United States

Department of

Agriculture

Forest Service

Northern

Research Station

General Technical

Report NRS-67

FORCARB2: 

An Updated Version of the U.S. 

Forest Carbon Budget Model

Linda S. Heath

Michael C. Nichols

James E. Smith

John R. Mills
Printed on Recycled Paper

Published by: For additional copies:

U.S. FOREST SERVICE U.S. Forest Service

11 CAMPUS BLVD SUITE 200 Publications Distribution

NEWTOWN SQUARE, PA 19073 359 Main Road

Delaware, OH 43015

August 2010 Fax: (740) 368-0152

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

The Authors

LINDA S. HEATH (Lheath@fs.fed.us), MICHAEL C. NICHOLS (Mnichols@fs.fed.us), and 

JAMES E. SMITH (Jsmith11@fs.fed.us), are, respectively, research forester, programmer 

analyst, and research plant physiologist, with the U.S. Forest Service’s Northern 

Research Station at Durham, New Hampshire. JOHN R. MILLS (jmills@fs.fed.us) is a 

research forester with the U.S. Forest Service’s Pacific Northwest Research Station at 

Portland, Oregon.

Manuscript received for publication October 2009

Abstract

FORCARB2, an updated version of the U.S. FORest CARBon Budget Model (FORCARB), 

produces estimates of carbon stocks and stock changes for forest ecosystems and 

forest products at 5-year intervals. FORCARB2 includes a new methodology for carbon 

in harvested wood products, updated initial inventory data, a revised algorithm for dead 

wood, and now includes public forest land, reserved forest land, and forest land of low 

productivity. The model has been used to provide estimates and projections for policyrelated needs, including the Resources Planning Act timber resource assessment and 

forest-related greenhouse gas inventories of the United States, and has provided the basis 

for an analysis of forest carbon for Ontario, Canada. The program is written in FORTRAN 

and is text based, though virtually every parameter is defined by input text-based files that 

can be modified or built by the user. We expect users who are fairly advanced in terms 

of knowledge about computers will be most capable in using this model. Step-by-step 

instructions for running the program, input and output files, and codes used are included, 

and input files for public forest lands of the United States are provided as an example. All 

electronic files for download, including the model source code, executable files, and input 

and output files are available at http://nrs.fs.fed.us/pubs/35613.

The computer program described in this publication is made available with the 

understanding that the USDA cannot assure its accuracy, completeness, reliability, or 

suitability for any other purpose than that reported. The recipient may not assert any 

proprietary rights thereto nor represent it to anyone as other than a Government-produced 

computer program. 

The use of trade, firm, or corporation names in this publication is for the information 

and convenience of the reader. Such use does not constitute an official endorsement 

by the U.S. Department of Agriculture or Forest Service of any product or service to the 

exclusion of others that may be suitable. 

Cover illustration by Eric Fiegenbaum.
Contents

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

Description .of .the .System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

FORCARB2 Methodology for Calculating Carbon Pools in Forest Ecosystems . . . . . . . . . . . . . . . . . . . 3

Down Dead Wood Carbon Pool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

 . . Mortality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

 . . Logging .Residue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

FORCARB2 .Methodology .for .Calculating .Carbon .in .HWP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Example .Dataset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Example .Graphics .from .FORCARB2 .Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Interpretation of Main Output from bicreg File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Forest Carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Carbon .in .Harvested .Wood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Description of the Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Step 1: ATLAS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

 . . IUSCAN05 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

 . . MUSCAN05 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

 . . HUSCAN05 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

 . . Other ATLAS05H Input Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Step 2: Running FORCARB2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Step .3: .Post-Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Future .Use .of .FORCARB2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Literature .Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Appendix .A . .Quick .Start .Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Appendix .B . .Step-by-Step .Instructions .to .Run .the .Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Appendix .C . .FORCARB2 .CD .Content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Appendix D. FORCARB2 Input Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Table D1. Data structure of coefs_atlas.txt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Table D2. Excerpt from coefs_atlas.txt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Table D3. Excerpt from coefs_bark.txt, bark multipliers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Table .D4 . .Excerpt .from .coefs_decay.txt, decay coefficients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Table D5. Excerpt from coefs_emitted.txt, energy recapture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Table D6. Excerpt from coefs_ff.txt, forest floor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Table D7. Excerpt from coefs_gs.txt, growing stock multipliers . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Table D8. Excerpt from coefs_gsvol.txt, growing stock fractions . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Table D9. Excerpt from coefs_livetree.txt, live tree density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Table .D10 . .Excerpt .from .coefts_mort.txt, .mortality .for .down .dead . . . . . . . . . . . . . . . . . . . . . . . . . 33
Appendix D. FORCARB2 Input Files (continued)

Table D11. Excerpt from coefs_owners.txt, broad owner groups . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Table D12. Excerpt from coefs_pfates.txt, disposition for harvest . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Table D13. Excerpt from coefs_resid.txt, dead wood sub pool ratios . . . . . . . . . . . . . . . . . . . . . . . . 35

Table D14. Excerpt from coefs_sdeadtree.txt, standing dead . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Table D15. Excerpt from coefs_soil.txt, soil carbon density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Table .D16 . .Excerpt .from .coefs_under.txt, .understory .carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Table D17. Excerpt from coefs_weight.txt, volume to carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Table D18. Excerpt from flags_output.txt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Table D19. Example lines from merch.txt, ATLAS to FORCARB . . . . . . . . . . . . . . . . . . . . . . . . . 38

Table .D20 . .Excerpt .from .mu_tables.txt, .MU .to .coefs .match . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Appendix E. FORCARB2 Output Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Table E1. Example bicmur.txt file, harvested wood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Table E2. Example bicreg.txt, summary carbon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Table .E3 . .Excerpt .from .findat.txt, FORCARB2 output file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Appendix .F . .Forest .Types .Used .in .FORCARB2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

Appendix .G . .Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
1

FORCARB2: An Updated Version 

of the U.S. Forest Carbon Budget Model

Introduction

FORCARB2 is an updated version of the U.S. FORest CARBon Budget Model,

FORCARB (Plantinga and Birdsey 1993). The model produces carbon stocks

and stock change projections for forest ecosystems and forest products at 5-year

intervals. Data from the U.S. Forest Service, Forest Inventory and Analysis (FIA)

Program (U.S. Forest Service 2009) were used as inputs to the modeling system

particularly for initial inventories, in construction of growth-yield curves, and for

harvest information such as utilization rates. 

FORCARB2 was developed to produce forest carbon projections consistent

with the 2005 update of the national timber resource assessment mandated by

the Forest and Rangeland Renewable Resources Planning Act (RPA) of 1974

(as amended by the National Forest Management Act of 1976 and the 1990

Food Protection Act). The RPA directs the Secretary of Agriculture to prepare a

Renewable Resources Planning Assessment with decadal updates. The 1990 Food

Protection Act requires the Forest Service to assess impacts of climate change

and identify opportunities to mitigate the buildup of carbon dioxide (Joyce and

Birdsey 2000). The assessment includes “an analysis of present and anticipated

uses, demand for, and supply of the renewable resources, with consideration of

the international resource situation, and an emphasis on pertinent supply, demand

and price relationship trends.” In practice, this has meant projecting resource

trends for the next 50 years. 

FORCARB2 was one of the suite of RPA timber resource assessment (Adams

and Haynes 1996; Haynes and others 2007) models used in the 1990s and

2000s that were linked with the Aggregate Timber Assessment (ATLAS) model

(Mills and Kincaid 1992). ATLAS provides areas and volumes of inventory

and harvests. Harvests were determined economically by the other models in

the assessment. ATLAS and FORCARB2 can be used without being linked to

the other assessment models, though harvest must be specified. See Birdsey 

and Heath (1995) and Joyce and others (1995) for FORCARB use in an

RPA assessment. FORCARB and FORCARB2 provided estimates for forest

greenhouse gas inventories of the United States (U.S. EPA 2002 and others in the

series; Woodbury and others 2007), and were the basis for the FORCARB-ON

model which provides similar analyses for the province of Ontario (Columbo and

others 2007; Chen and others 2008). Heath and Birdsey (1993) used the model to

test an hypothesis about the effects of harvest on carbon sequestration, and Smith

and Heath (2004) projected carbon on National Forest System and other public

lands.
2

FORCARB2 includes a new methodology for carbon in harvested wood

products, updated initial inventory data, a revised algorithm for dead wood,

and now covers public forest land, reserved forest land, and forest land of low

productivity. It has been further tested and used. This is a legacy model: it is

written in FORTRAN and uses text-based input and output files. Knowledgeable 

computer users will be most capable of using the model. 

In this user’s guide, we discuss facets of the system being modeled, including

definitions of important terms, illustrations of the types of information generated 

by the model, and descriptions of models needed to produce carbon projections. 

Step-by-step instructions for running FORCARB2, input and output files, and 

codes used are presented in the appendices. Input data for public forest lands of

the United States are provided as an example. These are the data files we have 

created and used for projecting forest carbon on public forestland for some

studies.

Description of the System

The amount of forest carbon in a changing landscape is determined by two

variables: the area of forest and carbon per area. FORCARB2 accounts for

changes in both. If forest area is constant, any change in total forest carbon is

due to change in the amount of carbon per area, for example from tree growth,

mortality, or removal through harvest. There always will be change in the forest

on a per-area basis, though the changes in carbon may balance out to zero over a

given time period. Vegetation on specific areas of land may change from forest 

to nonforest such as cropland, or from nonforest to forest. Changes in carbon are

common following land cover or land use changes, or due to growing forests on

areas that remain forest. A stand-level model focuses on changes on a particular

area of land. This inventory system covers the landscape. The projected forest

carbon pools are above- and belowground live tree, standing dead tree, down

dead wood, forest floor, and soil carbon. Figure 1 shows these forest carbon pools 

and the processes and relationships between them.

The disposition of carbon in harvested wood products (HWP) is estimated in

four categories over time based on Smith and others (2006), following Row and

Phelps (1996) and Birdsey (1996): products in use, landfilled carbon, carbon in 

wood burned for energy, and carbon emitted without energy capture. Products in

use include end-use products such as wood used in homes and other buildings,

wooden furniture, wooden containers, and paper products. Carbon in landfills is 

assumed to be deposited for the long term, with slow decay rates. Carbon emitted

with energy capture is primarily from recycling of harvested wood byproducts

associated with processing at mills, but also includes wood burned in utility

plants to produce electricity as well as wood burned directly for heating. Carbon

emitted without energy capture includes mill residues or other wood products

burned or decayed without capture and use of the heat produced. Because

FORCARB2 estimates carbon stocks in forests, carbon in HWP pools should be

added to the forest carbon stocks for an estimate of stored carbon. 
3

Figure 1.—Stocks and flows 

of forest carbon in FORCARB2 

(boxes indicate outputs).

Imports and exports of harvested wood from trade can be a significant factor 

in a forest carbon budget for a region. In this approach, the resulting carbon in

harvested wood products includes carbon changes in wood grown in the region

that may actually be exported and no longer remains in the region, and does not

include carbon in wood products that have been imported into the region. The

fate of exported wood is assumed to be similar to that of wood used locally,

following the principles of production approach accounting (Penman and

others 2003).

FORCARB2 Methodology 

for Calculating Carbon Pools in Forest Ecosystems

To estimate and project forest carbon, FORCARB2 was linked to the ATLAS

model (Mills and Kincaid 1992), which in turn was linked to other parts of the

RPA timber assessment modeling system (U.S. EPA 2002). This linked system

provided consistent estimates of timber, biomass, carbon, growth and harvest,

and area change estimates. Beginning with an initial inventory, ATLAS projects

timber inventories by allowing for growth, harvest, land-use change, and changes

in management intensity through time. The input files contain information such 

as starting inventory in terms of area and volume per area by age class, growthyield relationships, projected areas of forest (accounting for future changes

in land use or forest type), harvest requests, and type of harvest. ATLAS is

essentially a forest area and volume accounting framework that can be used at a

variety of scales based on the stratification of input data. FORCARB2 uses output 

files from ATLAS containing projections, converts these tree projections to 
4

above- and belowground live tree carbon stocks, and estimates carbon in standing

dead trees, down dead wood, forest floor, and soil carbon, including carbon in 

harvested wood products. 

Like FORCARB, the backbone of FORCARB2 is made up of sets of equations

for estimating stocks for each carbon pool, including live tree, standing dead tree,

understory, down dead wood, forest floor, and organic portion of soil, based on 

forest inventory information from ATLAS combined with data from ecological

studies. Definitions for each pool are included in Appendix G. The equations 

are used to estimate mass density of carbon within each pool. These values are

multiplied by the forest area to obtain values for total carbon. With this method,

values can be obtained similarly for carbon in inventory (current carbon), carbon

in removals (including carbon in harvested areas and carbon in thinned areas),

and net carbon from areas that changed land use. Change in carbon stocks is

calculated by subtracting consecutive carbon stocks, and dividing by the time

interval between stock estimates.

The mass densities of live and standing dead trees are calculated following

methods of Smith and others (2003), who described models that estimate

aboveground live and standing dead tree carbon as a function of plot-level

merchantable growing-stock volume. Models differ by region, forest type, and

owner/land-status category. For live trees, models differ only by type of wood

(hardwood or softwood). The estimate of mass density of the forest floor is based 

on equations of Smith and Heath (2002) based on region, forest type, and age. 

