HomeMy WebLinkAboutCordova_Forest Inventory_2012
2012
Douglas Hanson
Department of Natural Resources
Division of Forestry
12/21/2012
Assessment of Woody
Biomass Energy Resources
in the Cordova Area
TABLE OF CONTENTS
I. Executive Summary .................................................................................................................................. 1
II. Objectives .................................................................................................................................................. 4
III. Methods ...................................................................................................................................................... 4
A. Base Imagery .......................................................................................................................................... 4
B. Vegetation Classification ..................................................................................................................... 4
C. Field Inventory Design ........................................................................................................................ 5
D. Data Summary ....................................................................................................................................... 5
E. Acreage Summary/GIS Analysis ........................................................................................................ 6
F. Description of Strata ........................................................................................................................... 6
1. Stratum 1, Sitka Spruce ................................................................................................................... 7
2. Stratum 2, Western Hemlock ....................................................................................................... 8
3. Stratum 3, Mixed Sitka Spruce/Black cottonwood ................................................................... 8
4. Stratum 4, Black Cottonwood ...................................................................................................... 9
G. Forest Volume Definitions ................................................................................................................. 9
1. Cubic and Board Foot Measurements ......................................................................................... 9
2. Ton Measurements ....................................................................................................................... 10
IV. Results ...................................................................................................................................................... 10
A. Volume Per Acre of Timberland.................................................................................................... 10
B. Sampling Error by Volume .............................................................................................................. 11
C. Log Grade ........................................................................................................................................... 12
D. Site Index............................................................................................................................................. 15
E. Timberland Area Age Class ............................................................................................................ 16
F. Regeneration ...................................................................................................................................... 17
G. Growth and Mortality Estimates ................................................................................................... 18
H. Volume of Timberland by Landowner .......................................................................................... 18
V. Economic Availability of Sustainable Biomass Fuels ....................................................................... 20
A. Current Delivered Costs ................................................................................................................ 20
B. Potential Accessible Biomass Volume by Slope Class ............................................................... 21
C. Annual Sustainable Biomass Yield by Slope Class ...................................................................... 24
VI. Volume Availability From Proposed Eyak Logging Road Brush Clearing .................................. 28
VII. Concentration of Biomass on a Portion of Eyak Corporation Lands ....................................... 29
I. Literature Cited ..................................................................................................................................... 30
LIST OF TABLES
Table 1. Inventory volume and acreage summary. .................................................................................... 2
Table 2. Inventory species and weight for poletimber and sawtimber. ............................................. 10
Table 3. Timberland net volume per acre by strata. ............................................................................. 11
Table 4. Gross cubic foot volume sampling error. ................................................................................ 11
Table 5. Puget Sound grading rules. ........................................................................................................... 13
Table 6. Log grade by species. .................................................................................................................... 14
Table 7. Site index by stratum and species. ............................................................................................. 16
Table 8. Average age by strata. ................................................................................................................... 16
Table 9. Number of trees per acre less than 5 inches dbh. ................................................................. 17
Table 10. Growth and mortality estimates. ............................................................................................. 18
Table 11. Project area timberland net volume by strata. ..................................................................... 19
Table 12. Accessible area Timberland Net Volume by Strata . ........................................................... 19
Table 13. Delivered cord prices by slope class. ...................................................................................... 21
Table 14. Accessible acreage by ownership class and strata. .............................................................. 21
Table 15. Cordova area accessible acreage and volume by slope class. ........................................... 22
Table 16. Annual volume availability by slope class and owner. ......................................................... 26
LIST OF FIGURES
Figure 1. Cordova area biomass vicinity map. ............................................................................................ 3
Figure 2. Stratum 1 sitka spruce (even Aged Young Growth). .............................................................. 7
Figure 3. Stratum 1 sitka spruce (Uneven Aged). ...................................................................................... 7
Figure 4. Stratum 2 western hemlock . ........................................................................................................ 8
Figure 5. Stratum 3 mixed sitka spruce/black cottonwood. ................................................................... 8
Figure 6. Stratum 4 black cottonwood. ....................................................................................................... 9
Figure 7. Accessible Timberland Strata distribution by area. ............................................................... 19
Figure 8. Accessible Biomass timber type map by slope class. ........................................................... 23
Figure 9. Delivered cost per cord. ............................................................................................................. 24
Figure 10. Delivered cost per ton. ............................................................................................................. 24
Figure 11. Cumulative annual volume availability by slope class to Cordova. .................................. 27
Figure 12. Supply curve for cords to Cordova. ...................................................................................... 27
Figure 13. Supply curve for tons to Cordova. ......................................................................................... 28
Figure 14. Eyak corporation timber types 0-15% slope. ....................................................................... 29
APPENDICES
Appendix A Acreage Summary by Stratum and Vegetation Type .................................................... A-1
Appendix B Per Acre Summary by Stratum and Species ..................................................................... B-1
Appendix C Stand Tables Per Acre by Strata and Species ................................................................. C-1
Appendix D Diameter/Height Relationships, Ten Year Growth, and Bark Thickness ................ D-1
Assessment of Woody Biomass Energy Resources in the Cordova Area
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I. EXECUTIVE S UMMARY
The Native Village of Eyak (NVE) is investigating the feasibility of using woody biomass to heat
various public buildings in Cordova. Potential sources of biomass include waste cardboard,
wood waste generated at a community burn pile, alder along logging roads and standing green
trees. This document focuses on quantifying the standing green tree biomass resource with
some added information on the potential for alder harvest. The inventory of the standing green
tree biomass resource utilizes a United States Forest Service (USFS) satellite image classified for
vegetation together with tree measurement plots installed by State Division of Forestry (DOF)
and NVE personnel. The project area generally coincides with the extent of the classified
satellite image which covers much of the Copper River Delta. From this extent, a subset of
potentially accessible biomass based on access, volume and topography was delineated. It is this
area that is analyzed and reported on in detail. Three major landowners in the area include the
Eyak Corporation, U.S. Forest Service and State of Alaska.
