J,lichens;and K,
litter.Other items shown are.!::.!
depth of organic layer;and.!!!.,
number of species present.Each
line represents the number
occurring of that unit.Graphs
with more than one line show
cumulative totals.
,
"
A.Tree categories
.""../...."."......,......
/'....,,/.....
./.,
./.'.......
B.Seedlings
Figure 19.-Successional trends
on white spruce sites.Shown are
densities of A,tree categories;
B,seedlings;C,saplings;D,
trees;E,tall Shrubs,willow;and
F,tall shrubs,non-willow.Also
shown are the covers of G,low
shrubs;.!:!...herbs;J..,mosses and
3,600 C.Saplings
3,200 ........\..............:-;.....-.,"
2 800 "'''*.,......"',-::;......'.\
2 400 /,:",,".....,\\
"~7 .~
2,000 //\\~..~
1,600 /.f"'~.\
1,200 /.7 \\~.,
800 //"\f'~
400 /"0.Jt-----~====;:=======~~;ii;;::--~.-~.,.~.-¥'-~-;~~--iIIi
Newly Moss-Tall shrub-Dense
burned herb sapling tree
(0-1)(1-5)(3-30)(26-45)(45-150)
Post-fire stage (years)
72,000
64,000
56,000
48,000
40,000
32,000
24,000
16,000 '...............................-.................
8,000 "_.-'....O+-_....:.........=--::;.::-:;=-.=.;--=':-:':-=--=-:":';--~-F--;;;;-=-=-=--=-=-~.=====::::::;:::==~.......~....
64,000
56,000 "'''''''''''''''
48,000 "",
"40,000 '"
"32,000 '....._.-._._.-.-.-.....-.-.'~
24,000 -.-._.....'"
16,000 .......'....
8,000 .::~~...
0+---........:.:·'u..'':.:.:'.~.':':"'.:..;'':":".;..'.;.;.•...;...'-'-''.,.'...;.''...;..';..:'''':''.:..'.:.:,''..:.'.:.:,'~¥........~..~...:::....:.::;..i,;a';;r;;,-~'-f..:,.'-.......&;;j-w:;.-w·~-.w;·-:w:·~
70
..
CDa.
tJ)
E
CD
~en
CD..
CO
~
(,)
CDs::.
2,400 D.Trees ,/f"""-:-....,
2,000 ~.~.~:-..
/.7 ".,1,600 -Betula papyrifera //7 '\.,
......Picea glauca .:-..
1,200 -·_·-Populus tremuloides /.~."~_.
800 0 h
//.-.":::..~-r---t erspecies f"-.:::::::::....,.-=_
4 00 If.•••/./....
OI.J------..;;;;;;;;;-:;;;;;;;:a;;.....::::lI:5-"'~·/.i..:·:..:·:..:·:..:·:..:·..:·..:·..:.·.:.,·-'-'r-'.-.-.-.--.;...;...:...:..:.':"':":'"-;'':';-.;...-.-----,
--Salix arbusculoides
••••••Salix bebbiana
-·-·-Salix glauca
----Other Salix spp.
E.Tall shrubs,willows24,000
21,000
18,000
15,000
12,000
9,000
6,000 ---3,000 - --:7".-:-..~•
0.1.·:.:,....:.,:·'.:..:'':":".:..':........_---__---~~~::t:C£:::P::!::I::I:scc-~
CD...
CO....,
(,)
CD
J:...
CD
Q.
(1)
E
CD....,
en
Spruce
(150-300)
Hardwood
-:....-..Alnus crispa
·.....Rosa acicularis
-.-.-Rubus idaeus and
other tall shrubs
----Viburnum edule
Tall shrub-Dense
sapling tree
(3-30)(26-45)(45-150)
Post-fire stage (years)
..-
Moss-
herb
(1-5)
,/',/,,/,,/,-,/,",,/,./,,/,././.....,,/'.'./,,/'./',/'./'/,".....,/,/...'.......,/..,/.. .....·.......
90,000 F.Tall shrubs,non-willow
80,000
70,000
60,000
50',000
40,000 ".
30,000
20,000
10,000
0.L----1iiiiioiIi~====~·===·=:";;:'~~::=::::=r====r=====i
Newly
burned
(0-1)
Figure 19.-(continued)
71
Spruce
(150-300)
Hardwood
--Calamagrostis spp.and
..Comus canaclensis
••.."•••Epildbium arigustifolium
-._.-Equisetum arvense and
Geocaulon lividum
----Other herbs
--Arctpstaphylus·uvi-ursa
'ana other low shrubs
.•.•..Ledum groenla(1dicufn
-·-'-Linnaea borealis·"
;..._....:--Vaccinium vitjs-idaea
Tall shrub-Dense
sapling tree
(3~30).'"(26-45)(45-150)
Post-fire stage (years)
-'_.-"-_.-'_.-'-.-'-'-'
Moss-
herb
(1-5),'
......e.••••__
",,-"-----.-..--.........:;,..,.;,..----..,.,.,'
",.----....-.""...,.""..,,,..,.""""",..................,.,".-._._._._._._._..---..........,.,,-..,'".................,,"--.-;'#"':::'-'-.--._.-.-.-._'""':'"'_~....~--.--.---:::::'._0
H.Herbs
12 G.Low shrubs
9
70 I.Mosses and liverworts
./6 Hylocomium splendens /
50 Marchantia polymorpha and.",'/'
Cera todon purpureus //
40 _._.-Pleurozium schreberi and h
30 Ptilium crista-castrensis I·
20 . ...------Polytrichum spp./
• • • • •."So-.".-L·"1·O·• • •.•••_._'------"""-'-'--_JI.:••••••••"--:.=..__._.-._._._._'_0
O~·~·.:~_·-.::.::.--.:.:.---:.::--:.::---:::,--=--.:.:--::.:--~--.::::;---::=.:--;.:.;:--~--~-::;..~-.-::::-~-.~==;====::::;..-~-...,
Newly
burned
(0-1)
6
3
0
45..4CD>35
0 30CJ....25c20CD
CJ 15..
CD 10c..5
0
Figure 19.-(continued)
72
--.--"---...------.-_.---------
J.Lichens _.-.-.-Cladonia spp.
••••••Peltigera spp.
~
CD>ou
5
4
3
2
1o ..'
....'
.....
..
'..........;--....:.............__.....:..._._e_e-
..".
..
--Charred material
• ••.••Leaves and twigs
-·-·-Dead wood and fallen logs
____-----~~~~~~~-r ...........................
....i 120
U 105~
CD 90
Q.75
60
45
30
15 .._._.-._.-..-.-._._.-._._.-._._.-.-._.-.-.-.-..-.--_.-.-.-._._._._._.-
O+-----..,.-----..,...------.;.~----""T"""-------,
tJ)
CD 15 L.Depth of organic layer....
CD 10
E
:i:5
C L----CD O'+:-----..,.-----..,...-----""T"""----""T"""---____,o
Spruce
(150-300)
Hardwood
--Always present
••••••Seral
Tall shrub-Dense
sapling tree
(3-30)(26-45)(45-150).1
Post-fire stage (years)
Moss-
herb
(1-5)
i CD 1 .
a.O,..J------.,.-----..,...-----""T"""-----r----____,
Newly
burned
(0-1)
CD -g 40 M.Species present
.c ~30 ..'O 'O 'O ••'O 'O .............E ll"2 ....VI ....'O'O.
Figure 19.-(continued)
73
Ground lichens are always present in small
quantities (fig.19J).Peltigera spp.appear to
peak in the tall shrub stage,and Cladonia spp.
peak in the dense tree stage.
Decaying logs occur on the forest floor in
small numbers at all times,but the numbers
increase with the passing of the hardwood
stage (fig.19K).Leaf and twig litter increases
as the deciduous vegetation develops,peaks in
the tall shrub,dense tre e,and hardwood
stages,and then declines in the spruce stage.
Charred ground surfaces,which are extensive
after fire,disappear rapidly and are gone by
the end of the moss-herb stage.
The organic layer reflects the accumulatipn of
litter (fig.19L).New litter keeps falling;old
litter decomposes and becomes more dense.
As thi s happens,the organic layer gradually
thickens from almost nothing after fire to 12
cm in old stands.
Lastly,the number of species present in a
given area increases continuously well into the
tall shrub-sapling stage and then remains al-
most constant (fig.19M).Most species are
present throughout succession but in varying
amounts.Other species occur in som e stages
but not all.Ceratodon purpureus,Marchantia
polymorpha,fireweed,willows,hardwoods,and
Cladonia spp.are examples of the latter group.
The end of succession is a fairly open to closed
stand of large white spruce under which prick-
ly rose,high bushcranberry,twin-flower,and a
continuous blanket of Hylocomium splendens
are usually found (see figs.6 and 7).
74
The six mature forest com munity types that
occur on white spruce"sites and are described
in this paper can now be seen in perspective.
Each is mature in the sense that the dominat-
ing trees are at their best development;how-
ever,in theory at least,the spruce~domin<lted
types are farthest along in terms of succes-
sion.Evidence suggasts that,in the absence
of fire,other stands will become white spruce
types in time.
Stages on Mesic Black Spruce Sites
I.-The newly burned stage (0-1 year after
fire)is a iime of initial impact and recovery
(fig.20).Fire is usually a combination of
ground and crown fires that leave the vegeta-
tion in a mosaic of conditions.Small patches
of exposed mineral soil are common and usu-
ally intermixed with larger patches of partially
burned or unburned vegetation on the forest
floor.Trees are usually killed except in
"stringers,"areas left completely untouched
by fire.Within days,shoots appear.Willow,
prickly rose,bog blueberry,Labrador-tea,
cloudberry,reedgrass,and Polytrichum spp.
can be among the first.Soon willow seedlings,
moss protonema,and liverwort thalli also
become visible.
Tables 22 and 28 (p.80 and 92),give the
findings from the stands studied.Bog blue-
berry,Labrador-tea,reedgrass,and cloudberry
were found in all newly burned stands;and
willow,prickly rose,woodland horsetail,and
Polytrichum spp.occurred in most stands.The
depth of the organic layer was quite vari able
but averaged II cm.Depth to permafrost
vari ed but averaged 49 c m.
A
·1
B
Figure 20.-Newly burned stage on black spruce sites 2 months after fire:A,
Severely burned area (stand no.002);.!!.,lightly burned patches among moderately
burned areas (stand no.006).
