United States

Department of

Agriculture

Forest Service

Northeastern

Research Station

General Technical

Report NE-310

R. A. Birdsey

G. M. Lewis

Carbon in U.S. Forests and

Wood Products, 1987-1997:

State-by-State Estimates

United States

Environmental

Protection Agency
Published by: For additional copies:

USDA FOREST SERVICE USDA Forest Service

11 CAMPUS BLVD SUITE 200 Publications Distribution

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Delaware, OH 43015-8640

August 2003 Fax: (740)368-0152

Visit our homepage at: http://www.fs.fed.us/ne

Abstract

Estimated changes in carbon stocks are reported for the forests and wood products

of the 50 U.S. States. Carbon stocks on forest land and in harvested wood products

increased between 1987 and 1997 at an annual rate of 190 million metric tons.

Most of this increase was in biomass, followed closely by wood products and

landfills. Changes in land use since 1987 caused a small decrease in carbon

stocks, but this loss was offset by large gains on existing forest land. The East had

the greatest gain in carbon stocks with smaller gains estimated for the West. Most

of the individual states showed increases in ecosystem and wood-products carbon.

Observed changes were attributed to distinct regional and local factors, e.g., timber

production, land-use change, and natural disturbance. The information in this report

can be the basis for determining the potential gain or loss of forest carbon resulting

from management and policy decisions.

The Authors

R. A. BIRDSEY is Manager of the Northern Global Change Research Program at

the USDA Forest Service’s Northeastern Research Station in Newtown Square,

Pennsylvania. G. M. LEWIS is a biological science technician with the Northern

Global Change Research Program at the USDA Forest Service’s Northeastern

Research Station in Newtown Square, Pennsylvania.

Manuscript received for publication 28 August 2002

This publication was sponsored by the USDA Forest Service’s Northern Global

Change Research Program and the U.S. Environmental Protection Agency, IAG

DW12938264-01-0.
Contents

Introduction .................................................................................................................. 1

Estimation Process and Accounting Methods .............................................................. 1

Forest Statistics of the United States ........................................................................... 3

Changes in Carbon Stocks for U.S. Forests and Forest Products, 1987-97 ................ 3

United States ..................................................................................................................... 3

Regional Overview ............................................................................................................. 6

Northeast and North Central Regions ................................................................................ 6

Southeast and South Central Regions ............................................................................. 11

Western Regions ............................................................................................................. 11

Summary and Conclusions ........................................................................................ 16

Acknowledgments ...................................................................................................... 16

Literature Cited ........................................................................................................... 16

Appendix 1: Description of Data and Methods ........................................................... 19

Appendix 2: Comparison of Estimates and Methods ................................................. 23

Appendix 3: Methods for Individual States ................................................................. 25

Appendix 4: Basic Tables for the 50 United States .................................................... 28

Appendix 5: Sample Tables for Pennsylvania ............................................................ 40
1

Introduction

In this publication we report estimated changes in

carbon stocks for the forests and wood products of the

50 U.S. States. A first approximation of carbon status

and trends for the forestry sector, these estimates were

developed to assist states in compiling greenhouse-gas

inventories for submission (on a voluntary basis) to the

U.S. Environmental Protection Agency (EPA). These

initial estimates are designed to raise awareness of

accounting issues, identify common sources of

information and methods, and quantify the approximate

contribution of the forestry sector to a state’s status in

emitting or sequestering greenhouse gases. Individual

states should view these estimates as a starting point for

developing their own estimates. It is important to

carefully consider the forestry situation in each state by

consulting with local experts who are familiar with the

most currently available data. Because we used the same

methodology and national databases for every state,

more recent data than are included in this report may be

available, and the available data for a particular state may

support use of different estimation methodology.

Summary statistics by region and state are presented in

this report. All of the tables and figures as well as

additional statistics can be accessed at:

http://www.fs.fed.us/ne/global.

Estimation Process

and Accounting Methods

The methods used for this report are similar to those of

Birdsey and Heath (1995). These methods were the basis

for reporting greenhouse-gas emissions for the forest

sector in annual EPA reports through 1998 (Environ.

Prot. Agency 2000). Since the beginning of this project,

improved methods have been developed for estimating

carbon pools and flows in the forest sector. These are

reflected in recent greenhouse-gas inventories (Environ.

Prot. Agency 2001), but are not included here.

Estimates are based on forest-inventory data collected for

each state by the USDA Forest Service’s Forest Inventory

and Analysis units. Until recently, U.S. forest lands were

inventoried periodically, i.e., each state was inventoried

every 5 to 15 years. Every 5 years, the most recent state

forest statistics are aggregated for a national assessment

of forest conditions and trends. These reports include

summaries of state-level forest statistics. For this study,

the primary sources of forest-inventory information were

inventory statistics for 1987 and 1997 (Waddell et al.

1989; Smith et al. 2001). These reports are accompanied

by supporting statistical databases that were used to

develop the inventory base for estimating carbon by

forest-ecosystem component.

The inventory data used in this study can be accessed at:

http://fia.fs.fed.us. This web site also contains relevant

information on forest-inventory methodology,

definitions of terminology, and state-level data for recent

inventory years.

In some cases, definitional or procedural changes in

collecting the underlying inventory data may cause

apparent shifts in carbon stocks. For example, the

definitions of forest land or forest type were not applied

consistently for some National Forest lands in the West.

Reported changes in stocks may be the consequence of

such inconsistencies rather than a reflection of actual

change in the forest resource. The most apparent

inconsistencies are listed in Appendix 3.

We used the “stock change” approach to estimate

changes in carbon stocks (also known as carbon flux) for

forest-ecosystem components. This entails estimating the

total stock of carbon at two points in time, taking the

difference between the two estimates, and converting the

difference to an annual rate of change. Other approaches

entail direct estimation of the annual or periodic carbon

flux, or its principal components: growth, decay, harvest,

and mortality. We chose the stock-change approach

because it is consistent with the comprehensive

inventory data that are available for two points in time:

1987 and 1997.

We report changes in carbon stocks between 1987 and

1997 to be consistent with the reported dates of the

forest-inventory statistics and supporting databases. The

dates of the original inventory data used in the

compilations of forest-inventory statistics for 1987 and

1997 are included in Appendix 3. The compilations for

1987 and 1997 include data from inventories conducted

up to those dates, with little updating or projecting of

the original statistics to account for the differences

between data collection and reporting dates. Therefore,

for most states, the changes we report represent trends

from a period earlier than 1987 to 1997.

Ecosystem carbon is divided into biomass, forest floor,

and soil. Harvested carbon is treated separately. Biomass

includes all aboveground and belowground portions of

all live and dead trees and understory vegetation,

including the merchantable stem, limbs, tops, cull

sections, stump, foliage, bark and rootbark, and coarse

roots (larger than 2 mm). The forest floor includes all

dead organic matter above the mineral soil horizons

except standing dead trees: litter, humus, and other

woody debris. The soil component includes all organic

carbon in mineral horizons to a depth of 1 m (excluding

coarse roots). Harvested carbon includes carbon

removed from the forest for wood products and
2

Growth

Removals

Litterfall,

Mortality Treefall

Harvest

residue

Humification

Decomposition

SOIL

COARSE

WOODY

DEBRIS

FOREST

FLOOR

ATMOSPHERE

STANDING

DEAD

HARVESTED

CARBON

BIOMASS

Above and Below

LANDFILLS ENERGY

Imports/

Exports

PRODUCTS

Mortality

Recycling

decay

processing

burning

disposal burning

burning

decay

decay

fuelwood. Each of the component pools is related

through transfers of carbon (Fig. 1).

Using data from forest inventories and intensive-site

ecosystem studies, estimates of average carbon storage by

age or volume classes of forest stands (analogous to a

forest yield table) are made for each ecosystem

component, and stratified by forest classes defined by

region, forest type, productivity class, and land-use

history. Carbon in biomass is estimated by applying

derived factors that convert estimates of forest volume to

carbon. Equations are used to estimate carbon storage in

the forest floor, soil, and understory vegetation for each

forest class (see Birdsey 1996). Derived equations are

applied to estimates of growing-stock inventory and

increment, harvested area and volumes, and timberland

area obtained from the forest-inventory databases.

We used a modification of the stock-change approach

for wood products because a complete inventory of the

volume or mass of carbon in wood products and

landfills is not available. We simulated the most dynamic

portion of the inventory of carbon retained in wood

products and landfills by compiling estimates of wood

production from 1952 to 1987 and for 1997, and using

a model of carbon retention in various harvest carbon

pools (Row and Phelps 1991). The estimate for 1987

was subtracted from the estimate for 1997 to obtain the

difference in a compatible way with that for forestecosystem components. We used the “production

approach” for wood products, that is, all of the

accounting is attributed to the land area where the wood

is grown regardless of the eventual location and

disposition of wood products (Heath et al. 1996).

Imported wood is ignored in this approach.

For land-use change, we began with the land base in

1987 and accounted only for land-use change between

1987 and 1997. This approach does not account for

long-term effects of prior land-use changes on soil

carbon. We counted only the real changes in carbon

stocks from land-use change as opposed to apparent

changes that can occur due to a change in land

classification. For example, if a land area was reclassified

from forest to nonforest, we deducted the change in soil

carbon caused by the shift but not the remaining soil

carbon that was transferred to the new land use.

Likewise, for land reclassified from nonforest to forest,

we did not include the estimated carbon already on the

land prior to reclassification as forest.

The U.S. forest inventory reflects all changes in carbon

stocks regardless of cause. Some causes of change in

carbon stocks can be identified from the inventory data,

particularly human causes such as timber harvesting. But

the inventory may not reveal other causes of change, e.g.,

the effects of increasing atmospheric carbon dioxide or

tropospheric ozone on growth rates and tree health.

These indirect effects are not easily separated from other

factors that affect forest productivity and health; thus,

they are implicitly included in the inventory data and

our estimates of carbon stocks that are dependent on

Figure 1.—Comprehensive accounting for carbon pools and flows in the

forest sector (energy consumption not shown; from Heath et al. 2002).
3

those data. Analysis of forest-inventory data suggests that

the effects of land-use change and land management are

more significant than the effects of environmental

factors (Casperson et al. 2001).

Details of the methodology and databases used in this

report are included in Appendix 1. A summary of the

methods used in the most recent annual EPA

greenhouse-gas inventory reports along with a

comparison of estimates from different reports are

included in Appendix 2. State-specific methodology is

described and database issues discussed in Appendix 3.

Forest Statistics of the United States

The following is a brief description of recent trends in

the forests of the United States. These are the underlying

factors that cause the most significant human-induced

changes in forest carbon stocks and wood products.

These summary statistics are from Smith et al. (2001).

• The area of forest land in the United States totals

747 million acres or 33 percent of the land base.

The area of forest land increased by 1 percent

between 1987 and 1997

• Nearly 60 percent of U.S. forest land is privately

owned. Most of this land is in nonindustrial private

ownership. About 33 percent of U.S. forest land is

in Federal ownership, and 9 percent is in other

public ownership (states, counties, and

municipalities).

• Of all forest land, about 504 million acres are

classified as timberland, 191 million acres as other

forest, and 52 million acres as reserved forest.

• Oak-hickory is the most common forest type in the

Eastern United States followed by maple-beechbirch and loblolly-shortleaf pine. A variety of

softwood forest types dominates forest land in the

West.

• The volume of growing stock has been increasing

since 1953 in all regions except the Pacific Coast,

where volume has been increasing since 1978. The

volume of growing stock in the Nation now totals

836 billion cubic feet.

• Sawtimber-size stands predominate in both the East

and West, followed by poletimber and seedling/

sapling stands. On average, U.S. forests are

relatively mature.