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Project Area Acres Accessible Area Acres
Owner Classification
Eyak Corporation 50,745 50,132
Chugach Alaska Corporation 40,868 527
National Forest 1,108,265 149,502
State 12,484 9,350
Private 2,201
Totals
182
1,214,563 209,693
Vegetation Type
Sitka Spruce 85,324 9,558
Western Hemlock 38,665 13,271
Sitka Spruce-Black Cottonwood 2,239 879
Black Cottonwood 16,649
Subtotal Timberland
13,712
142,878 37,420
Shrubland 333,481 79,701
Harvested 4,832 4,832
Wetland 230,863 38,631
Non-Forest Other 29 28
Barren 146,843 23,209
Water 355,638
Totals
25,871
1,214,563 209,693
Project Area Volume Accessible Area Volume
Total Net Volume
Cubic Feet (> 5”diameter) 644,822,705 142,616,749
Cords (> 5”diameter) 7,164,697 1,584,631
Tons (> 5”diameter) 12,471,553 2,904,116
Board Feet (> 9”diameter) 2,748,695,864 604,933,059
TABLE 1. INVENTORY VOLUME AND ACREAGE SUMMARY.
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FIGURE 1. CORDOVA AREA BIOMASS VICINITY MAP.
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II. OBJECTIVES
The objective of this report is to provide reliable forest inventory data to assist in determining
the feasibility of proposed biomass development projects in the Cordova area. A geographic
information system (GIS) dataset was utilized for the analysis and allows interactive querying of
the spatial data.
III. METHODS
Forest inventory information was collected through a stratified random sampling design. The
project area was divided into subpopulations (timber types) in order to account for variation in
species composition. Each timber type was then treated as a random sample population. The
number of stands sampled within each timber type was based on the overall area occupied and
achievement of acceptable statistics within the available field work funding constraints. A total
of 32 individual timber stands were field sampled during the first week of October, 2012.
These field samples comprise 320 individual measurement plots. The sample timber types were
selected randomly and access to the stands was by foot. Field measurements were made in the
selected stands to provide estimates of volume, stocking, defect and growth by individual tree
species.
A. BASE IMAGERY
Natural color .6 meter resolution digital satellite imagery scenes were used for the project.
This mosaic was recently acquired by the USFS and made available to NVE. These scenes were
utilized for the field sampling phase and provided a means to accurately navigate to individual
sample stands. Timber type polygons, ownership boundaries, roads and sample stands were
overlaid onto the base imagery.
B. VEGETATION CLASSIFICATION
The USFS contracted out the vegetation classification and it is still on going. NVE acquired a
draft classification map that forms the basis of the acreage estimates in this study. Upon
completion of the field work DOF made some edits to the classification to more accurately
identify the major timber types. An additional timber type, mixed hemlock-spruce, was added
to the coverage. This timber type acreage was combined with the hemlock acreage during data
analysis. DOF also classified timber stands on state lands near the town of Cordova that were
not included in the draft map. Since the inventory acreage results are generated from the GIS
coverage, subsequent changes to the classification map by the USFS can easily be captured and
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revisions can be made. For the most part the classification proved reasonably accurate in
identifying the major timber types in the Cordova area.
C. FIELD INVENTORY DESIGN
The variable plot radius sampling method was used for field data collection of poletimber and
sawtimber size trees. The basal area factor utilized was 40 square feet. In each timber stand
sampled, ten plots were spaced uniformly on a traverse located systematically through the
stand. The traverse was located in such a manner as to attempt to sample the variation within
a stand. To minimize travel time, plots were generally located with a maximum interval of 330
feet. Tally trees were selected or rejected with a relascope prism. On five of the ten plots,
species, tree vigor, crown ratio, defect type and estimated defect percentage, were recorded
and tree diameter, total tree height, bark thickness, and ten-year growth were measured
(measure plots). Tree diameters were measured 4.5 feet above ground, commonly known as
“diameter breast height” or dbh. Co-dominate and dominant trees were cored at dbh to
determine average age and site index of the sample stand. On the other alternating five plots,
only the number of trees by species and size class selected by the relascope were recorded
(count plots). Count plots generally serve to lower the sample error by increasing the overall
plot numbers, but economize time spent in the field collecting data. Only trees five inches dbh
and greater were measured utilizing the variable plot sampling method.