Mass density of soil organic carbon to a depth of 1 meter is estimated for each

region and forest type following Amichev and Galbraith (2004). The calculation

of mass density of understory carbon is based on models with coefficients 

specific to region, forest type, and owner/land-status category described in 

Plantinga and Birdsey (1993). The current approach for estimating the mass of

carbon in down dead wood is described in the next section.

Down Dead Wood

Carbon Pool

The pool of down dead wood is based on two separate simulations. The first 

is naturally occurring down dead wood, such as from mortality or nonharvest

disturbance, and the second is logging residue. The simulations track existing

pools as a series of periodic estimates, each of which is modified according to 

factors controlling gains and losses. The two sub-pools, mortality and logging

residue, are summed for results.

The majority of down dead wood is dependent on inputs from fallen live or

standing dead trees and large branches. All tree mortality or natural disturbances

(which are reflected in mortality statistics) during a simulation interval contribute 

directly to the pool of standing dead trees, which in turn contributes to the pool

of down dead wood. Statistical estimates of mortality determine the increase

in standing dead wood over an interval. Similarly, statistics on the relative

abundance of standing dead trees limit the size of this pool, with any additional

increase in dead wood being allocated to down dead wood. Tree mortality is

based on plot-level data from the 1997 Forest Resources database (Smith and

others 2001) with region, wood type (softwood and hardwood), and age class as

Mortality
5

predictors (Table D10). Mortality is expressed in terms of volume in the Forest

Resources database; we converted these to carbon density based on inventory

data and volume-based biomass equations (Smith and others 2003). Net annual

change in standing-dead tree carbon mass is based on periodic inventory

estimates.

The annual increment for new accumulation of down dead wood is average

annual mortality minus the average annual change in standing dead. The mass

of new down dead wood is modified by a factor (0.85) to account for damage to 

fallen trees that leaves a portion of the carbon mass in the form of small woody

debris (and thus forest floor in this model). Minor additional contributions to 

down dead wood are from fallen large branches of live trees. We model inputs

from fallen large branches as a constant proportion of live-tree biomass; this is

currently set at 0.01 percent of live carbon mass per year. The loss of carbon

mass from down dead wood over time is determined as first-order decay: 

mass(t=year) = mass(t=0) × exp(–year/K), with decay coefficient K provided in 

Table D4. Softwood and hardwood carbon mass are modeled separately within

each forest type.

The accumulation of logging residue is through harvest and stand thinning. The

difference between tree carbon inventory before harvest and carbon removed

during harvest determines logging residue. The logging residue equation is:

Logging residue = initial inventory – mass of removals – remaining inventory

Carbon in inventory is based on Smith and others (2003); carbon in harvested

volume mass is based on specific gravities according to forest type (Table D8). 

Harvested volumes need two additional modifications to account for all carbon 

removed during harvest. First, they do not include bark on logs removed: a factor

is needed to increase carbon to account for bark. Second, amounts of woody

biomass greater than that in merchantable volume usually is removed and sent

to mills. A factor is used to increase carbon to account for additional removals

such as fuelwood. Currently, carbon in volume removed is multiplied by 1.12 to

account for these two effects based on information in Tables 39-41 of Smith and

others (2001). 

The distinction between above- and belowground logging residue is based on

differences between the whole-tree vs. aboveground-only forms of the tree mass

equations of Smith and others (2003). Aboveground logging residue includes the

aboveground portion of stumps because that portion of the tree is included in the

whole-tree equation. Logging residue is also modified by a factor to account for 

damage during harvest that leaves a portion of the carbon mass in the form of

small woody debris. As with down dead wood, the factor 0.85 reduces the carbon

mass of aboveground logging residue; this assumes that 15 percent becomes

forest floor. The factor 0.9 is applied to belowground logging residue to account 

for an expected rapid loss in smaller woody roots. 

Logging Residue
6

Annual loss of carbon mass from logging residue also is based on decay

constants according to wood type as provided in Table D4. The loss of mass over

time is determined with the same relationship describing decay as applied to

down dead wood. We assume that logging residue does not include a significant 

amount of large pieces; thus, we use the values for pulpwood to decay all logging

residue. We assume decay rates are significantly slower belowground; we assume 

the belowground logging residue decay rate is equal to three times the pulpwood

decay constant.

FORCARB2 Methodology 

for Calculating Carbon in HWP

FORCARB2 follows the methodology of Smith and others (2006), using the

average disposition patterns of carbon in harvested wood from their Table 6. The

WOODCARB II model (Skog 2008) is based on similar information. Information

such as ratios of industrial roundwood to growing-stock volume is produced

by data collected by the FIA program, specifically work on the timber products 

output such as reported by Johnson (2001). Using average disposition rates

means that the current average disposition rates may be less applicable when

projections are based on alternative scenarios in which major changes in product

mix are expected, such as increased use of recycling. Therefore, some thought

should go into interpreting the output from this part of the model.

Example Dataset

Input files included with this guide are for all public forest land in the 

conterminous United States. For purposes of this dataset, U.S. forest land

is divided into as many as ten geographical regions (see Figure 2). Some

subdivisions and combinations are unique to ATLAS and some to FORCARB2. 

The regions chosen represent relatively distinct forest environments and

generally follow political boundaries. In the example input data included in

this study, two public owner groups are included: National Forests and Other

Government. The FIA program was a major source of data for initial inventory

(volumes and areas by age class), growth-yield curves, harvest information, and

forest-type transitions to some extent. In addition to owner group and region,

input data are categorized by forest type (or grouping of forest types), and land

status (reserved versus not reserved, and productive versus low productivity). 

Because FIA historically focused on higher productivity lands that produce

timber, data often are separated into timberland (productive and not reserved),

productive reserved lands (timber harvesting prohibited), and nontimberlands

(low-productivity forest land, often designated as “other forest”). Specific file 

construction techniques with accompanying data sources are described in the

following section. Note that variables in input files are in English units whereas 

results in output files are in metric units.
7

Example Graphics from FORCARB2 Output

Figure 2.—Definitions of regions for outputs and their name, abbreviation and numerical label: 0, Pacific Northwest, West 

(PWW—sometimes labeled PNWW); 1, Pacific Northwest, East (PWE—sometimes labeled PNWE); 2, Pacific Southwest 

(PSW); 3, Rocky Mountain, North (RMN); 4, Rocky Mountain, South (RMS); 5, Northern Prairie States (NPS); 6, Northern Lake 

States (NLS); 7, Northeast (NE); 8, South Central (SC); and 9, Southeast (SE). Note that regions are merged or subdivided 

for some input tables, these combinations include: NLS and NPS as North Central; the States of North and South Dakota, 

Nebraska, and Kansas as the Great Plains (GP); PWW, PWE, and PSW as Pacific Coast; RMN and RMS as Rocky Mountain; 

SC and SE as South; and RMN, RMS, PWW, PWE, and PSW as West except where stated otherwise. A few states may be 

included in different regions (i.e., North and South Dakota are sometimes included with the NPS and Ohio is sometimes placed 

in the NE) (Smith and others 2006).

Figures 3-9 illustrate graphics that can be produced from FORCARB2 output

files. These examples are not meant to be comprehensive. A variety of results 

featuring many combinations of forest type, grouped by softwood and hardwood,

comprising several age classes and over various projection years, is available

at the subregional to regional to national level of aggregation. Figure 3 shows

carbon in HWP in the four categories. Figure 4 illustrates current projected forest

carbon stocks projected by age class. Figure 5 depicts carbon removed by age

class due to harvest. Figures 6 and 7 show aggregate forest carbon stocks (Fig. 6)

and stock change (Fig. 7) by subregions and regions. The trend in forest areas is

shown in Figure 8, and Figure 9 shows carbon removed by age class due to land

use change.
8

Figure 3.—Example output 

of carbon in harvested wood 

pools from wood harvested 

from the North Central Prairie 

States region, National Forest 

ownership, oak-hickory forest 

type (data from output file 

bicmur.txt).

Figure 4.—Example output 

of total forest carbon by age 

class, management unit Pacific 

Northwest—Westside region, 

Other Government ownership, 

Douglas-fir forest type, 2000-

2050 (data from output file 

carbdb.txt). Each age class 

represents a stand age range 

of 10 years, with the last age 

class containing all stands at 

least 170 years old. 

Figure 5.—Example output of 

carbon in merchantable portion 

of growing stock harvested by 

age class by softwoods and 

hardwoods in the management 

unit Southeast region, Other 

Government ownership, oakpine forest type, 2010 (data 

from output file finhar.txt). Each 

age class represents a stand 

age range of 5 years with the 

last age class containing all 

stands at least 85 years old. 

There are no bars at age class 

less than 25 years old and 

younger (age classes 0 to 5) 

because the specified minimum 

harvest is 25 years in this run.
9

Figure 6.—Example output of 

forest carbon stocks by region, 

public timberlands (data from 

output file bicreg.txt).

Figure 7.—Example output of 

changes in forest carbon stock 

by large region, U.S. public 

timberlands (data from output 

file bicregs_all.txt).

Figure 8.—Example output 

of area of growth and area of 

removals, management unit 

Pacific Southwest region, forest 

industry ownership, redwood 

forest type, 2000-2050 (data 

from output file findat.txt).
10

Figure 9.—Example output of 

volumes removed due to area 

loss, management unit South 

Central region, forest industry 

ownership, upland hardwood 

forest type, year 2000 (data 

from output file volumesac.txt). 

Each age class represents a 

stand age range of 5 years with 

the last age class containing 

all stands at least 85 years old. 

There are no bars at age class 

less than 25 years of age and 

younger (age classes 0 to 5) 

because there is no harvest at 

this young age by assumption.

Interpretation of Main Output from bicreg File

The bicreg files contain the main summary output from FORCARB2. Example 

output that includes land use change is shown in Table 1. Outputs are in units of

thousands of hectares of area and petagrams of carbon. (In the bicregmu files, 

which contain the same summary output by management unit, carbon is given

in teragrams.) Within the files, the section on Forest Area Summary (Table 1) 

provides forest area and the estimated area affected by removals (both harvests

and land use change). The Forest Carbon Inventory section lists carbon stocks

in the respective pools by year. There are two rows for soil carbon, one labeled

Soil and the other Soil w/LUC soil. There are two rows because transferring

area into or out of forest transfers a large amount of carbon, but that carbon does

not necessarily go into the atmosphere. Rather, it changes categories. For treeplanting scenarios in which management units of millions of hectares appear, the

amount of soil carbon transferring in to forests can be misleading if the amount

of carbon that transfers in is included in the total. Soil w/LUC soil includes

only lands present at the beginning of the projection. In this example, forests

are losing area so that Soil is showing a loss over time while Soil w/LUC soil is

constant.

The section labeled Tree Carbon Fluxes provides detailed information on

the gains and losses of tree carbon in aboveground only or for all tree carbon

including roots. “Removals” is used instead of harvests because removals include

land-use change. The estimates of flux are total change over the period. The 

difference between inventories (e.g., 0.00159 for 1990-2000) is the increment

(0.01790) minus the removals (0.01556) plus the change in tree carbon due to

net area change (–0.00075); it is the same as the difference between the 2000 and

1990 total live-tree stocks (0.10279 – 0.10120). The section Net Area Change

(see Table 1) lists the area and carbon changes attributed directly to net area

change over the period.

Forest Carbon
11

Table 1.—Excerpt from bicreg.txt, the summary of projected forest area and carbon data 

by broad owner/land-status category

** BICREG **

NC FOREST INDUSTRY Total Over All Forest Types

YEARS

1990 2000 2010 ... 2040 2050

 . . . . . .

Thousand Hectares

FOREST AREA SUMMARY . . . . . .

TOTAL FOREST AREA 1536.69 1530.16 1506.81 ... 1416.80 1396.13

AREA OF REMOVALS 149.64 86.71 ... 10.21 7.48

 . . . . . .