• Removals of timber volume for wood products now

totals about 16 billion cubic feet per year. Harvest

trends on Federal lands have declined substantially,

particularly in the West.

• Net growth (net after mortality is deducted) exceeds

harvest by a substantial margin, totaling about 24

billion cubic feet per year. Mortality from all causes

is about 6 billion cubic feet per year.

These statistics vary considerably by state. For

convenience, the area of forest land for 1987 and 1997,

by region, state, and land class is presented in Appendix

4, Tables 1-2. Detailed forest statistics at the state level

are available from the sources cited in this report.

Changes in Carbon Stocks for U.S.

Forests and Forest Products, 1987-97

United States

Estimates were compiled by aggregating individual

estimates for each of the 50 U.S. States. Most states are

gaining carbon in forests and wood products. The

change in carbon stocks for biomass is a good indicator

of the overall trend in ecosystem carbon stocks. Using

this indicator, 7 states are losing and 43 are gaining

carbon in forests (Fig. 2). Generally, forests in the Lake

States, Great Plains, and the Northeast are gaining

carbon at the fastest rates.

Changes in individual carbon components show

different patterns than that for the total of all

components (Fig. 2). These differences reflect unique

resource characteristics and trends for each state.

Biomass is both a large and a dynamic carbon stock,

changing in response to management for wood products

and natural disturbances. The stock of carbon in the

forest floor and coarse woody debris is affected by the

same dynamics but the apparent trend is somewhat

different than for biomass carbon, reflecting additional

impacts of shifts in forest type. Changes in soil carbon,

the largest stock of carbon in forests, show another

pattern, one that is more responsive to land-use change

than to forest management (Fig. 2).

According to our estimates, U.S. forests gained carbon at

an annual rate of 190 Mt (million metric tons). Gains in

carbon for U.S. forests and wood products were highest

for biomass, followed by wood products and soils (Table

1). We have the most confidence in the estimates for

biomass and wood products, and the least confidence in

the estimates for soils and forest floor/coarse woody

debris.
4

There are significant changes in forest carbon among

ownership groups. The gains and losses reflect both

transfers among ownership groups and actual changes in

carbon stocks on the land. Nonindustrial private owners

gained the most carbon by a significant margin, followed

by National Forests (Table 2). Forest industry and other

public ownership groups lost carbon. The loss of carbon

on other public forests is attributed primarily to a

Figure 2.—Rate of change in carbon stocks for forest land, by state and carbon

component, 1987-97. Data are not available for west Texas and west Oklahoma,

and estimates for Alaska and Hawaii are not included due to scaling difficulties.

Total Carbon Biomass Carbon

Forest Floor and Coarse 

Woody Debris Carbon Product Carbon

Soil Carbon Land-use Change 

Total Carbon

reclassification of forest land owned in trust for Native

Americans into the nonindustrial private group. The loss

of carbon on forest industry land can be attributed to a

5-percent shift in the area of forest land to nonindustrial

private owners. Increases in carbon on forest land

retained by industry nearly offset all of the loss due to

ownership change.
5

Land-use changes since 1987 caused a loss of forest

carbon (Table 3) even though the overall area of forest

land has increased. The reason for this is that carbon is

lost more quickly from deforestation than gained from

afforestation. If our accounting methods for land-use

change began several decades earlier than in 1987, our

estimate of the change in carbon attributed to this factor

would be closer to zero or positive, since carbon gains on

Table 1.—Total carbon stock on forest land and in harvested wood products

in the United States, and annual change by accounting component, in Mt1

Avg. change

per year

Component 1987 1997 1987-97

Biomass 15,833.2 16,838.1 100.50

Forest floor/coarse woody debris 9,401.3 9,455.6 5.43

Soils 28,421.6 28,663.5 24.19

Wood products and landfills 2,919.6 3,520.4 60.08

Total 56,575.7 58,477.6 190.19

1

Million metric tons.

Table 2.—Total carbon stock on forest land and in harvested wood products

in the United States, and annual change by owner, in Mt

Avg. change

per year

Owner group 1987 1997 1987-97

National forest 11,703.5 12,245.6 54.22

Other public 13,482.4 13,345.5 -13.69

Forest industry 5,696.8 5,559.1 -13.77

Nonindustrial private 25,693.1 27,327.4 163.43

Total 56,575.7 58,477.6 190.19

areas afforested prior to 1987 would have compensated

for losses of carbon from deforestation after 1987. Note

that the effects of land-use change estimated in Table 3

are included in Tables 1-2. By subtracting the estimates

in Table 3 from those in Table 1, it is possible to estimate

the change in carbon for land that was classified as forest

in both 1987 and 1997.

Table 3.—Change in total carbon stock on forest land and in harvested

wood products attributed to land-use change since 1987, United States,

in Mt

Avg. change

Total change per year

Component 1987-97 1987-97

Biomass -104.8 -10.48

Forest floor/coarse woody debris -77.7 -7.77

Soils -129.6 -12.96

Wood products and landfills 84.4 8.44

Total -227.7 -22.77
6



	














	





	






 

	


	



Regional Overview

Because the United States is so large and diverse with

respect to physiography, climate, and human impacts,

understanding and monitoring carbon changes in U.S.

forests requires analysis on a disaggregated scale. We

identified seven regions of the conterminous United

States for compiling many of the estimates and analyzing

the results (Fig. 3). Alaska and Hawaii usually were

treated separately.

Every region except the Great Plains has significant

stocks of carbon in forests, but the distribution of

carbon stocks among ecosystem components and wood

products varies considerably (Fig. 4). Carbon in soils is

consistently the largest stock, followed by biomass

carbon except in Alaska, where carbon pools are higher

in the forest floor and coarse woody debris. Carbon

pools in the forest floor and coarse woody debris also are

high in the Intermountain States. The relative

importance of wood products varies according to the

importance of forest industry in a region. The Southeast,

South Central, and Pacific Coast have the highest

amounts of carbon in wood products.

The change in carbon stocks for U.S. forests between

1987 and 1997 was highly variable, both between

regions and between components among regions (Fig. 5).

The rate of accumulation of carbon in forests is highest

in the four eastern regions. Other regions also are

accumulating carbon in forests except for Alaska, though

the rate of accumulation is slower than in the eastern

regions. For most regions, the accumulation of carbon in

U.S. forests is highest in biomass and wood products.

There were small losses of carbon in soil, forest floor,

and coarse woody debris for the Pacific Coast and

Alaska.

Northeast and North Central Regions

Carbon stocks in forests of the Northeast and North

Central regions increased by 71 Mt/yr between 1987 and

1997 (Table 4). Most of the increase was in biomass and

wood products. Forests in nonindustrial private

ownership gained the most carbon. Forest industry lost

carbon due primarily to a transfer of forest land to the

nonindustrial private group (Table 5).

There was a significant shift in carbon stocks among

forest types because of shifting species composition and

increased occupancy of land by trees (Table 6). Maplebeech-birch and oak-hickory types gained carbon, while

spruce-fir and white-red-jack pine types lost carbon. The

area of nonstocked forest land (defined as forest but

stocked with few trees) declined significantly as tree

stocking and the amount of carbon/acre increased.

Because of the decline in area, total carbon on

nonstocked forest land decreased.

Land-use change between 1987 and 1997 in the

Northeast and North Central caused a loss in carbon of

approximately 6 Mt/yr, primarily in soil carbon pools

(Table 7). These regions are similar in carbon stocks (Fig.

4) and rate of change (Fig. 5). North Central States

gained 43 Mt/yr and Northeast States gained 28 Mt/yr

from 1987 to 1997 (Table 8). All of the Northern states

gained carbon except Maine and Delaware; Michigan

and West Virginia gained the most forest carbon. Losses

in Maine are attributed to harvest exceeding growth;

losses in Delaware likely resulted from changes in landuse.

Figure 3.—The regions identified for this report.
7















	
 

 	 	



















	




















	
 

 	 	



















	




	
















	
 

 	 	



















	





















	
 

 	 	



















	





	
















	
 

 	 	



















	




	















	
 

 	 	



















	




















	
 

 	 	



















	




	
















	
 

 	 	



















	






Figure 4.—Carbon stocks of U.S. forests by region and ecosystem component,

1997 (FF & CWD refers to forest floor and coarse woody debris).
8

 	



 
	


	 

	
 

 	
 
  























 	
 
  























 	
 
  























 	
 
  























 	
 
  























 	
 
  























 	
 
  























 	
 
  







































































































Figure 5.—Change in carbon stocks of U.S. forests by region and ecosystem

component, 1987-1997 (FF & CWD refers to forest floor and coarse woody debris).
9

Table 4.—Total carbon stock on forest land and in harvested wood products

in the Northeast and North Central regions, and annual change by

accounting component, in Mt

Avg. change

per year

Component 1987 1997 1987-97

Biomass 3,549.6 4,059.3 50.97

Forest floor/coarse woody debris 1,440.3 1,465.1 2.47

Soils 8,878.5 8,954.7 7.62

Wood products and landfills 488.2 592.0 10.38

Total 14,356.7 15,071.1 71.44

Table 5.—Total carbon stock on forest land and in harvested wood

products, in the Northeast and North Central regions, and annual

change by owner, in Mt

Avg. change

per year

Owner group 1987 1997 1987-97

National forest 971.1 1,028.8 5.78

Other public 2,371.9 2,548.4 17.65

Forest industry 1,622.4 1,433.5 -18.89

Nonindustrial private 9,391.3 10,060.3 66.90

Total 14,356.7 15,071.1 71.44

Table 6.—Total carbon stock on forest land and in harvested wood products

in the Northeast and North Central regions, and annual change by forest

type, in Mt

Avg. change

per year

Forest type 1987 1997 1987-97

White-red-jack pine 1,202.0 1,121.1 -8.09

Spruce-fir 1,739.3 1,528.4 -21.09

Longleaf-slash pine (planted) 0.0 0.0 0.00

Longleaf-slash pine (natural) 0.0 0.0 0.00

Loblolly-shortleaf pine (planted) 0.0 -1.0 -0.10

Loblolly-shortleaf pine (natural) 136.1 136.6 0.05

Oak-pine 237.6 258.0 2.04

Oak-hickory 3,970.4 4,363.0 39.26

Oak-gum-cypress 65.9 73.5 0.76

Elm-ash-cottonwood 843.9 791.8 -5.21

Maple-beech-birch 4,490.6 5,263.3 77.27

Aspen-birch 1,440.8 1,408.8 -3.20

Other forest types 67.0 75.9 0.89

Nonstocked 163.0 51.7 -11.13

Total 14,356.7 15,071.1 71.44
10

Table 7.—Change in total carbon stock on forest land and in

harvested wood products attributed to land-use change since 1987

in the Northeast and North Central regions, in Mt

Avg. change

Total change per year

Component 1987-97 1987-97

Biomass -13.4 -1.34

Forest floor/coarse woody debris -14.7 -1.47

Soils -40.1 -4.01

Wood products and landfills 8.1 0.81

Total -60.1 -6.01

Table 8.—Total carbon stock on forest land and in harvested wood products in

the Northeast and North Central regions, and annual change by state, in Mt

Avg. change

per year

State 1987 1997 1987-97

Northeast

Connecticut 158.9 165.2 0.63

Delaware 32.7 32.1 -0.06

Maine 1,701.0 1,685.8 -1.52

Maryland 246.9 257.3 1.03

Massachusetts 271.6 290.4 1.88

New Hampshire 491.3 521.7 3.04

New Jersey 134.8 150.0 1.51

New York 1,702.2 1,754.2 5.20

Pennsylvania 1,567.8 1,588.8 2.10

Rhode Island 30.4 30.9 0.05

Vermont 440.5 490.0 4.95

West Virginia 999.4 1,091.6 9.23

Subtotal 7,777.4 8,057.9 28.05

North Central

Illinois 382.8 387.7 0.49

Indiana 392.8 435.5 4.27

Iowa 141.4 155.7 1.44

Michigan 1,546.2 1,695.7 14.94

Minnesota 1,322.8 1,350.1 2.73

Missouri 916.1 976.6 6.05

Ohio 598.4 672.1 7.37

Wisconsin 1,278.8 1,339.8 6.10

Subtotal 6,579.3 7,013.2 43.39

Total 14,356.7 15,071.1 71.4
11

Table 9.—Total carbon stock on forest land and in harvested wood products in

the Southeast and South Central regions, and annual change by accounting

component, in Mt

Avg. change

per year

Component 1987 1997 1987-97

Biomass 4,692.8 5,017.8 32.49

Forest floor/coarse woody debris 1,077.2 1,141.5 6.43

Soils 6,150.6 6,274.6 12.39

Wood products and landfills 1,327.4 1,682.7 35.53

Total 13,248.1 14,116.5 86.84

Southeast and South Central Regions

Carbon stocks in the Southeast and South Central

regions increased by 87 Mt/yr from 1987 to 1997 (Table

9). Most of this increase was in biomass and wood

products. Forests in all ownership classes, led by

nonindustrial private ownerships, gained carbon (Table

10).