The fixed plot sampling method was used for field data collection of trees less than five inches
dbh. At every other plot in the ten plot traverse (measure plots) seedling and sapling size trees
were measured. Species and quality were recorded and tree diameter and total tree height
were measured. The fixed plot was a circular 1/250th acre plot (7.45 foot radius).
D. DATA S UMMARY
Upon completion of the field work, sampled stand data were entered into TCruise, a timber
inventory software program. The inventory software calculated volume attributes for the
individual sampled stands. These stands were then grouped into strata and re-processed in
TCruise. The inventory contains four separate sample strata for which estimates of gross and
net volume per acre have been calculated. The strata contain field data from 32 individual
timber stands containing 320 plots (Table 4). Total inventory volume was calculated by
multiplying the average per acre volume figures for each stratum by the number of acres each
sample stratum represents. These calculations were performed in a Microsoft Access database
and utilize the GIS acreage figures. Output reports written in Access display numerous stand
attributes from the associated database tables and queries.
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E. ACREAGE SUMMARY/GIS ANALYSIS
Topographic features were examined to determine potentially accessible biomass. Areas where
steep topography, extensive wetlands or numerous rivers existed were deleted from the
operable area. When the operable subset was finally drawn, most of the area east of the
Copper River was deemed inaccessible and was not included. The resulting subset area
represents land with reasonable access to biomass resources. The operable area polygon was
then queried in the GIS to determine vegetation area by land ownership. After the GIS
operable vegetation and ownership layer was created a digital elevation layer was overlaid and
values extracted to determine average slope of the individual vegetation polygons. Much of the
land area near Cordova lies either in the Copper River Delta which is relatively flat to steep
slopes that create more difficult harvest operations. By classifying the acreage and volume by
slope classes more accurate estimates of operable biomass resources can be made. Relatively
low slopes such as those less than 15% can generally be accessed by ground based harvest
systems. As slope increases from this level greater investments in logging machinery are
required for harvest and access construction activities.
F. DESCRIPTION OF STRATA
The four volume strata are described below. Generally the inventory project area is comprised
of Sitka Spruce dominated stands with lesser amounts of Western Hemlock and Black
Cottonwood. The composition of hemlock increases with elevation and cottonwood increases
where riparian areas exist. The Copper River forms the dividing line between mostly spruce
dominated lands to the west to a more cottonwood and mixed forest to the east.
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1. STRATUM 1, SITKA SPRUCE
This stratum is found throughout the project area. Sitka spruce (Picea sitchensis
) occurs in
pure stands and in mixed stands with
Western hemlock, and Black
cottonwood. It is common on the
low elevation, wet, well-drained
alluvial fans and outwash plains. On
these sites many of the stands are
quite young (approximately 55 years)
and appear to be a primary colonizing
forest on recently deposited alluvial
outwash. There is little downed
large woody debris and soil depths
are quite shallow over river cobbles.
These young stands have rapid
FIGURE 2. STRATUM 1 SITKA SPRUCE (EVEN AGED YOUNG GROWTH).
growth rates and given their easy
access would be prime candidates
for use as a sustainable biomass
resource. Other low elevation
areas however have a more typical
uneven age older forest ranging in
the 200 year and greater class. At
higher elevations and steeper
slopes, the stands become more
mixed with Western hemlock.
Ages here are again more typical
of an uneven age older forest.
FIGURE 3. STRATUM 1 SITKA SPRUCE (UNEVEN AGED).
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2. STRATUM 2, WESTERN HEMLOCK
This stratum is found throughout the project area but in lesser amounts than stratum 1.
Within the accessible area
however it occupied greater
acreage. Western Hemlock (Tsuga
heterophylla
) occurs in pure stands
but generally was mixed with Sitka
spruce. Stand ages were variable.
Biomass use could be applied as a
thinning and improvement tool in
some areas with removal of the
more defective trees.
FIGURE 4. STRATUM 2 WESTERN
HEMLOCK .
3. STRATUM 3, MIXED SITKA SPRUCE/BLACK COTTONWOOD
This stratum is found near riparian areas and on recently deposited alluvial outwash. It is
dominated by Sitka spruce with lesser
amounts of cottonwood. Most
stands that were sampled were quite
young and mostly comprised of
poletimber or sapling sized trees.
Some of the sites were underlain
with river cobbles and gravel with an
extremely thin top soil layer. Much
of the stratum is too young at this
time for efficient biomass use.
FIGURE 5. STRATUM 3 MIXED SITKA SPRUCE/BLACK COTTONWOOD.
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4. STRATUM 4, BLACK COTTONWOOD
This stratum is found near riparian areas and on recently deposited alluvial outwash. It is
dominated by cottonwood but
also has lesser amounts of Sitka
spruce mixed in. Stand ages were
variable and ranged from around
55 years to an underdetermined
amount of probably 150 or so.
Ages were unable to be
determined in some stands due
to large trees containing
extensive amounts of rot. The
younger stands are growing
rapidly and would be prime
candidates for use as a sustainable
biomass resource.
FIGURE 6. STRATUM 4 BLACK COTTONWOOD.