At the end of the first growing season after
fire,willows (mostly Scouler)averaged 1,181
stems/ha;other tall shrubs (mostly prickly
rose)averaged 625 stems/ha.Low shrubs (bog
blueberry and Labrador-tea)covered,on the
average,I percent of the area,herbs (mostly
reedgrass and cloudberry)covered an addi-
tional I percent,while mosses and lichens
together covered less than I percent of the
ground.Charred material was visible on 96
percent of the forest floor.Rev~getation had
begun but areas still looked mostly black.
75
B
76
figure 21.-:v1oss-hero stage on
black spruce sites:A.Low
shrubs and bare patches domi-
nate the forest floor in this
4-year-old stand (no.109)whi ch
nad been lightly to moderately
burned;13.a 3-year-old black
spruce stand (BS-3H)which had
been severely burned.
2.-The moss-herb stage (1-5 years after fire)
is a time of introduction and expansion of spe-
cies (fig.21).The number of species present
will double during this stage.In addition to
the species found at the end of the newly
burned stage.black spruce.quaking aspen.
paper birch.numerous willow species.resin
birc h.mount ain-cra nber ry.C er a todon pur-
pureus.and Marchantia polymorpha were
com mono Ceratodon purpureus.Marchantia
polymorpha.and all tree seedlings do best on
areas of moist mineral soil.Shoots appear on
both mineral soil and organic surfaces.pro-
vi ded vegetative parts exist underground.In
2-year-old stands,the organic layer averaged
15 cm in depth,and charred surfaces remained
visible on 76 percent of the forest floor.The
unshaded and blackened ground is an excellent
heat sink.Consequently,both the active thaw
zone and the depth to permafrost increase.
Densities averaged 17,954 stems/ha for black
spruce;10,901 for q,.faking aspen (sucker shoots
and seedlings),and 355 seedlings/ha for paper
birch (tables 23 and 28,p.82 and 92).Wil-
lows (one-half diamondleaf and one-fourth
Scouler)averaged 1.392 stems/hal whereas
other tall shrubs (mostly prickly rose and resin
birch)averaged 3.362.Low shrubs (mostly bog
blueberry,Labrador-tea,and mountain-
cranberry)covered,on the average,10 percent
of the area,and herbs (mostly reedgrass,
cloudberry,and woodland horsetail)covered II
percent.Mosses (mostly Ceratodon purpureus,
Sphagnum spp.,and Polytrichum spp.)covered
14 percent of the are a.
With time,many plants will spread into sur-
rounding areas and the taller growing species
will overtop the remaining vegetation;the tall
shrub-sapling stage will develop.
3.-During the tall shrub-sapling stage (5-30
years after fire),the vegetation is dominated
by tall shrubs and/or saplings in the overstory
with mosses,herbs,low shrubs,and tree seed-
lings below (fig.22).The vegetation is basi-
cally a continuation of that established earlier,
but additional species become established.Li-
chens are sometimes present but only in small
amounts.
Ten years after fire,willows,the most visually
dominant vegetation in the stands studied,
averaged 14,859 stems/ha and stood 1-5 m tall
(tables 24 and 28,p.84 and 92).Half the
willows were Bebb,the other half mostly
Scouler,diamondleaf,grayleaf,littletree,and
feltleaf.Other tall shrubs (one-third prickly
rose and one-third resin birch)averaged 5,977
stems/ha.Saplings (mostly quaking aspen)
averaged 1,461 stems/ha;seedlings (over one-
half black spruce and one-third hardwoods)
averaged 22,589.The lower growing vegeta-
tion was dominated by mosses (mostly Cerato-
don purpureus),herbs (mostly reedgrass and
fire weed),and low shrubs (bog blueberry,
Labrador-tea,and mountain-cranberry).Total
cover averaged 37,18,and 15 percent for
mosses,herbs,and low shrubs,respectively.
Charred surfaces w.:re still visible on 20 per-
cent of the area and deadfall litter covered
about half the ground.The organic layer aver-
aged 17 cm in depth,and the active thaw zone
extended to a depth of 82 cm.
As this stage advances,herbs become less ex-
tensive,low shrubs and mosses cover increas-
ingly more area,while saplings grow into trees.
4.--The dense tre e stage (30-55 years after
fire)is characterized by numerous young trees
in the overstory and extensive patches of low
shrubs,feathermosses,and lichens below
(fig.23).Other mosses,Polytrichum spp.and
Dicranum spp.,occur in small amounts.Tall
shrubs and herbs are sometimes present.Lit-
ter occurs but is rapidly incorporated in the
moss layer.
Figure 22.-Tall shrub-sapling
stage on black spruce sites.This
is a 23-year-old spruce-hardwood
stand (no.146).
Figure 23.-Dense tree stage on
black spruce sites.This 70-year-
old black spruce/feathermoss-
Ii chen stand (n o.132)has 2,080
tre es/na.
77
Trees (mostly black spruce)in 50-year-old
stands sampled averaged 2,595 stems/ha,
5A-cm d.b.h.,and 5-7 m tall (tables 25 and 28,
p.86 and 92).Saplings (mostly black spruc e)
averaged 1,682 stems/ha.Low shrubs (one-
half mountain-cranberry,one-fourth bog blue-
berry,and one-fourth Labrador-tea)covered,
oil the average,32 percent of the ground.
Mosses covered 60 percent of the forest floor.
Of the mosses,Pleurozium schreberi domi-
nated with an average cover of 36 percent;
Hylpcoiriium splendens,Sphagnum spp.,Poly-
trichum spp.,and Dicranum spp.occurred in
lesser amounts.Lichens (one-fourth Peltigera
spp.,one-fourth Cladina spp.,and one-fourth
Cladoniaspp.)covered 18 percent of the area.
Willows,mostly Scouler,were infrequent aver-
aging 1,261 stems/ha.Other tall shrubs (resin
birch,prickly rose,and American green alder)
averaged 5,396.Herbs (mostly reedgrass,
cloudberry,and Geocaulon Iividum),covered 5
percent of the ground.Litter was visible on
23 percent of the forest floor and logs on 6
percent.Charred ground was no longer ex-
posed.The depth of the organic layer aver-
aged 17 cm,and the permafrost table lay
82 cm below the surface.
As stands of the dense tree stage develop,
trees self-thin,the survivors increase in height
and diameter,and the feathermoss and low
shrub layers continue to expand.
78
Snags,dead lower branches,and a well-
developed layer of low shrubs,feathermosses,
and lichens make these stands flam mabie.
Fire terminates succession in many stands dur-
ing this stage.Other stands evolve into either
the hardwood-spruce stage or the spruce stage,
depending on the presence or absence of quak-
ing aspen or paper birch.
5.--The mixed hardwood-spruce stage (56-90
years after fire)is characterized by a mixed
canopy of black spruce,quaking aspen,and/or
paper birch (see figs.9 and 10).The hard-
woods sometimes dominate but more often do
not.In either case,this is the period in which
the hardwood trees are mature.As the stage
progresses,the hardwoods will stagnate and
die.On the forest floor,prickly rose,low
shrubs,a few herbs,and fea thermosses are
usually found.In general,when few hardwoods
are present,feathermosses cover extensive
areas of the forest floor.But when hardwoods
are numerous,leaf litter,not feathermoss,
dominates the forest floor.
The stands studied averaged 70 years in age.
Trees averaged 2,211 stems/ha and were one-
fourth hardwoods and three-fourths black
spruce (tables 26 and 28,p.88 and 92)••
Quaking aspen averaged I 5.6-em d.b.h.,paper
birch 11.9-cm d.b.h.,and black spruce 7.3-cm
d.b.h.All trees were 5-15 m tall.Willows
(mostly Bebb)averaged 1,136 stems/ha,other
tall shrubs (two-thirds prickly rose and one-
third American green alder)averaged 3,920,
and tree seedlings (mostly black spruce)aver-
aged 10,125.Low shrubs (mostly mountain-
cranberry and bog blueberry)covered,on the
average,17 percent of the area,herbs (mostly
reedgrass and bunchberry)covered 6 percent,
and mosses (half Pleurozium schreberi and half
Hylocomium splendens)covered 7 percent.
Litter covered 46 percent of the forest floor
and logs were found on 5 percent of the ground
surface.The organic layer averaged 14 cm in
thickness and depth to permafrost was 57 cm.
As this stage ages,the hardwoods stagnate and
die,producing increasingly pure stands of
spruce.Like stands in the dense tree stage,
spruce-hardwood stands are quite fl am mabIe
because of both live and dead material on the
forest floor.Each year,fire burns many
stands in this development stage.In the ab-
sence of fire,however,the spruce stage will
evolve.
6.--The spruce stage (91-200+years after fire)
is the oldest of the mesic black spruce stages.
The overstory is mostly black spruce,although
in a few locations white spruce and relic paper
birch may occur (see figs.II and 12).Ameri-
can green alder,smaller black spruce,and
sometimes prickly rose form a mid-height
layer beneath the trees.The forest floor is
dominated by feathermosses,Sphagnum spp.,
low shrubs,litter,and herbs.Permafrost is
frequently present.As the stand ages,the
mounds of Sphagnum spp.become larger,the
moss layer thicker,and the permafrost table
closer to the soil surface.
This stage is seldom found in the forest land-
scape since most stands succumb to fire be-
fore they develop to this point;however,they
do exist.Those surveyed in this study aver-
aged 121 years in age.Black spruce trees
averaged 1,800 stems!ha,15.2-cm d.b.h.,and
II m in height (tables 27 and 28,p.90 and
92).Saplings and seedlings (again mostly
black spruce)averaged 225 and 4,719 stems!
ha,respectively.Many so-called seedlings are
really layerings or lower tree branches that
rooted and turned skyward after they were
buried by the thickening moss layer.Tail
shrubs (two-thirds American green alder and
one-third prickly rose)averaged 7,750 stems!
ha.Low shrubs (one-half mountain-cranberry
and one-fourth Labr·ador-tea)covered,on the
average,29 percent of the forest floor,while
herbs (mostlyreedgrass and Geocaulon
lividum)covered 16 percent.Mosses (mostly
Pleurozium schreberi and Hylocomium
splendens)covered 80 percent and lichens
(mostly Cladina rangiferina and Cetraria
cucul1ata)covered 2 percent of the forest
floor.Litter was visible on 18 percent of the
forest floor,and logs on an additional 6 per-
cent.The organic layer averaged 16 cm in
depth.Permafrost was found 59 cm beneath
the ground surface.