There was a significant shift in carbon stocks among

forest types due to the ongoing conversion of natural

pine types to pine plantations, a shift in species

composition, and an increase in the occupancy of forest

land by trees (Table 11). Planted loblolly-shortleaf pine,

oak-pine, oak-hickory, and oak-gum-cypress gained

significant amounts of carbon, while natural loblollyshortleaf pine lost the most carbon. The area of

nonstocked forest land declined significantly as tree

stocking and amount of carbon/acre increased. Because

of the decline in area, total carbon on these lands

decreased.

Changes in land use in the Southeast and South Central

since 1987 led to a loss in carbon of about 7 Mt/yr. All

carbon pools were affected except that for wood

products, which showed a gain (Table 12). Utilization of

harvested wood from land-use change helped offset

losses of ecosystem carbon.

The Southeast and South Central are similar in carbon

stocks (Fig. 4) and carbon fluxes (Fig. 5). South Central

States gained 57 Mt/yr and Southeast States gained 30

Mt/yr from 1987 to 1997 (Table 13). All of the

Southern States gained carbon except for Texas, which

lost about 6 Mt/yr. Mississippi, Arkansas, Alabama, and

Georgia gained the most forest carbon. Estimates for

Texas primarily reflect changes in forested area and shifts

in forest-type classifications in east Texas; complete forest

inventories have not been conducted in central and west

Texas.

Western Regions

Carbon stocks in Western regions (Great Plains,

Intermountain, Pacific Coast, Alaska, and Hawaii)

increased by 32 Mt/yr from 1987 to 1997 (Table 14).

Most of the increase was in biomass and wood products

while carbon pools in the forest floor and coarse woody

debris showed a loss. National Forest lands gained a

significant amount of forest carbon (Table 15). A shift in

land classification from other public to nonindustrial

private caused respective losses and gains in these two

ownership groups.

There was a significant shift in carbon stocks among

forest types (Table 16). In part this reflects shifting

species composition, but an important confounding

factor was changes in the way forests were classified by

forest type. These changes were particularly significant

for Alaska and for National Forest lands, both of which

comprise large areas of the West. Another classification

issue is the inclusion of the Great Plains States with the

other Western States in this tabulation. The eastern

portions of the Great Plains include eastern forest types

that were added to similar western forest types in Table

16. Many forest types gained carbon while losses of

carbon were significant in chaparral, fir-spruce, larch,

and Douglas-fir.
12

Table 10.—Total carbon stock on forest land and in harvested wood products in

the Southeast and South Central regions, and annual change by owner, in Mt

Avg. change

per year

Owner group 1987 1997 1987-97

National forest 870.4 911.0 4.06

Other public 720.1 858.6 13.85

Forest industry 2,341.5 2,425.5 8.40

Nonindustrial private 9,316.1 9,921.4 60.53

Total 13,248.1 14,116.5 86.84

Table 11.—Total carbon stock on forest land and in harvested wood products

in the Southeast and South Central regions, and annual change by forest type,

in Mt

Avg. change

per year

Forest type 1987 1997 1987-97

White-red-jack pine 69.5 83.0 1.35

Spruce-fir 4.8 1.0 -0.38

Longleaf-slash pine (planted) 396.6 419.8 2.32

Longleaf-slash pine (natural) 440.7 345.9 -9.48

Loblolly-shortleaf pine (planted) 672.6 1,197.3 52.47

Loblolly-shortleaf pine (natural) 2,235.1 1,883.4 -35.17

Oak-pine 1,718.3 1,924.7 20.64

Oak-hickory 5,211.4 5,388.9 17.75

Oak-gum-cypress 1,954.8 2,118.5 16.37

Elm-ash-cottonwood 211.6 159.2 -5.24

Maple-beech-birch 103.6 129.7 2.61

Aspen-birch 0.0 0.0 0.00

Other forest types 99.4 405.5 30.61

Nonstocked 129.6 59.4 -7.01

Total 13,248.1 14,116.5 86.84

Table 12.—Change in total carbon stock on forest land and in harvested

wood products attributed to land-use change since 1987 in the Southeast

and South Central regions, in Mt

Avg. change

Total change per year

Component 1987-97 1987-97

Biomass -51.5 -5.15

Forest floor/coarse woody debris -21.3 -2.13

Soils -46.0 -4.60

Wood products and landfills 47.0 4.70

Total -71.8 -7.18
13

Table 14.—Total carbon stock on forest land and in harvested wood products,

and annual change by accounting component, Western regions, in Mt

Avg. change

per year

Component 1987 1997 1987-97

Biomass 7,590.7 7,761.0 17.03

Forest floor/coarse woody debris 6,883.8 6,849.1 -3.47

Soils 13,392.4 13,434.2 4.18

Wood products and landfills 1,104.0 1,245.7 14.17

Total 28,970.9 29,290.0 31.91

Table 13.—Total carbon stock on forest land and in harvested wood products

in the Southeast and South Central regions, and annual change by state, in Mt

Avg. change

per year

State 1987 1997 1987-97

Southeast

Florida 881.5 916.2 3.47

Georgia 1,514.5 1,624.1 10.96

North Carolina 1,363.3 1,427.3 6.39

South Carolina 790.0 813.7 2.37

Virginia 1,123.6 1,187.8 6.42

Subtotal 5,672.9 5,969.1 29.62

South Central

Alabama 1,309.1 1,426.3 11.73

Arkansas 1,090.0 1,234.8 14.49

Kentucky 873.8 909.1 3.53

Louisiana 916.6 972.4 5.58

Mississippi 1,088.7 1,246.9 15.81

Oklahoma 327.3 364.5 3.72

Tennessee 859.9 940.3 8.05

Texas 1,109.8 1,053.0 -5.67

Subtotal 7,575.1 8,147.4 57.23

Total 13,248.1 14,116.5 86.84
14

Table 15.—Total carbon stock on forest land and in harvested wood

products, and annual change by owner, Western regions, in Mt

Avg. change

per year

Owner group 1987 1997 1987-97

National forest 9,862.0 10,305.8 44.39

Other public 10,390.4 9,938.5 -45.19

Forest industry 1,732.9 1,700.0 -3.29

Nonindustrial private 6,985.7 7,345.6 36.00

Total 28,970.9 29,290.0 31.91

Table 16.—Total carbon stock on forest land and in harvested wood products,

and annual change by forest type, Western regions, in Mt

Avg. change

per year

Forest type 1987 1997 1987-97

Douglas-fir 4,337.3 4,262.6 -7.47

Ponderosa pine 2,314.8 2,463.0 14.82

Western white pine 66.1 59.2 -0.69

Fir-spruce 6,171.1 6,037.0 -13.41

Hemlock-Sitka spruce 1,753.0 2,049.2 29.62

Larch 284.7 129.5 -15.53

Lodgepole pine 1,266.7 1,234.7 -3.20

Redwood 177.0 142.1 -3.48

Other hardwoods 2,669.5 2,980.0 31.05

Other forest types 5,647.8 6,087.4 43.97

Pinyon-juniper 3,293.1 3,228.4 -6.47

Chaparral 614.7 390.3 -22.44

Nonstocked 375.3 226.7 -14.86

Total 28,970.9 29,290.0 31.91

Table 17.—Change in total carbon stock on forest land and in harvested

wood products attributed to land-use change since 1987 in the Western

regions, in Mt

Avg. change

per year

Component 1987-97 1987-97

Biomass -40.0 -4.00

Forest floor/coarse woody debris -41.7 -4.17

Soils -43.4 -4.34

Wood products and landfills 29.3 2.93

Total -95.8 -9.58
15

Table 18.—Total carbon stock on forest land and in harvested wood products

in the Western regions, and annual change by state, in Mt

Avg. change

per year

State 1987 1997 1987-97

Great Plains

Kansas 96.3 119.5 2.32

Nebraska 50.1 64.0 1.39

North Dakota 32.3 44.2 1.19

South Dakota 123.0 117.8 -0.52

Subtotal 301.6 345.4 4.38

Intermountain

Arizona 1,267.2 1,303.1 3.59

Colorado 1,490.4 1,494.7 0.42

Idaho 1,820.8 1,858.2 3.74

Montana 1,751.8 1,869.3 11.75

Nevada 648.5 699.3 5.08

New Mexico 950.5 926.7 -2.37

Utah 1,130.5 1,110.5 -2.00

Wyoming 781.2 811.1 2.99

Subtotal 9,840.9 10,072.9 23.20

Pacific Coast

Alaska 10,158.2 10,073.2 -8.50

California 3,375.5 3,436.4 6.09

Hawaii 90.3 90.3 0.00

Oregon 2,873.8 2,962.4 8.86

Washington 2,330.7 2,309.5 -2.12

Subtotal 18,828.5 18,871.7 4.32

Total 28,970.9 29,290.0 31.91

Changes in land use in the West since 1987 caused a loss

of carbon of about 10 Mt/yr, affecting all carbon pools

except that for wood products, which showed a gain

(Table 17). The utilization of harvested wood resulting

from land-use change helped offset losses of ecosystem

carbon.

In contrast to the North and South, regions in the West

differed in patterns of carbon stocks (Fig. 4) and changes

in carbon stocks (Fig. 5). The Great Plains, with little

forest land, has the least amount of forest carbon. The

Intermountain and Pacific Coast have large carbon

stocks, but changes from 1987 to 1997 were not as

significant as for the eastern regions. Because of

increasing fire frequency since 1997, it is likely that the

carbon stock in the Intermountain and Pacific Coast is

increasing at a much lower rate than shown in Figure 5,

or even decreasing. Alaska has high carbon stocks in

forests, though the only available trend data indicate a

small loss of carbon from 1987 to 1997. This reflects the

harvesting of old forests and replacement by young

forests (primarily in southeast Alaska), widespread

mortality due to pests and fire, and shifts in species

composition.