G. FOREST VOLUME DEFINITIONS
Estimates of timber volume on forested lands have been calculated with three different
measurements; cubic foot volume, board foot volume and green tons. The cubic foot
measurement includes all timber greater than or equal to five inches dbh and is divided among
the live and dead poletimber and sawtimber components of the forest. The board foot
measurement is commonly used to determine the amount of lumber that can be sawn from a
log. Because the measurement is based on actual boards that can be sawn from a log, it
disregards all material wasted in the process such as slabs and sawdust. The board foot
measurement only includes timber equal to or greater than 9 inches dbh. Although the focus of
the inventory is on biomass use some stands may contain material more suited to milling. It is
this possibility of merchandizing some of the trees to a use other than biomass that this
measurement is included.
1. CUBIC AND BOARD FOOT MEASUREMENTS
Volume calculations for both cubic and board foot measurements are based on volume
equations produced by the USFS for the Chugach National Forest. The National Volume
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Estimator Library (NVEL) equations (A01DEMW000) are used. The NVEL volume equations
are available on the internet as a Microsoft Excel add-in function. Board foot volume is
reported in Scribner Decimal C scale and is based on 16-foot log segments (short log scale) and
is reported to a 6-inch top. Cubic volume is reported in Smalian’s rule and includes volume to a
4-inch top. In terms of calculations for wood energy resources, the cubic foot value is
important in that it can readily be converted into cords and the measurement relates well to
delivered wood in round log form. The equations were entered into TCruise, for processing of
the volume calculations.
2. TON MEASUREMENTS
Computation of green tons is somewhat less straight forward because published volume tables
by ton are much less available. In past DOF inventory projects for the Copper River Basin and
the Tanana Valley computation of green tons was derived from weight ratios produced for
Alaska wood species (Sturgeon 1979. Wood As A Fuel.). Wood As A Fuel lists the weight of green
cord wood which can be converted into pounds per cubic foot. Thus the inventory cubic foot
values can be converted to a green ton basis. A cord of wood is assumed to contain 90 cubic
feet of solid wood.
Species Pounds per Cubic Foot Tons per Cord
Sitka Spruce 34 1.53
Western Hemlock 50 2.25
Black Cottonwood 43 1.935
TABLE 2. INVENTORY SPECIES AND WEIGHT FOR POLETIMBER AND SAWTIMBER.
IV. RESULTS
Selected results of the analysis are displayed in the following tables. “Timberland Area” refers
to those portions of the land area that have been associated with forest inventory volume
strata and have woody biomass estimates. It does not include shrubland vegetation types.
A. VOLUME PER ACRE OF TIMBERLAND
Table 4 lists volume per acre by strata. As can be seen in the data the spruce and hemlock
strata have similar volumes per acre. Appendices B and C provide detailed per acre volume
figures by strata. Overall the average volume per acre weighted by accessible acres is 3,811
cubic feet per acre or 78 tons per acre or 16,166 board feet per acre. Utilizing an average
conversion of 90 cubic feet of solid wood per cord, roughly 42 cords per acre are present.
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Stratum Description Net
CF/Acre
Net
Cords/Ac.
Net
Tons/Ac.
Net
BF/Ac.
1 Sitka Spruce 4,958 55 90 21,700
2 Western Hemlock 4,672 52 102 18,321
3 Sitka Spruce-Black Cottonwood 656 7 12 1,137
4 Black Cottonwood 2,381 26 50 11,186
Average Timberland 3,811 42 78 16,166
TABLE 3. TIMBERLAND NET VOLUME PER ACRE BY STRATA.
B. SAMPLING ERROR BY VOLUME
Sample error was calculated for the gross cubic foot estimate by strata and size class (Table 4).
The sample error percent is given within one standard deviation of the mean. This means that
there is a 68% chance (one standard deviation) that the volume of the individual size class
components are within plus or minus the error percentage indicated. Sample error is relatively
high for the mixed spruce-cottonwood stratum 3. This is indicative of the variation of the
sawtimber and poletimber component within the mostly sapling sized dominated stands. The
other 3 strata which comprise the majority of the useable volume are below the target design
sample error value of 10%. Overall sample error for all strata combined was 4.8%.
TABLE 4. GROSS CUBIC FOOT VOLUME SAMPLING ERROR.
Poletimber Sawtimber Combined
Stratum Number
Of Plots
Gross
CF/Ac
%
Sampling
Error
Gross
CF/Ac
%
Sampling
Error
Gross
CF/Ac
%
Sampling
Error
1 160 891 10.3 4,294 7.6 5,185 6.5
2 50 963 16.6 4,066 9.3 5,029 8.2
3 60 409 20.1 263 52.9 672 24.0
4 50 135 74.9 2,524 7.7 2,659 8.2
Summary 320 694 8.2 3,226 5.5 3,920 4.8
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C. LOG GRADE
Log grade estimates were made during field sampling. Although log grade has little meaning in
terms of biomass utilization, it gives an idea of potential value added products that could be
made available in the course of biomass harvest. Generally log grades of #1 or #2 are the
higher value logs that could have additional value as an alternative to biomass and could possible
meet export grades. Although a significant area of Eyak Corporation lands was previously
harvested for export, markets are less available at this time. Local use of sawlog quality material
however could still be a possibility.