These stands will live until burned or impacted
by other disturbances.As they age,the moss
layer continues to thicken,the soil tempera-
ture slowly drops,the perm afrost table moves
closer to the surface,and growth stagnates.
The oldest stands in this study were around
200 years old.
Tables 22-27 are grouped together"on p.80-91
to aid the reader in following the succession of
common species on mesic black spruce sites
through the six developmental stages.A
summary appears in table 28,p.92.
79
Table 22-Quantitative description of the newly burned st~ge of plant succession on mesic black spruce sites in the taiga of
interior Alaska.by dominant plant species and litter comp:onent Y
Quantitative description of the newly burned stage
Species and litter
component y Fre quency 'if Cover if Density ~D.b.h.~
Mean
Standard
deviation Mean
Standard
deviation Mean
Standard
deviation Mean
Standard
deviation
-----------Percent-----------Stems/ha Centimeters
Table 22-Quantitative description of the newly burned stage of plant succession on mesic black spruce sites in the taiga of
interior Alaska,by dominant plant species and litter component l!(continued)
Quantitative description of the.newly burned stage
Spec ies and Ii tt er
component ~Frequency ~Cover if Density ~D.b.h.~
Mean
Standard
deviation Mean
Standard
deviation Mean
Standard
deviation Mean
Standard
deviation
- - - - - - - - - - -Percent - - - - - - - - ---Stems/ha Centimeters
Mosses:
Aulacomnium palustre 0 0 0 0
Aulacomnium turgidum 0 0 0 0
Ceratodon purpureus 0 0 0 0
Dicranum spp.0 0 0 0
Drepanocladus uncinatus 0 0 0 0
Hylocomium splendens 0 0 0 0
Marchantia polymorph a 0 0 0 0
Pleurozium schreberi 0 0 0 0
P olytri chum spp.13 19 7/7/
Sphagnum spp.0 0 -0 -0
Unidentified moss 3 6 2!2!
Li chens:
Cetraria cucullata 0 0 0 0
Cetraria islandica 0 0 0 0
Cladina arbuscula 0 0 0 0
Clad ina rangiferina 2 3 7/7/
Cladonia spp.9/0 0 -0 -0
Nephroma arctlcum 0 0 0 0
P eltigera aphthosa 0 0 0 0
P eltigera spp.J!!j 2 3 2!2!
Litter components:
Charred material 100 0 96 2
Leaves and twigs 98 3 8 I .
Dead wood and
fallen logs 100 0 2
1/Number of stands sampled:3;age:mean 5 weeks after fire (standard deviation 0);number of species found:mean
i2 (standard deviation 3);depth of organic layer:mean II em (standard deviation 8);depth of active thaw zone:mean
49 em (standard deviation 9).
2/Only species with a frequency of at least 30 percent in at least I stand are listed in tables 22-27.Not all of those
species occur in every stage of succession;all are listed for each stage,however,to enhance comparison-bf their
development.
3/The percent of plots in which a given species occurs.It is based on the equation:Frequency =I (mean stand
frequency value for a species)7 total number of stands sampled.Values have been rounded to the nearest whole number.
4/The percent of area shaded by the canopy of a given species or litter component.It is based on the equation:Cover
=-1 (mean stand cover value for a species)';total number of stands sampled.Values have been rounded to the nearest
whole number.
5/The computed or counted number of stems occurring in a given area.It is based on the equation':Density,:".I (mean
stand density value for a species)';total number of stands sampled.Values have been rounded to the nearest whole
number.
6/D.b.h.is the diameter of a tree at breast height.The values given are for trees 2.5 em in d.b.h.or larger a.nd are
based on the equatio.n:D.b.h.=I (mean d.b.h.values for a species in a stand)';total number of stands sampled.
2!Less than 0.5 percent.
~Includes Lycopodium clavatum.
Y Includes Cladonia amaurocraea,So:alpestris,and Cladina spp.
~Includes Peltigera canina.
',81
Table 23-Quantitative description of the moss~herb stage of plant succession on mesic black spruce sites in the taiga of
interior Alaska,by dominant plant species and litter component!!
Quantitative description of the moss-herb stage
Species and litter
component y Frequency ~Cover ~Density ~D.b.h.~
Mean
Standard
deviation Mean
Standard
de viation Mean
Standard
deviation Mean
Standard
deviation
- - - - - - - - - - -Perc ent - - - - - - - - ---Stems/ha Centimeters
Tree layer:
Betula papyrifera-
Mature trees 0 0 0 0
Saplings 0 0 0 0
Seedlings 2 4 355 1,263
Picea glauca-
~ture trees 0 0 0 0
Saplings 0 0 0 0
Seedlings 0 0 0 0
Picea mariana-
Mature trees '!J (23)(39)(48)(154)(6.8)(1.4)
Saplings (23)(40)(13) (23)(0.6) (0.9)
Seedlings 58 35 17,954 14,972
Populus tremuloides-
Mature trees 0 0 0 0
Saplings 0 0 0 0
Seedlings 6 23 10,901 45,443
Tall shrub layer:
Alnus cri spa 4 8 434 1,168
Alnus tenuifolia 0 0 0 0
Betula glandulosa 27 27 993 1,204
Rosa acicularis 14 23 1,928 6,227
Rubus idaeus 8/1 7 29
Salix alaxensis -0 0 0 0
Salix arbusculoides 0 0 0 0
Salix bebbiana 3 12 118 516
Salix glauca ~1 59 258
Salix planifolia
ssp.pulchra 10 12 728 869
Sa Ii x scoul eriana 2 7 454 1,979
Other Salix spp.I 4 33 101
Low shrub layer:
Empetrum nigrum 4 8 8/8/
Ledum decumbens 16 22 8/-I
Ledum groenlandicum 65 30 -3 3
Vaccinium oxycoccus 17 20 I 1
Vaccinium uliginosum 62 32 3 3
Vaccinium vitis-idaea 53 35 2 3
Herb layer:
Calamagrostis spp.63 24 3 6
Cornus canadensis 7 12 8/8/
Epilobium angustifolium 8 8 8/8/
Equisetum arvense 3 10 8/8/
Equisetum scirpoides 4 16 8/8/
Equisetum sylvaticum 65 40 -4 -4
Geocaulon lividum 2 5 8/ 8/
Lycopodium annotinum 9/~I 8/8/
Mertensia paniculata I 4 8/8/
Petasites frigidus 9 10 8/8/
Rubus chamaemorus 54 35 -2 -2
See footnotes at end of table.
82
Table 23-Quantitative description of the moss-herb stage of plant succession on mesic black spruce sites in the taiga of
interior Alaska,by dominant plant species and litter component!J _(continued)
Quantitative description of th«:moss-herb stage
Mosses:
Aulacomnium palustre 10 14 1 I
Aulacomnium turgidum 0 0 0 0
Cera.todon purpureus 37 39 6 10
Dicranum spp.2 5 8/8/
Drepanocladus uncinatus 0 0 -0 -0
l-Iylocomium splendens 2 3 8/I
Marchantia polymorpha 6 6 8/8/
Pleurozium schreberi 13 18 -I -2
Polytrichum spp.71 27 2 2
Sphagnum spp.19 22 4 5
Unidentified moss 9 14 ~~
Lichens:
Cetrari a cucullata I 5 8/ 8/
Ce.traria islandica I 2 8/8/
Cladina arbuscula I 2 8/8/
Cladina rangiferina 2 5 8/8/
Cladonia spp.10/6 12 8/8/
Nephroma arcticum I 2 8/8/
Peltigera aphthosa I 2 8/8/
Peltigera spp.!!J 4 10 !J !J
Litter components:
Charred material 97 6 79 13
Leaves and twigs 98 7 17 17
Dead wood and
fallen logs 98 5 4 3
Standard
deviation
D.b.h.§I
Centimeters
Mean
Standard
deviation
Stems/ha
Density ~
Mean
Standard
deviation
Cover ~
Mean
Standard
deviation
Frequency ~
Mean
-----------Percent -----------
Species and Ii tter
component ~
1/Number of stands sampled:19;age:mean 2 years after fire (standard deviation 2);number of species found:mean
i2 (standard deviation 5);depth of organic layer:mean 15 cm (standard deviation 7);depth of active thaw zone:mean
90 cm (standard deviation 39).
2/Only species with a frequency of at least 30 percent in at least 1 stand are listed in tables 22-27.Not all of those
species occur in every stage of succession;all are listed for each stage,however,to enhance comparison g,f-their
development.
3/The percent of plots in which a given species occurs.It is based on the equation:Frequency =I (mean stand
frequency value for a species)';'total number of stands sampled.Values have been rounded to the nearest whole number.
4/The percent of area shaded by the canopy of a given species or litter component.It is based on the equation:Cover
=-1 (mean stand cover value for a species)';total number of stands sampled.Values have been rounded to the nearest
whole number.
5/The computed or counted number of stems occurring in a given area.It is based on the equation,:Density =I (mean
stand density value for a species)';total number of stands sampled.Values have been rounded to the nearest whole
number.
6/D.b.n.is the diameter of a tree at breast height.The values given are for trees 2.5 cm in d.b.h.or larger and are
based on the equation:D.b.h.=I (mean d.b.h.values for a species in a stand)';total number of st~nds sampled.
7.J Numbers in parentheses indicate the number of trees that originated before the fire.
!!Less than 0.5 percent.
~Includes Lycopodium clavatum.
J!llinciudes Cladonia amaurocraea,£:alpestris,and Cladina spp.