Petagrams

FOREST CARBON INVENTORY

TOTAL LIVE TREE 0.10120 0.10279 0.10618 ... 0.12595 0.13438

TOTAL ABOVEGROUND TREE 0.08450 0.08582 0.08862 ... 0.10508 0.11212

TOTAL DEAD TREE 0.01139 0.01107 0.01094 ... 0.01123 0.01141

TOTAL ABVEGRD DEAD TREE 0.00952 0.00925 0.00914 ... 0.00937 0.00952

TOTAL DOWNED WOOD 0.00854 0.01089 0.01187 ... 0.01205 0.01175

ABOVEGROUND DOWN DEAD 0.00636 0.00852 0.00954 ... 0.01082 0.01104

BELOWGROUND RESIDUE 0.00219 0.00238 0.00233 ... 0.00123 0.00071

SOIL 0.23236 0.23133 0.22742 ... 0.21388 0.21111

SOIL w/ LUC SOIL 0.23236 0.23236 0.23236 ... 0.23236 0.23236

FOREST FLOOR 0.03233 0.03223 0.03172 ... 0.03268 0.03365

UNDERSTORY 0.00265 0.00275 0.00277 ... 0.00281 0.00289

TOTAL 0.38847 0.39107 0.39089 ... 0.39860 0.40519

TOTAL w/ LUC SOIL 0.38847 0.39210 0.39584 ... 0.41708 0.42644

TREE CARBON FLUXES

TREE CARBON INCREMNT -TOT . . 0.01790 0.01935 ... 0.01448 0.01352

TREE CARBON INCREMENT -AG . . 0.01495 0.01616 ... 0.01209 0.01129

REMOVALS - TOTAL 0.01556 0.01309 ... 0.00473 0.00326

REMOVALS - ABOVEGROUND . . 0.01300 0.01096 ... 0.00395 0.00273

DIFF BTWN INVNTORIES -TOT . . 0.00159 0.00339 ... 0.00694 0.00843

DIFF BTWN INVENTORIES -AG . . 0.00132 0.00280 ... 0.00579 0.00704

NET AREA CHANGE

AREA (1000HA) -6.53 -23.35 ... -38.04 -20.68

TOTAL TREE -0.00075 -0.00287 ... -0.00281 -0.00182

ABOVE GROUND -0.00063 -0.00241 ... -0.00235 -0.00153

SOIL -0.00103 -0.00391 ... -0.00574 -0.00277

FLOOR -0.00016 -0.00080 ... -0.00101 -0.00054

UNDER -0.00001 -0.00003 ... -0.00007 -0.00004

TOTAL -0.00195 -0.00762 ... -0.00963 -0.00517
12

In Table 2, a summary of forest carbon is given at the bottom in the Summary

block of information total net sequestration and emissions. All forest ecosystem

carbon-change pools that show a net increase of carbon into the forest from

the atmosphere (sequestration) are summed in the Total carbon sequestration

row. Similarly, all forest ecosystem pools that show a net decrease of carbon

in the forest are summed into the Total carbon emissions row. So, the variables

representing tree carbon increment or removals and changes in inventory for

standing dead, down dead wood, aboveground logging residue, belowground

logging residue, soil, forest floor, and understory are summed into one of these 

two categories depending on their value. The total is the difference between

sequestration and emissions. These are totals over the period; to obtain annual

values, divide by the interval (in this case, 10 years).

** BICREG **

YEARS

1990 2000 2010 ... 2040 2050

Petagrams

CUMULATIVE FATES OF

REMOVALS CARBON

IN USE 0 0.00417 0.00352 ... 0.00476 0.00510

LANDFILL 0 0.00049 0.00119 ... 0.00275 0.00331

ENERGY (EMISSION) 0 0.00339 0.00428 ... 0.00791 0.00916

EMITTED (EMISSION) 0 0.00266 0.00350 ... 0.00685 0.00804

TOTAL 0 0.01071 0.00862 ... 0.01542 0.01774

ALL LOGGING RSD - ABOVEGD 0.00166 0.00293 0.00238 ... 0.00218 0.00201

- BELOWGD 0.00111 0.00256 0.00211 ... 0.00199 0.00188

HARVEST RESIDUE - ABOVEGD 0 0.00220 0.00257 ... 0.00467 0.00537

- BELOWGD 0 0.00217 0.00253 ... 0.00446 0.00511

SUMMARY OF CARBON

SEQ. AND EMISSIONSa

TOTAL CARBON SEQUESTERED . . 0.10481 0.10143 ... 0.08326 0.07265

TOTAL CARBON EMITTED . . 0.01431 0.00336 ... 0.00432 0.00450

NET CHANGE IN CARBON . . 0.09050 0.09807 ... 0.07894 0.06814

Table 2.—Excerpt from bicreg.txt, the summary of projected carbon in harvested wood by 

broad owner/land-status category

a Summary of carbon sequestration and emissions only includes tree carbon increment or removals and changes

in inventory for standing dead, down dead wood, aboveground logging residue, belowground logging residue,

soil, forest floor, and understory.
13

Carbon in

Harvested Wood

Table 2 also displays example output from a sample bicreg.txt for carbon in

harvested wood products. No carbon is displayed in the first year because 

this is the start of the projection; no wood has been harvested. As the section

Cumulative Fates of Removals Carbon indicates, the estimates are cumulative. 

For changes between years, estimates in the consecutive respective pools would

be differenced and divided by the length of the period for an average annual

change in carbon. Note that although all values in the fates section are positive,

the Energy row (emissions from wood burned with energy capture) are emissions

as well as the Emissions row (emissions from wood burned or combusted without

energy capture). The Total cumulative fates row adds to the amount of carbon

removed from the forest.

The rows labeled All Logging Residue show the amount of carbon in that pool,

either aboveground or belowground at the given year. We estimate an existing

amount of logging residue in the beginning period. The rows labeled Harvest

Residue is a cumulative amount in the pools, including only that amount

harvested during the projection period, that is, not accounting for existing

amounts on the ground.

Description of the Programs

Three steps are needed to use the FORCARB2 model to produce carbon

estimates: 1) running the ATLAS model (including production of input files 

containing up-to-date timberland data and projections), 2) running the main

FORCARB2 model (which converts tree volume to carbon and adds on all

other carbon pools), and 3) post-processing of FORCARB2 results. The

postprocessors aggregate the results in different ways. Appendix A, a Quick Start

Guide, summarizes how to run the programs; Appendix B includes step-by-step

instructions that are particularly useful should problems arise in following the

Quick Start Guide. A description of the files on the CD is given in Appendix C.

There are three main input files to the ATLAS model: the initial inventory; factors 

including growth and yield, area and area change, and forest type compiled in a

file called manage; and harvest requests. The initial inventories are defined by 

compiling areas together, called inventory units (IUs). The IUs are matched to a

management unit (MU) that contains the information used to project growth and

yield for that inventory. Several IUs can be assigned to an MU in which case the

model aggregates the data to the MU level or most commonly, the inventory is

aggregated outside of the MU and the units are matched one-to-one. MUs can be

aggregated into larger harvest units (HUs) to allocate inventory among a group of

MUs. Several HUs with their associated inventories can be projected in the same

simulation. However, the higher-level units cannot be disaggregated. The reason

for the aggregation is that MUs often represent groups of related species or forest

productivity classes and harvest data often are available only over larger areas,

representing multiple species and site conditions. However, with sufficient data 

all units could be of the same size, with one HU associated with a MU with an

IU, each level (harvest, management, inventory) covering the same area. 

Step 1: ATLAS
14

The current ATLAS version, ATLAS05H, requires the following input files to 

run: inven.dat, manage.dat, harvest.dat, gsrsum.txt, sevatlas2.txt, sevatlas2w.txt, 

period.txt and param.dat. In this data set, multiple versions of several of these

are required to run the model for the forest categories used for the coterminous

United States. The file param.dat specifies folders for input and output files. 

There are four separate executable programs that must be run in set order to

produce output from the ATLAS model: IUSCAN05, MUSCAN05, HUSCAN05,

and ATLAS05H. The example files configured here are in two groups: public 

timberland in one group and the reserved and lower productivity lands are in the

other. Each group is subdivided by geographic region. There is a set of inven.dat

and manage.dat files for each of the larger groupings and these contain the 

IUs and MUs for all regions within the group. The programs IUSCAN05 and

MUSCAN05 read and process these files and need be run only once for each 

land status category, whereas HUSCAN05 and ATLAS05H must be run on each

region/owner-land status category separately. In the example dataset, we include

two owner-land status categories, designated by a three-letter file suffix: pbl

(public timberland), and rsv (includes both reserved lands and unreserved lowproductivity “other” forest lands). IUSCAN05 is a pre-processor that prepares

the IU files; MUSCAN05 is a pre-processor that prepares the MU files. 

Inven.dat, which contains areas and volumes for each IU stratified by age class 

(and management intensity where applied) is processed by IUSCAN05. An IU

represents a particular forest type or a group of related types within a region. To

construct corresponding Inven input files for each owner/land-status category, 

we used inventory datasets that are produced as a part of forest resource statistics

developed for the Forest RPA. RPA datasets used were those compiled for 2002. 

These correspond to published summary statistics (Smith and others 2001, 2004).

MUSCAN05 requires an input file named manage.dat that identifies MUs used 

in both ATLAS and FORCARB2. Separate versions of the file were created for 

each owner/land-status category.

1 Each MU represents a particular forest type

within a region and contains numerous stocking and management parameters,

including base growth yield table volumes with which to project inventory for

each age class. For these examples, custodial management intensity was assumed

(intensity ID set to 1), representing average or medium productivity. The yield

tables for public timberlands and the Reserved category and the manage file 

for the Reserved and Other Forest category were developed to match those in

Mills and Zhou (2003) and Zhou and others (2007). However, we also assumed

that the growth yield table volumes for the Other Forest category were limited

to an increase of 15 cubic feet per year. Without this assumption, the volumes

increased quickly on Other Forest. Many of the remaining growth and harvest

parameters were borrowed from other input data sets and not calibrated for

individual MUs.

IUSCAN05

MUSCAN05

1 These files are example inputs that provide users with a template with which to run the 

model and examine the input and output structures.
15

HUSCAN05

Other ATLAS05H

Input Files

HUSCAN05 reads the output files produced by IUSCAN and MUSCAN and 

links the IUs to the MUs and organizes them by HUs as specified in the file 

harvest.dat. The HU represents the highest level of aggregation and each HU is

assigned a set of harvest (removals) to apply to the member MUs for each period

of the projection. In our example, within each owner/land-status category, each

HU represents a region, an owner, and a wood type (softwood or hardwood). 

The harvest.dat file also contains projection information for each group of MUs, 

including the number of periods in the projection and the length of a period in

years (5 years for the southern regions and 10 years elsewhere).

Currently, we run 18 of these MUs: the two owner/land-status categories and nine

regions (Fig. 2; we combine NLS and NPS into one region). This file contains 

projected removals for each HU. To construct the harvest files for the Public 

category, growing-stock removals by ownerships within the owner/land-status

category by softwood (SW) or hardwood (HW) were used from the March 30,

2006 ATLAS RPA base run. Since all inventories in the HUs in ATLAS contain

both HW and SW components, it was necessary to apply the following equations

to obtain the necessary harvest data. For a particular hardwood HU, harvests =

(HW removals + SW removals) / (1 + Ratio of SW to HW for that HU in the

1997 harvest file). For the corresponding SW HU, harvests = those hardwood 

harvests multiplied by the same ratio. For the Reserved and Unreserved Other

category, harvests were set to 0.0.

The remaining input files are required by ATLAS05H: 

1. gsrsum.txt: contains growing-stock removals by region/owner-land status

category and wood type by period. All regions are in a specific order in each file, 

but there is a separate file for each of the large owner/land-status categories. The 

gsrsum file was constructed using data obtained to create the harvest files, as 

described previously. In the Reserved and Other gsrsum file, all removals were 

set to 0.0.

2. sevatlas2.txt and sevatlas2w.txt: contain a set of distributions for ATLAS

to use when regenerating land among various management intensities within

an MU. They are a bridge between a version of ATLAS linked to the TAMM

model for the 2005 Timber Assessment Update (Haynes and others 2007) and

the stand-alone (portable) version called ATLAS05H. These files were created 

by the TAMM/ATLAS model in a soil expectation calculation procedure using

costs and projected stumpage prices to calculate the best expected returns from

a set of investment options in each period of the ATLAS simulation. The standalone model reads the files and uses them to substitute for the MU card type 

44, which was used previously to distribute regeneration among management

intensities. Card type 44 is input for each MU as a predetermined and fixed set 

of distributions for regenerating harvested or converted land among the model’s

12 management intensities. These files allow the distribution to change for each 

period based on market conditions at the time. Each line starts with the MU

identifier followed by 12 columns representing management intensities 1 through 

12. These arrays are grouped in large blocks, one block for each projection

period. We currently do not apply these shifts in the MUs but we include blank

files should there be a need for applying shifts.
16

3. period.txt: contains the maximum number of periods for which the simulation

will run. Generally, it is set to 10 and does not need to be changed. Ten periods

are required to project the Southern regions for 50 years. Parameters in the

harvest.dat file control the actual projection length for each HU, for example, five 

periods for the PNWW HUs where the period length is 10 years.

Running the suite of ATLAS programs produces output files which are used as 

input files for the FORCARB2 model. 

The FORCARB2 model uses two output files generated by ATLAS 

(merch.txt and coefs_atlas.txt; see Appendix D). These files provide estimates 

and projections of areas and tree volume by age class for the specified categories 

of forest land. The executable program is forcarb2.exe. If the input files are 

available and in the correct folders, running FORCARB2 will produce all

summary files for both forest ecosystem carbon and carbon in harvested wood 

products. The file flags_output.txt contains the user’s preferences for output; it

can be edited before running FORCARB2. FORCARB2 output files, described 

in Appendix E, are created for each individual region/owner-land status

combination run. If running FORCARB2 for multiple regions and/or categories,

it is advisable to move the output files to another folder between each run to 

avoid overwriting previous results.

The parameters for the equations are contained in text files that are read by the 

FORCARB2 program; these text files must be kept in the same folder as the 

executable program (forcarb2.exe). A detailed list of these files (with example 

text) is included in Appendix D. In general, the equations estimate carbon for

specific region/forest type combinations, with additional details for pools in 

which there is more information. Because the equation sets were developed

separately and depend on different physical parameters, they often have different

regional demarcations or different forest type definitions, or both. Therefore, a 

“cross-table” was set up to relate the ATLAS/FORCARB2 region/forest types

(management units) to those used in each parameter file. This cross-table is found 

in mu_table.txt.