Log grade was only tallied for the sawtimber sized trees (> 9 inches dbh). A grade of one
through five was given for each of the first two 32-foot log segments. Blank grades are where
logs were deemed culls. Log grades use Puget Sound grading rules which contain specifications
for various species including Sitka spruce, Western hemlock and Black cottonwood (Table 5).
Table 6 lists log grade results. Log grade by species was not computed by volume but provides
grade estimates in straight percentage terms of trees measured in the field. This gives a
reference point for the overall grade distribution. Blank table entries indicate that a particular
log was cull and did not have useable volume. Sitka spruce contained the most trees where the
first 32 foot log was classified as a # 2 log grade (26% of measurements) which has a minimum
top diameter of 12 inches. Most of the hemlock and cottonwood were in grades of #3 or
higher indicating smaller trees with top diameters less than 12 inches or lower quality utility
grade logs.
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Logs will meet the minimum exterior characteristics. Diameter refers to top of log diameter.
1. Sitka Spruce, Hemlock
Gross Diameter: 24 inches
Grade No. 1
Surface: 75% clear
Gross Diameter: 12 inches
Grade No. 2
Surface: Sound, tight knots not to exceed 2 ½ inches in diameter. Any larger knots must
be well distributed.
Gross Diameter: 6 inches
Grade No. 3
Surface: Sound, tight knots not to exceed 3 inches in diameter. Any larger knots must be
well distributed.
Minimum volume 50 board feet NET scale
Gross Diameter: 5 inches
Grade No. 4
Minimum volume 10 board feet NET scale
2. Cottonwood
Gross Diameter: 10 inches
Grade No. 1
Surface: Not to exceed 4 knots per log
Gross Diameter: 6 inches
Grade No. 2
Gross Diameter: 5 inches
Grade No. 4
Minimum volume 10 board feet NET scale
3. All Species
Shall be logs that do not meet the minimum requirements for sawmill grades, but are suitable
for the production of firm useable chips to an amount not less than 50% of GROSS scale.
Grade No. 5 Utility Logs
Gross Diameter: 4 inches
Minimum volume 10 board feet NET scale
Note: A log that is burned or charred or is not mechanically barkable, shall not qualify as a
Utility log.
TABLE 5. PUGET SOUND GRADING RULES.
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Grade 1st Grade 2nd # Of Trees
Log Log Measured % Of Trees
Cottonwood
11 16%
1 2 3 4%
1 4 2 3%
1 5 3 4%
2 10 14%
2 1 1 1%
2 4 8 11%
2 5 7 10%
4 8 11%
5 13 19%
5 5 4 6%
Total for Cottonwood 70
Hemlock
5 6%
5 1 1%
2 2 1 1%
2 3 6 7%
3 10 11%
3 3 1 1%
3 4 10 11%
3 5 2 2%
4 16 18%
4 4 2 2%
4 5 6 7%
5 22 25%
5 4 1 1%
5 5 6 7%
Total for Hemlock 89
TABLE 6. LOG GRADE BY SPECIES.
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Sitka Spruce
16 5%
1 2 7 2%
2 2 26 9%
2 3 43 15%
2 4 5 2%
3 30 10%
3 2 1 0%
3 3 22 8%
3 4 14 5%
3 5 14 5%
4 56 19%
4 4 3 1%
4 5 2 1%
5 45 15%
5 3 3 1%
5 4 3 1%
5 5 3 1%
Total for Sitka Spruce 293
Grand Total Trees Measured 452
TABLE 6. CONTINUED, LOG GRADE BY SPECIES
D. SITE INDEX
Tree height has been found as the most reliable indicator of site productivity. In essence, the
taller the tree the more productive is the growing site. When height is combined with tree
age, the measurements can be reported as a site index number. This number gives the height in
feet of a particular stand at a reference base age. Site index of spruce and hemlock uses a base
age of 100 years whereas site index of cottonwood uses a base age of 50 years. Site index
reflects the combined effect of all environmental factors and is therefore a good index of stand
productivity. Site index calculations for spruce and hemlock are based on site index equations
produced for Alaska: U.S. Forest Service research paper PNW-53. Site index calculations for
cottonwood are based on site index equations U.S. Forest Service research paper NOR-2.
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Site Index (Feet)
Stratum 1 Sitka Spruce
Sitka Spruce 103
Western Hemlock 76
Stratum 2 Western Hemlock
Sitka Spruce 78
Western Hemlock 61
Stratum 3 Sitka Spruce – Black Cottonwood
Sitka Spruce ---
Black Cottonwood ---
Stratum 4 Black Cottonwood
Sitka Spruce ---
Black Cottonwood 76
Species Average
Sitka Spruce 98
Western Hemlock 68
Black Cottonwood 76
TABLE 7. SITE INDEX BY STRATUM AND SPECIES.
E. TIMBERLAND AREA AGE CLASS
Timberland productivity can also be examined in terms of overall age class distribution.