!!J Includes Peltigera canina.83
Table 24-Quantitative description of the tall shrub-sapling stage of plant succession on mesic black spruce sites in the
taiga of interior Alaska,by dominant plant species and litter;component y
Quantitative description of the tall shrub-sapling stage
Species and Ii tter
component ~Frequency y Cover ~Density ~D.b.h.~
Mean
Standard
deviation Mean
Standard
de viation Mean
Standard
deviation Mean
Standard
deviation
-----------Percent -----------Ste ms/ha Centimeters
Tree layer:
Betula papyrifera-
~ure trees 2 5 I 2
Saplings 16 33 76 247
Seedlings 17 23 1,262 2,017
Picea glauca-
~ture trees '!J (3)(9)(I)(2)
Saplings 6 16 2 5
Seedlings 14 30 1,631 3,606
Picea mariana~
Mature trees (8)(20)(2)(5)
Saplings 8 18 4 7
Seedlings 40 40 12,881 29,251
Populus tremuloides-
Mature trees (5)(22)(43)(195)
Saplings 15 34 1,377 5,930
Seedlings 27 36 6,012 18,131
Tall shrub la yer:
Alnus crispa 3 6 387 1,055
Alnus tenuifolia I 4 310 1,418
Betula glandulosa 10 15 2,262 4,317
Rosa acicularis 33 24 2,952 3,320
Rubus idaeus 3 8 66 200
Salix alaxensis 1 2 25 85
Salix arbusculoides II 24 1,804 5,351
Salix bebbiana 25 35 6,280 12,243
Salix glauca 9 23 1,458 5,453
Salix planifolia
ssp.pulchra 8 14 1,905 5,864
Salix scouleriana 8 14 1,857 4,148
Other Salix spp.14 29 1,530 3,809
Low shrub layer:
Empetrum nigrum 2 9 8/8/
Ledum decumbens I 3 8/-I
Ledum groenlandicum 39 34 -6 9
Vaccinium oxycoccus 8/1 8/8/
Vaccinium uliginosum 40 30 -5 -6
Vaccinium vitis-idaea 39 33 3 4
Herb layer:
Calamagrostis spp.57 28 5 6
Cornus canadensis 23 24 2 3
Epilobium angustifolium 63 33 3 ~
Equisetum arvense 9 35 I 3
Equisetum scirpoides 23 32 2 3
Equisetum sylvaticum 13 26 2 5
Geocaulon lividum I 4 8/ 8/
Lycopodium annotinum 9/0 0 -0 -0
Mertensia paniculata 8 16 I 2
Petasites frigidus 5 12 8/8/
Rubus chamaemorus 7 15 !J -2.
See footnotes at end of table.
84
3.8 1.4
1.2 0.6
(11.8)(4.8)
1.2 0.6
(8.6)(3.9)
1.5 0.6
(5.2)(0)
0.9 0.4
Table 24-Quantitative description of the tall shrub-sapling stage of plant succession on mesic black spruce sites in the
taiga of interior Alaska,by dominant plant species and litter component JJ (continued)
Quantitative description of the<tall shrub-sapling
Frequency ~
Standard
deviation
D.b.h.<~
f
Mean
Standard
deviation
Density ~
Mean
Standard
deviation
Cover ~
Mean
Standard
deviationMean
Species and litter
component 'Y
- - - - - - - - - - -Percent - - - - - - - - ---Stems/ha Centimeters
Mosses:
Aulacomnium palustre 19 32 2 5
Aulacomnium turgidum 8 22 2 8
Ceratodon purpureus 68 34 22 24
Dicranum spp.2 5 8/8/
Drepanocladus uncinatus I 3 8/8/
Hylocomium splendens 2 5 8/8/
Marchantia polymorpha 12 21 -2 -4
Pleurozium schreberi 6 12 81 I
Polytrichum spp.52 35 -8 15
Sphagnum spp.I 4 81 I
Unidentified moss 5 12 -I I
Licnens:
Cetraria cucullata 0 0 0 0
Cetraria islandica 0 0 0 0
Cladina arbuscula 0 0 0 0
Cladina rangiferina I I 8/8/
Cladonia spp.101 7 16 8/-I
Nephroma arcticum 0 0 -0 0
P eltigera aphthosa 9 20 I I
Peltigera spp.!.JJ 22 29 2 3
Litter components:
Charred material 50 41 20 29
Leaves and twigs 97 12 48 25 .L
Dead wood and
fallen logs 76 25 6 3
II Number of stands sampled:21;age:mean 10 years after fire (standard deviation 6);number of species found:mean
i6 (standard deviation II);depth of organic layer:mean 10 cm (standard deviation 4);depth of active thaw zone:mean
83 cm (standard deviation 21).
21 Only species with a frequency of at least 30 percent in at least I stand are listed in tables 22-27.Not all of those
species occur in every stage of succession;all are listed for each stage,however,to enhance comparison 91 their
development.
31 The percent of plots in which a given species occurs.It is based on the equation:Frequency =1:(mean stand
frequency value for a species)-total number of stands sampled.Values have been rounded to the nearest whole number.
4/The percent of area shaded by the canopy of a given species or litter component.It is based on the equation:Cover
';-1:(mean stand cover value for a species)-total number of stands sampled.Values have been rounded to the nearest
whole number.
5/The computed or counted number of stems occurring in a given area,It is based on the equation:Density:=1:(mean
stand density value for a species)-total number of stands sampled.Values have been rounded to the nearest whole
number.
61 D.b.h.is the diameter of a tree at breast height.The values given are for trees 2.5 cm in d.b.h.or larger and are
based on the equation:D.b.h.=1:(mean d.b.h.values for a species in a stand)-total number of stands sampled.
JJ Numbers in parentheses indicate the number of trees that originated before the fire.
!J Less than 0.5 percent.
2J Includes Lycopodium clavatum.
"-lEi Includes Cladonia amaurocraea,C.alpestris,and Cladina spp.
!.JJ Includes Peltigera canina.85
Table2S-Qllantitative description of the dense tree stage of plant succession on mesic black spruce sites in the taiga of
interior Alaska,by dominant plant species and litter component.!}
-Quantitative description of the dense tree stage
Species and litter
component Y Frequency 'if Cover ~Density ~D.b.h.E.!
Mean
Standard
deviation Mean
Standard
deviation Mean
Standard
deviation Mean
Standard
deviation
- - - - - - - - - - -Percent - - - - - - - - ---Stems/ha Centimeters
Tree layer:
Betula papyrifera-
Mature trees II 26 39 62
Saplings 8 20 4 8
Seedlings I 3 42 97
Picea glauca-
----,;ti'"tu retrees 3 5 30 46
Saplings 6 9 22 67
Seedlings 2!I 21 72
Picea mariana-
Mature trees 86 26 2,163 1,408
Saplings 83 32 1,652 1,182
Seedlings 77 33 11,708 9,430
Populus tremuloides-
Mature tre es 17 33 358 736
Saplings I I I I
Seedlings 3 6 240 534
Tall shrub la yer:
Alnus crispa 8 15 822 1,773
Alnus teniiITolia 0 0 0 0
Betula glandulosa 16 30 2,750 4,979
Rosa acicularis 21 21 1,698 2,013
~ubus idaeus 0 0 0 0
Salix alaxensis I 3 21 72
Salix arbusculoides 0 0 0 0
Salix bebbiana 2 4 42 III
Salix glauca 0 0 0 0
Salix planifolia
ssp.pulchra 5 12 292 752
Salix scouleriana 3 7 458 1,255
Other Salix spp.5 II 448 1,055
Low shrub layer:
Empetrum nigrum 12 28 I I
Ledum decumbens 18 30 I 3
Ledum groenlandicum 68 32 6 4
Vaccinium oxycoccus 6 14 7/I
Vaccinium uliginosum 65 36 -8 8
Vaccinium vitis-idaea 96 8 15 4----
Herb layer:
Calamagrostis spp.50 38 I I
Cornus canadensis 13 19 7/7/
Epilobium angustifolium 4 12 7/-I
Equisetum arvense 25 34 7/7/
Equisetum scirpoides 6 12 7/7/
Equisetum sylvaticum II 25 7/-I
Geocaulon Iividum 28 30 -I 2
Lycopodium annotinum !!II 8 7/7/
Mertensia paniculata 0 0 -0 -0
Petasites frigidus 8 13 7/7/
Rubus chamaemorus 22 33 -I -2
See footnotes at end of table.
86
6.4 2.5
1.9 0.4
6.2 2.6
1.5 0.6
5.4 0.7
1.6 0.3
8.1 0.4
1.8 0.2
Table 25-Quantitative description of the dense tree stage of plant succession on mesic black spruce sites in the taiga of
interior Alaska,by dominant plant species and litter component JJ (continued)
Quantitative description of the"dense tree stage
Frequency ~
Standard
deviation
D.b.h'J~,
Mean
Standard
deviation
Density ~
Mean
Standard
deviation
Cover ~
Mean
Standard
deviationMean
Species and litter
component ~
-----------Percent -----------Stems/ha Centimeters
Mosses:
Aulacomnium palustre 17 26 2 5
Aulacomnium turgidum 2 6 7/7/
Ceratodon purpureus 2 3 -I 11
Dicranum spp.40 21 I -I
Drepanocladus uncinatus 14 23 7/I
Hylocomium splendens 45 26 10 8
Marchantia polymorpha 0 0 0 0
Pleurozium schreberi 90 10 36 19
Polytrichum spp.64 20 4 5
Sphagnu m spp.19 28 6 12
Unidentified moss II 14 !J 1
Lichens:
Cetraria cucullata 6 13 7/ 7/
Cetraria islandica 19 29 7/-I
Cladina arbuscula 16 28 -I 3
Cladina rangiferina 46 25 4 4
Cladonia spp.9/56 24 3 3
Nephroma arctlcum 13 14 1 2
P eltigera aphthosa 31 34 I 2
Peltigera spp.~45 26 4 I
Litter components:
Charred material 0 0 0 0
Leaves and twigs 100 I 23 24
Dead wood and
fallen logs 80 22 6 3
1/Number of stands sampled:12;age:mean 48 years after fire (standard deviation 9);number of species found:mean
33 (standard deviation 3);depth of organic layer:mean 17 cm (standard deviation 4);depth of active thaw zone:mean
82 cm (standard deviation 41).
2/Only species with a frequency of at least 30 percent in at least I stand are listed in tables 22-27.Not all of those
species occur in every stage of succession;all are listed for each stage,however,to enhance comparison O'f their
development.
3/The percent of plots in which a given species occurs.It is based on the equation:Frequency =1:(mean stand
frequency value fora species)7 total number of stands sampled.Values have been rounded to the nearest whole number.
4/The percent of area shaded by the canopy of a given species or litter component.It is based on the equation:Cover
~1:(mean stand cover value for a species)~total number of stands sampled.Values have been rounded to the nearest
whole number.
5/The computed or counted number of stems occurring in a given area.It is based on the equatioJ;l:Density =1:(mean
stand density value for a species)';total number of stands sampled.Values have been rounded to the nearest whole
number.
6/D.b.h.is the diameter of a tree at breast height.The values given are for trees 2.5 cm in d.b.h.or larger and are
based on the equation:D.b.h.=1:(mean d.b.h.values for a species in a stand)';total number of stands sampled.
!J Less than 0.5 percent.
!jlncludes Lycopodium clavatum.
~Includes Cladonia amaurocraea,.f:alpestris,and Cladina spp.