Additional utility programs were created for post-processing of FORCARB2

results. Because FORCARB2 is run for specific categories of land, its output 

files must be processed further to obtain summarized information. The program 

total_bicregs_condense produces summaries of forest carbon on a regional and

national basis at various owner/land-status group aggregations. It is found in

the FORCARB2 folder of the accompanying electronic files. The output files 

written by this program are bicreg_all.txt and bicreg_all_condensed.txt. All

of the data values in the bicreg output files from FORCARB2 are summarized 

at the regional, expanded regional, and national levels. Expanded regions are

aggregations of the original regions (Pacific Coast = Pacific Northwest Westside 

+ Pacific Northwest Eastside + Pacific Southwest, Rocky Mountain = Rocky 

Mountain North + Rocky Mountain South, North = North Central + Northeast,

and South = South Central + Southeast). 

Step 2: Running

FORCARB2

Step 3: 

Post-Processing
17

The original regions and owner/land-status categories are run over different

periods and at different scales, for example, southern regions are run at 5-year

intervals and 10-year intervals are used elsewhere. To facilitate comparison and

allow aggregation, this program uses interpolation and extrapolation procedures

to produce data values for each 5-year period from 1990 to 2050 for all possible

combinations of region and owner-land status.

Future Use of FORCARB2

Acknowledgments

Because the input files to ATLAS and FORCARB2 define the initial volume, 

growth, harvests, and area change, the model can be used for any size area so

long as the input files are modified accordingly. A new forest modeling system is 

being developed for the 2010 RPAAssessment, so the economically determined

harvest forecasts that were used directly in FORCARB2 will no longer be

available. However, the programs can forecast carbon stocks when harvests

and land use change are prescribed.

We thank Andrew Plantinga, Oregon State University, and Richard Birdsey, U.S. 

Forest Service, Northern Research Station, for providing the original version of

FORCARB, and the U.S. Forest Service’s RPA Program for its support.
18

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137 p.

Smith, W.B.; Vissage, J.S.; Darr, D.R.; Sheffield, R.M. 2001. Forest resources 

of the United States, 1997. Gen. Tech. Rep. NC-219. St. Paul, MN: U.S. 

Department of Agriculture, Forest Service, North Central Research Station. 

190 p.

Turner, D.P.; Koerper, G.J.; Harmon, M.E.; Lee, J.J. 1995. A carbon budget 

for forests of the conterminous United States. Ecological Applications. 

5: 421-436.

U.S. Department of Agriculture, Soil Conservation Service. 1991. State soil 

geographic (STATSGO) data base data use information. Misc. Publ. 

1492, Fort Worth, TX: U.S. Department of Agriculture, Natural Resources

Conservation Service, National Soil Survey Center. 88 p.

U.S. Department of Agriculture, Forest Service. 2009. Forest Inventory and 

Analysis National Program home page. http://fia.fs.fed.us/

U.S. Environmental Protection Agency. 2002. Inventory of U.S. greenhouse gas 

emissions and sinks: 1990-2000. USEPA #430-R-02-003. Washington, D.C.:

U.S. Environmental Protection Agency, Office of Atmospheric Programs. 

Available at http://epa.gov/climatechange/emissions/usgginv_archive.html

[1 June 2009].

U.S. Environmental Protection Agency. 2008. Inventory of U. S. greenhouse 

gas emissions and sinks: 1990-2006. USEPA #430-R-08-005. Washington,

D.C.: U.S. Environmental Protection Agency, Office of Atmospheric 

Programs. Available at http://www.epa.gov/climatechange/emissions/

usinventoryreport.html (7 November 2008).
21

Woodbury, P.B.; Smith, J.E.; Heath, L.S. 2007. Carbon sequestration in the 

US forest sector from 1990 to 2010. Forest Ecology and Management. 

241(2007): 14-27.

Zhou, X.; Mills, J.R.; Haynes, R.W. 2007. Projecting other public 

inventories for the 2005 RPA timber assessment update. Gen. Tech. Rep. 

PNW-GTR-717. Portland, OR: U.S. Department of Agriculture, Forest

Service, Pacific Northwest Research Station. 31 p.
22

Appendix A. Quick Start Guide

Output files from FORCARB2 corresponding to the input files are included on 

the CD. They can be reproduced by the user by running the included programs. 

“Batch” files have been created that quickly run the entire process from 

beginning to end. Instructions on how to run these is included here. Users who

wish to work their way through the model step by step should refer to the detailed

instructions in Appendix B. 

1) Insert the disc into the compact disc drive on your PC.

2) This disc should contain two (2) folders, ATLAS and FORCARB2. Copy

these folders to your PC.

3) Right-click each folder and click on Properties. Remove the marker that

indicates that the folder is “Read-only” by clicking on it. Apply to all

subfolders and files. 

4) Double-click the ATLAS folder to proceed. 

5) Double-click the file ATLAS.bat to run the ATLAS model. This “batch” file 

runs all of the model programs and places the output files into appropriate 

subfolders. The subfolders are labeled by region and owner/land-status

category. There are 18 subfolders that comprise nine regions and two

owner/land-status categories. 

Regions and abbreviations are as follows:

Abbreviation Region

NC North Centrala

NE Northeast

PNWE Pacific Northwest – east side

PNWW Pacific Northwest – west side

PSW Pacific Southwest

RMN Rocky Mountains – North

RMS Rocky Mountains – South

SC South Central

SE Southeast

a

When running the inputs as provided here, two North Central subregions 

(NLS and NPS) are combined into one large region (Fig. 2). The output can 

be split into the separate subregions later.

Descriptions and abbreviations for owner/land-status categories are

as follows:

Abbreviation Owner/land-status description

pbl Publicly owned timberlands—includes 

 National Forests and other government-

 owned (federal, state, or local)

rsv Reserved timberland (land where harvest 

 is prohibited) and nontimberland (low 

 productivity forest land where it is 

 assumed there is no commercial harvest)
23

6)	 A running log is written to the file atlas_out.txt. System-related errors 

(such as the absence of files/folders) are written to this file. A runtime

summary of program steps is written to atlas05_out.txt. In addition, the 

ATLAS program keeps a record of program information in atlog.txt, which 

is written to each region/owner/land-status category folder. Processing

errors and warnings are found there.

7) To run FORCARB2, navigate to the FORCARB2 folder.

8)	 Double-click the file FORCARB2.bat to run FORCARB2 and 

total_bicregs_condense. FORCARB2 produces output files for each of

the 18 region/owner/land-status combinations and places them in their

corresponding subfolders in the OUTPUT_FILES folder. The program 

total_bicregs_condense creates two files named bicreg_all.txt and 

bicreg_all_condensed.txt, which contain summary information for 

every category.

9)	 A running log is written to the file forcarb2_out.txt. System-related 

errors such as the absence of files/folders are written to this file. Runtime

summaries of program steps are written to FORCARB2prog_out.txt and 

total_bicregs_condense_out.txt. Internal processing errors can be found in 

errors.txt, which is written to the region/owner/land-status subfolders.
24

Appendix B. Step-by-Step Instructions to Run the Model

Output files from FORCARB2 corresponding to the input files are included on 

the CD. They can be reproduced by the user by running the included programs. 

More experienced users who wish to modify one or more of the input data files to 

include different or additional data should refer to Mills and Kincaid (1992) for

guidance.

1) Insert the disc into the compact disc drive on your PC.

2) This disc should contain two (2) folders, ATLAS and FORCARB2. Copy

these folders to your PC.

3) Right-click each folder and click on Properties. Remove the marker that

indicates the folder is “Read-only” by clicking on it. Apply to all subfolders

and files. 

4) If you do not wish to run the programs again but would like to examine the

results, skip to step 19. If you do not wish to run ATLAS again, but would

like to run FORCARB2, skip to step 14. If running ATLAS, double-click

the ATLAS folder to proceed.

5) Copy the file param.dat from the folder named

REGIONAL_INPUT_FILES to the main ATLAS folder. This file lists 

the directories to which the output files are written. You can edit the file in 

a text processor, such as Notepad or one of your choosing. (A warning may

be displayed concerning the editing of a .dat file; it is safe to ignore it.) Edit 

the first line (characters 4-11) if you wish to change the file extension that 

will be given to each of the ATLAS output files; for ease of use, we have 

assigned an extension of “.txt”. You can change the directory locations. 

They are initially set to the main ATLAS folder. If running multiple

regions and/or owner/land-status categories, it is advisable to change the

folder to which “Atlas report files” are written between each run to avoid 

overwriting the output files from the previous run. 

6) The REGIONAL_INPUT_FILES folder contains two subfolders, one for

each of the currently designated owner/land-status categories. Descriptions

and abbreviations for owner/land-status categories are as follows:

Abbreviation Owner/land-status description

pbl Publicly owned timberlands—includes 

 National Forests and other government-

 owned (federal, state, or local)

rsv Reserved timberland (land where harvest 

 is prohibited) and nontimberland (low 

 productivity forest land where it is 

 assumed there is no commercial harvest)
25

Each owner/land-status category is run separately. Within each of these

subfolders are three files (gsrsum.txt, inven.dat, and manage.dat) and nine

subfolders, one for each region of the United States. The three files contain 

the following data parameters to be used in the model:

inven.dat: For each inventory unit (IU), contains initial acreages and

volumes within each age class.

manage.dat: For each management unit (MU), contains growth and yield

tables and thinning, stocking, and area-change parameters.

gsrsum.txt: For each MU, contains data on growing-stock removal for

each region/owner/land-status combination for each period.

To run a particular owner/land-status category, copy the three files 

(gsrsum.txt, inven.dat, and manage.dat) to the main ATLAS folder. For

example, to run publicly owned timberlands, copy inven.dat, manage.dat,

and gsrsum.txt from the pbl folder to the ATLAS folder. 

7) Run iuscan05.exe by double-clicking its filename.

8) Run muscan05.exe.

9) Navigate back to the folder from which you copied the files in step 6. 

Within this folder are nine subfolders, one for each region of the United

States. The region abbreviations are as follows:

Abbreviation Region

NC North Centrala

NE Northeast

PNWE Pacific Northwest – east side

PNWW Pacific Northwest – west side

PSW Pacific Southwest

RMN Rocky Mountains – North

RMS Rocky Mountains – South

SC South Central

SE Southeast

a

When running the inputs as provided here, two North Central subregions 

(NLS and NPS) are combined into one large region (Fig. 2). The output can 

be split into the separate subregions later.

Each region should be run separately. Within each regional subfolders is a

single file named harvest.dat that contains data on harvest volume for the

particular region/owner/land-status combination. Choose a region to run

and copy the harvest.dat file for that region to the main ATLAS folder. 

This is the input file for the next program.

10) Run huscan05.exe.

11) If running multiple regions and/or owner/land-status categories, you must

change the output folder to avoid overwriting the previously produced

report files. Edit the file param.dat in the ATLAS folder if necessary.

12) Run atlas05h.exe.
26

13) Many output files are produced by ATLAS. FORCARB2 requires only two 

of these: coefs_atlas.txt and merch.txt. Copy these files to the FORCARB2

folder and skip to step 16.

14) To run FORCARB2, first navigate to the FORCARB2 folder.

15) If using the ATLAS output files created by the authors, navigate to the 

REGIONAL_INPUT_FILES subfolder within FORCARB2 folder. 

Here, there are 18 subfolders, one for each region/owner/land-status

combination. See Steps 6 and 9 for abbreviations. Each combination

will require a separate run of FORCARB2. Each subfolder contains

two files (coefs_atlas.txt and merch.txt), output from ATLAS for that

particular category. Copy the files for the category you want to run to the 

FORCARB2 folder.

16) You can edit flags_output.txt should you wish to request particular output

files. In this file, each of the FORCARB2 output files is assigned a flag 

of 0 or 1. A flag assignment of 1 indicates that the file will be produced 

upon running FORCARB2; output files with an assignment of 0 are not 

produced. By default, all output files are assigned a flag of 1 and thus are 

created.

17) Run forcarb2.exe.

18) Repeat for additional regions and/or owner/land-status categories. If you

want to keep the output files, rename them or move them to other folders 

so that they will not be overwritten.

19) For a description of FORCARB2 output files, see Appendix E. Output files 

produced by the authors are found in FORCARB2\OUTPUT_FILES\

(region).(owner/land-status category) by each of the 18 region/owner/landstatus combinations discussed previously.

20) Summary FORCARB2 output at the regional and national levels can

be produced by running the included program total_bicregs_condense.

exe (with associated program code in total_bicregs_condense.for). This

program summarizes data from any bicreg.txt files that were produced by 

FORCARB2 and outputs two files, bicreg_all.txt (in the same format as

bicreg.txt) and bicreg_all_condensed.txt (in a condensed tabular format). 

The program is currently set up to read the bicreg.txt files from a region/

owner/land-status category directory structure included on the CD;

if you set up a different directory structure, you must modify the path

in total_bicregs_condense.for and recompile.
27

Appendix C. FORCARB2 CD Content

The main directory contains two folders, ATLAS and FORCARB2, a file with 

basic information in two formats (readme.doc and readme.txt), and a copy of the

User’s Guide.

The folder ATLAS contains two “batch” files that run the entire suite of ATLAS 

programs (ATLAS.bat and ATLAS05H.bat), executable files used in running 

the ATLAS model (iuscan05.exe; muscan05.exe; huscan05.exe; atlas05h.exe),

input files needed by the model which apply to all region/owner-land status 

categories (period.txt; sevatlas2.txt; sevatlas2w.txt), and three subfolders

(REGIONAL_INPUT_FILES, OUTPUT_FILES and CODE).