The Intermountain gained 23 Mt/yr of carbon from

1987 to 1997 (Table 18). Pacific Coast and Great Plains

States gained small amounts of carbon. Of the Western

States, Montana and Oregon gained the most carbon,

while South Dakota, New Mexico, Utah, and

Washington lost small amounts. The estimated

substantial loss of carbon in Alaska is suspect due to

sparse remeasurement data from inventory plots. The

reported losses are attributed almost entirely to the

reclassification of forest types and may not reflect a true

change in carbon stocks.
16

Summary and Conclusions

According to our estimates, carbon stocks on forest land

and in harvested wood products increased between 1987

and 1997 at an annual rate of 190 Mt. Most of this

increase was in biomass, followed closely by wood

products and landfills. Changes in land use since 1987

caused a small decrease in carbon stocks, but this loss

was offset by large gains on existing forest land. The East

had the greatest gain in carbon stocks with smaller gains

for the West; Alaska showed a small decrease but this is

suspect due to a reliance on sparse trend data from forest

inventories. Some regions showed significant shifts in

carbon stocks among forest types, an indication of

changes in species composition and management

intensity. For example, in the South there was a

significant shift in carbon stocks from natural to

plantation pines.

Most of the individual states showed increases in

ecosystem and wood-products carbon. Observed changes

were attributed to distinct regional and local factors, e.g.,

timber production, land-use change, and natural

disturbance. This information can be the basis for

determining the potential gain or loss of forest carbon

resulting from management and policy decisions.

By analyzing the underlying inventory data, it is possible

to identify many of the factors that cause changes in

forest carbon stocks. However, it may be difficult to

determine the relative influence of the identified factors

without conducting a more detailed analysis than

attempted here. Inconsistency in the way data were

collected or reported, or unavailability of previously

compiled data, can obscure the factors that cause

changes in carbon stocks.

The methods demonstrated here for converting

inventory data to carbon stocks can be applied more

rigorously at the state level. Ongoing changes in the way

inventory data are collected, e.g., the conversion from a

periodic to annual inventory, will facilitate reporting

changes in ecosystem and wood-products carbon on an

annual basis. Gaps in data collection are being filled,

particularly for Alaska, Hawaii, Texas, Oklahoma, and

parts of the Southwest. These changes, along with

improvements in methodology, will reduce the

uncertainty of estimates of forest carbon from inventory

data.

Acknowledgments

We thank the following for their valuable review

comments: Steve Prisley, James Smith, Ken Andrasko,

Tom Wirth, Jim Cathcart, Bryan Hensley, Jim

Kerstetter, and Rick Handley. We also thank the U.S.

Environmental Protection Agency, particularly Denise

Mulholland and Julie Rosenberg, for financial support

and for managing the external review process.

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19

Appendix 1: Description of Data and Methods

The second sample phase consists of more than 150,000

permanent field sample locations that are remeasured

periodically to provide statistics on disturbance (e.g.,

harvest and mortality), growth, change in species

composition, and numerous observed and calculated site

descriptors such as ownership and forest type. At each

sample location, a rigorous protocol is followed to select

and measure a representative sample of trees. These

measurements are then expanded to the population level

using statistics from phase 1. A subsample of phase 2

plots (Forest Health Monitoring plots) is the basis for

more intensive ecosystem measurements. Soils, coarse

woody debris, understory vegetation, and other

ecological variables may be collected on this subsample,

which is linked statistically to the phase 1 and 2 samples.

The subsample of phase 2 consists of about 5,000 plots.

Successive measurements have been initiated on about

half of this subsample.

Estimating Carbon in Trees

The quantity of carbon in live and dead trees is derived

from volume and biomass estimates from the national

forest inventory. Methods for estimating volume,

biomass, and the components of change (growth,

removals, and mortality) are reviewed in Birdsey and

Schreuder (1992). Estimates of growing-stock volume

(the merchantable part of trees) are converted to tree

carbon in a two-stage process. First, total tree volume is

estimated from growing-stock volume using a ratio to

account for the additional tree parts excluded from the

definition of growing stock: tops and branches, rough

and rotten trees, small trees (less than 5.0 inches in

diameter at breast height), standing dead trees, stump

sections, roots, and bark. A factor is added to account

for carbon in foliage. Separate ratios are computed for

softwoods and hardwoods to account for differences in

the average ratio of total volume to growing-stock

volume. Ratios are derived from two principal sources: a

nationwide biomass study prepared by the USDA Forest

Service containing estimates of above-ground biomass by

tree component (Cost et al. 1990), and a report

containing estimates of the proportion of below-ground

tree volume.1

 Separate ratios are derived for each region

of the United States to account for differences in tree

Forest-Ecosystem Databases

An extensive and comprehensive forestry data collection,

management, and reporting system underlies carbon

estimates and analyses (Powell et al. 1993; Smith et al.

2001). The comprehensive national inventory of forest

lands in the United States began in the 1930s. By the

early 1950s, all states except Alaska (interior) had been

inventoried at least once. Until recently, each state was

inventoried about every 5 to 15 years, with national

statistics compiled every 5 years. Recent compilations of

national statistics are for 1987, 1992, and 1997. For

most states, data for 1992 are identical or only partially

updated from 1987; therefore, the principal databases we

used are those for 1987 and 1997. Ongoing changes in

the way national forest inventories are implemented will

facilitate annual reporting of basic statistics, which, in

turn, will facilitate reporting of carbon flux on an annual

basis.

The most comprehensive ecosystem measurements

available are from intensive, long-term ecosystem studies

such as those comprising the network of Long Term

Ecological Research (LTER) sites. LTER and similar sites

typically have a long history of repeated measurements of

a common and comprehensive suite of ecological

variables, including soil and litter carbon, that are

unavailable from extensive statistical sampling networks.

Unlike national forest inventories, intensive studies are

concentrated on relatively undisturbed sites. This

information can be used only in conjunction with forestinventory data by making appropriate adjustments (see

assumptions described elsewhere in this section) to

represent the range of conditions in the statistical

sample.

Sampling Design of Forest Inventories

Since World War II, U.S. forest inventories have used

multiphase sampling designs that include remote sensing

and ground measurements (Birdsey and Schreuder

1992). The first sample phase typically consists of

interpretation of high-altitude color infrared

photography, widely available and highly accurate for

estimating changes in forest area and locating field

sample plots. Interpreters classify more than 3 million

sample points nationally to monitor activities such as

timber harvest and land use that may change the photo

classification from forest to nonforest cover. The

inventory is in the process of changing from highaltitude photography to satellite imagery for phase 1.

1

Koch, P. 1989. Estimates by species group and region in

the USA of: I. Below-ground root weight as a percentage of

ovendry complete-tree weight; and II. carbon content of

tree portions. Unpublished report on file at USDA Forest

Service, Newtown Square, PA.
20

form and to be consistent with regional data used to

develop yield tables for timber-projection models. The

validity of this method rests on the assumption that the

ratio of total above-ground biomass to merchantable

biomass (estimated in dry weight units) equals the ratio

of total above-ground volume to merchantable volume.

There is considerable variation in the ratios of total to

merchantable volumes among regions and species groups

(Birdsey 1992). For the Nation, the average ratio of total

to merchantable volume is 1.91 for softwoods and 2.44

for hardwoods.

The second step entails converting total tree volume in

cubic feet to carbon in pounds. Separate factors are used

for major forest types and for softwoods and hardwoods

within each forest type, and for broad geographic

regions. The volume-to-carbon conversion factor is

computed in two steps. First, volume in cubic feet is

converted to biomass in dry pounds by multiplying the

number of cubic feet by the mean specific gravity by the

weight of a cubic foot of water (62.4 lb). A weighted

mean specific gravity for softwoods or hardwoods is

estimated from the relative frequency of the three

predominant hardwood or softwood species in each

forest type and region. Second, the biomass in dry

pounds is multiplied by a factor to account for the

average carbon content of the tree. Estimates of the

carbon content of trees used in past studies generally

have ranged from 45 to 50 percent (Houghton et al.

1985) though another study1

 for the United States found

that the average percentage of carbon was 52.1 for

softwoods and 49.1 for hardwoods; there were slight

regional variations. The final factors used to convert

volume (cubic feet) to carbon (pounds) for U.S. forest

types range from 11.41 to 17.76 for softwoods, and

from 11.76 to 19.82 for hardwoods (Birdsey 1992). A

separate set of conversion factors for pure stands of

plantation species also was developed (Birdsey 1996).

Estimating Carbon in Forest Floor

and Coarse Woody Debris

Estimates of the amount of carbon or organic matter on

the forest floor, including coarse woody material, are

available for both broad forest classifications and for

specific ecological types. The estimates of Vogt et al.

(1986) for broad forest-ecosystems are applied to the

forest types common in each state. These reference

estimates are assumed to be representative of relatively

undisturbed, unmanaged, mature secondary forests.

A weighting procedure is used to account for the relative

age structure of forest types in a state or region. This

procedure is identical to that used for estimating soil

carbon, that is, comparing the average age with the

reference age to determine a weighting factor. The factor

is then multiplied by the corresponding estimate of

carbon in the forest floor from Vogt et al. (1986).

Additional assumptions are made to estimate the

dynamics of carbon in the forest floor. For reforestation

of cropland or pasture, it is assumed that there is no

organic matter on the forest floor at age zero, and that

the reference estimates are reached at age 50 in the South

and age 55 elsewhere. For cutover forest land in the

South, it is assumed that there is no organic matter on

the forest floor after harvest because of the general use of

intensive site preparation prior to planting. Elsewhere, it

is assumed that the quantity of organic matter on the

forest floor is equal to 33 percent of the reference

estimate after harvest. After the reference estimates at age

50 or 55 are reached, organic matter accumulates on the

forest floor at a decreasing rate.

Woody debris after harvest is estimated by inverting the

factors used to convert merchantable volume to carbon,

assuming that nonmerchantable carbon remained in the

forest and merchantable carbon entered the harvested

carbon pool. Then, the rate of loss of carbon in woody

debris is estimated using published decomposition

constants (Turner et al. 1995).

Estimating Carbon in Soils

Carbon in soil is estimated with models that relate the

quantity of organic matter to temperature, precipitation,

age class, and land-use history. Data are from a variety of

ecosystem studies. The approach follows that of Burke et

al. (1989), who used a multiple regression procedure to

find the best predictive equations for soil organic carbon

in cropland and grassland in the Central Plains and

adjacent areas. Data from Post et al. (1982) were used to

estimate regression coefficients for a similar, compatible

model for forest lands. The methodology is explained in

Plantinga and Birdsey (1993) and Birdsey (1992).

Estimates of soil carbon developed by Post et al. (1982)

for temperate forests and used to derive estimates for the

United States represent relatively undisturbed,

unmanaged, mature secondary forests. These estimates

are considered reference points and used to generate

simple functions to describe changes in soil carbon

associated with harvesting and land-use change.

Diagrams of the different cases of harvesting and landuse change are in Plantinga and Birdsey (1993).

Because we lack comprehensive statistical databases of

soil carbon linked with above-ground measurements,
21

which could be used to derive empirical estimates of soil

carbon changes from harvesting and land use, we

develop a series of assumptions based on continuing

literature reviews. The most recent compilation of our

assumptions is presented in Heath and Smith (2000). In

general, we use assumptions about: (1) soil carbon at

initial conditions, (2) age associated with the reference

estimates for mature secondary forests, (3) rate of

transition from initial conditions to reference

conditions, and (4) changes after reference conditions are

attained. The literature is inconclusive about many

aspects of the dynamics of soil carbon. For example,

Johnson (1992) found a variety of responses of soil

carbon to harvesting, including both increases and

decreases in soil carbon.

Our assumptions about changes in soil carbon are

similar to those of Houghton et al. (1983, 1985). For the

South, we assume that clearcut harvest is followed by

intensive site preparation, which results in a loss in soil

carbon of 20 percent by age 10. After age 10 we assume

a linear increase to the reference age. For less intensive

harvesting such as partial cutting or regeneration

methods that exclude soil disturbance, no soil carbon

loss is estimated. It is assumed that changes between

reference points are linear, and the rate of change after

reaching reference levels (assumed to be 50 years) is

reduced linearly to zero over a few decades. For regions

other than the South, loss of soil carbon after clearcut

harvest is assumed to be zero, resulting in a constant

level throughout the yield period.