->
IO/lncludes Peltigera canina.
&1
Table 26-Quantitative description of the mixed hardwood-spr~cestage of plant succession on mesic black spruce sites in
the taiga of interior Alaska,by dominant plant species and liuh component!!
Quantitative description of the mixed hardwood-spruce stage
Species and litter
component Y Frequency ~Cover ~Density ~D.b.h.~
Mean
Standard
deviation Mean
Standard
deviation Mean
Standard
deviation Mean
Standard
deviation
--------- - -Percent - ---- ------Ste ms/ha Centi meters
Tree layer:
Betula papyrifera-
Mature trees 19 23 129 129
Saplings 8 II 4 9
Seedlings I 2 68 130
Picea glauca-
--rYiaiure tre es 6 8 49 87
Saplings 8 II 5 9
Seedlings !.J 2 II 38
Picea mariana-
Mature trees 85 20 1,550 1,183
Saplings 92 9 417 718
Seedlings 68 22 9,295 6,765
Populus tremuloides-
Mature tre es 30 43 470 678
Saplings 3 8 4 12
Seedlings 10 19 750 1,548
Tall shrub la yer:
Alnus crispa 15 22 1,557 2,456
AI nus tenuifolia 0 0 0 0
Betula glandulosa 0 0 0 0
Rosa acicularis 41 36 2,125 2,052
Rubus idaeus 0 0 0 0
Salix alaxensis 0 0 0 0
Salix arbusculoides 7/2 II 38
Salix bebbiana 12 22 682 1,336
Salix glauca !.J 2 23 75
Salix planifolia
ssp.pulchra 0 0 0 0
Salix scouleriana 4 8 295 725
Other Salix spp.I 4 125 414
Low shrub la yer:
Empetrum nigrum 7 II 7/ 7/
Ledum decumbens 1 3 7/7/
Ledum groenlandicum 35 32 -2 -4
Vaccinium oxycoccus 0 0 0 0
Vaccinium uliginosum 59 30 5 6
Vaccinium vitis-idaea 87 15 8 6
Herb layer:
Calamagrostis spp.56 27 2 2
Cornus canadensis 55 35 2 3
Epilobium angustifolium 7 -10 7/7/
Equisetum arvense 13 30 -I -2
Equisetum scirpoides 4 8 7/ 7/
Equisetum sylvaticum 5 13 7/7/
Geocaulon lividum 23 32 -I -I
Lycopodium annotinum 8/8 12 7/7/
Mertensia paniculata 7 10 7/7/
Petasites frigidus I 3 7/7/
Rubus chainaemorus 3 II !J !J
See footnotes at end of table.
88
11.9 4.2
1.7 0.4
10.7 4.4
1.6 0.4
7.3 1.5
1.5 0.2
15.6 4.6
1.4 0.2
Table 26-Quantitative description of the mixed hardwood-spruce stage of plant succession on mesic black spruce sites in
the taiga of interior Alaska,by dominant plant species and litter component y (continued)
Quantitative description of the mixed hardwood-spruce stage
Species and litter
component y Frequency ~Cover ~Density ~D.b.h.!J,
Standard Standard Standard Standard
Mean deviation Mean deviation Mean deviation Mean deviation
-----------Percent - ------ - ---Stemslha Centimeters
Mosses:
Aulacomnium palustre 2 3 71 I
Aulacomnium turgidum I 3 71 71
Ceratodon purpureus I 3 71 71
Dicranum spp.23 25 -I -2
Drepanocladus uncinatus 14 22 71 I
Hylocomium splendens 60 27 23 29
Marchantia polymorph a 0 0 0 0
Pleurozium schreberi 61 32 23 25
P olytri chum spp.34 33 I I
Sphagnum spp.2 8 71 I
Unidentified moss 13 17 Jj '!J
Lichens:
Cetraria cucullata 0 0 0 0
Cetraria islandica 8 24 71 I
Cladina arbuscula 8 26 -I 2
Clad ina rangiferina 13 15 71 I
Cladonia spp.91 25 23 -I 2
Nephroma arctlcum 15 27 I 2
P eltigera aphthosa 13 24 71 I
Peltigera spp.J!lj 23 30 -2 2
Litter components:
Charred material I '2 I 2 -.
Lea ves and twi gs 100 0 46 34
Dead wood and
fallen logs 74 30 5 3
II Number of stands sampled:II;age:mean 70 years after fire (standard deviation 26);number of species found:mean
31 (standard deviation 4);depth of organic layer:mean 14 cm (standard deviation 3);depth of active thaw zone:mean
57 cm (standard deviation 25).
y Only species with a frequency of at least 30 percent in at least I stand are listed in tables 22-27.Not a 11.of those
species occur in every stage of succession;all are listed for each stage,however,to enhance .comparison of their
development.
31 The percent of plots in which a given species occurs.It is based on the equation:Frequency =I (mean stand
frequency value for a species)-::total number of stands sampled.Values have been rounded to the nearest whole number.
41 The percent of area shaded by the canopy of a given species or litter component.It is based on the equation:Cover
=-I (mean stand cover value for a species):-total number of stands sampled.Values have been rounded to the nearest
whole number.
51 The computed or counted number of stems occurring in a given area.It is based on the equation!Density =I (mean
stand density value for a species)-;total number of stands sampled.Values have been rounded to the nearest whole
number.
61 D.b.h.is the diameter of a tree at breast height.The values given are for trees 2.5 cm in d.b.h.or larger and are
based on the equation:D.b.h.=I (mean d.b.h.values for a species in a stand)-;total number of stands sampled.
'!J Less than 0.5 percent.
~Includes Lycopodium clavatum.
2/Includes Cladonia amaurocraea,.f:alpestris,and Cladina spp.
J!lj Includes Peltigera canina.
89
Table 27-'-Quantitative description of the spruce stage of plant succession on mesic black spruce sites in the taiga of
interior Alaska,by dominant plant species and litter component if
Quantitative description of the spruce stage
Species and litter
component 11 Frequency ~Cover ~Density ~D.b.h.~
Mean
Standard
deviation Mean
Standard
deviation Mean
Standard
deviation Mean
Standard
deviation
-----------Percent -----..,-----Ste ms/ha Centi meters
Tree layer:
Betula papyrifera-
Mature tre es 6 8 26 30
Saplings 0 0 0 0
Seedlings I 2 31 62
Picea glauca-
~ure trees 9 14 88 128
Saplings 0 0 0 0
Seedlings 0 0 0 0
Picea mariana-
-Ma"ture tre es 99 2 1,680 473
Saplings 52 55 225 300
Seedlings 40 37 4,688 4,942
Populus tremuloides-
Mature tre es 0 0 0 0
Saplings 0 0 0 0
Seedlings 0 0 0 0
Tall shrub layer:
Alnus crispa 34 17 5,062 3,686
Alnus tenuifolia 0 0 0 0
Betula glandulosa 0 0 0 0
Rosa acicularis 39 48 2,656 3,161
Rubus idaeus 0 0 0 0
Salix alaxensis 0 0 0 0
Salix arbusculoides I 2 31 62
Salix bebbiana 0 0 0 0
Salix gl auca I 2 156 312
Salix planifolia
~pulchra 0 0 0 0
Salix scouleriana 0 0 0 0
Other Salix spp.I 2 31 62
Low shrub layer:
Empetrum nigrum 14 24 I 2
Ledum decumbens 16 32 2 3
Ledum groenlandicum 58 45 8 8
Vaccinium oxycoccus 9 18 7/I
Vaccinium uliginosum 42 40 -2 3
Vaccinium vitis-idaea 100 0 16 10
Herb layer:
Calamagrostis spp.78 26 4 4
Cornus canadensis 2 5 7/7/
Epilobium angustifoHum 0 0 -0 -0
E.quisetum arvense 6 10 7/7/
Equisetum scirpoides 21 42 -I -2
Equisetum syl vaticu m 49 54 4 5
Geocaulon Iividum 70 16 4 2
Lycopodium annotinum ~8 12 7/I
Mertensia paniculata 0 0 -0 0
Petasites frigidus 0 0 0 0
Rubus chamaemorus 24 44 2 4
See footnotes at end of table.
90
17.0 11.7
17..8 7.5
15.2 1.2
1.6 0.4
r ·..'",'"L'
~..;;~
~
Table 27--Quantitative description of the spruce stage of plant succession on mesic black spruce sites in the taiga of
interior Alaska,by dominant plant species and litter component J.J (continued)
Quantitative description of.the spruce stage
Species and litter
component Y Frequency ~Cover ~Density ~D.b.h.11
Mean
Standard
deviation Mean
Standard
deviation Mean
Standard
deviation Mean
Standard
deviation
- - - - - - - - - - -Percent - - - - - - - - ---
Mosses:
Aulacomnium palustre 9 12 I 2
Aulacomnium turgidum 0 0 0 0
Ceratodon purpureus 0 0 0 0
Dicranum spp.18 17 I 71
Drepanocladus uncinatus 15 17 71 7/
Hylocomium splendens 85 13 34 22
Marchantia polymorpha 0 0 0 0
Pleurozium schreberi 74 40 34 26
Polytrichum spp.26 34 2 3
Sphagnum spp.19 38 5 10
Unidentified moss 9 10 ?J ?J
Lichens:
Cetraria cucullata 0 0 0 0
Cetraria islandica 6 12 71 71
Cladina arbuscula 15 3 -I -I
Cladina rangiferina 14 28 I 2
Cladonia spp.91 16 6 71 71
Nephroma arcticum 0 0 -0 -0
I'eltigera aphthosa 2 3 71 71
P eltigera spp.J2.!16 26 Ii -I
Litter components:
Charred material 0 0 0 0
Leaves and twigs 100 0 18 10
Dead wood and
fallen logs 90 9 6 4
Ste mslha Centimeters
II Number of stands sampled:4;age:mean 121 years after fire (standard deviation 56);number of species found:mean
3i (standard deviation II);depth of organic layer:mean 16 em (standard deviation 5);depth of active thaw zone:mean
59 em (standard deviation 31).
21 Only species with a frequency of at least 30 percent in at least I stand are listed in tables 22-27.Not all of those
species occur in every stage of succession;all are listed for each stage,however,to enhance comparison oj their
development.
31 The percent of plots in which a given species occurs.It is based on the equation:Frequency =1:(mean stand
frequency value for a species)~total number of stands sampled.Values have been rounded to the nearest whole number.