The subfolder REGIONAL_INPUT_FILES within the ATLAS folder contains

a generic param.dat file for use by experienced users, and subfolders for each 

of the two owner/land-status categories (public[pbl], reserved and other[rsv]). 

Within each of these subfolders are three input files needed by the ATLAS model 

(gsrsum.txt, inven.dat, and manage.dat) and nine subfolders for each region. 

Each regional subfolder contains a file named harvest.dat and a file named 

param.dat which specifies folder locations for all the files input or output from 

the model programs. Each file must be copied into the folder containing the 

program files for each region/owner/land-status combination before executing the 

model programs (this is performed automatically if running the “batch” files). 

The subfolder OUTPUT_FILES within the ATLAS folder contains subfolders

for each of the region/owner-land status combinations that contain ATLAS

output files. Two of these files, coefs_atlas.txt and merch.txt, are input files to 

the FORCARB2 model. Other ATLAS output files may contain data of interest 

to some (atacre; atavail; athar; athur; athur2; atinv; atlis2; atlist; atlog; atmur;

atmurdb; avail.txt; comdif.txt; gainloss; invout; regen.txt). Many of these are

described in Mills and Kincaid (1992).

The subfolder CODE within the ATLAS folder contains the FORTRAN source

code (iuscan05.for; muscan05.for; huscan05.for; atlas05h.for) and several

“include” files used by the programs (atpar.inc; atpath.inc; atrosum.inc;

hudet.inc; huset.inc; husum.inc; linkbl.inc; mudata.inc; mudet.inc; parset.inc;

ttet.inc). This subfolder is included for the benefit of advanced users who may 

wish to modify the code and recompile for their own applications.

The folder FORCARB2 contains three “batch” files that run the 

FORCARB2 programs (FORCARB2.bat, FORCARB2prog.bat and

total_bicregs_condense.bat), executable files used in running the 

FORCARB2 model (forcarb2.exe and total_bicregs_condense.exe),

text files which contain parameters needed by the programs (coefs_bark.txt;

coefs_decay.txt; coefs_emitted.txt; coefs_ff.txt; coefs_gs.txt; coefs_gsvol.txt;

coefs_livetree.txt; coefs_mort.txt; coefs_owners.txt; coefs_pfates.txt;

coefs_resid.txt; coefs_sdeadtree.txt; coefs_soil.txt; coefs_under.txt;
28

coefs_weights.txt; flags_output.txt; mu_table.txt), and three subfolders

(REGIONAL_INPUT_FILES, OUTPUT_FILES and CODE). The text

files are described elsewhere in this document. 

The subfolder REGIONAL_INPUT_FILES within the FORCARB2 folder

contains subfolders for each of the region/owner-land status combinations that

contain FORCARB2 input files. These files are output by the ATLAS model. 

Each subfolder contains files named coefs_atlas.txt and merch.txt (Appendix D). 

Each file must be copied into the folder containing the FORCARB2 program files 

for each region/owner/land-status combination before executing the FORCARB2

program (performed automatically if running “batch” files). 

The subfolder OUTPUT_FILES within the FORCARB2 folder contains

subfolders for each of the region/owner/land-status combinations. These

contain FORCARB2 output files (bicmur.txt, bicreg.txt, bicregmu.txt,

carbdb.txt, carbhu.txt, errors.txt, findat.txt, findat0.txt, finhar.txt, volumes.txt

and volumesac.txt). Each of these is described in Appendix E. It also contains the

two forest carbon summary files (bicreg_all.txt and bicreg_all_condensed.txt).

The subfolder CODE within the FORCARB2 folder contains the FORTRAN

source code (forcarb.for and total_bicregs_condense.for) and several “include”

files used by the programs (biccom.inc, carbvars.inc, coefvars.inc, ddwcom.inc,

forpar.inc, lrcom.inc, and merch.inc). This subfolder is included for the benefit 

of advanced users who may wish to modify the code and recompile for their own

applications.
29

Appendix D. FORCARB2 Input Files

Twenty input files are required to run FORCARB2. Two of them, merch.txt and

coefs_atlas.txt, are output files from ATLAS. The file flags_output.txt indicates

which output files the user would like to produce, and is meant to be edited by the 

user. Mu_table.txt is used to link management units (MUs) with coefficients for 

equations. All other input files contain coefficients for equations for carbon pools. 

Each file is described in alphabetical order as follows:

Coefs_atlas.txt contains miscellaneous information produced during the ATLAS

run that is needed by FORCARB2. Included on the initial line are start year of

model run, number of years in each interval (or period), and number of periods

desired. The remainder of the file consists of MU information. Each row contains 

the elements listed in Table D1. Definitions of the variables are given as follows. 

An example file is given in Table D2.

Coefs_atlas.txt

Table D1.—Data structure of coefs_atlas.txt, an output file of ATLAS used as an input file 

to FORCARB2

Element Data Type Length Columns

Management Unita Character – Upper Case 15 1-15

Region Identifierb Integer 2 18-19

Owner-Land Status Identifierc Integer 2 22-23

Forest Type Identifierd Integer 2 26-27

Site Quality Identifiere Integer 2 30-31

Possible Harvesting Types Identifierf Integer 2 34-35

Partial Cutting Occurrence Flagg Integer 1 38

a The name of the level of aggregation which includes the growth and yield lookup table, and area change. This

is the leftmost column in the mu_table.txt file. The sequential order of the MU matches the order of the data in 

the merch.txt file. b The number assigned to the geographic area in which the MU is located. See Figure 2 for a description of

regions used in FORCARB2. c Identification of the broad owner/land-status group to which the MU belongs. See the description of coefs_

owners.txt below for a complete category list. d See Appendix F for a list of the forest types. e If site quality has been assigned to the particular MU, the codes are: 00, no site quality assigned; 01, high (or

good) site quality; 02, medium site quality; 03, low (or poor) site quality. f Values are 01, clearcut only; 02, partial cutting only; 03, both clearcut and partial cutting allowed. Note that 02

with a target age class of 0 is the same as clearcutting. g 0=no partial cutting, 1=partial cutting.

Table D2.—Excerpt of coefs_atlas.txt file

1990 10 5 . . .

PNWW NF ALDER 0 1 45 0 1 0

PNWW NF HWMIX 0 1 50 0 1 0

PNWW NF DFIR 0 1 50 0 2 0

PNWW NF W.HEM 0 1 50 0 2 0

PNWW NF FR-SP 0 1 25 0 1 0

PNWW NF PINES 0 1 30 0 1 0

PNWW NF SWMIX 0 1 35 0 1 0

PNWW NF NOSTK 0 1 44 0 1 0

PNWW OG ALDER 0 2 45 0 1 0

PNWW OG HWMIX 0 2 50 0 1 0

PNWW TR ALDER 0 6 45 0 1 0

PNWW TR HWMIX 0 6 50 0 1 0

PNWW OG DFIR 0 6 50 0 2 0

... ... ... ... ... ... ...
30

Coefs_bark.txt Coefs_bark.txt: see partial listing in Table D3. The file includes factors for 

estimating the sum of wood plus bark on harvested wood; see Table 5 of Smith

and others (2006).

Table D3.—Excerpt of coefs_bark.txt listing factors to estimate the sum of wood plus bark 

on harvested wood (Smith and others 2006)

Region Wood type Wood size Multiplier

Northeast SW Saw log 1.182

Northeast SW Pulpwood 1.185

Northeast HW Saw log 1.199

Northeast HW Pulpwood 1.218

North Central SW Saw log 1.182

North Central SW Pulpwood 1.185

North Central HW Saw log 1.199

North Central HW Pulpwood 1.218

Pacific Coast SW Saw log 1.181

Pacific Coast SW Pulpwood 1.185

Pacific Coast HW Saw log 1.197

Pacific Coast HW Pulpwood 1.219

Rocky Mountain SW Saw log 1.181

... ... ... ...

Coefs_decay.txt Coefs_decay.txt: see partial listing in Table D4. The file contains the decay 

coefficient (Turner and others 1995) for first-order decay of wood according 

to region, type (hardwood/softwood) and size of piece (pulpwood, saw log, or

large saw logs). These are applied to down dead wood from mortality as well as

logging residue from harvest.

Region Wood type Wood size Decay coefficients

MtWest HW Pulpwood 18.13476536

MtWest HW Saw log 28.60139984

MtWest SW Pulpwood 43.45532048

MtWest SW Saw log 58.81511143

MtWest SW Large saw 76.88340190

North HW Pulpwood 12.11287488

North HW Saw log 19.11993958

North SW Pulpwood 17.88187843

... ... ... ...

Table D4.—Excerpt from coefs_decay.txt showing decay coefficients for calculations of 

dead wood decay 

Coefs_emitted.txt Coefs_emitted.txt: see partial listing in Table D5. These are needed to calculate

harvested wood carbon. The file contains coefficients for estimating fractions 

of emitted carbon associated with energy recapture for industrial roundwood,

see Table D7 of Smith and others (2006). Estimates are calculated according to:

fraction =A × exp(–((year/B)C)). Fractions differ by region, wood type, and

wood size.
31

Table D5.—Excerpt from coefs_emitted.txt, containing coefficients for estimating fractions 

of emitted carbon associated with energy recapture for industrial roundwood (Smith and 

others 2006)

Region Wood type SL/PW a A B C

Northeast SW Saw log 0.5582 2594 0.6557

Northeast SW Pulpwood 0.6289 3062 0.5432

Northeast HW Saw log 0.6143 6812 0.5953

Northeast HW Pulpwood 0.5272 3483 0.5364

North Central SW Saw log 0.6728 2162 0.6550

North Central SW Pulpwood 0.6284 3494 0.5117

North Central HW Saw log 0.6097 5144 0.6236

North Central HW Pulpwood 0.5243 3399 0.5451

Pacific Northwest; East SW All 0.5421 1144 0.7958

... ... ... ... ... ...

a SL=sawlog; PW=pulpwood

Coefs_ff.txt Coefs_ff.txt: see partial listing in Table D6. The file contains coefficients used in 

FORCARB2 to calculate mass density of the forest floor (Smith and Heath 2002). 

Coefficients differ by region and forest type. Using these coefficients for A, 

B, C, and D, forest-floor mass density (Mg/ha) = ((A × YR) / (B+YR)) + 

(C × exp(–(YR/D))), where YR is the number of years since clearcut harvest. 

Coefficient A also serves as a flag; if A equals 0, C is the estimate for forest-floor 

carbon.

Table D6.—Excerpt from coefs_ff.txt, showing a sample of coefficients used in 

FORCARB2 to calculate forest floor mass density (Smith and Heath 2002)

Region/Forest type A B C D

N pine 19.1 25.6 13.8 8.4

N spruce, fir, hemlock 62.9 57.8 33.7 8.4

N mixed conifer-hardwood 65.0 79.5 29.7 8.4

N aspen-birch 18.4 53.7 10.2 9.2

N maple-beech-birch 50.4 54.7 27.7 9.2

N mixed hardwood, oak 24.9 134.2 8.2 9.2

N nonstocked 0.0 1.0 4.8 9999.9

S pine 20.4 27.1 12.2 3.8

S mixed conifer-hardwood 15.4 20.1 10.3 3.8

... ... ... ... ...

Coefs_gs.txt Coefs_gs.txt: See partial listing in Table D7. These are needed to calculate carbon

in harvested wood. File contains factors applied to estimate carbon in harvested

wood based on growing-stock volume; see Table 5 of Smith and others (2006). 

These include the ratio of industrial roundwood to growing-stock removals as

roundwood (IndRwd/GSRwd), the ratio of carbon in bark to carbon in wood

(Bark/Wood), the fraction of growing-stock volume removed as roundwood

(GSRwd/AllRwd), and the ratio of fuelwood to growing-stock removals as

roundwood (FW/GSRwd). Ratios are included for each region/wood type/wood

size combination.
32

Table D7.—Excerpt from coefs_gs.txt, showing various factors applied to estimate carbon 

in harvested wood based on growing-stock volume

Wood IndRwd/ Bark/ GSRwd/ FW/

Region typea Wood size GSRwd wood AllRwd GSRwd

NE SW Saw log 0.991 0.182 0.948 0.136

NE SW Pulpwood 3.079 0.185 0.948 0.136

NE HW Saw log 0.927 0.199 0.879 0.547

NE HW Pulpwood 2.177 0.218 0.879 0.547

NC SW Saw log 0.985 0.182 0.931 0.066

NC SW Pulpwood 1.285 0.185 0.931 0.066

NC HW Saw log 0.960 0.199 0.831 0.348

NC HW Pulpwood 1.387 0.218 0.831 0.348

PC SW Saw log 0.965 0.181 0.929 0.096

... ... ... ... ... ... ...

a SW = softwood; HW = hardwood

Coefs_gsvol.txt Coefs_gsvol.txt: see partial listing in Table D8. These are needed to calculate

carbon in harvested wood. The file contains factors for calculating carbon in 

growing-stock volume; see Table 4 of Smith and others (2006). These include

the fraction that is softwood, fractions that are of sawtimber size, and average

specific gravity. These are given for each region/forest type combination.