Tree plantations or natural vegetation established on

agricultural land with depleted organic matter can cause

a substantial accumulation of soil organic matter

depending on species, soil characteristics, and climate

(Johnson 1992). For example, Populus spp. established

on sandy soils showed large increases in soil and forestfloor carbon due to high litter production (Dewar and

Cannell 1992).

For replanted pasture in all regions, soil carbon at age

zero is the higher of either: (1) the level estimated with

the equation from Burke et al. (1989), or (2) two-thirds

of the average for secondary forests at the reference age.

For replanted cropland in all regions, soil carbon at age

zero is the higher of either: (1) the level estimated by

Burke et al. (1989), or (2) one-half of the average for

secondary forests at the reference age. It is assumed that

soil carbon increases linearly from the lowest level to the

reference age. In all cases after the reference age is

reached, the rate of accumulation of soil carbon declines

as the forest matures.

Carbon in Wood Products and Landfills

Harvested carbon includes wood removed from the

forest for manufacturing of products or fuelwood.

Logging debris, which remains in the forest, is included

in the forest floor and coarse woody debris.

We used a modification of the stock-change approach

for wood products because a complete inventory of the

volume or mass of carbon in wood products and

landfills is not available. We simulated the most dynamic

portion of the inventory of carbon retained in wood

products and landfills by compiling estimates of wood

production periodically from 1952 to 1997, and

applying to these estimates a model of carbon retention

in various harvest carbon pools (Row and Phelps 1991).

We calculated the carbon inventory in wood products

and landfills for 1987 and 1997 by estimating the

amount of carbon remaining in these pools from each of

the periodic estimates, which were summed to obtain the

totals. Then the estimate for 1987 was subtracted from

the 1997 estimate to obtain the difference in a

compatible way with that for forest-ecosystemcomponents. We used the “production approach” for

wood products, that is, all of the accounting is attributed

to the land area where the wood is grown regardless of

the eventual location and disposition of wood products

(Heath et al. 1996). Imported wood is ignored in this

approach.

The model HARVCARB (Row and Phelps 1991)

estimates four disposition categories— products,

landfills, energy, and emissions. Products and landfills

are combined to monitor the stock of carbon in

harvested wood products. Products are goods

manufactured or processed from wood, including

lumber and plywood for housing and furniture, and

paper for packaging and newsprint. Landfills store

carbon as discarded products that eventually decompose,

releasing carbon as emissions.

The harvested carbon model tracks the fate of carbon as

the harvested wood is processed from roundwood to

products in use to eventual disposition in landfills, or as

burned or decomposed carbon emitted to the

atmosphere. HARVCARB traces removals through three

transformation phases. In the first phase, roundwood is

processed into primary products, e.g., lumber, plywood,

paper, and paperboard. Then, primary products are

transformed into end-use products such as housing,

packaging, and newsprint. The first two phases generate

substantial amounts of byproducts that are used

primarily in energy cogeneration. The third phase

describes the disposal of end-use products, reflecting the
22

length of time products remain in use, and final

disposition patterns. HARVCARB was run by region,

species group, and harvest type to develop equations that

track the harvested carbon pools for use in the

estimation process.

Accounting for Land-Use Change

For land-use change we began with the land base in

1987 and accounted only for change between 1987 and

1997. This approach does not account for any long-term

effects of prior land-use changes on soil carbon. We

counted only the real changes in carbon stocks from

land-use change, ignoring apparent changes that can

occur because of a change in land classification. For

example, if a land area was reclassified from forest to

nonforest, we deducted the change in soil carbon caused

by the shift but not the remaining soil carbon that was

transferred to the new land use. Likewise, for land

reclassified from nonforest to forest, we did not include

the estimated carbon already on the land prior to

reclassification as forest.

The area of land-use change was estimated by using

1987 as the base year. Estimates of losses of forest land to

agriculture and urban use, and corresponding gains in

forest land, are from forest- inventory databases from

successive and recent inventories (if available), and from

USDA Natural Resources Inventory data when forestinventory data are not available (Nat. Resour. Conserv.

Serv. 2000).

Average changes in each carbon pool are estimated by

region and forest type and multiplied by the estimated

area change. There was a separate accounting for effects

of land-use change on each carbon pool. Biomass of new

forest plots from nonforest plots was estimated from the

inventory databases. Biomass of new nonforest plots

from forest plots was estimated from values published

for urban areas by Dwyer et al. (2000). Estimates for

soil, forest floor, and coarse woody debris carbon were

made following the assumptions described previously.

Estimates of carbon retained in wood products from

land clearing were made by estimating the quantity of

merchantable biomass and assuming that all was used for

products.

Note that the effects of land-use change, while treated

separately in the estimation process, are embedded in

each of the reported tables (except where noted) for

complete accounting. Some of the tables include only

the changes in carbon stock attributed to land-use

change between 1987 and 1997. Estimates in these

tables can be subtracted from corresponding tables with

complete carbon accounting to determine how carbon

stocks changed on lands that were classified as forest in

both 1987 and 1997.

Estimation Errors and Data Gaps

The most comprehensive and accurate regional estimates

of carbon flux using inventory data are for above-ground

biomass. However, there are significant gaps in data for

areas that are not inventoried frequently, e.g., interior

Alaska. In addition to sampling and measurement errors,

which are typically small, there also are estimation errors

of the regression models used to estimate tree biomass

from field measurements.

Data on soil and litter carbon are from ecosystem studies

that were not part of a regional statistical sample.

Therefore, regional estimates from these sources include

unknown estimation errors when such data are

extrapolated using empirical models. Also, for many

long-term but suspected significant changes in quantities

of soil carbon, we use assumptions that are logical but

that remain untested.

We did not attempt to estimate the uncertainty of the

estimates presented here because of the variety of

information sources, most of which did not include

error estimates. Estimated changes of small magnitude

may not be significant due to the uncertainty of the

estimation process. Important progress has been made in

applying the principles of uncertainty analysis (Smith

and Heath 2000) and error analysis (Phillips et al. 2000)

in evaluating the results of our estimation process, and in

determining where resources should be allocated for

significant improvements.

The inventory approach does not include all factors of

environmental change. For example, atmospheric

deposition of nitrogen compounds to forest soils affects soil

carbon dynamics and perhaps the allometric

relationships used to estimate tree biomass, yet deposition

effects are not considered. Such factors could be addressed

by linking the current integrated modeling system with

process models that model key dynamic factors.
23

Appendix 2: Comparison of Estimates and Methods

Summary

Continuing studies have produced estimation methods

that were unavailable at the time the estimates for this

report were compiled. As a result, our estimates differ

from those in the EPA greenhouse gas inventory for

2000 (Environ. Prot. Agency 2002) and similar Forest

Service reports published over the last decade. The

following tabulation compares EPA estimates for 1990

and 1997 with the estimates in this report (1987-97,

excluding Alaska and Hawaii), in Mt/yr:

EPA inventory Average for

Carbon component 1990 1997 1987-97

Biomass 131 128 102

Forest floor/ 22 8 11

coarse woody debris

Soil 58 15 25

Products and landfills 57 58 58

Total 268 207 196

Even with many differences in methodology outlined in

the following section, the estimates of changes in carbon

stock by component are similar except for changes in soil

carbon.

Tree Biomass

The higher estimate for 1997 in the EPA inventory is

attributed primarily to the use of a new set of biomass

equations and application of unique volume-to-carbon

conversion factors by tree-size class rather than one

factor for all tree classes. The new nationally consistent

set of biomass equations (Jenkins et al. 2003) produces a

higher estimate for most tree species and diameter classes

than is contained in biomass estimates of inventory

databases. The higher estimate for 1990 has a different

cause: trees were accumulating carbon at a faster rate in

1990 than 1997 due to numerous factors that affect

growth rates.

Forest Floor and Coarse Woody Debris

For this report and some older Forest Service reports,

data for forest floor and coarse woody debris were

combined. Because the data used in the estimation

models did not sufficiently represent coarse woody

debris, that component was underestimated. The

estimates in the EPA greenhouse-gas report are

calculated individually by region, owner, and forest type,

and as a function of the area by age class for each of

these categories. In this report, the calculations were a

function of the volume by region and owner.

Soil

Many approaches are being considered for the difficult

task of estimating changes in soil carbon for forests.

Differences in estimates are attributed to several factors.

The stock of soil carbon in the EPA greenhouse-gas

report was based on soil and forest-type maps rather

than on simple models. Land-use change and the longterm effects of past land-use change were treated

differently in accounting, so the estimation processes

were different. Likewise, the effects of forest type shifts

were treated differently. The high estimate for 1990

(relative to other years) is the result of an estimation

process that linked below-ground to above-ground

carbon in a proportional manner.

Wood Products

The new estimates of carbon flux in wood products and

landfills are nearly identical to the old estimates at both

the national and regional scales. A different model of the

disposition of carbon in wood products was used, as was

the historical starting point for the calculations. These

changes in methodology may have produced offsetting

results.

Point-by-point Comparison

The following tabulation is intended to provide

additional details about the ongoing development of

estimation methods. The table does not strictly compare

the methods used in this or the EPA greenhouse-gas

report, but looks at how methods are changing. The

italics under the column labeled “Birdsey and Heath

1995” identify specific accounting changes for this

report.
24

Carbon pool Birdsey and Heath 1995 Heath et al. 2002

Tree biomass Used FIA standard biomass equations Used nationally consistent biomass equations

(Cost et al. 1990) (Jenkins et al. 2003)

Live and dead trees combined Live and dead trees separate

Root ratios for softwoods and Root ratios for 10 species groups

hardwoods Volume-to-carbon conversion factors by region,

Volume-to-carbon conversion factors species, and size class (Smith et al. 2003)

by region and forest type

Historical estimates from conversion of RPA

Historical estimates from conversion volume estimates to mass

of RPA volume estimates to mass

Understory biomass Percent of overstory biomass by Percent of overstory biomass by forest type

forest type and age class and age class

Forest floor/coarse Forest floor and coarse woody debris Developed equations by region, forest type,

woody debris combined and age class (Smith and Heath 2002)

Used data in Vogt et al. (1986) Data from a comprehensive literature

Single estimate by region and forest review (Smith and Heath 2002)

type, weighted by age class Historical estimates calculated as a

distribution function of region and forest type

Simple dynamics for harvesting and Simulated ratio of woody residue to live

land-use change tree C from growth, management,

and harvest (Chojnacky and Heath 2002)

Data from research studies

Separate relationships by region,

forest type, and owner

CWD decay functions from Turner et al. CWD decay functions from Turner et al. (1995)

1995 (used for logging debris)

Historical estimates calculated as a Historical estimates calculated as a

function of RPA volume function of region and forest type

Soil Multiple regression procedure to Soil carbon based on U.S. soil map

estimate soil carbon from with GIS overlay of forest types

temperature and precipitation

(Post et al. 1982) Type shifts affect historical and projected soil

Type shifts affect soil carbon in carbon

projections only Assumed clearcut did not affect

Assumed clearcut affected soil carbon soil carbon anywhere

in the South Simple dynamics for land-use change

Simple dynamics for land-use change beginning in 1909

projections beginning in 1980 Data for land-use change effects from

(1987) Post and Kwon (2001)

Assumptions for land-use change Soil carbon changes deducted

effects from Houghton et al. for land-use change

(1983, 1985)

Soil carbon changes deducted for

land-use change

Wood products Used model results from Row and Used model results from Skog and

Phelps (1991) Nicholson (1998)

Based on wood production from all Based on wood production from all domestic

domestic sources (by state) sources

Historical data began in 1980 (1952) Historical data began in 1900
25

Appendix 3: Methods for Individual States

The following are considerations for developing a forest

carbon budget at the state level:

• Conflicts between actual dates of the original forest

inventory data and required reporting dates.