41 The percent of area shaded by the canopy of a given species or litter component.It is based on the equation:Cover
';-1:(mean stand cover value for a species)';'total number of stands sampled.Values have been rounded to the nearest
whole number.
51 The computed or counted number of stems occurring in a given area;It is based on the equation:Density =1:(mean
stand density value for a species)~total number of stands sam pled.Values have been rounded to the nearest whole
number.
61 D.b.h.is the diameter of a tree at breast height.The values given are for trees 2.5 em in d.b.h.or larger and are
based on the equation:D.b.h.=1:(mean d.b.h.values for a species in a stand)-:-total number of stands sam pled.
?J Less tilan 0.5 percent.
~Includes Lycopodium clavatum.
~Includes Cladonia amaurocraea,.f:alpestris,and Cladina spp.
!!y Includes Peltigera canina.
91
Table 28-Summary of the quantitative descriptions of the 6 stages of plant succession on mesic black spruce sites In the taiga of Interior Alaska!!
Tall shrub-Mixed hardwood-
Newly burned stage Moss-herb stage sapling stage Dense tree stage spruce stage Spruce stage
Item
Standard Standard Standard Standard Standard Standard
Mean deviation Mean deviation Mean deviation Mean deviation Mean deviation Mean deviation
Stand age,years 0.1 0 2 2 10 6 48 9 70 26 121 56
Plant species found,
number 2/12 3 22 5 26 II 33 3 31 4 31 II
Deptho{organlc layer,
centimeters II 8 15 7 10 4 17 4 14 3 16 5
Depth of active thaw zone,
centimeters 49 9 90 39 83 21 82 41 57 25 59 31
Number of stems per hectare
Density:~~
Tree layer-
Mature tre es 0 0 H(48)(154)47 194 2,595 1,267 2,211 984 1,800 539
Saplings 0 0 13 23 1,461 5,915 1,682 1,204 430 718 225 300
Seedlings 0 0 29,210 43,669 22,589 32,098 12,062 9,077 10,125 6,501 4,719 4,972
Tall shrub layer-
Salix spp.1,042 1,181 1,392 1,948 14,859 15,733 1,261 1,460 1,136 1,414 218 438
Other tall shrubs 625 760 3,362 6,059 5,977 5,226 5,396 4,624 3,920 2,737 7,750 5,070
Percent
Cover:4/6/
Low Shrubs I I 10 9 15 15 32 14 17 8 29 22
Herbs 2 I II 8 18 14 5 3 6 3 16 6
Mosses 7/7/14 II 37 30 60 23 50 34 80 18
Lichens 7/7/I I 3 3 18 10 7 10 2 2
Litter components 106 -2 100 14 74 26 29 26 51 32 23 II
!!Number of stands sampled:newly 'burned,3;moss-herb,19;tall shrub-sapling,21;dense tree,12;mixed hardwood-spruce,II;spruce,4.
y.Also includes the 3 stages of tree development:mature,sapling,and seedling.When present,each stage of a species Is counted as I.
~'The computed or counted number of stems occurring in a given area.
~Totals may be off because of rounding and because data listed were only for the species.,occurring most frequently.;
E Numbers.In parentheses Indicate the number .of trees that originated befci.re the fire.
!!The percent of area shaded by the canopy of a given plan't layer or Iltt'ercomp~nent.
2!Less than 0.5 perc ent.
Patterns of Change
on Mesic Black Spruce Sites
As with white spruce sites,each develop-
mental stage on black spruce sites can be de-
scribed individually,yet together they form
patterns that change through tim e.Figure 24
illustra tes the changes;each graph in the fig-
ure is limited to one stratum.
Trees.begin as seedlings of black spruce or as
seedlings and suckers of quaking aspen or
paper birch.Young trees appear in the newly
burned stage,are present in greatest numbers
during the moss-herb stage,and decrease in
number thereafter (fig.24A).A small number
of seedlings and suckers become saplings and
trees;most of them die.Seedlings of black
spruce are more numerous than those of other
species throughout black spruce succession
(fig.24B).The hardwood seedlings develop
faster than black spruce.Most saplings in the
tall shrub-sapling stage are quaking aspen a-nd
paper birch,whereas most saplings in the
dense tree stage are black spruce (fig.24C).
Black spruce trees and saplings usually domi-
nate from the dense tree stage on (fig.24D).
Hardwood species occur during the dense tree
and mixed hardwood-spruce stages but rapidly
decrease in numbers thereafter.
Willows appear in the newly burned stage,
increase slowly to their greatest numbers in
the tall shrub-sapli ng stage,and decrease
thereafter (fig.24E).All willows follow this
general trend.Bebb willow was the most
extensive in the stands studied,but Scouler,
grayleaf,littletree,and diamondleaf willows
were also important.
The non-willow tall shrubs show four trends
(fig.24f).(I)Am erican green alder,appear-
ing in small quantities in the newly burned
stage,increases steadily in numbers to becom e
the most extensive non-willow tall shrub in the
spruce stage.(2)Prickly rose appears in the
newly burned stage,reaches greatest density
during the tall shrub-sapling stage,then de-
creases slightly and maintains that level.(3)
Resin birch appears in the newly burned stage
and increases slowly to greatest density in the
dense tree stage.Thereafter in this study,it
was found only near timberline.(4)American
red raspberry is present in small quantities in
the young successional stages but is not found
after the tree-dominated stages develop.
Low shrubs appear in the newly burned stages,
develop slowly but steadily through the tall
shrub-sapling stage,and provide the most cov-
er duri ng the dense tree and spruce stages (fig.
24G).They appear to be less important in the
mixed hardwood-spruce stage.All species
tend to follow this trend,although Labrador-
tea expands slightly faster than other species,
and bog blueberry may decrease slightly during
the spruce stage.Mountain-cranberry appears
to be the most extensive low shrub in the tree-
dominated stages.
Herb cover begins in the newly burned stages
and increases to peak early in the tall shrub-
sapling stage and again in the spru"ce stage
(fig.24H).Herb cover is less during the dense
tree and mixed hardwood-spruce stages.This
general pattern is the result of three over-
lapping trends:(I)species such as Geocaulon
lividum and Lycopodium spp.appear early,
i ncre ase slowly,and reach greatest cover in
the spruce stage;(2)species such as fire weed
and tall bluebell appear early,inc1ease rapidly,
develop greatest cover in the tall shrub-
sapl ing stage,and decline thereafter;and (3)
many species are present through all stages;of
tnese,reedgrass,cloudberry,and woodland
horsetail are the most common and extensive.
93
--Trees
----Saplings
-.-.-Seedlings
A.Tree categories32,000
28,000 /-.-._._
.-....--.24,000 /.-.......
./-.-.-.20,000 /_.
............,.
16,000 //-._._._._._
12,000 /._.-._._.
8,000 /-.-.-._.
/
4,0001.JL./_-.,;;-=--=-:.::-:=.-;;o--_-;;:,;-_-_-iiiiiioi-iiiiiioi-_-iiiii-~-~-~-=-::-=-=--=-:;-=-=-=-=-~-~-~-:;=-::-=-=-=-=-=-~-
Spruce
(90-200)
Hardwood-
spruce mix
(55-90)
--Betula papyrifera
--------Picea glauca
.•••••Picea mariana
--_·-Populus tremuloides
- - -Other species
Tall shrub-
sapling
Dense
tree
(5-30)(30-55)
Post-fire stage (years)
---Picea mariana
-'-'-Populus tremuloides
__-;-..::.:::'-&- - -Other species----::.--....-'\:,~/.----~
//~~//-&
//~
//'~-~//.~
/-~~
/-/~"~/-~
//~"'.....""l;,J:iiiol:l:.llltQ~._//q'
h·
.Moss-
herb
(1-5)
B.Seedlings
1,800 C.Saplings
1,60
1.400
1,200
1,000
800
60
40
200
O+--=-===-=~====::f----_,.----..,._---.....,
Newly
burned
(0-1)
32,000
28,000
24,000
20,000
16,000
12,000
8;000
4,00
Ol~----....,..------,r------.,.._----_r_----.....,
CD..
tV...
()
CD.r:...
CDa.
In
E
CD...en
figure 24.-Successional trends
on black spruce sites.Shown are
densities of A,tree categories;
B,seedlings;C,saplings;D,
trees;~tallShrubs,willow;and
.!:J tall shrubs,non-willow.Also
shown are the covers of G,low
shrubs;.!!.herbs;.!I mosses and
liverworts;j,lichens;and K,
litter.Other items shown are !:...
deptn of organic layer;M,thick-
ness of ground thaw zone;and N,
number of species present.Each
line represents the number
occurring of that unit.Graphs
with more than one line show
cumulative totals.
94
D.Trees2,800
2,400 A':"::..--__--Betula papyrifera ~"•.•-;.-._.:::::.-:-_
2,'000 .....'Picea mariana $..•••••-'-'-.---:--.........__$;_..•-.---.-~1,600 _·_·-Populus tremuloides 4'.~'.••..•••••••.••:-:-.....
- --Other species ..:Ii ;1,200 ~.'.IlII •800 .IlII.'.4 ••
400 .&.'
o .J-----....,....,;;;;;;;;,,;-iiii::::Ei::iiiiiiE:.i:==5::!;.~=~~.~.----..,..------,------,
--Salix arbusculoides
••••••Salix bebbiana
-·-·-Salix glauca
-------Salix planifolia
ssp.pulchra
_..-··-Salix scouleriana
- - -Other Salix spp.
Spruce
(90-200)
Tall shrub-Dense Hardwood-
sapling tree spruce mix
(5-30)(30-55)(55-90)
Post-fire stage (years)
Moss-
herb
(1-5)
--Alnus crispa
8 0 --- -Betula glandulosa,00 F.Tall shrubs,non-willow Rosaacicularis ./
7,000 -._.-Rubusidaeusand .~.'./.
6,000 ....,;..?::-..:.."'=:~-=-'':-'':':::._,_.other tall ./:•
.;.'"--__.........shrubs /:•5,000 ./;.~--.:..::::-./:.-::r>'"-'":::::..........4 000 0:,..0 -..;...."/.,.;"...--'/.'.
3 0 .~"".. . . . . . .. .,00 .~". .....'.......::::"~.".......
2 000 ~'0-,-.?'"••1'00~i·"'~·~:~~.~..~.~~~===:::====~====~_...:!.k~_..,
Newly
burned
(0-1)
Fi gure 24.-(conti nued)
95
35 G.Low shrubs
30 --Ledum decumbens,Empetrum nigrum,
25 and Vaccinium oxycoccus ......--:
•••••Ledum groenlandicum <..