Table D8.—Excerpt from file coefs_gsvol.txt containing factors to calculate carbon in 

growing-stock volume (Smith and others 2006)

Softwood Hardwood Softwood Hardwood

Forest-type Softwood sawtimber sawtimber specific specific

Region group fraction fraction fraction gravity gravity

Northeast Aspen-birch 0.247 0.439 0.330 0.353 0.428

Northeast Elm-ash-cottonwood 0.047 0.471 0.586 0.358 0.470

Northeast Maple-beech-birch 0.132 0.604 0.526 0.369 0.518

Northeast Oak-hickory 0.039 0.706 0.667 0.388 0.534

Northeast Oak-pine 0.511 0.777 0.545 0.371 0.516

Northeast Spruce-fir 0.870 0.508 0.301 0.353 0.481

Northeast White-red-jack pine 0.794 0.720 0.429 0.361 0.510

Northern

Lake States Aspen-birch 0.157 0.514 0.336 0.351 0.397

... ... ... ... ... ... ...

Coefs_livetree.txt Coefs_livetree.txt: see partial listing in Table D9. The file contains coefficients 

used in FORCARB2 to calculate mass density of live trees following methods of

Smith and others (2003). Coefficients differ by region, forest type, owner/landstatus category, and type of wood. Values are given for both full tree (above- and

belowground) and aboveground portion of tree only. Using these coefficients for 

F, G, and H, live mass density (Mg/ha) = F × (G+(1–exp(–volume/H))). When

the coefficient for H equals 0, the coefficient for F is the predicted value for live 

mass density. The mass density is then multiplied by the forest area to estimate

total live-tree carbon.
33

Table D9.—Excerpt from coefs_livetree.txt, coefficients used in FORCARB2 to calculate 

mass density of live trees (Smith and others 2003)

Wood Tree

Region Forest type Owner typea partb F G H

NE Aspen- Birch All all ag 438.47703 0.034680 410.705746

NE Aspen- Birch All all full 508.51010 0.036143 397.427168

NE Aspen- Birch All HW ag 581.27948 0.023864 574.944090

NE Aspen- Birch All HW full 683.59185 0.024465 566.852986

NE Aspen- Birch All SW ag 60.339938 0.018041 38.4255956

NE Aspen- Birch All SW full 73.331860 0.018273 38.2625320

NE MBB/ Other HW Priv all ag 357.40011 0.046993 255.054236

NE MBB/ Other HW Priv all full 425.25821 0.047576 254.727135

... ... ... ... ... ... ... ...

a HW = hardwood, SW = softwood, all = based on both hardwood and softwood. b ag = aboveground; full = above- and belowground (roots).

Coefs_mort.txt Coefs_mort.txt: see partial listing in Table D10. The file contains annual 

estimated mortality percentages derived from the 1997 RPA plot level dataset

used for estimating carbon in down dead wood. The particular set of numbers

to use in the FORCARB2 run depends on the region, the type of dominant

wood (hardwood or softwood) in the forest type, and the age class group. The

applicable percentage is multiplied by the live-tree carbon mass density to obtain

the annual mortality in carbon density. To calculate mortality over an interval

of p years, mortality is calculated for each end of the interval (year and year+p)

and these are averaged to give the mean annual mortality. See text for detailed

information on the calculations.

Table D10.—Example of annual estimated mortality percentages derived from the 1997 

RPA plot level dataset from coefs_mort.txt

Region Wood typea ACGRPb Percent

NE HW AC1_3 2.3

NE HW AC4_plus 0.8

NE SW AC1_3 12.6

NE SW AC4_plus 1.0

NLS HW AC1_3 2.2

NLS HW AC4_plus 1.1

NLS SW AC1_3 1.5

NLS SW AC4_plus 1.2

NPS HW AC1_3 1.1

NPS HW AC4_plus 1.0

pjW SW AC4_plus 0.5

... ... ... ...

a HW = hardwood, SW = softwood. b ACGRP = included age-class groups. AC1_3 includes age classes 1 through 3; AC4_plus includes all age

classes 4 and greater.
34

Coefs_owners.txt Coefs_owners.txt: see partial listing in Table D11. The file is a list of the broad 

owner/land-status groups used for FORCARB2 output. The order of the groups

must match the numbers assigned to the corresponding MUs in the manage files 

used by MUSCAN in the ATLAS model. (Note: Several of the groups listed in

this file are not discussed in this guide.)

Table D11.—Broad owner/land-status groups used in FORCARB2 output from 

coefs_owners.txt

National Forest

Other Government

Forest Industry

Other Private (including Farm)

Miscellaneous Corporate

Tribal Lands

Reserved

Other Forest

Coefs_pfates.txt Coefs_pfates.txt: see partial listing in Table D12. These are needed to calculate

harvested wood carbon. The file contains estimates of disposition patterns of 

carbon as fractions from industrial roundwood over time from 0 to 100 years

after harvest (see Table 6 of Smith and others 2006). Fractions vary by region,

wood type, and wood size. Possible product fates include continued use as

products, stored in landfills, consumed for the production of energy or emitted 

without energy recapture.

Table D12.—Excerpt of the coefs_pfates.txt file, containing disposition patterns of carbon 

as fraction of industrial roundwood over time (Smith and others 2006) 

Number of years

Region Wood type Wood size since harvesta In Use Landfills Energy Emitted

NC Softwood Saw log 0 0.630 0.000 0.249 0.121

NC Softwood Saw log 1 0.599 0.016 0.257 0.127

NC Softwood Saw log 2 0.570 0.032 0.265 0.133

NC Softwood Saw log 3 0.544 0.045 0.272 0.138

NC Softwood Saw log 4 0.520 0.058 0.279 0.143

NC Softwood Saw log 5 0.499 0.069 0.285 0.147

NC Softwood Saw log 10 0.410 0.115 0.310 0.165

NC Softwood Saw log 15 0.349 0.145 0.327 0.178

NC Softwood Saw log 20 0.306 0.166 0.339 0.189

NC Softwood Saw log 25 0.272 0.181 0.348 0.198

NC Softwood Saw log 30 0.245 0.193 0.356 0.206

NC Softwood Saw log 40 0.203 0.210 0.367 0.220

NC Softwood Saw log 50 0.173 0.221 0.374 0.231

NC Softwood Saw log 60 0.151 0.229 0.379 0.241

NC Softwood Saw log 70 0.133 0.236 0.382 0.249

NC Softwood Saw log 80 0.118 0.241 0.384 0.257

NC Softwood Saw log 90 0.106 0.246 0.385 0.263

NC Softwood Saw log 100 0.096 0.250 0.385 0.269

NC Softwood Pulpwood 0 0.514 0.000 0.305 0.180

NC Softwood Pulpwood 50 0.014 0.091 0.504 0.391

NC Softwood Pulpwood 100 0.008 0.084 0.504 0.403

... ... ... ... ... ... ... ...

a Data is annual; only select years are shown for illustration.
35

Coefs_resid.txt

Coefs_sdeadtree.txt

Coefs_resid.txt: see partial listing in Table D13. The file contains the average 

ratios of types of woody residue biomass to live-tree biomass for each region/

forest type/owner/land-status combination. The types of woody residue are down

wood due to mortality, and logging residue, which is split into aboveground and

belowground. See text for additional information on the algorithm.

Table D13.—Excerpt from file coefs_resid.txt

Mu_id Owner group ddwood2treea aglres2treeb bglres2treec

NC FI CS private 0.0206 0.0000 0.0000

NC FI CS-LH private 0.0371 0.0095 0.0089

NC FI CS-MB private 0.0369 0.0000 0.0011

NC FI CS-OH private 0.0392 0.0213 0.0194

NC FI CS-OP private 0.0357 0.0098 0.0095

NC FI CS-PN private 0.0274 0.0248 0.0243

NC FI LS-AB private 0.0402 0.0245 0.0245

... ... ... ... ...

a Ratio of down dead wood to live tree. b Ratio of aboveground logging residue to live tree. c Ratio of belowground logging residue to live tree.

Coefs_sdeadtree.txt: see partial listing in Table D14. The file contains coefficients 

used in FORCARB2 to calculate mass density of standing dead trees (Smith

and others 2003). Coefficients differ by region, forest type and owner/landstatus category. Values are given for both full tree (above- and belowground)

and aboveground portion of tree only. Using these coefficients for A, B, and C, 

standing-dead mass density (Mg/ha) = (predicted live-tree mass density) × A ×

exp(–((volume/B)C)). If the coefficient for C equals 0, A is the predicted value.

Table D14.—Excerpt from coefs_sdeadtree.txt (Smith and Heath 2003)

Forest Owner Tree 

Region type group Foresta partb A B C

NE Aspen-Birch all all ag 0.0438829 697.1841396 3.4784987

NE Aspen-Birch all all full 0.0436075 704.7826187 3.5064502

NE MBB/Other HW Priv all ag 0.1193884 240.2169916 2.3834805

NE MBB/Other HW Priv all full 0.1189334 240.3618154 2.3909855

NE MBB/Other HW Publ all ag 0.1193884 240.2169916 2.3834805

NE MBB/Other HW Publ all full 0.1189334 240.3618154 2.3909855

NE Oak-Hickory all all ag 0.0614742 459.1132221 1.6087507

... ... ... ... ... ... ... ...

a All = all forests versus productive forests or low-productivity forests. b ag = aboveground; full = above- and belowground (roots).
36

Coefs_soil.txt Coefs_soil.txt: see partial listing in Table D15. The file contains estimates of 

mass density of soil organic carbon for each region-forest type combination in

tons per hectare. This includes all fine organic material in the soil to a depth of 

1 meter but excludes coarse roots larger than 2 mm in diameter (which are

included in other pools). These estimates were derived from the national

STATSGO spatial database (USDA Soil Conserv. Serv. 1991) using the general

approach of Amichev and Galbraith (2004).

Table D15.—Excerpt from coefs_soil.txt with estimates of mass density of soil organic 

carbon (Mg/ha) for each region-forest type combination

Region/Forest type soilC1m_tpha

GP Spruce/Fir 48.024310

GP Pinyon / Juniper 59.470494

GP Ponderosa Pine 48.509203

GP Exotic softwoods 123.313204

GP Oak / Pine 67.809404

GP Oak / Hickory 85.503725

GP Elm / Ash / Cottonwood 79.014500

GP Maple / Beech / Birch 97.145771

GP Aspen / Birch 68.320741

GP Non stocked 48.458307

NE White / Red / Jack Pine 78.127857

NE Spruce / Fir 97.985485

... ...

a Soil carbon (Mg/ha) to a depth of 1 meter.

Coefs_under.txt Coefs_under.txt: see partial listing in Table D16. The file contains coefficients 

used in FORCARB2 to calculate mass density of the understory developed

by Plantinga and Birdsey (1993). Coefficients differ by region, forest type, 

and owner/land-status category. The equation used in FORCARB2 depends

on whether stand age has reached the age in variable INTYR. If younger, the

understory mass density = A0Y+(B1Y × YR)+(B2Y × YR2), where YR is the

number of years since afforestation. If older, then understory mass density =

A0V+(B1V × VOLAC)+(B2V × VOLAC2), where VOLAC is volume per area.

Table D16.—Excerpt of file coefs_under.txt showing coefficients to calculate understory 

mass density (Plantinga and Birdsey 1993)

Region/owner/

forest type A0Y B1Y B2Y INTYR A0V B1V B2V

NC FI LS-OH 1849. -8.40 0.0 15. 1920. -0.81885 0.000428

NC FI LS-LH 1817. -2.00 0.0 15. 1671. -0.05883 0.000109

NC FI LS-MB 1889. -16.48 0.0 15. 1506. -0.51967 0.000247

NC FI LS-AB 1805. 0.50 0.0 15. 2078. -0.48959 0.000165

NC FI NONSTOCK 1889. -16.48 0.0 15. 1506. -0.51967 0.000247

NC FI CS-OH 1849. -8.40 0.0 15. 1920. -0.81885 0.000428

NC FI CS-LH 1833. -5.20 0.0 15. 2281. -1.09687 0.000448

NC FI CS-MB 1889. -16.48 0.0 15. 1506. -0.51967 0.000247

NC FI CS NONSTO 1849. -8.40 0.0 15. 1920. -0.81885 0.000428

... ... ... ... ... ... ... ...
37

Flags_output.txt

Merch.txt

Coefs_weights.txt Coefs_weights.txt: see partial listing in Table D17. The file contains factors used 

to convert growing-stock volume of wood to mass of carbon. Factors differ by

region, forest type, and species within forest type (based on Table 4 of Smith and

others 2006).

Table D17.—Excerpt from coefs_weights.txt containing factors used to convert growingstock volume of wood to mass of carbon (Smith and others 2006)

Specific v2c_lbs v2c_tons Wood

Region/forest type gravity (ft3-lbs)a (m3- tonnes)b Typec

NE Aspen-Birch 0.428554187 13.37089064 0.214277094 HW

NE Aspen-Birch 0.355927137 11.10492668 0.177963569 SW

NE MBB/Other HW 0.515042451 16.06932446 0.257521225 HW

NE MBB/Other HW 0.366181708 11.42486929 0.183090854 SW

NE Oak-Hickory 0.538236597 16.79298183 0.269118299 HW

NE Oak-Hickory 0.391929346 12.22819561 0.195964673 SW

... ... ... ... ...

a v2c_lbs(ft3

-lbs) = factor to convert volume in cubic feet to carbon in pounds. b v2c_tons (m3

-tonne) = factor to convert volume in cubic meters to carbon in tonnes. c HW = hardwood, SW = softwood.

Flags_output.txt: see partial listing in Table D18. The file contains flags 

indicating which output files you want FORCARB2 to produce. Available output 

files include carbdb.txt, carbhu.txt, findat.txt, finhar.txt, bicmur.txt, bicreg.

txt, bicregmu.txt, volumes.txt, and volumesac.txt. (See Output Files section for

description of each.) A value of 1 indicates the file (or files) will be produced; if a 

0 is present, the file(s) will not be created.