Typically as trees become older productivity declines. Cottonwood generally begins to decline
after year 80 or 90 when rot becomes more frequent. Spruce and Hemlock can be much
longer lived, but generally starts to decline after year 225 or so. At this age the conifers
become more susceptible to rot and insect damage. Table 8 shows the average stand age by
strata. Stratum 1 average age is relatively young and reflects the numerous spruce stands that
are growing on recently deposit alluvial outwash. Stratum 2 ages are more typical of the
hemlock and spruce mixed stands that occur on various topographic features in the area.
Stratum 3 is the youngest and is comprised of a significant amount of sapling size trees. Stratum
4 is comprised of stands that are growing near the riparian areas where flooding is frequent.
These stands for the most part are being replaced by flooding before they reach old age.
Stratum Average Age
1 Sitka Spruce 107
2 Western Hemlock 168
3 Sitka Spruce-Black Cottonwood 32
4 Black Cottonwood 62
TABLE 8. AVERAGE AGE BY STRATA.
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F. REGENERATION
Another measure of productivity is whether individual timber stands are being replaced by
regeneration. Coastal Alaska tree species comprise a combination of even and uneven-aged
stand types and are replaced through natural regeneration following wind, flooding or insect
outbreaks. Past timber harvest has occurred in the Cordova area and also influences stand
development. In the absence of disturbance, stands are slowly replaced by understory
regeneration. In many cases such as the dense spruce and hemlock stands, regeneration is poor
because of thick moss cover and cold soils. There may be a high tree count of small hemlock
seedlings, but regeneration of quality crop trees is poor. These stands are slow to regenerate
unless a stand replacing disturbance such as an extreme wind event occurs. In other cases
stands are actively being replaced even in the absence of disturbance. These stands typically are
the mixed spruce-cottonwood stands that contain a shallow moss layer conducive to seed
germination. Table 9 gives numbers of trees per acre less than 5 inches by species and stratum.
Trees are of desirable and acceptable quality as determined in field. Undesirable trees not
expected to become future crop trees are not included in the table. Stratum 3 contains the
greatest number of seedlings and saplings which is typical of a newly developing forest.
Stratum 1 Sitka Spruce Trees/Acre
Black Cottonwood 16
Sitka Spruce
244
Western Hemlock 53
Total Trees Per Acre 313
Stratum 2 Western Hemlock
Sitka Spruce
270
Western Hemlock 230
Total Trees Per Acre 500
Stratum 3 Sitka Spruce – Black Cottonwood
Black Cottonwood 108
Sitka Spruce
850
Western Hemlock 42
Total Trees Per Acre 1,000
Stratum 4 Black Cottonwood
Sitka Spruce
460
Total Trees Per Acre 460
TABLE 9. NUMBER OF TREES PER ACRE LESS THAN 5 INCHES DBH.
Assessment of Woody Biomass Energy Resources in the Cordova Area
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G. GROWTH AND MORTALITY ESTIMATES
Growth estimates have been determined through projections made with the timber cruise
software TCruise. Periodic annual gross growth has been projected utilizing the past 10-year
diameter growth increment and bark thickness measurements collected in the field. These
measurements sampled trees 5-inch dbh and greater across all diameter classes. By collecting
both the growth increment and bark thickness measurement, the software is able to discount
changes in bark thickness that would affect the accurate determination of diameter growth.
Growth was computed by a regression approach for both diameter and height. The desired
growth projection interval used was 10 years (i.e. 2012-2022). The increased volume growth
was then divided by 10 to calculate an annual growth rate. This volume figure was then divided
by the growing stock base (live tree volume) to calculate a percentage growth rate. The trees
were grown out initially by ten years instead of just one year to smooth growth rates because
some of the 10-year diameter growth increments were too small to be accurately projected for
just one year. Diameter-height relationships, diameter growth and calculated bark thickness
ratios (Husch et al. 2002. Forest Mensuration, Fourth Edition.) are shown in Appendix D. In the
field sampling protocol dead standing trees estimated to have died within 5 years were sampled
to include potentially useable volume and to develop mortality estimates. Field work tree
measurement results however, did not sample any recently dead trees and thus percent
mortality estimates are zero for the inventory. Some standing dead trees were observed but
were all significantly older than 5 years. The average net annual growth for the project area is
155 cubic feet per acre which is equivalent to 1.7 cords per acre or 3 tons per acre (Table 10).
Strata %
Annual
Net
Growth
CF Per
Acre Per
Year
Growth
Cords
Per Acre
Per Year
Growth
Tons Per
Acre Per
Year
Growth
1 Sitka Spruce 3.42% 170 1.9 3.1
2 Western Hemlock 2.12% 99 1.1 2.2
3 Sitka Spruce-Black Cottonwood 6.75% 44 0.5 0.8
4 Black Cottonwood 4.18% 100 1.1 2.1
Timberland Average 3.44% 155 1.7 3
TABLE 10. GROWTH AND MORTALITY ESTIMATES.
H. VOLUME OF TIMBERLAND BY LANDOWNER
In Tables 11 and 12 strata volume figures have been multiplied by acreage to calculate total
volume on the entire project as well as accessible area lands.
