United States

Department of

Agriculture

Forest Service

Pacific Northwest

Research Station

Resource Bulletin

PNW-RB-234

June 2001

Summary Estimates of Forest

Resources on Unreserved Lands of

the Chatham Inventory Unit, Tongass

National Forest, Southeast Alaska,

1998

Willem W.S. van Hees
Author Willem W.S. van Hees is a research forester, Forestry Sciences Laboratory,

3301 C. St., Suite 200, Anchorage, AK 99503.
1

van Hees, Willem W.S. 2001. Summary estimates of forest resources on unreserved

lands of the Chatham inventory unit, Tongass National Forest, southeast Alaska,

1998. Resour. Bull. PNW-RB-234. Portland, OR: U.S. Department of Agriculture,

Forest Service, Pacific Northwest Research Station. 12 p.

Summary estimates are presented of forest resource area, timber volume, and growth

and mortality of timber on unreserved national forest land in the Chatham inventory unit

of the Tongass National Forest. Pacific Northwest Research Station, Forest Inventory

and Analysis crews collected inventory data from 1995 to 2000. Productive forest land

area (timberland) was estimated at 1,302 thousand acres, cubic-foot volume on timberland at 7,561 million cubic feet, and net annual growth and mortality at 31,613 and

28,341 thousand cubic feet, respectively.

Keywords: Forest surveys, timber resources, statistics (forest), Alaska (southeast),

Chatham.

The total land and water area of the Chatham inventory unit of the Tongass National

Forest is 8,140,000 acres. Unreserved lands within the area encompass 5,380,341

acres, 66 percent of the total. Thirty-seven percent (2,011,602 acres) of this unreserved area is forested and almost 65 percent of the forest land is timberland

(1,302,152 acres). Cubic-foot volume on timberland is estimated at about 7.5 billion

cubic feet. Nearly 82 percent of this volume is in western hemlock and Sitka spruce

trees. Net annual growth of growing stock on timberland is estimated at 31.6 million

cubic feet and average annual mortality is about 28.3 million cubic feet.

Forest Inventory and Analysis (FIA) is a nationwide project of the USDA Forest Service

authorized by the Forest and Rangeland Renewable Resources Research Act of 1978.

Work units, located at Forest Service research and experiment stations, conduct forest

resource inventories throughout the 50 states. The FIA program of the Pacific Northwest Research Station is responsible for forest inventories in Alaska, Washington,

Oregon, California, Hawaii, and the Pacific Trust Islands.

The forest resources on unreserved, national forest lands within the Chatham inventory unit (fig. 1) were sampled with a single-phase, unstratified, systematic grid sample

(grid spacing is 2.98 miles). No ground sampling occurred in wilderness areas. Ground

plots (2.47 acres) were established at each grid intersection and were subsampled by a

cluster of four, 24-foot, fixed-radius subplots. Three other subplots were sited, one each

at 120 feet north, southeast, and southwest from the first, centrally located subplot.

Each subplot was mapped for land cover.

Some plots were either entirely or partially physically inaccessible owing to dangerous

terrain. For these locations, land cover was estimated; detailed measurements of trees

and other vegetation were not made. These locations contribute to estimates of other

forest land and nonforest area.

Estimates presented in this report are based on sampling and are subject to two types

of error. The first is sampling error. This type of error can be estimated mathematically.

The second type of error comes from measurement mistakes or equipment limitations;

it cannot be estimated mathematically but is minimized through proper training, supervision, and emphasis on careful work.

Abstract

Summary

Preface

Inventory Area

Sampling Error
2

Bootstrap estimation was used to estimate sampling error. The bootstrap process is

an iterative resampling, with replacement, of the sample list. For each sample, a new

estimate of the total is constructed. The variances of the estimated totals provide the

estimate of standard error. The estimated errors presented in table 1 resulted from

1,000 iterations. Sixty-eight percent confidence bands (one standard error) can be

calculated from these figures.

• Thirty-seven percent of the Chatham inventory unit’s unreserved land base of 5,380

thousand acres was classified as forest land (2,012 thousand acres). Sixty-five percent of this forest land was timberland (1,302 thousand acres) (fig. 2).

• Western hemlock and Sitka spruce dominate the forest type composition of the

Chatham inventory unit’s timberland component.1 As pure types, western hemlock

and Sitka spruce comprise 37 and 22 percent, respectively, of the net cubic-foot

volume on timberland. Mixed western hemlock/Sitka spruce stands account for an

Figure 1—Chatham inventory unit, southeast Alaska, 1998.