Table D18.—Example flags_output.txt

CARBs FINDAT FINHAR BICMUR BICREG BICREGMU VOLUMES VOLUMESAC

Select output

(0,1) 1 1 1 1 1 1 1 1

Merch.txt: see partial listing in Table D19. The file contains MU-level values of 

merchantable inventory, growth, and removals, and net area-change volumes. 

These are reported for each age class and period. There are 18 age classes

(numbered 0 to 17); each represents a stand age span of 10 years (5 in the south). 

This corresponds with the period length specified in coefs_atlas.txt. Following a

clearcut, a stand would be placed in age class 0. After the specified time interval, 

it would move to age-class 1, and so on. If a stand reaches the maximum age

class, it would remain at that level until harvested.

Each group of 18 rows contains estimates for a particular MU for a particular

period. Data for each period are grouped together. The order of the MUs matches

the order found in coefs_atlas.txt. The final period’s MU block contains three 

additional rows (a total of 21). The contents of each row are as follows:
38

ROW TYPE OF DATA

1 Age class

2 Inventory area

3 Softwood inventory volume

4 Hardwood inventory volume

5 Volume of softwood growth

6 Volume of hardwood growth

7 Area harvested

8 Volume of softwood removed

9 Volume of hardwood removed

10 Thinning area

11 Softwood volume thinned

12 Hardwood volume thinned

13 Net area change

14 Net change in softwood volume due to change in area

15 Net change in hardwood volume due to change in area

16 Area loss

17 Softwood volume on lost area recovered by harvest

18 Hardwood volume on lost area recovered by harvest

The additional three rows in the final period’s MU block are as follows:

ROW TYPE OF DATA

19 Final inventory area

20 Final softwood inventory volume

21 Final hardwood inventory volume

Areas are in thousands of acres; volumes are in millions of cubic feet. Each data

value has a maximum length of 10, with resolution to the nearest thousandth.

Table D19.—Excerpt of several lines of merch.txt, an input file to FORCARB2 that 

contains MU level estimates of merchantable inventory, growth, and removals, and net 

area-change volumes for each age class and period

0 1 2 3 4 ... 13 14 15 16 17

95.287 75.429 93.155 87.996 175.234 ... 5.220 1.410 0.000 0.000 0.000

0.724 0.743 1.393 1.958 3.757 ... 0.161 0.030 0.000 0.000 0.000

31.330 32.114 60.238 84.700 162.470 ... 6.946 1.284 0.000 0.000 0.000

0.000 0.135 0.374 0.443 0.320 ... 0.066 0.027 0.000 0.000 0.000

0.000 5.852 16.169 19.155 13.859 ... 2.869 1.158 0.000 0.000 0.000

0.000 0.000 0.000 0.000 0.000 ... 1.483 0.400 0.000 0.000 0.000

0.000 0.000 0.000 0.000 0.000 ... 0.054 0.010 0.000 0.000 0.000

0.000 0.000 0.000 0.000 0.000 ... 2.334 0.432 0.000 0.000 0.000

0.000 0.000 0.000 0.000 0.000 ... 0.000 0.000 0.000 0.000 0.000

0.000 0.000 0.000 0.000 0.000 ... 0.000 0.000 0.000 0.000 0.000

0.000 0.000 0.000 0.000 0.000 ... 0.000 0.000 0.000 0.000 0.000

0.000 0.000 0.000 0.000 0.000 ... 0.000 0.000 0.000 0.000 0.000

0.000 0.000 0.000 0.000 0.000 ... 0.000 0.000 0.000 0.000 0.000

... ... ... ... ... ... ... ... ... ... ...
39

Mu_table.txt Mu_table.txt: see partial listing in Table D20. The file contains references linking 

MUs to the region/forest type/owner/land-status combinations in the various

“coef_” files listed previously. The more data underlying a carbon pool, likely the 

more categories in a “coef_” file.

Table D20.—Several sample abbreviated lines from mu_table.txt, which links the ATLAS/

FORCARB MUs with their corresponding region-forest type from each of the coef files

Management unit TREES/(WEIGHTS-1:25) Forest floor ...

PNWW FI DFIR—H PWW Douglas-fir Priv PNWW Douglas-fir, western hemlock ...

PNWW FI DFIR—M PWW Douglas-fir Priv PNWW Douglas-fir, western hemlock ...

PNWW FI DFIR—L PWW Douglas-fir Priv PNWW Douglas-fir, western hemlock ...

PNWW FI W.HEM-H PWW Western Hemlock all PNWW Douglas-fir, western hemlock ...

PNWW FI W.HEM-M PWW Western Hemlock all PNWW Douglas-fir, western hemlock ...

... ... ... ...
40

Bicmur.txt

Appendix E. FORCARB 2 Output Files

The user has a choice of output files from FORCARB2. These may be specified 

in the file flags_output.txt by turning the flags on (=1) or off (=0). Each of the 

optional output files is described as follows:

Bicmur.txt: see partial listing in Table E1. The file contains projections of 

carbon flows resulting from the harvesting and use of wood and wood products. 

Estimates are made of the amounts in use (as wood products), in landfills, burned 

for energy as a substitute for for fossil fuel, or emitted or left as logging residue

for each MU. Values are given in teragrams of carbon and are tracked from time

of harvest to the last period in the model. Each row indicates how much of a

year’s removals remain in that category over time. Each column indicates the

total amounts of carbon in that category for each year in the model.

Bicreg.txt

Table E1.—Example of bicmur.txt file, which contains projections of carbon flows resulting 

from the harvesting and use of wood and wood products

** BICMUR **

 . . . POST REMOVALS CARBON FLOWS

NC NF CS-OH

 . . . . PERIOD

1990 2000 2010 2020 2030 2040 2050

 . . . . . Teragrams

PERIOD REMOVALS ---- ------ ------ --IN USE- ------ ------ ------

1990 0 0 0 0 0 0 0 0

2000 1.1243 . . 0.5474 0.3322 0.2631 0.2253 0.1978 0.1759

2010 0.4265 . . . 0.2076 0.126 0.0998 0.0855 0.075

2020 0.3921 . . . . 0.1909 0.1159 0.0918 0.0786

2030 0.3901 . . . . . 0.1899 0.1153 0.0913

2040 0.4002 . . . . . . 0.1948 0.1182

2050 0.3982 . . . . . . . 0.1938

TOTAL . . 0 0.5474 0.5398 0.58 0.6309 0.6852 0.7329

 . . . . . . . .

PERIOD REMOVALS ---- ------ ------ -LANDFILL ------ ------ ------

1990 0 0 0 0 0 0 0 0

2000 1.1243 . . 0.077 0.1579 0.1786 0.1883 0.1956 0.2019

... ... ... ... ... ... ... ... ...

Bicreg.txt: see partial listing in Table E2. The file contains a summary of 

projected forest area and carbon data by broad owner/land-status category. Areas

are given in thousands of hectares and carbon is reported in petagrams.
41

** BICREG **

B I C A R B

REGIONAL CARBON SEQUESTRATION AND EMISSIONS

PNWW NATIONAL FOREST Total Over All Forest Types

YEARS

1990 2000 2010 ... 2040 2050

Thousand Hectares

FOREST AREA SUMMARY

TOTAL FOREST AREA 2878.2 2878.2 2878.2 ... 2878.2 2878.2

AREA OF REMOVALS 52.39 7.92 ... 11.63 10.94

Petagrams

FOREST CARBON INVENTORY

TOTAL LIVE TREE 0.54362 0.61592 0.69734 ... 0.90528 0.96231

TOTAL ABOVEGROUND TREE 0.44875 0.50847 0.57572 ... 0.74748 0.79459

TOTAL DEAD TREE 0.06073 0.0661 0.07166 ... 0.08359 0.08633

TOTAL ABVEGRD DEAD TREE 0.03956 0.04284 0.04618 ... 0.05324 0.05483

TOTAL DOWNED WOOD 0.01844 0.02882 0.03593 ... 0.06023 0.064

ABOVEGROUND DOWN DEAD 0.01733 0.02625 0.03381 ... 0.05824 0.06212

BELOWGROUND RESIDUE 0.00111 0.00256 0.00211 ... 0.00199 0.00188

SOIL 0.25896 0.25896 0.25896 ... 0.25896 0.25896

SOIL w/ LUC SOIL 0.25896 0.25896 0.25896 ... 0.25896 0.25896

FOREST FLOOR 0.10609 0.10789 0.1108 ... 0.11909 0.12139

UNDERSTORY 0.00866 0.00933 0.0104 ... 0.01586 0.01816

TOTAL 0.99651 1.08702 1.18509 ... 1.44301 1.51115

TOTAL w/ LUC SOIL 0.99651 1.08702 1.18509 ... 1.44301 1.51115

TREE CARBON FLUXES

TREE CARBON INCREMNT -TOT . . 0.08661 0.08378 ... 0.06704 0.06125

TREE CARBON INCREMENT -AG . . 0.07153 0.0692 ... 0.05538 0.05059

REMOVALS - TOTAL 0.01431 0.00236 ... 0.00427 0.00422

REMOVALS - ABOVEGROUND . . 0.01181 0.00195 ... 0.00353 0.00349

DIFF BTWN INVNTORIES -TOT . . 0.0723 0.08142 ... 0.06277 0.05703

DIFF BTWN INVENTORIES -AG . . 0.05972 0.06725 ... 0.05185 0.04711

NET AREA CHANGE

AREA (1000HA) 0 0 ... 0 0

TOTAL TREE 0 0 ... 0 0

ABOVE GROUND 0 0 ... 0 0

SOIL 0 0 ... 0 0

FLOOR 0 0 ... 0 0

UNDER 0 0 ... 0 0

TOTAL 0 0 ... 0 0

Table E2.—Excerpt from bicreg.txt, the summary of projected forest area and carbon data 

by broad owner-land status category

(Table E2 continued on next page)
42

Bicregmu.txt

Carbdb.txt

(Table E2 continued)

** BICREG **

YEARS

1990 2000 2010 ... 2040 2050

Petagrams

CUMULATIVE FATES OF

REMOVALS CARBON

IN USE 0 0.00417 0.00352 ... 0.00476 0.0051

LANDFILL 0 0.00049 0.00119 ... 0.00275 0.00331

ENERGY 0 0.00339 0.00428 ... 0.00791 0.00916

EMITTED 0 0.00266 0.0035 ... 0.00685 0.00804

TOTAL 0 0.01071 0.00862 ... 0.01542 0.01774

 . . . . .

LOGGING RESIDUE - ABOVEGD 0.00166 0.00293 0.00238 ... 0.00218 0.00201

BELOWGD 0.00111 0.00256 0.00211 ... 0.00199 0.00188

 . . . . .

ALL LOGGING RSD - ABOVEGD 0 0.0022 0.00257 ... 0.00467 0.00537

BELOWGD 0 0.00217 0.00253 ... 0.00446 0.00511

 . . . . .

SUMMARY OF CARBON . . . . .

SEQUESTRATION AND EMISSIONS . . . . . .

TOTAL CARBON SEQUESTERED . . 0.10481 0.10143 ... 0.08326 0.07265

TOTAL CARBON EMITTED . . 0.01431 0.00336 ... 0.00432 0.0045

NET CHANGE IN CARBON 0.0905 0.09807 ... 0.07894 0.06814

... ... ... ... ... ... ...

Bicregmu.txt contains a summary of projected forest area and carbon data

by MU. Areas are given in thousands of hectares and carbon is reported in

teragrams. The file structure is similar to bicreg.txt; see Table E2 for example.

Carbdb.txt contains carbon estimates for the age classes of each MU for each

year in the simulation. Values are given for total carbon in hardwood types,

total carbon in softwood types, total carbon in all types not broken up by pool,

total nonsoil carbon and forest area. The total includes live tree, standing dead,

forest floor, soil (where applicable), understory, and down dead wood. Output 

is comma-separated to facilitate its use in other analytical software. The table

format is as follows:

Element Data Type Length a Columns

Region Character – Upper Case 4 2-5

Year Integer 4 7-10

Harvest Unit Character 55 12-66

Management Unit Character – Upper Case 15 68-82

Age Class Integer 2 84-85

Softwood Total Carbon Integer 10 87-96

Hardwood Total Carbon Integer 10 98-107

Total Carbon Integer 10 109-118

Total Nonsoil carbon Real 10(5) 120-129

Forest Area Real 12(5) 131-142

a For elements of Data Type Real, the number in parentheses indicates the number of digits after the decimal

point, while the other number indicates the total number of characters including the decimal point. For example,

a length of 10(5) would be of the format 0000.00000.
43

Carbhu.txt

Errors.txt

Findat.txt

Table E3.—Data structure of findat.txt, an output file of FORCARB2

Carbhu.txt contains carbon estimates for the age classes of each harvest unit

(HU) for each year in the simulation. The table format is as follows:

Errors.txt contains information describing errors should any be detected. This

may be useful in diagnosing and correcting of data problems.

Findat.txt contains carbon amounts for inventory, growth, removals, and net

area change for each period for each MU. Values are included for the various

components of the forest ecosystem, including soils, forest floor, and understory. 

For trees, both hardwood and softwood values are given as well as both total and

aboveground only. Area is in thousands of hectares; carbon is given in teragrams. 