Assessment of Woody Biomass Energy Resources in the Cordova Area
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26%
35% 2%
37%
AccessibleTimberland Strata
Sitka Spruce
Western Hemlock
Sitka Spruce - Black Cottonwood
Black Cottonwood
TABLE 11. PROJECT AREA TIMBERLAND NET VOLUME BY STRATA.
TABLE 12. ACCESSIBLE AREA TIMBERLAND NET VOLUME BY STRATA .
FIGURE 7. ACCESSIBLE TIMBERLAND STRATA DISTRIBUTION BY AREA.
Stratum Acres Cords Tons Board Feet
1 Sitka Spruce 85,324 4,700,847 7,680,168 1,851,527,422
2 Western Hemlock 38,665 2,007,059 3,935,624 708,366,728
3 Sitka Spruce-Black
2,239 16,317 27,388 2,546,818
4 Black Cottonwood 16,649 440,406 828,240 186,231,668
Total Timberland 142,878 7,164,68
12,471,52
2,748,690,957
Stratum Acres Cords Tons Board Feet
1 Sitka Spruce 9,558 526,589 860,333 207,408,222
2 Western Hemlock 13,271 688,901 1,350,860 243,139,221
3 Sitka Spruce-Black Cottonwood 879 6,406 10,752 999,845
4 Black Cottonwood 13,712 362,716 682,132 153,379,100
Total Timberland 37,420 1,584,612 2,904,078 604,926,387
Assessment of Woody Biomass Energy Resources in the Cordova Area
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V. ECONOMIC AVAILABILITY OF S USTAINABLE BIOMASS FUELS
The economics of available biomass were examined with a delivery point to Cordova. The
context of the accessible area was analyzed to develop delivered biomass costs and volume
estimates by landowner. For any proposed biomass project the scope and extent of the raw
resource must be known prior to project development. The success of biomass projects over
the long term requires an accurate estimate of economic and sustainable biomass resources.
With volume estimates and locations of biomass resources known, harvest scheduling and
infrastructure development can be better planned. Although some of the resource for biomass
utilization may originate from the brushing and utilization of alder along the Eyak Corporation’s
logging road system, additional sources will most likely consist of harvested firewood and
commercial grade timber. When biomass is used in this form it is referred to as “fuelwood”.
This is the most expensive of biomass sources (Ashton et al. 2008. Woody Biomass Desk Guide
and Toolkit). This supply scenario is quite different than the Lower 48 where biomass projects
generally rely on a combination of urban wood waste, mill waste, logging residues and
increasingly biomass from intensively managed fast growing woody crops.
A. CURRENT DELIVERED COSTS
Delivered firewood costs are generally correlated to distance traveled from the harvest site.
The range of costs however can cover a relatively wide spectrum of distances and prices may
be constant until the haul distance significantly lengthens. This is because there are many other
variables that contribute to the cost of the delivered product including stumpage price, logging
costs, transportation and equipment depreciation. In the Cordova area since the accessible
area is mostly adjacent to the limited road system the haul distance is a small factor in the
overall cost. A far greater affect is terrain which can greatly influence logging costs. The
topography ranges from near level in the Copper River Delta to well over 70% slopes on
steeper lower and mid slope hillsides. Harvesting timber on level terrain can consist of a simple
operation of ground based logging equipment that employs a small dozer, flatbeds, pickup
trucks and chainsaw hand felling. On steeper slopes larger and more expensive equipment is
needed including tower yarders, dump trucks, front end loaders, and larger dozers.
In the Cordova area individual firewood vendors are not present to establish a base price for
delivered wood. Instead delivered costs to other Alaskan communities were examined to
arrive at a base price. A biomass analysis study recently prepared by DOF for the Alaska
Energy Authority on the Kenai Peninsula researched delivered firewood rates. Firewood
generally originates from state beetle killed forest lands. These harvest sites are mostly level
and relatively easy to access. In the Kenai area firewood sales originating off of beetle killed
Assessment of Woody Biomass Energy Resources in the Cordova Area
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state forest lands sells for about $150.00 per cord. Seward however is more remote and tends
to be more expensive than the other Peninsula communities. Here firewood sells for about
$225.00 per cord. It is estimated based on harvest costs on past DOF sales that delivered
prices are 25% higher on more complex sales such as those on steeper terrain. Coastal sales
on state lands on southern southeast Alaska may increase by 50% due to extensive heavy
equipment use and mobilization costs associated with mountainous logging terrain. Below in
Table 13 delivered prices are displayed by an associated representative slope class.
Delivery
Location
Delivered
Price/Cord
Configuration Slope
Class
Cordova $225 Flat Bed 0-15%
Cordova $285 Log Truck 16-25%
Cordova $340 Log Truck >25%
TABLE 13. DELIVERED CORD PRICES BY SLOPE CLASS.
Utilizing the data from Table 13 equations have been established to predict delivered costs for a
range of topographic steepness in slope percent from the harvest locations to Cordova. The
calculated regression equations for cords and tons respectively are shown below.