• Changes in standards for data collection.

• Missing data.

• Availability of unique state-level data sets.

• Applicability of generic regional or national

estimation methods to specific states.

• Familiarity of staff with inventory methods and

methods for estimating carbon.

The actual dates of data collection used in the most

recent compilation of National Forest statistics are

shown in Table 19. These also are the most recent data

used in compiling the state estimates in this report. In

some cases, more recent inventory data may be available

for states that already have adopted a continuous

(annual) inventory system, or that recently completed

periodic inventories. Estimated trends between 1987 and

1997 are based on the dates shown in Table 19 and the

most recent prior inventory, which on average for the

United States was completed 10 years prior to the dates

shown. If the date of the most recent inventory is earlier

than 1987, reported trends between 1987 and 1997 are

highly suspect.

Changes in data collection standards occur frequently. In

many cases, particularly for the estimates reported in

Smith et al. (2001), adjustments are made to older data

to make them conform to newer data. Nonetheless, we

discovered the following inconsistencies that likely

affected the conversion of inventory data to carbon

estimates as well as the reported trends between 1987

and 1997:

• Change in the definition of forest land for some

western National Forests.

• Changes in the definitions of forest types for some

western National Forests and some states.

• Information on age class not available from earlier

inventories, or collected in a different manner than

for subsequent inventories.

• Forest areas within a state not fully inventoried,

e.g., only forest-area statistics available for the

Adirondack Preserve in New York, and large

portions of West Texas and West Oklahoma.

As mentioned previously, data may be missing or absent,

e.g., parts of Alaska have not been inventoried, or

variables may be missing from online databases. We used

an “imputation” technique for some areas that lacked

data, and for small states with too few inventory sample

points to develop statistically accurate distributions of

areas by age class and owner group. Imputation entails

assigning values to areas with missing data based on

values for other areas with similar characteristics.

The availability of additional and possibly unique data

sets should be evaluated. Remote sensing products can

be used to monitor changes in land cover. Also, some

states have completed fire fuel inventories, and special

land-resource studies may have been conducted for states

or regions.

The applicability of the generic estimation process used

here should be questioned. We applied regionally

specific methods to states within a region. Improved

methods for estimating carbon stocks and stock changes

in forests are becoming available and should be

considered as substitutes for our methods.

Our estimates represent a first approximation of the

contribution of the forestry sector to a state’s

greenhouse-gas inventory. We encourage individual

states to develop expertise in the estimation process so

that individual circumstances can be evaluated carefully

and, where feasible, represented in the estimates. For

some states, the data used in this report may not be the

most recent available, or there may be other data sets

available that can improve the estimates. Methodology

for monitoring carbon changes on the land is changing,

so it may be worthwhile for states to consider

enhancements to the methods used here, or alternate

methods.
26

Table 19.—Dates of most recent FIA data used for carbon

estimates by state

 State Non-NFS lands NFS lands

Northeast

 Connecticut 1985

 Delaware 1986

 Maine 1995 1995

 Maryland 1986

 Massachusetts 1985

 New Hampshire 1997 1997

 New Jersey 1986

 New York 1993 1995

 Pennsylvania 1989 1995

 Rhode Island 1985

 Vermont 1997 1997

 West Virginia 1989 1995

North Central

 Illinois 1985 1985

 Indiana 1997 1997

 Iowa 1990

 Michigan 1993 1993

 Minnesota 1990 1990

 Missouri 1989 1989

 Ohio 1994 1995

 Wisconsin 1996 1996

Southeast

 Florida 1995 1995

 Georgia 1997 1997

 North Carolina 1990 1990

 South Carolina 1993 1993

 Virginia 1992 1992

South Central

 Alabama 1990 1990

 Arkansas 1995 1995

 Kentucky 1988 1988

 Louisiana 1991 1991

 Mississippi 1994 1994

 Oklahoma 1989-93 1993

 Tennessee 1989 1989

 Texas 1992 1992

Great Plains

 Kansas 1990

 Nebraska 1994 1994

 North Dakota 1994 1994

 South Dakota 1996 1986
27

Intermountain

 Arizona 1985 1996

 Colorado 1983 1981-88

 Idaho 1990 1990-95

 Montana 1988 1995

 Nevada 1989 1987

 New Mexico 1987 1987

 Utah 1993 1993

 Wyoming 1984 1985-93

Pacific

 Alaska 1977-94 1978-95

 Oregon 1992 1994-96

 Washington 1988-91 1995

 California 1994 1995

 Hawaii 1985

Table 19.—Continued

 State Non-NFS lands NFS lands
28

Appendix 4: Basic Tables for the 50 United States

Table 20.—Area of forest land in the United States by region, state, and forest land class,

1987, in thousands of acres

 Forest-land class

All Unreserved Reserved Other

State forest land timberland timberland forest land

Southeast

Florida 16,721 14,983 493 1,245

Georgia 24,187 23,660 509 18

North Carolina 19,281 18,749 489 43

South Carolina 12,257 12,179 78 0

Virginia 16,108 15,570 476 62

Subtotal 88,554 85,140 2,045 1,368

South Central

Alabama 21,725 21,659 66 0

Arkansas 16,987 16,673 91 223

Kentucky 12,256 11,908 267 81

Louisiana 13,883 13,873 10 0

Mississippi 16,694 16,673 9 12

Oklahoma 7,283 6,087 11 1,185

Tennessee 13,258 12,839 395 24

Texas 20,505 12,414 780 7,311

Subtotal 122,591 112,126 1,629 8,836

Northeast

Connecticut 1,815 1,776 23 16

Delaware 398 388 3 7

Maine 17,713 17,175 276 262

Maryland 2,632 2,461 153 18

Massachusetts 3,097 3,010 0 87

New Hampshire 5,021 4,803 70 148

New Jersey 1,985 1,914 41 30

New York 18,776 15,799 2,739 238

Pennsylvania 16,997 15,918 708 371

Rhode Island 399 368 8 22

Vermont 4,509 4,424 39 46

West Virginia 11,942 11,799 116 27

Subtotal 85,281 79,835 4,177 1,270

North Central

Illinois 4,266 4,030 236 0

Indiana 4,439 4,296 143 0

Iowa 1,562 1,459 76 27

Michigan 18,221 17,364 623 234

Minnesota 16,583 13,571 1,178 1,834

Missouri 12,523 11,996 224 303

Ohio 7,309 7,141 119 49

Wisconsin 15,319 14,727 261 331

Subtotal 80,222 74,584 2,860 2,778

Continued
29

Great Plains

Kansas 1,358 1,207 23 128

Nebraska 722 536 23 163

North Dakota 460 337 0 123

South Dakota 1,689 1,447 23 220

Subtotal 4,229 3,527 69 634

Intermountain

Arizona 19,384 3,789 2,066 13,529

Colorado 21,338 11,739 1,933 7,665

Idaho 21,818 14,533 3,790 3,495

Montana 21,909 14,736 2,795 4,379

Nevada 8,928 221 294 8,413

New Mexico 15,826 5,180 1,233 9,413

Utah 16,234 3,078 990 12,165

Wyoming 9,966 4,332 3,253 2,381

Subtotal 135,403 57,608 16,355 61,440

Pacific Coast

Alaska 129,045 15,763 8,042 105,240

California 39,381 16,712 4,903 17,766

Hawaii 1,749 700 196 853

Oregon 28,773 22,801 1,923 4,049

Washington 22,521 17,514 3,297 1,710

Subtotal 221,469 73,490 18,361 129,618

Total 737,749 486,310 45,495 205,944

Table 20.—Continued

 Forest-land class

All Unreserved Reserved Other

State forest land timberland timberland forest land
30

Table 21.—Area of forest land in the United States by region, state, and forest land class,

1997, in thousands of acres

 Forest-land class

All Unreserved Reserved Other

State forest land timberland timberland forest land

Southeast

Florida 16,254 14,605 602 1,047

Georgia 24,413 23,796 595 22

North Carolina 19,298 18,639 615 44

South Carolina 12,651 12,419 232 0

Virginia 16,047 15,345 655 47

Subtotal 88,662 84,803 2,699 1,160

South Central

Alabama 21,964 21,911 52 0

Arkansas 18,790 18,392 231 167

Kentucky 12,684 12,347 305 32

Louisiana 13,783 13,693 90 0

Mississippi 18,595 18,587 8 0

Oklahoma 7,665 6,234 45 1,387

Tennessee 13,603 13,265 337 0

Texas 18,354 11,766 133 6,455

Subtotal 125,438 116,196 1,202 8,040

Northeast

Connecticut 1,863 1,815 23 25

Delaware 389 376 3 10

Maine 17,710 16,952 346 412

Maryland 2,701 2,423 153 124

Massachusetts 3,264 2,965 149 150

New Hampshire 4,955 4,551 117 287

New Jersey 1,991 1,864 105 21

New York 18,581 15,406 2,953 222

Pennsylvania 16,905 15,853 833 219

Rhode Island 409 356 8 45

Vermont 4,607 4,461 91 55

West Virginia 12,108 11,900 181 27

Subtotal 85,484 78,923 4,963 1,598

North Central

Illinois 4,294 4,058 236 0

Indiana 4,501 4,342 159 0

Iowa 2,050 1,944 88 19

Michigan 19,335 18,667 577 90

Minnesota 16,796 14,819 1,136 842

Missouri 14,047 13,411 325 311

Ohio 7,855 7,568 140 147

Wisconsin 15,963 15,701 201 61

Subtotal 84,842 80,510 2,862 1,470

Continued
31

Great Plains

Kansas 1,545 1,491 18 37

Nebraska 947 898 32 18

North Dakota 674 442 0 232

South Dakota 1,632 1,487 22 123

Subtotal 4,798 4,317 71 409

Intermountain

Arizona 19,926 4,073 1,771 14,082

Colorado 21,270 11,555 2,407 7,307

Idaho 21,937 17,123 3,529 1,285

Montana 23,232 19,164 3,620 448

Nevada 9,928 169 688 9,071

New Mexico 15,505 4,833 1,420 9,252

Utah 15,705 4,700 770 10,235

Wyoming 10,945 5,085 3,903 1,957

Subtotal 138,448 66,702 18,108 53,637

Pacific Coast

Alaska 127,380 12,395 9,836 105,148

California 38,546 17,952 5,968 14,626

Hawaii 1,749 700 196 853

Oregon 29,720 23,749 2,482 3,489

Washington 21,893 17,418 3,495 980

Subtotal 219,288 72,214 21,977 125,096

Total 746,959 503,666 51,883 191,410

Table 21.—Continued

 Forest-land class

All Unreserved Reserved Other

State forest land timberland timberland forest land
32

Table 22.—Average storage of carbon in the United States by region, state, and forest-ecosystem