20 -'-'-Vaccinium uliginosum . .
15 -----Vacciniumvitis-idaea - •_--"".'"------....,...,.~,..
10 /~--~-.._..~~....."".'"....;'
5 _.-'.J'..........oo • • • •",,-
.:..:...~._..-:-----------O..pc.:;";;";~--.,------r------,r------...,------
..'
Spruce
(150-300)
_.--'.-'.-.........--...-
Hardwood-
spruce mix
-.-.
Tall shrub-
sapling
Dense
tree
(5-30)(30-55)(55-90)
Post-fire stage (years)
Moss-
herb
(1-5)
--Calamagrostis spp.,Rubus chamaemorus,
20 H H .."and Equisetum sylvaticum
15 .erbs ... ....'.....Epilobium angustifolium,,Mertensia
.paniculata,and other
10 .'..~..:...-------··..herbs
5 ....'·_._._Geocaulon lividum and .•.••••........•.
.Lycopodium spp.,"_.._._._._._.-.-.-.-.-
Ol-t------.,......~...;....--,....=:.:.:·::.:.~.=.-~.~~~~;;",:.;;;;;;;..r..------,
16 J.Lic hens
14 /'
/.,'12 ---Cladina spp.//.•• "••:--,
10 _.-.-Cladonia spp./ •.,
P /.•••....
• • • •••eltigera spp.••.....8 /..,'....- - - -Other lichens / ./'........•.........
6 /......................
/.,/.....~.""
4 ,.-......
(../'-'-....
2 ~,(.......
.-r.~r:.•".~~"':':-.~.-rr"',II'.
O-t-::a;.......;:;;::::::.......~-rI;:::.;·;::.:,:'~.·:.:..~·-r..........iIiiIi·==·=-=·-=·r::------_r_-----_.,------.,
Newly
burned
(0-1)
80 I.Mosses and liverworts ;;
70 .._..Ceratodonpurpureus ,',"',................
--Hylocomium splendens ,':-'60 /.~~"••••..Marchantia polymorpha ~~"-":'-~':'''!;;;-P."'-~...
50 ~..;y"/------:~p.'-·-·-Pleurozium schreberi /Y"./'/-----~~~/•.>.-//'----_----::=.?40 -------Polytrichum spp..........,.../,
----Sphagnum spp.......-:~;.;;.,//
30 --Othermossesan~..::;:::·,:';"··,,//'.
20 liverworts ~:,.;..,,'"/-',/....~.,:~~..,,,",,"10 .'~:,.;....-------------;~.,,/...~.~-::-;~=::,;:.::.::.:_----".o ."""_~_._._._._._._._J1_."':....-:-=-:
..
G)
>o
CJ
~
C
G)
CJ..
G)
Q.
Figure 24.-(continued)
96
._._-_.------_._.--_.--_.-._--.-._-----_._._-....-_._.._.-.-----
--Charred material
,••••.•Leaves and twigs
-.-·-Dead wood and
fallen logs
.-.......
K.Litter
..........................
120..
CD 105 r----_
>90o
(J 75
60
45
30
15
o
20 L.Depth of organic layer
15 ._-
10
~5
.!O+-------r-----r-------r-----.....,.----......,CD
E.-~i 100 M.Thickness f round thaw zone
o 80
60.
40'
20
O-t------or------r------,...-------r------,
Figure 24.-(continued)
Spruce
(90-200)
Hardwood-
spruce mix
(55-90)
--Always present
•••.••Seral
Tall shrub-Dense
sapling tree
(5-30)(30-55)
Post-fire stage (years)
Moss-
herb
(1-5)
40 N.Species present ..............................30 .....................20 ......
10
O+------r------r-----.........----....,....-----,
Newly
burned
~(0-1)
:i~*"C:]
y~C('~(Uij
~~
;":;tn€
i ..
I CD
Q.
I ..
CD.c
-ii EJ
I ::J
Z
.~
~~
97
Mosses begin in the newly burned stage and in-
crease almost steadily to cover the most area
duri ng the spruce stage (fig.241).This trend is
reversed during the mixed hardwood-spruce
stage,when mosses tend to be slightly less ex-
tensive beneath hardwoods.This pattern is the
result of three overlapping trends.(I)Feath-
ermoss and Sphagnum species appear sometime
during the first three stages but increase si-
multaneously and suddenly with the emergence
of black spruce trees.Pleurozium schreberi
expands first and coVers the most area in the
dense tree stage.Hylocomium splendensex-
pands next most rapidly and codominates the
forest floor with Pleurozium schreberi there-
after.Sphagnum spp.increase more slowly
and dominate only in the wetter sites.(2)
Polytrichum spp.are always present but
amounts vary.(3)Ceratodon purpureus and
i~archantia polymorpha appear soon after fire,
expand rapidly to cover the greatest area
during the early tall shrub-sapling stage,and
decline rapidly thereafter.
Ground lichens all follow one pattern (fig.
24J).They appear slowly and increase grad-
ually to cover the.greatest area during the
dense tree stage,after which they slowly de-
cline.Peltigera spp.are the first to appear,
and they usually occur in the greatest
amounts.Cladina spp.and Cladonia spp.ac-
count for most of the remaining lichen cover.
On mesic sites in this studY,only small quan-
tities of lichens were found in stands repre-
senti ng the spruce stage of development.
Litter in the newly burned stage is composed
mostly of charred surfaces (fig.24K).With
time,these surfaces disappear and most are
covered by the end of the tall shrub-sapling
stage.Deadfall litter increases as vegetation
develops and is most abundant during the tall
98
shrub-sapl ing stage and again duri ng the mixed
hardwood-spruce stage,when deciduous and
annual leaf fall is greatest.Exposed logs are
always present on the forest floor.The area
they cover increases gradually,levels off dur-
ing the tall shrub-sapling stage,and stays
fairly constant thereafter.Dead trees fall and
become logs,old logs decay and are gradually
covered by moss.
Beneath the forest floor,patterns of change
also occur.Thickness of the organic layer and
the thaw zone above permafrost change (figs.
24L and M).The organic layer is thinnest im-
mediately after fire and increases with time.
On the other hand,thickness of the thaw zone
increases with time but only for a while.It
then slowly decreases until it reaches equi-
librium with the insulating vegetation layer
above.1m mediately after fire,the blackened
and burned surfaces absorb radiant energy,
raising soil temperatures and melting perma-
frost.This heatsink state continues until the
surface becomes less black and vegetation,
especially feathermoss,once again insulates
the ground from solar heating.In time,the
permafrost stops melting and may start
reforming.
The number of plant species present changes
with time (fig.24N).Species are found im-
mediately after fire.This number steadily
increases,with the greatest number occurring
duri ng the dense tree stage;thereafter the
number stabilizes or decreases slightly.Few
species are seral;that is,present only in the
younger stages of succession.Most species,
once they appear,remain throughout succes-
sion but vary in importance.The following
species,listed in approximate order of in-
creasing duration,come the closest to being
seral:Marchantia polym orpha,C eratodon
purpureus.fireweed,American red raspberry,
most willows,quaking aspen,and paper birch.
The result of succession on mesic black spruce
sites is a somewhat open stand of black spruce
trees under which are found American green
alder,mountain-cranberry,Labrador-tea,bog
blueberry,Geocaulon Iividum,reedgrass,
Pleurozium schreberi,Hylocomium splendens,
and Sphagnum spp.in varying amounts.The
feathermosses,Pleurozium schreberi and
Hylocomium splendens,dominate the forest
floor which is usually underlain by permafrost.
The six mature forest com munity types that
occur on black spruce sites can now be seen in
perspective.Each is the most mature phase of
its respective com munity type.This study
suggests,however,that in the absence of fire,
types 7 through 10 (see tabl e 2),or all the
black spruce found on mesic sites that have
been discussed,will become type 9,the Picea
mariana/Vaccinium uliginosum-Ledum groen-
landicu m/PI eurozium schreberi com munity
type.Since fire burns most areas before they
reach 100 years in age,and since most old~r
stands show at least some evidence of earlier
burni ng,type 9 may represent the vegetation
best able to withstand fire and not necessarily
the theoretical end point of succession.
Two types,I I and 12 (see table 2),do not
reflect mesic black spruce sites so were not
used in the-discussion of succession.They may
be important,however,because of what they
tell us about lichen cover.Type II,the Picea
mariana-Picea glauca/Betula glandulosa/lichen
com munity type,occurs near timberline.The
question is whether its extensive lichen cover
is due to its proximity to tundra,where lichens
may be ext ens ive,or to the presence of two
dominant age classes.The latter possibility
suggests that the most recent fire,which oc-
curred about 55 years ago,burned a 55-to
100-year-old spruce/lichen stand.At least
some of the lichens survived the fire and have
since expanded to produce what occurs today.
Type 12,the Pi cea mari ana/Sphagnum sP~.
Cladina community type,occurs on valley
bottoms in a muskeg-bog setting.Here trees,
lichens,and Sphagnum spp.occur on areas
raised above the water table by developing ice
lenses or by islands of bedrock.In these areas,
lichens are found in 60-and 130-year-old
stands.At least under these conditions,it
appears lichens do not die out as succession
advances.
Comparison of Patterns of Change
Succession on white spruce and on black spruce
sites is both similar and dissimilar.It may be
useful to compare the two processes.
I.Successional series of both white spruce
and mesic black spruce may pass through six
developmental stages:newly burned,moss-
herb,tall shrub-sapli ng,dense tree,hardwood
(or hardwood-spruce),and spruce.The length
of each stage varies,however,depending on
the growth rate and development of the taller
growi ng species present.The first three
stages last 20-25 years on white spruce sites
and 30-35 years on black spruce sites,or the
time it takes the trees to overtop the lower
growing vegetation.The hardwood stage on
white spruce sites lasts 50-100 years and on
black spruce sites 30-50 years,but may be
compl etely absent.In theory,the spruce stage
on both sites can last indefinitely.
.it
2.Revegetation for both successional seri,es
starts from shoots,seeds,spores,etc.,but
these propagules are not equally available on
all sites.Vegetative and in situ seed repro-
duction im mediately after fire tends to be
greater on black spruce sites than on white
spruce sites.