Delivered Price Per Cord = 3.4508 * Percent Slope + 205.12
Delivered Price Per Ton = 2.2509 * Percent Slope + 133.98
B. POTENTIAL ACCESSIBLE BIOMASS VOLUME BY SLOPE CLASS
The accessible biomass area has been categorized by slope to provide a more realistic
calculation of the economic availability of biomass. The total accessible timberland acreage by
ownership class and strata is shown in Table 14 and by ownership and slope class in Table 15.
Figure 3 illustrates three slope classes with the accessible biomass area identified surrounding
Cordova.
Stratum Chugach AK Corp Eyak Corp National Forest Private State Totals
1
1,814 6,480 45 1,219 9,558
2
2,918 8,124 2 2,227 13,271
3
491 386 0 2 879
4 412 6,868 6,162 2 268 13,712
Totals 412 12,091 21,152 49 3,716 37,420
TABLE 14. ACCESSIBLE ACREAGE BY OWNERSHIP CLASS AND STRATA.
Assessment of Woody Biomass Energy Resources in the Cordova Area
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Slope Owner Acres Gross CF Net CF Gross Net Gross Net Gross BF Net BF
Cords Cords Tons Tons
0-
15%
Chugach Alaska 412 1,096,371 981,564 12,182 10,906 22,965 20,511 5,177,748 4,611,859
Corp.
Eyak Corp. 10,286 34,031,010 31,217,926 378,122 346,866 701,581 641,277 150,181,694 137,046,447
National Forest 8,169 26,560,435 24,445,502 295,116 271,617 532,249 487,553 119,551,646 109,628,655
Private 47 237,327 226,640 2,637 2,518 4,339 4,127 1,036,628 993,361
State 1,287 5,966,789 5,644,316 66,298 62,715 113,089 106,476 25,991,887 24,619,908
Total 20,201 67,891,932 62,515,948 754,355 694,622 1,374,223 1,259,944 301,939,603 276,900,230
16-
25%
Eyak 430 2,118,307 1,971,873 23,537 21,910 45,508 42,254 8,463,997 7,839,193
National Forest 5,548 27,988,898 26,201,745 310,988 291,131 583,673 544,533 113,675,706 106,131,328
Private 1 5,520 5,128 61 57 121 112 21,781 20,108
State 927 4,670,432 4,347,856 51,894 48,310 100,738 93,552 18,569,318 17,197,662
Total 6,906 34,783,157 32,526,602 386,480 361,407 730,040 680,451 140,730,802 131,188,291
>25%
Eyak Corp. 1,376 6,525,576 6,111,198 72,506 67,902 133,417 124,463 27,097,870 25,325,034
National Forest 7,435 36,552,040 34,361,260 406,134 381,792 736,370 689,399 152,315,213 143,060,249
Private 1 4,695 4,361 52 48 102 95 18,526 17,103
State 1,503 7,598,961 7,097,379 84,433 78,860 160,837 149,764 30,564,923 28,442,150
Total 10,315 50,681,272 47,574,198 563,125 528,602 1,030,726 963,721 209,996,532 196,844,536
Grand Total 37,420 153,356,361 142,616,749 1,703,960 1,584,631 3,134,988 2,904,116 652,666,937 604,933,059
TABLE 15. CORDOVA AREA ACCESSIBLE ACREAGE AND VOLUME BY SLOPE CLASS.
Assessment of Woody Biomass Energy Resources in the Cordova Area
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FIGURE 8. ACCESSIBLE BIOMASS TIMBER TYPE MAP BY SLOPE CLASS.
Assessment of Woody Biomass Energy Resources in the Cordova Area
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FIGURE 9. DELIVERED COST PER CORD.
FIGURE 10. DELIVERED COST PER TON.
C. ANNUAL SUSTAINABLE BIOMASS YIELD BY SLOPE CLASS
Volume availability on an annual basis was determined by multiplying the inventory net growth
rate percentages with the accessible area volume. By using the growth rates applied to the
available volume the harvest is considered sustainable because only the amount of overall tree
y = 3.4508x +205.12
100
150
200
250
300
350
400
450
500
0 10 20 30 40 50 60 70 Price per Cord Percent Slope
Delivered Cost Per Cord
y = 2.2509x + 133.98
$30
$80
$130
$180
$230
$280
0 10 20 30 40 50 60 70 Price per Ton Percent Slope
Delivered Cost Per Ton
Assessment of Woody Biomass Energy Resources in the Cordova Area
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growth is harvested each year. The data was then merged into the five land ownership classes
(Table16).
The delivered cost information was then applied to the annually available operable volume to
develop supply curves in cords and tons (Figures 12 and 13) for the Cordova area. The
delivered cost per cord is converted from the total available cubic feet at a ratio of 90 cubic
feet per cord.
Across all slope classes and land owners there would potentially be available on an annual basis
a sustainable net volume of approximately 48,209 cords, 87,302 tons or about 19 million board
feet. This volume could be available at a cost of up to $340.00 per cord or $222.00 per ton.
Maintaining a simpler harvest operation where only slopes between 0 and 15% were accessed, a
sustainable net volume of approximately 24,946 cords, 45,154 tons or about 10 million board
feet would potentially be available. This volume could be available at about $225.00 per cord
or $147.00 per ton.