component, 1987, in pounds per acre

 Forest-ecosystem component

State Total Trees Soil Forest floor Understory

Southeast

Florida 106,874 30,972 64,451 10,820 632

Georgia 120,349 45,098 63,477 10,853 920

North Carolina 141,438 62,489 67,548 10,126 1,275

South Carolina 126,612 50,125 64,317 11,147 1,023

Virginia 141,915 63,350 67,904 9,369 1,293

Average 127,438 50,407 65,539 10,463 1,029

South Central

Alabama 115,947 41,730 59,940 13,425 852

Arkansas 123,931 49,504 62,650 10,767 1,010

Kentucky 152,083 65,151 75,262 10,340 1,330

Louisiana 128,032 54,090 60,679 12,159 1,104

Mississippi 123,410 49,581 61,611 11,208 1,012

Oklahoma 93,999 16,628 63,160 13,872 339

Tennessee 130,861 56,036 63,598 10,084 1,144

Texas 110,811 34,229 63,362 12,521 699

Average 122,384 45,869 63,783 11,797 936

Northeast

Connecticut 185,460 58,306 108,897 17,066 1,190

Delaware 169,145 64,567 88,284 14,977 1,318

Maine 203,133 38,927 140,154 23,257 794

Maryland 184,613 72,274 95,064 15,800 1,475

Massachusetts 191,418 55,285 116,662 18,343 1,128

New Hampshire 210,188 55,056 132,580 21,428 1,124

New Jersey 142,628 38,281 89,650 13,916 781

New York 195,511 45,400 130,526 18,659 927

Pennsylvania 198,533 59,544 118,584 19,190 1,215

Rhode Island 161,262 45,534 99,309 15,490 929

Vermont 209,309 48,329 139,268 20,725 986

West Virginia 180,375 53,849 107,408 18,020 1,099

Average 185,964 52,946 113,865 18,072 1,081

North Central

Illinois 186,965 58,275 109,133 18,368 1,189

Indiana 187,337 58,260 110,783 17,106 1,189

Iowa 168,789 42,130 108,272 17,527 860

Michigan 180,858 45,321 115,249 19,363 925

Minnesota 171,597 35,017 116,251 19,615 715

Missouri 154,557 32,860 103,327 17,699 671

Ohio 174,170 47,422 107,718 18,062 968

Wisconsin 176,630 42,625 114,324 18,811 870

Average 175,113 45,239 110,632 18,319 923

Continued
33

Great Plains

Kansas 126,289 33,018 79,292 13,304 674

Nebraska 126,727 38,156 74,206 13,588 779

North Dakota 134,619 28,452 90,116 15,470 581

South Dakota 153,285 42,650 79,298 30,466 870

Average 135,230 35,569 80,728 18,207 726

Intermountain

Arizona 137,699 38,111 68,084 30,726 778

Colorado 153,172 38,546 70,973 42,867 787

Idaho 174,305 56,899 79,680 36,565 1,161

Montana 166,680 53,546 79,034 33,008 1,093

Nevada 160,131 35,867 67,700 55,832 732

New Mexico 128,318 28,245 67,964 31,533 576

Utah 152,688 32,885 70,591 48,541 671

Wyoming 154,252 39,950 78,464 35,022 815

Average 153,406 40,506 72,811 39,262 827

Pacific Coast

Alaska 173,287 35,776 87,000 49,781 730

California 179,328 52,858 87,000 38,392 1,079

Hawaii 113,815 5,681 86,985 21,032 116

Oregon 197,560 69,522 87,112 39,507 1,419

Washington 207,610 82,532 87,234 36,160 1,684

Average 174,320 49,274 87,066 36,974 1,006

U.S. average 153,408 45,687 84,918 21,871 932

Table 22.—Continued

 Forest-ecosystem component

State Total Trees Soil Forest floor Understory
34

Table 23.—Average storage of carbon in the United States by region, state, and forest-ecosystem

component, 1997, in pounds per acre

 Forest-ecosystem component

State Total Trees Soil Forest floor Understory

Southeast

Florida 111,748 33,428 65,533 12,105 682

Georgia 124,780 47,255 64,214 12,346 964

North Carolina 144,691 64,529 68,476 10,369 1,317

South Carolina 122,591 46,992 62,500 12,140 959

Virginia 148,533 67,823 69,770 9,557 1,384

Average 130,469 52,005 66,099 11,303 1,061

South Central

Alabama 120,959 45,118 61,172 13,748 921

Arkansas 125,717 51,389 61,850 11,429 1,049

Kentucky 151,825 68,879 72,102 9,438 1,406

Louisiana 133,301 55,945 64,086 12,127 1,142

Mississippi 124,378 47,846 61,820 13,736 976

Oklahoma 98,408 24,922 60,814 12,163 509

Tennessee 137,879 63,976 62,993 9,604 1,306

Texas 114,297 36,153 64,957 12,449 738

Average 125,845 49,279 63,724 11,837 1,006

Northeast

Connecticut 187,546 58,718 109,550 18,080 1,198

Delaware 168,581 71,425 80,544 15,153 1,458

Maine 199,397 38,352 138,019 22,244 783

Maryland 186,838 74,237 94,785 16,301 1,515

Massachusetts 193,187 58,213 115,102 18,683 1,188

New Hampshire 224,535 66,952 134,969 21,248 1,366

New Jersey 157,734 50,424 91,053 15,228 1,029

New York 202,824 50,077 133,043 18,682 1,022

Pennsylvania 201,290 60,363 120,761 18,934 1,232

Rhode Island 159,437 44,804 97,298 16,421 914

Vermont 227,104 67,267 137,458 21,006 1,373

West Virginia 194,114 68,568 106,442 17,705 1,399

Average 191,882 59,117 113,252 18,307 1,206

North Central

Illinois 186,564 57,892 109,082 18,409 1,181

Indiana 203,714 76,014 109,030 17,119 1,551

Iowa 143,618 42,575 82,207 17,967 869

Michigan 185,832 54,745 110,533 19,437 1,117

Minnesota 171,600 36,439 114,935 19,482 744

Missouri 146,439 33,320 94,908 17,531 680

Ohio 181,639 59,575 102,391 18,458 1,216

Wisconsin 175,875 46,185 110,992 17,755 943

Average 174,410 50,843 104,260 18,270 1,038

Continued
35

Great Plains

Kansas 142,937 39,757 88,631 13,737 811

Nebraska 127,053 42,401 69,933 13,854 865

North Dakota 131,224 29,829 82,581 18,205 609

South Dakota 150,160 36,891 82,817 29,699 753

Average 137,844 37,220 80,990 18,874 760

Intermountain

Arizona 137,274 37,354 68,966 30,192 762

Colorado 153,791 39,752 71,247 41,982 811

Idaho 175,622 60,089 78,724 35,582 1,226

Montana 164,911 52,614 75,515 35,708 1,074

Nevada 155,243 36,107 62,327 56,072 737

New Mexico 127,899 26,467 69,472 31,420 540

Utah 154,896 34,330 72,203 47,662 701

Wyoming 148,134 40,090 73,105 34,121 818

Average 152,221 40,850 71,445 39,092 834

Pacific Coast

Alaska 173,978 36,006 87,850 49,388 735

California 184,771 56,840 88,403 38,367 1,160

Hawaii 113,809 5,680 86,964 21,050 116

Oregon 196,230 71,964 84,976 37,822 1,469

Washington 208,688 81,430 88,916 36,681 1,662

Average 175,495 50,384 87,422 36,661 1,028

U.S. average 155,452 48,528 83,885 22,049 990

Table 23.—Continued

 Forest-ecosystem component

State Total Trees Soil Forest floor Understory
36

Table 24.—Total storage of carbon in the United States by region, state, and forest-ecosystem component, 1987,

in thousands of metric tons

Forest-ecosystem component

State Total Trees Soil Forest floor Understory Products

Southeast

Florida 881,457 234,901 488,820 82,063 4,794 70,880

Georgia 1,514,509 494,782 696,418 119,070 10,098 194,143

North Carolina 1,363,318 546,512 590,762 88,562 11,153 126,329

South Carolina 790,006 278,680 357,583 61,977 5,687 86,079

Virginia 1,123,620 462,869 496,141 68,454 9,446 86,710

Subtotal 5,672,911 2,017,744 2,629,724 420,125 41,178 564,140

South Central

Alabama 1,309,064 411,225 590,665 132,296 8,392 166,485

Arkansas 1,089,981 381,443 482,741 82,963 7,785 135,049

Kentucky 873,848 362,204 418,416 57,483 7,392 28,353

Louisiana 916,608 340,611 382,106 76,566 6,951 110,375

Mississippi 1,088,740 375,438 466,532 84,867 7,662 154,241

Oklahoma 327,266 54,932 208,651 45,827 1,121 16,735

Tennessee 859,862 336,987 382,467 60,641 6,877 72,890

Texas 1,109,773 318,363 589,331 116,462 6,497 79,120

Subtotal 7,575,142 2,581,203 3,520,910 657,104 52,678 763,248

Northeast

Connecticut 158,877 48,002 89,653 14,050 980 6,192

Delaware 32,657 11,647 15,926 2,702 238 2,144

Maine 1,700,979 312,757 1,126,052 186,859 6,383 68,929

Maryland 246,916 86,284 113,491 18,863 1,761 26,518

Massachusetts 271,579 77,653 163,863 25,764 1,585 2,713

New Hampshire 491,268 125,386 301,941 48,800 2,559 12,581

New Jersey 134,827 34,466 80,714 12,529 703 6,415

New York 1,702,154 386,652 1,111,637 158,909 7,891 37,066

Pennsylvania 1,567,850 459,073 914,255 147,948 9,369 37,205

Rhode Island 30,407 8,234 17,957 2,801 168 1,247

Vermont 440,539 98,848 284,846 42,389 2,017 12,439

West Virginia 999,358 291,680 581,795 97,606 5,953 22,324

Subtotal 7,777,410 1,940,681 4,802,131 759,219 39,606 235,773

North Central

Illinois 382,816 112,765 211,177 35,543 2,301 21,031

Indiana 392,802 117,304 223,059 34,442 2,394 15,603

Iowa 141,353 29,850 76,712 12,418 609 21,763

Michigan 1,546,249 374,572 952,530 160,035 7,644 51,468

Minnesota 1,322,776 263,397 874,437 147,545 5,375 32,021

Missouri 916,081 186,655 586,932 100,538 3,809 38,147

Ohio 598,370 157,230 357,147 59,885 3,209 20,900

Wisconsin 1,278,826 296,189 794,400 130,710 6,045 51,482

Subtotal 6,579,273 1,537,962 4,076,394 681,116 31,387 252,414

Continued
37

Great Plains

Kansas 96,264 20,337 48,839 8,195 415 18,478

Nebraska 50,073 12,490 24,291 4,448 255 8,590

North Dakota 32,291 5,937 18,803 3,228 121 4,202

South Dakota 122,997 32,682 60,765 23,346 667 5,536

Subtotal 301,626 71,446 152,699 39,217 1,458 36,806

Intermountain

Arizona 1,267,238 335,096 598,629 270,159 6,839 56,515

Colorado 1,490,435 373,073 686,928 414,902 7,614 7,918

Idaho 1,820,791 563,120 788,574 361,875 11,492 95,729

Montana 1,751,765 532,139 785,443 328,035 10,860 95,288

Nevada 648,534 145,245 274,150 226,091 2,964 84

New Mexico 950,454 202,761 487,888 226,363 4,138 29,304

Utah 1,130,492 242,148 519,792 357,432 4,942 6,178

Wyoming 781,152 180,600 354,706 158,322 3,686 83,837

Subtotal 9,840,859 2,574,182 4,496,110 2,343,180 52,534 374,853

Pacific Coast

Alaska 10,158,232 2,094,119 5,092,489 2,913,879 42,737 15,007

California 3,375,477 944,209 1,554,093 685,808 19,270 172,098

Hawaii 90,271 4,506 68,992 16,682 92

Oregon 2,873,802 907,354 1,136,927 515,621 18,517 295,382

Washington 2,330,685 843,107 891,137 369,387 17,206 209,847

Subtotal 18,828,468 4,793,295 8,743,638 4,501,378 97,822 692,334

Total 56,575,690 15,516,515 28,421,605 9,401,338 316,664 2,919,569

Table 24.—Continued

Forest-ecosystem component

State Total Trees Soil Forest floor Understory Products
38

Table 25.—Total storage of carbon in the United States by region, state, and forest-ecosystem component, 1997,