Key Findings

1 Scientific names for all trees are given in the

appendix.

Table 1—Bootstrap estimates of the standard error for

selected forest resource estimates, Chatham inventory

unit, southeast Alaska, 1998

Resource Estimate Standard error

Productive acres 1,302,152 71,726

Nonproductive acres 709,450 59,047

Nonforest acres 3,368,739 82,717

Net volume (ft3) 7,561,291,112 536,971,963

Gross growth (ft3) 59,953,509 3,863,259
3

additional 19 percent of the net cubic-foot volume (fig. 3). Forty-six percent of the

net cubic volume, by species, is in western hemlock trees; 36 percent is in Sitka

spruce trees. The highest net cubic volumes per acre were found in stands of the

Sitka spruce forest type, where average volume per acre was estimated at 7,994

cubic feet.

• Average annual mortality did not exceed gross annual growth for any forest type in

the Chatham inventory unit (fig. 4). Total net annual growth for all forest types was

estimated at 31,613 thousand cubic feet. Gross annual per-acre growth in the Sitka

spruce forest type (67 cubic feet per acre) exceeded that in all other forest types.

Forest land—Land at least 16.7 percent stocked by live trees of any size, or land

formerly having such tree cover and not currently developed for nonforest use. The

minimum area for classification as forest land or subclasses of forest land is 1 acre.

Roadside, streamside, and shelterbelt strips of timber must be at least 120 feet wide

to be classified as forest land. Unimproved roads and trails, streams, and clearings in

forest areas must be less than 120 feet wide to be classified as forest land. (See also

timberland, other forest land, reserved forest land, and nonforest land.)

Figure 2—Area of land, by land cover, unreserved national forest

land, Chatham inventory unit, southeast Alaska, 1998.

Figure 3—Net volume of growing stock (million cubic feet) on timberland by forest

type, unreserved national forest land, Chatham inventory unit, southeast Alaska,

1998.

Glossary

Land cover

Forest type
4

Forest type—A classification of forest land based on the species forming a plurality of

stocking on the area currently occupied by tree cover.

Growing stock volume—Net volume in cubic feet of live sawtimber and poletimber

growing stock trees from stump to a minimum 4.0-inch top (of central stem) outside

the bark. Net volume equals gross volume less deductions for rot and missing bole

sections.

Land class—A classification of land by major use, such as timberland, other forest,

or nonforest. The minimum size area for classification is 1 acre.

Mean annual increment (m.a.i.)—A measure of the productivity of forest land in terms

of the average increase in cubic-foot volume per acre per year. The minimum standard

for timberland is the ability to produce 20 cubic feet per acre per year at culmination of

m.a.i.

Mortality, average annual, of growing stock—The volume of sound wood in live

sawtimber and poletimber trees dying annually from natural causes during the 5 years

prior to measurement.

Net annual growth—The increase in net volume of wood for growing stock trees during a specified year. Components of net annual growth are (a) the increment in net

volume of trees alive at the beginning of the specified year, plus (b) the net volume of

trees reaching sawtimber or poletimber size during the year, minus (c) the net volume

of trees that died during the year.

Net volume—The gross volume of a tree less deductions for rot, sweep, or other

defect affecting product use.

Figure 4—Gross annual growth and average annual mortality of growing stock on

timberland by forest type, unreserved national forest land, Chatham inventory unit,

southeast Alaska, 1998. Forest type
5

Nonforest land—Land that does not qualify as forest land. Includes land that has

never supported forests and lands formerly forested where forest use is precluded by

development for nonforest uses. Included are lands used for agricultural crops, improved pasture, residential areas, city parks, improved roads, operating railroads and

their right-of-way clearings, and pipeline clearings. If intermingled in forest areas, unimproved roads, streams, canals, and nonforest strips must be more than 120 feet wide,

and clearings or other areas must be 1 acre or larger to qualify as nonforest land.

Other forest land—Forest land not capable of producing 20 cubic feet per acre per

year or more of wood at culmination of mean annual increment (m.a.i.) and not withdrawn from timber use by administrative statute.

Productive forest land—Forest land producing or capable of producing 20 cubic feet

per acre per year or more of wood at culmination of mean annual increment (m.a.i.).

Poletimber trees—Growing stock trees greater than 5.0 inches in diameter at breast

height and less than sawtimber sized.