99
3.Most species occur on both white spruce
and black spruce sites;quaki ng aspen,paper
birch,prickly rose,mountain-cranberry,
bunchberry,reedgrass,fireweed,Pleurozium
schreberi,Hylocomium splendens,Ceratodon
purpureus,and Marchantia polymorpha are
some.No species are restricted to one site
type but some show a preference.White
spruce,high bushcranberry,twin-flower,and
field horsetail are good indicators of warm,
well-d,rained sites.31ack spruce,Sphagnum
spp.,bog blueberry,cloudberry,and woodland
horsetail are indicators of moister and cooler,
but still mesic sites.
4.Some species in both successional series
develop their greatest numbers and/or cover in
the early stages and decline or disappear in
later stages.Marchantia polymorpha,Cerato-
don purpureus,fireweed,and American red
raspberry follow this trend.In terms of den-
sity only,quaking aspen and paper birch fall in
this group.
5.Other species in both series develop their
greatest numbers and/or cover in the interme-
diate stages and decline or disappear there-
after.Bebb,gray"\eaf,and Scouler willows as
well as Peltigera spp.are important in the tall
shrub stage.Cladonia spp.and Cladina spp.
are important in the dense tree stage.And
quaking aspen and paper birch may be import-
ant in the dense tree and hardwood stages.
The lichen species are more extensive on black
spruce sites and the hardwood species on white
spruce sites.
100
6.Still other species attain their greatest
densities and cover in the spruce stage of both
successional seri es.Am eri can green alder,
tWin-flower,Geocaulon Iividum,and white
spruce (trees only)develop slowly and contin-
uously after they first appear.Pleurozium
schreberi,Hylocomium splendens,and Sphag-
num spp.expand very little during the first
three stages,expand explosively during the
dense tree stage,and hold their own or con-
tinue to expand thereafter.
7.Some species fluctuate but are~always
present.Prickly rose and reedgrass follow this
pattern on all sites,field horsetail and high
bushcranberry on white spruce sites,and
woodland horsetail and cloudberry on black
spruce sites.
8.Fire can terminate succession at any point.
Fire on black spruce sites is com mon,and
most sites burn before stands are 100 years
old.Fire on white spruce sites is less com mon,
and many white spruce stands are more than
100 years old.
9.Today's landscape is the product of succes-
sional changes.Each forest-dominated stand
is in one of the three tree-dominated stages.
Mature types 1,2,3,7,and 8 (see table 2)all
contain hardwood species,and stands typifying
them are exam pies of the hardwood stage of
development.Types 4,5,and 9-12 (see table
2)are primarily spruce-dominated.Stands of
these types are in the spruce stage of devel-
opment.
Metric Equivalents
°C =5/9 (OF -32)
I centimeter (cm)=0.39 inch
I meter (m)=3.28 feet
I hectare (ha)=2.4 7 acres
I cubic meter per hectare (m 3 /ha)
=14.29 cubic feet per acre
I kilometer (km)=0.62 mile
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Appendix
Sci"entific and
Common Names of Plants .§I
TREES:
Betula papyrifera Marsh.Yar.humilis
9/10/(Reg.)Fern.&Raup--
Larixlaricina (Du Roi)K.Koch
~glauca (Moench)Voss21 J.!lj
Picea mariana (Mill.)B.s.p.21 J..!!../
--.9/10/
Populus balsam Ifera L.--
Populus tremuloides Michx.9 /J!!.J
TALL SHRUBS:
Alnus crispa (Ait.)Pursh21
Alnus tenuifolia Nutt.
Betula glandulosa Michx.9 /
Betula glandulosa X B.papyrifera
Oplopanax horridus (Sm.)Miq.21
Rosa acicularis Lindl.9 /
Rubus idaeus L.Yar.strigosus
(Michx.)Maxim.
Salix alaxensis (Anderss.)COY.
Salix arbusculoides Anderss.
Salix bebbiana Sarg.9 /
Salix glauca L.~"../
8/Sources for names:trees,tall shrubs,and
low shrubs-Viereck and Little (1972)and
Kelsey and Dayton (1942);herbs-Hulten
(1968),Welsh (1974),and Kelsey and Dayton
(1942);mosses-Worley and Watuski (1970);
and lichens-Hale and Culberson (1970).
9/Species used in the reduced species list for
the clustering analysis of stands.
J.!ljSeedlings,saplings,and mature trees were
treated as separate entities in the cluster
analysis.
Paper birch
Tamarack,Alaska larch
White spruce
Black spruce
Balsam poplar
Quaking aspen
American green alder
Thinleaf alder
Resin birch,bog birch
Hybrid birch
DeYilsclub
Prickly rose
American red raspberry
Feltleaf willow
Littletree willow
Bebb willow
Grayleaf willow
105
Salix planifolia Pursh.ssp.pulchra
(Cham.)Argus 9/
Salix scouleriana Barratt9 /
Viburnum edule (Michx.)Raf.9 /
LOW SHRUBS:
Arctostaphylos uva-ursi (L.)Spreng.
Betula nana L.9 /--
Chamaedaphne calyculata (L.)Moench
Empetrum nigrum L.9 /
Ledum decumbens (Ait.)Small9 /
Ledum groenlandicum Oeder 9 /
Li nnaea borealis L.9 /
Ribes spp.
Spiraea beauverdiana Schneid.9 /
Vaccinium oxycoccus L.~
Vaccinium uliginosum L.9 /
Vaccinium vitis-idaea L.9 /
HERBS:
Calamagrostis canadensis (Michx.)
Beauv.~
Ca la magrostis sp p.9/
Carex spp.
Cornus canadensis L.9 /
Dryopteris dilatata (Hoffm.)Gral/
Epilobium angustifolium L.9 /
Equisetum arvense L.9 /
Equisetum pratense Ehrh.
Equisetum scirpoides Michx.9 /
106
Diamondleaf willow
Scouler willow
High bushcranberry
Bearberry
Dwarf arctic birch
Leatherleaf
Crowberry,black crowberry
Narrow-I eaf Labrador-tea,
sprawling crystaltea ledum
Labrador-tea,Labradortea ledum
Twin-flower,American twinflower
Currant
Beauverd spirea
Bog cranberry,small cranberry
Bo g blueberry,bog bi Iberry
Mountain-cranberry,cowberry
BI uejoint
Reedgrass
Sedge
Bunchberry,dwarf dogwood
Spinulose shield-fern,mountain
woodfern
Fireweed
Field horsetail,meadow horsetail
Meadow horsetail
Dwarf scouring-rush,sedgelike
horsetail
t~.
E ·I'L 9!qUlsetum sy vatlcum.~
Eriophorum vaginatum L.
Galium boreale L.
Galium triflorum Michx.
Geocaulon lividum (Richards.)Fern2J
Lycopodium annotinum L.
Lycopodium clavatum L.ssp.monospachyon
(Grev.&Hook.)Set.
,9!
Lycopodium complanatum L.-
lvtertensia paniculata (AiL)G.Don2l
Moehringia lateriflora (L.)Frenzl 9 !
Pedicularis labradorica Wirsing
P etasites fri gidus (L.)Fri es
Polygonum alaskanum (Small)Wright
Pyro la asarifolia Michx.
Pyrola chlorantha Sw.
Pyro la secunda L.
Rubus chamaemorus L.9 !
Streptopus amplexifolius (L.)DC.
MOSSES AND LIVERWORTS:
Aulacomnium palustre (Hedw.)
Schwaegr .2/
Aulacomnium turgidum (Wahlenb.)
Schwaegr.
Ceratodon purpureus (Hedw.)Brid.2J
Dicranum spp.
Drepanocladus uncinatus (Hedw.)Warnst.
Hylocomium splendens (Hedw.)B.S.G.9 !
l'vtarchantia polymorpha L.2/
Woodland horsetail,Sylvan horsetail
Tussock cottongrass,sheathed
cottensedge
Northern bedstraw
Sweet-scented bedstraw
(No com mon nam e)
Stiff cluhmoss
Running clubmoss
Ground cedar
Tall bluebell,panicle bluebell
Blunt-leaved sandwort
Labrador lousewort
Arctic sweet coltsfoot
Alaska wild rhubarb
Liverleaf wintergreen,alpine pyrola
Green pyrola
One-sided wintergreen sidebells
pyrola
Cloudberry
Clasping twisted-stalk,claspleaf
twistedstalk .I
(No common name)
(No com mon nam e)
(No common name)
(No common name)
(No common name)
Fea therm oss
(No common name)
107
Pleurozium schreberi (Brid.)Mitt.~
Polytrichum spp.9/JJJ
Ptilium crista-castrensis (Hedw.)De Not.
Rhytidiadelphus triquetrus (Hedw.)
Warnst.
Sphagnum spp.9/
LICHENS:
Cetraria cucullata (Bell.)Ach.2!
Cetraria islandica (L.)Ach.2!
Cetraria richardsonii Hook
Cladina arbuscula (WaIlL)Hale &
~~.Culb.(=Cladonia sylvatica (L.)
t-\offm.~
Cladina rangiferina (L.)Harm.
(=Cladonia rangITerina (L.)web.)2!
Cladonia gracilis (L.)Willd.
~~spp.9/
Nephro ma arcticum (L.)Torss.2!
Peltigera aphthosa (L.)Willd.
Peltigera canina (L.)Willd.2!
Peltigera spp.9/
..!.Jilncludes three species:Polytrichum
commune Hedw.,P.juniperinum Hedw.,and.!:
piliferum Hedw.-
108
F ea th er moss
(No common name)
Fea thermoss
Fea thermoss
(No common name)
(No common name)
(No common name)
(No common name)
Reindeer lichen
Reindeer Ii chen
(No common name)
(No commo,n name)
(No common name)
(No common name)
(No common name)
(No common name)
Foote,M.Joan.Classification,description,and dynamics
of plant communities after fire in the taiga of interior
Alaska.Res.Pap.PNW-307.Portland,OR:U.S.De-
partment of Agriculture,Forest Service,Pacific North-
west Forest and Range E'xperiment Station;1983.108 p.
One hundred thirty forest stands ranging in age from I
month postfire to 200 years were sampled and described
by successional series (white spruce and black spruce)and
by devel-opmental stage (newly burned,moss-herb,tall
shrub-sapling,dense tree,hardwood,and spruce).Pat-
terns of change in the two 5ucces-sional series are de-
scribed.In addition,12 mature forest communities are
described in quantitative and qualitative terms.
Keywords:Com munities (plant),classification (plant
communities),fire (-plant ecology,taiga,Alaska (interior).
ARLIS
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..