in thousands of metric tons

Forest-ecosystem component

State Total Trees Soil Forest floor Understory Products

Southeast

Florida 916,173 246,454 483,162 89,249 5,030 92,279

Georgia 1,624,103 523,277 711,078 136,714 10,679 242,355

North Carolina 1,427,267 564,845 599,389 90,760 11,527 160,746

South Carolina 813,720 269,670 358,663 69,665 5,503 110,219

Virginia 1,187,812 493,659 507,832 69,560 10,075 106,686

Subtotal 5,969,074 2,097,905 2,660,123 455,948 42,814 712,284

South Central

Alabama 1,426,321 449,496 609,438 136,968 9,173 221,246

Arkansas 1,234,842 437,992 527,145 97,414 8,939 163,353

Kentucky 909,113 396,299 414,845 54,305 8,088 35,576

Louisiana 972,417 349,766 400,661 75,820 7,138 139,032

Mississippi 1,246,852 403,568 521,441 115,862 8,236 197,745

Oklahoma 364,492 86,652 211,444 42,290 1,768 22,336

Tennessee 940,338 394,739 388,670 59,256 8,056 89,618

Texas 1,053,030 300,990 540,791 103,642 6,143 101,464

Subtotal 8,147,405 2,819,503 3,614,434 685,555 57,541 970,371

Northeast

Connecticut 165,157 49,611 92,560 15,276 1,012 6,698

Delaware 32,052 12,618 14,229 2,677 258 2,270

Maine 1,685,808 308,092 1,108,755 178,690 6,288 83,983

Maryland 257,266 90,939 116,110 19,968 1,856 28,393

Massachusetts 290,414 86,193 170,425 27,663 1,759 4,373

New Hampshire 521,669 150,482 303,359 47,758 3,071 17,000

New Jersey 149,970 45,542 82,237 13,753 929 7,508

New York 1,754,185 422,062 1,121,331 157,458 8,614 44,721

Pennsylvania 1,588,828 462,858 925,983 145,183 9,446 45,357

Rhode Island 30,938 8,316 18,059 3,048 170 1,345

Vermont 490,012 140,575 287,259 43,899 2,869 15,410

West Virginia 1,091,609 376,586 584,592 97,237 7,685 25,508

Subtotal 8,057,907 2,153,874 4,824,900 752,610 43,957 282,566

North Central

Illinois 387,708 112,770 212,484 35,859 2,301 24,294

Indiana 435,537 155,207 222,621 34,955 3,167 19,587

Iowa 155,754 39,593 76,450 16,709 808 22,195

Michigan 1,695,653 480,124 969,388 170,464 9,798 65,879

Minnesota 1,350,092 277,618 875,656 148,426 5,666 42,725

Missouri 976,576 212,297 604,712 111,702 4,333 43,533

Ohio 672,114 212,269 364,827 65,768 4,332 24,918

Wisconsin 1,339,790 334,411 803,670 128,563 6,825 66,321

Subtotal 7,013,224 1,824,290 4,129,808 712,445 37,230 309,451

Continued
39

Great Plains

Kansas 119,463 27,864 62,117 9,627 569 19,286

Nebraska 63,986 18,222 30,054 5,954 372 9,384

North Dakota 44,218 9,114 25,231 5,562 186 4,124

South Dakota 117,763 27,305 61,298 21,983 557 6,620

Subtotal 345,429 82,505 178,700 43,126 1,684 39,414

Intermountain

Arizona 1,303,092 337,613 623,332 272,886 6,890 62,370

Colorado 1,494,658 383,527 687,394 405,042 7,827 10,868

Idaho 1,858,184 597,918 783,352 354,065 12,202 110,647

Montana 1,869,287 554,445 795,772 376,290 11,315 131,466

Nevada 699,284 162,603 280,677 252,510 3,318 175

New Mexico 926,744 186,141 488,598 220,976 3,799 27,230

Utah 1,110,523 244,553 514,343 339,524 4,991 7,112

Wyoming 811,091 199,030 362,938 169,398 4,062 75,663

Subtotal 10,072,863 2,665,830 4,536,406 2,390,692 54,405 425,531

Pacific Coast

Alaska 10,073,220 2,080,362 5,075,902 2,853,571 42,456 20,928

California 3,436,367 993,819 1,545,685 670,831 20,282 205,751

Hawaii 90,289 4,506 68,992 16,700 92 ————

Oregon 2,962,380 970,136 1,145,547 509,871 19,799 317,026

Washington 2,309,458 808,649 882,986 364,261 16,503 237,059

Subtotal 18,871,715 4,857,473 8,719,112 4,415,234 99,132 780,764

Total 58,477,619 16,501,381 28,663,483 9,455,609 336,763 3,520,382

Table 25.—Continued

Forest-ecosystem component

State Total Trees Soil Forest floor Understory Products
40

Appendix 5: Sample Tables for Pennsylvania

A set of tables in this format is available for each state at: http://www.fs.fed.us/ne/global.

Table 1.—Area in Pennsylvania by land class, in thousands of acres

Average annual change

Land class 1987 1992 1997 1987-92 1992-97 1987-97

Timberland 15,918 15,885 15,853 -7 -7 -7

Other forest land 371 295 219 -15 -15 -15

Reserved timberland 708 771 833 12 12 12

Total 16,997 16,951 16,905 -9 -9 -9

Table 2.—Area of forest land in Pennsylvania by forest type, in thousands of acres

Average annual change

Forest type 1987 1992 1997 1987-92 1992-97 1987-97

White-red-jack-pine 887 851 814 -7 -7 -7

Spruce-fir 56 66 75 2 2 2

Longleaf-slash pine (planted) 0 0 0 0 0 0

Longleaf-slash pine (natural) 0 0 0 0 0 0

Loblolly-shortleaf pine (planted) 0 0 0 0 0 0

Loblolly-shortleaf pine (natural) 147 145 143 0 0 0

Oak-pine 288 324 359 7 7 7

Oak-hickory 8,457 8,237 8,016 -44 -44 -44

Oak-gum-cypress 0 12 24 2 2 2

Elm-ash-cottonwood 569 485 400 -17 -17 -17

Maple-beech-birch 5,995 6,319 6,644 65 65 65

Aspen-birch 441 414 387 -5 -5 -5

Other forest types 0 0 0 0 0 0

Nonstocked 155 99 43 -11 -11 -11

Total 16,997 16,951 16,905 -9 -9 -9
41

Table 3.—Total carbon stock on forest land and in harvested wood products in Pennsylvania, and annual

change by forest type, in Mt

Average annual change

Forest type 1987 1992 1997 1987-92 1992-97 1987-97

White-red-jack-pine 88.7 87.7 86.6 -0.20 -0.23 -0.21

Spruce-fir 5.3 5.9 6.3 0.11 0.10 0.10

Longleaf-slash pine (planted) 0.0 0.0 0.0 0.00 0.00 0.00

Longleaf-slash pine (natural) 0.0 0.0 0.0 0.00 0.00 0.00

Loblolly-shortleaf pine (planted) 0.0 0.0 0.0 0.00 0.00 0.00

Loblolly-shortleaf pine (natural) 7.6 8.1 8.4 0.09 0.08 0.08

Oak-pine 19.9 21.3 22.8 0.29 0.30 0.29

Oak-hickory 724.4 703.7 682.2 -4.14 -4.29 -4.21

Oak-gum-cypress 0.0 0.6 1.1 0.11 0.11 0.11

Elm-ash-cottonwood 31.5 26.7 21.9 -0.97 -0.95 -0.96

Maple-beech-birch 641.1 680.4 718.9 7.86 7.70 7.78

Aspen-birch 32.3 31.3 30.2 -0.21 -0.21 -0.21

Other forest types 6.6 7.2 7.7 0.13 0.11 0.12

Nonstocked 10.4 6.4 2.5 -0.80 -0.78 -0.79

Total 1,567.8 1,579.2 1,588.8 2.27 1.93 2.10

Table 5.—Total carbon stock on forest land and in harvested wood products in Pennsylvania, and

annual change by owner, in Mt

Average annual change

Owner group 1987 1992 1997 1987-92 1992-97 1987-97

National forest 58.0 55.8 53.5 -0.44 -0.45 -0.45

Other public 358.7 359.2 359.2 0.10 0.01 0.05

Forest industry 82.3 76.9 71.4 -1.07 -1.10 -1.09

Other private 1,068.9 1,087.3 1,104.7 3.68 3.48 3.58

Total 1,567.8 1,579.2 1,588.8 2.27 1.93 2.10

Table 4.—Total carbon stock on forest land and in harvested wood products in Pennsylvania, and annual

change by accounting component, in Mt

Average annual change

Component 1987 1992 1997 1987-92 1992-97 1987-97

Biomass 468.4 470.3 472.3 0.37 0.40 0.39

Forest floor/coarse woody debris 147.9 146.6 145.2 -0.27 -0.29 -0.28

Soils 914.3 920.1 926.0 1.17 1.17 1.17

Wood products and landfills 37.2 42.2 45.4 0.99 0.64 0.82

Total 1,567.8 1,579.2 1,588.8 2.27 1.93 2.10
42

Table 6.— Change in total carbon stock on forest land and in harvested wood products in

Pennsylvania, attributed to land-use change, in Mt

Average annual change

Component 1987 1992 1997 1987-92 1992-97 1987-97

Biomass 0.0 -2.7 -5.1 -0.55 -0.47 -0.51

Forest floor/coarse woody debris 0.0 -1.0 -1.9 -0.19 -0.19 -0.19

Soils 0.0 -3.0 -5.5 -0.59 -0.50 -0.55

Wood products and landfills 0.0 0.3 0.7 0.06 0.07 0.07

Total 0.0 -6.3 -11.8 -1.27 -1.09 -1.18
Printed on Recycled Paper

Birdsey, R.A.; Lewis, G.M. 2003. Carbon in U.S. forests and wood products,

1987-1997: state-by-state estimates. Gen. Tech. Rep. NE-310. Newtown

Square, PA: U.S. Department of Agriculture, Forest Service, Northeastern

Research Station. 42 p.

Estimated changes in carbon stocks are reported for the forests and wood products

of the 50 U.S. States. Carbon stocks on forest land and in harvested wood products

increased between 1987 and 1997 at an annual rate of 190 million metric tons.

Most of this increase was in biomass, followed closely by wood products and

landfills. Changes in land use since 1987 caused a small decrease in carbon

stocks, but this loss was offset by large gains on existing forest land. The East had

the greatest gain in carbon stocks with smaller gains estimated for the West. Most

of the individual states showed increases in ecosystem and wood-products carbon.

Observed changes were attributed to distinct regional and local factors, e.g., timber

production, land-use change, and natural disturbance.

Keywords: global change, forest carbon, forest inventory
Headquarters of the Northeastern Research Station is in Newtown Square,

Pennsylvania. Field laboratories are maintained at:

Amherst, Massachusetts, in cooperation with the University of Massachusetts

Burlington, Vermont, in cooperation with the University of Vermont

Delaware, Ohio

Durham, New Hampshire, in cooperation with the University of New Hampshire

Hamden, Connecticut, in cooperation with Yale University

Morgantown, West Virginia, in cooperation with West Virginia University

Parsons, West Virginia

Princeton, West Virginia

Syracuse, New York, in cooperation with the State University of New York,

College of Environmental Sciences and Forestry at Syracuse University

Warren, Pennsylvania

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