Reserved forest land—Forest land withdrawn from timber utilization through statute or

administrative regulation.

Sawtimber trees—Growing stock trees at least 11.0 inches in diameter at breast

height for hardwoods and 9.0 inches for softwoods.

Timberland—Forest land producing or capable of producing 20 cubic feet per acre per

year or more of wood at culmination of mean annual increment (m.a.i.) and not withdrawn from timber use by administrative statute.

Completion of this inventory, from design through data collection and compilation, resulted from the efforts of many people. Thanks go to Ray Koleser, data collection team

leader, and the data collection staff: Ken Anderson, DeAnna Barbaria, Kent Barkhau,

Aaron Bergdahl, Don Bertolette, J. Buck, Whitney Burgess, Brian Charlton, Ian

Doleman, Jason Downing, Jason Edney, Walter Foss, Jahn Haddeland, Seth Hazard,

Ken Hehr, Albert Helgenberg, Corey Henderson, Keith Kanoti, Dan Kenney, Tristan

Kelley, Brad Kriekhaus, Chris Krum, Theresa Lysak, Joel Markis, Mary Miller, Jeremy

Mills, L. Pejchar, Frank Pendleton, David Pierce, Brandy Reed, Julie Roller, Sadie

Rosenthal, John Saddler, Adam Smith, Chris Teutsch, David Thompson, Fred

Thorsteinson, Michael West, Marin Wilson, and August Wright. Thanks also to Kevin

Dobelbower, information management team leader, for database development and field

data recorder and compilation programming, and to Edward Ezzell for database and

systems maintenance.

Viereck, L.A.; Little, E.E., Jr. 1972. Alaska trees and shrubs. Agric. Handb. 410.

Washington, DC: U.S. Department of Agriculture. 265 p.

Literature Cited

Acknowledgments
6

Common name Scientific name

Softwoods:

Alaska-cedar Chamaecyparis nootkatensis (D. Don) Spach

Lodgepole pine Pinus contorta (Dougl.) ex Loud.

Mountain hemlock Tsuga mertensiana (Bong.) Carr.

Pacific silver fir Abies amabilis (Dougl.) ex Forbes

Sitka spruce Picea sitchensis (Bong.) Carr.

Western hemlock Tsuga heterophylla (Raf.) Sarg.

Western redcedar Thuja plicata (Donn) ex D. Don

Hardwoods:

Black cottonwood Populus trichocarpa Torr. & Gray

Paper birch Betula papyrifera Marsh.

Red alder Alnus rubra Bong.

Appendix

Names of trees2

2 Scientific names according to Viereck and Little (1972).
7

Table 3—Area of timberland by forest type, unreserved

national forest land, Chatham inventory unit, southeast

Alaska, 1998a

Forest type – – – – – – Area – – – – – –

Thousand acres Percent

Softwoods:

Alaska-cedar/hemlock 25 1.9

Lodgepole pine 7 .5

Mixed conifer 183 14.1

Mountain hemlock 145 11.1

Sitka spruce 204 15.7

Western hemlock/Sitka spruce 274 21.0

Western hemlock 418 32.1

Total, softwoods 1,256 96.4

Hardwoods:

Poplar 23 1.8

Red alder 6 .5

Total, hardwoods 29 2.2

Mixed:

Poplar-spruce 17 1.3

Total, mixed 17 1.3

All types 1,302 100.0

a Totals may be off due to rounding. Estimates are subject to sampling error.

Table 2—Area by land class, unreserved national forest land, Chatham

inventory unit, southeast Alaska, 1998a

Land class

Other forest Total forest Nonforest All

Timberland land land land land

Thousand acres

1,302 709 2,012 3,369 5,380

(24.2%) (13.1%) (37.4%) (62.6%) (100%)

a Totals may be off due to rounding. Estimates are subject to sampling error.
8

Table 4—Net volume of growing stock on timberland by

species, unreserved national forest land, Chatham

inventory unit, southeast Alaska, 1998a

Species – – – – – Volume – – – – –

Thousand ft3 Percent

Softwoods:

Alaska-cedar 524,484 6.9

Lodgepole pine 5,554 t

Mountain hemlock 753,179 10.0

Pacific silver fir 4,265 t

Sitka spruce 2,715,593 35.9

Western hemlock 3,486,750 46.1

Western redcedar 1,563 t

Total, softwoods 7,491,388 99.1

Hardwoods:

Black cottonwood 52,082 .7

Paper birch 2,602 t

Red alder 15,220 .2

Total, hardwoods 69,904 .9

All types 7,561,291 100.0

t = trace.

a Totals may be off due to rounding. Estimates are subject to sampling error.
9

Table 5—Net volume of growing stock on timberland by forest type, unreserved national forest land, Chatham inventory unit, southeast Alaska,

 1998a

Forest type – – – – – – – Volume – – – – – – –

Thousand ft3 Percent Ft3/ acre

Softwoods:

Alaska-cedar/hemlock 115,371 1.5 4,591

Lodgepole pine 2,845 t 409

Mixed conifer 819,207 10.8 4,472

Mountain hemlock 639,105 8.5 4,418

Sitka spruce 1,629,415 21.5 7,994

Western hemlock/Sitka spruce 1,469,048 19.4 5,364

Western hemlock 2,828,459 37.4 6,767

Total, softwoods 7,503,450 99.2 5,976

Hardwoods:

Poplar 16,917 .2 733

Red alder 9,347 .1 1,515

Total, hardwoods 26,264 .3 898

Mixed:

Poplar-spruce 31,577 .4 1,825

Total, mixed 31,577 .4 1,825

All types 7,561,291 100.0 5,807

t = trace.

a Totals may be off due to rounding. Estimates are subject to sampling error.
10

Table 6—Gross annual growth of growing stock on timberland by

forest type, unreserved national forest land, Chatham inventory

unit, southeast Alaska, 1998a

Forest type – – – – – Growth – – – – –

Cubic feet Ft3/ acre

Softwoods:

Alaska-cedar/hemlock 870,100 35

Lodgepole pine 23,728 3

Mixed conifer 6,804,810 37

Mountain hemlock 5,470,277 38

Sitka spruce 13,669,579 67

Western hemlock/Sitka spruce 12,886,339 47

Western hemlock 18,526,870 44

Total, softwoods 58,251,703 46

Hardwoods:

Poplar 311,245 13

Red alder 499,011 81

Total, hardwoods 810,256 28

Mixed:

Poplar-spruce 891,551 52

Total, mixed 891,551 52

All types 59,953,509 46

a Totals may be off due to rounding. Estimates are subject to sampling error.
11

Table 7—Net annual growth of growing stock on timberland by

forest type, unreserved national forest land, Chatham inventory

unit, southeast Alaska, 1998a

Forest type – – – – – Growth – – – – –

Cubic feet Ft3/ acre

Softwoods:

Alaska-cedar/hemlock 517,658 21

Lodgepole pine 23,728 3

Mixed conifer 661,348 4

Mountain hemlock 3,964,765 27

Sitka spruce 7,375,531 36

Western hemlock/Sitka spruce 7,879,663 29

Western hemlock 9,503,647 23

Total, softwoods 29,926,339 24

Hardwoods:

Poplar 311,245 13

Red alder 499,011 81

Total, hardwoods 810,256 28

Mixed:

Poplar-spruce 876,346 51

Total, mixed 876,346 51

All types 31,612,940 24

a Totals may be off due to rounding. Estimates are subject to sampling error.
12

Table 8—Average annual mortality of growing stock on timberland by forest type, unreserved national forest land, Chatham

inventory unit, southeast Alaska, 1998a

Forest type – – – – – Mortality – – – – –

Cubic feet Ft3/ acre

Softwoods:

Alaska-cedar/hemlock 352,442 14

Lodgepole pine — —

Mixed conifer 6,143,462 34

Mountain hemlock 1,505,511 10

Sitka spruce 6,294,048 31

Western hemlock/Sitka spruce 5,006,676 18

Western hemlock 9,023,223 22

Total, softwoods 28,325,363 23

Hardwoods:

Poplar — —

Red alder — —

Total, hardwoods — —

Mixed:

Poplar-spruce 15,205 1

Total, mixed 15,205 1

All types 28,340,568 22

— = no data were collected. a Totals may be off due to rounding. Estimates are subject to sampling error.
The Forest Service of the U.S. Department of Agriculture is

dedicated to the principle of multiple use management of the

Nation’s forest resources for sustained yields of wood, water,

forage, wildlife, and recreation. Through forestry research, cooperation with the States and private forest owners, and management of the National Forests and National Grasslands, it

strives—as directed by Congress—to provide increasingly

greater service to a growing Nation.

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