The table format is given in Table E3. 

Element Data Type Length Columns

Region Character – Upper Case 4 2-5

Year Integer 4 7-10

Harvest Unit Character 55 12-66

Age Class Integer 2 68-69

Softwood Tree Carbon Integer 10 71-80

Hardwood Tree Carbon Integer 10 82-91

Total Carbon Integer 10 93-102

Heading Element Data Type Lengtha Columns

P Period Numberb Integer 2 1-2

R Region Identifierc Integer 2 3-4

O Owner-Land Status Identifierd Integer 1 6

F Forest Type Identifiere Integer 2 7-8

S Site Quality Identifierf Integer 1 10

I Management Intensity Identifierg Integer 1 12

INAREA Inventory Area Real 11(5) 14-24

SWMRCH Carbon in Merchantable Portion Real 11(5) 26-36

of Tree - Softwood

HWMRCH Carbon in Merchantable Portion Real 11(5) 38-48

of Tree - Hardwood

SWTOTL Total Live Tree Carbon – Softwood Real 11(5) 50-60

HWTOTL Total Live Tree Carbon – Hardwood Real 11(5) 62-72

SWABGR Above Ground Live Tree Carbon – Real 11(5) 74-84

Softwood

HWABGR Above Ground Live Tree Carbon – Real 11(5) 86-96

Hardwood

SDTOTL Total Standing Dead Tree Carbon Real 11(5) 98-108

SDABGR Above Ground Standing Dead Tree Carbon Real 11(5) 110-120

SWLRAG Above Ground Logging Residue Real 11(5) 122-132

Carbon – Softwood

HWLRAG Above Ground Logging Residue Real 11(5) 134-144

Carbon – Hardwood

SWLRBG Below Ground Logging Residue Real 11(5) 146-156

Carbon – Softwood

HWLRBG Below Ground Logging Residue Real 11(5) 158-168

Carbon – Hardwood

SWALRAG Above Ground Undecayed Logging Real 11(5) 170-180

Residue Carbon – Softwood

HWALRAG Above Ground Undecayed Logging Real 11(5) 182-192

Residue Carbon – Hardwood

(Table E3 continued on next page)
44

SWALRBG Below Ground Undecayed Logging Real 11(5) 194-204

Residue Carbon – Softwood

HWALRBG Below Ground Undecayed Logging Real 11(5) 206-216

Residue Carbon – Hardwood

SWDDW Down Dead Wood Carbon – Softwood Real 11(5) 218-228

HWDDW Down Dead Wood Carbon – Hardwood Real 11(5) 230-240

SOIL Soil Carbon Real 11(5) 242-252

FLOOR Forest Floor Carbon Real 11(5) 254-264

UNDER Understory Carbon Real 11(5) 266-276

TOTAL Total Inventory Carbon Real 11(5) 278-288

TOTAG Total Above Ground Carbon Real 11(5) 290-300

GTAREA Area of Growth Real 11(5) 302-312

GTSWMRCH Growth of Carbon in Merchantable Real 11(5) 314-324

Portion of Tree - Softwood

GTHWMRCH Growth of Carbon in Merchantable Real 11(5) 326-336

Portion of Tree – Hardwood

GTSWTOTL Growth of Total Live Tree Carbon – Softwood Real 11(5) 338-348

GTHWTOTL Growth of Total Live Tree Carbon – Hardwood Real 11(5) 350-360

GTSWABGR Growth of Above Ground Live Tree Real 11(5) 362-372

Carbon – Softwood

GTHWABGR Growth of Above Ground Live Tree Real 11(5) 374-384

Carbon – Hardwood

RMAREA Area of Removals Real 11(5) 386-396

RMSWMRCH Removals of Carbon in Merchantable Real 11(5) 398-408

Portion of Tree – Softwood

RMHWMRCH Removals of Carbon in Merchantable Real 11(5) 410-420

Portion of Tree – Hardwood

RMSWTOTL Removals of Total Live Tree Carbon – Softwood Real 11(5) 422-432

RMHWTOTL Removals of Total Live Tree Carbon – Hardwood Real 11(5) 434-444

RMSWABGR Removals of Above Ground Live Tree Real 11(5) 446-456

Carbon – Softwood

RMHWABGR Removals of Above Ground Live Tree Real 11(5) 458-468

Carbon – Hardwood

NCAREA Net Area Change Real 11(5) 470-480

NCSWMRCH Net Change in Carbon of Merchantable Portion Real 11(5) 482-492

of Tree Due to Area Change – Softwood

NCHWMRCH Net Change of Carbon in Merchantable Portion Real 11(5) 494-504

of Tree Due to Area Change – Hardwood

NCSWTOTL Net Change of Live Tree Carbon Real 11(5) 506-516

Due to Area Change – Softwood

NCHWTOTL Net Change of Live Tree Carbon Real 11(5) 518-528

Due to Area Change – Hardwood

NCSWABGR Net Change of Above Ground Live Tree Carbon Real 11(5) 530-540

Due to Area Change – Softwood

NCHWABGR Net Change of Above Ground Live Tree Carbon Real 11(5) 542-552

Due to Area Change – Hardwood

NCSOIL Net Change of Soil Carbon Due to Area Change Real 11(5) 554-564

NCFLOOR Net Change of Forest Floor Carbon Real 11(5) 566-576

Due to Area Change

NCUNDER Net Change of Understory Carbon Real 11(5) 578-588

Due to Area Change

NCTOTAL Net Change of Total Carbon Real 11(5) 590-600

Due to Area Change

NCTOTAG Net Change of Total Above Ground Carbon Real 11(5) 602-612

Due to Area Change

a For elements of Data Type Real, the number in parentheses indicates the number of digits after the decimal

point, while the other number indicates the total number of characters including the decimal point. For

example, a length of 10(5) would be of the format 0000.00000. b The number of the time period (or interval) for which the data has been calculated, beginning with 0. 

Typically, each period represents 10 years (5 years in the southern regions). c The number assigned to the geographic area in which the MU is located. In this table, results are given by

subregions for the NC region. See Figure 2 for a description of regions used in FORCARB2.

(Table E3 continued)
45

Findat0.txt

d See the description of coefs_owners.txt above for a complete group list. e See Appendix F for a list of the forest types used in FORCARB2. f If site quality has been assigned to the particular MU, the codes are: 00, no site quality assigned; 01, high (or

good) site quality; 02, medium site quality; 03, low (or poor) site quality. g This identifier is used to label a user-defined level of forest management to be applied to stands in the specific 

MU. In the RPAAssessment, only the private timberlands in the PNWW, SC, and SE regions made use of more

than one management intensity. The meaning of a particular identifier differs by region and owner/land-status 

category; discussion of their structure are found in Mills and Kincaid (1992) and their implementation in Adams

and others (2003).

Findat0.txt contains carbon estimates for logging residue and down dead wood

present at the beginning of the model run (initial conditions) for each MU. 

Structure is similar to findat.txt, except that only the MU identifiers and those 

data elements pertaining to logging residue and down dead wood are present. 

Carbon is given in teragrams. The table format is as follows:

Heading Element Data Type Lengtha Columns

P Period Number Integer 2 1-2

R Region Identifier Integer 2 3-4

O Owner-Land Status Identifier Integer 1 6

F Forest Type Identifier Integer 2 7-8

S Site Quality Identifier Integer 1 10

I Management Intensity Identifier Integer 1 12

SWLRAG Above Ground Logging Residue Carbon – Real 11(5) 14-24

Softwood

HWLRAG Above Ground Logging Residue Carbon – Real 11(5) 26-36

Hardwood

SWLRBG Below Ground Logging Residue Carbon – Real 11(5) 38-48

Softwood

HWLRBG Below Ground Logging Residue Carbon – Real 11(5) 50-60

Hardwood

SWALRAG Above Ground Undecayed Logging Real 11(5) 62-72

Residue Carbon – Softwood

HWALRAG Above Ground Undecayed Logging Real 11(5) 74-84

Residue Carbon – Hardwood

SWALRBG Below Ground Undecayed Logging Real 11(5) 86-96

Residue Carbon – Softwood

HWALRBG Below Ground Undecayed Logging Real 11(5) 98-108

Residue Carbon – Hardwood

SWDDW Down Dead Wood Carbon – Softwood Real 11(5) 110-120

HWDDW Down Dead Wood Carbon – Hardwood Real 11(5) 122-132

Finhar.txt Finhar.txt contains harvest information for each MU by age class and period. 

Each group of 13 rows contains output for a particular MU for a particular

period. Data for each period are grouped together. The order of the MUs matches

the order in coefs_atlas.txt.

Each column corresponds to an age class. There are 18 age classes (numbered

0 to 17); each represents a stand age span of 10 years (5 in the south). This

corresponds with the period length specified in coefs_atlas.txt. The final column 

(age class 17) contains all subsequent stand ages. Carbon is given in tens of

tonnes. The row variables are as follows:

a For elements of Data Type Real, the number in parentheses indicates the number of digits after the decimal

point, while the other number indicates the total number of characters including the decimal point. For example,

a length of 10(5) would be of the format 0000.00000.
46

Volumes.txt

Row Type of Data

1 Age class

2 Carbon in merchantable portion of growing stock harvested – softwood

3 Carbon in merchantable portion of growing stock harvested – hardwood

4 Carbon in merchantable portion of growing stock thinned – softwood

5 Carbon in merchantable portion of growing stock thinned – hardwood

6 Total carbon in live trees harvested – softwood

7 Total carbon in live trees harvested – hardwood

8 Above ground carbon in live trees harvested – softwood

9 Above ground carbon in live trees harvested – hardwood

10 Total carbon in live trees thinned – softwood

11 Total carbon in live trees thinned – hardwood

12 Above ground carbon in live trees thinned – softwood

13 Above ground carbon in live trees thinned – hardwood

Volumes.txt contains timber volume data for each MU for each period. Values

are given for softwood, hardwood, and totals for inventory, harvest, thinning,

removals, area loss, and net area change. Data are reported in millions of cubic

meters. The format is as follows:

Element Data Type Lengtha Columns

Management Unit Name Text 15 1-15

Year Integer 4 18-21

Softwood Inventory Real 10(4) 24-33

Hardwood Inventory Real 10(4) 36-45

Total Inventory Real 10(4) 48-57

Softwood Harvest Real 10(4) 60-69

Hardwood Harvest Real 10(4) 72-81

Total Harvest Real 10(4) 84-93

Softwood Thinned Real 10(4) 96-105

Hardwood Thinned Real 10(4) 108-117

Total Thinned Real 10(4) 120-129

Softwood Removals Real 10(4) 132-141

Hardwood Removals Real 10(4) 144-153

Total Removals Real 10(4) 156-165

Loss in Softwood Inventory Due to Area Loss Real 10(4) 168-177

Loss in Hardwood Inventory Due to Area Loss Real 10(4) 180-189

Loss in Total Inventory Due to Area Loss Real 10(4) 192-201

Net Change in Softwood Inventory Due to Area Change Real 10(4) 204-213

Net Change in Hardwood Inventory Due to Area Change Real 10(4) 216-225

Net Change in Total Inventory Due to Area Change Real 10(4) 228-237

a For elements of Data Type Real, the number in parentheses indicates the number of digits after the decimal

point, while the other number indicates the total number of characters including the decimal point. For example,

a length of 10(5) would be of the format 0000.00000.
47

Volumesac.txt Volumesac.txt contains timber-volume data for each MU for each period for each

age class. There are 18 age classes (numbered 0 to 17); each represents a stand

age span of 10 years (5 in the south). Values are given for softwood, hardwood,

and totals for inventory, harvest, thinning, removals, area loss, and net area

change. Data are reported in millions of cubic meters. The format is as follows:

Element Data Type Lengtha Columns

Management Unit Name Text 15 1-15

Year Integer 4 18-21

Age Class Integer 2 23-24

Softwood Inventory Real 10(4) 27-36

Hardwood Inventory Real 10(4) 39-48

Total Inventory Real 10(4) 51-60

Softwood Harvest Real 10(4) 63-72

Hardwood Harvest Real 10(4) 75-84

Total Harvest Real 10(4) 87-96

Softwood Thinned Real 10(4) 99-108

Hardwood Thinned Real 10(4) 111-120

Total Thinned Real 10(4) 123-132

Softwood Removals Real 10(4) 135-144

Hardwood Removals Real 10(4) 147-156

Total Removals Real 10(4) 159-168

Loss in Softwood Inventory Due to Area Loss Real 10(4) 171-180

Loss in Hardwood Inventory Due to Area Loss Real 10(4) 183-192

Loss in Total Inventory Due to Area Loss Real 10(4) 195-204

Net Change in Softwood Inventory Due to Area Change Real 10(4) 207-216

Net Change in Hardwood Inventory Due to Area Change Real 10(4) 219-228

Net Change in Total Inventory Due to Area Change Real 10(4) 231-240

a For elements of Data Type Real, the number in parentheses indicates the number of digits after the decimal

point, while the other number indicates the total number of characters including the decimal point. For example,

a length of 10(5) would be of the format 0000.00000.
48

Appendix F. Forest Types used in FORCARB2 

There is a management unit in the dataset for each forest type per region. The

numeric codes are based on the ATLAS model (Mills and Kincaid 1992).

0, PACIFIC NORTHWEST – WESTSIDE

10 Douglas-Fir 

20 Western Hemlock 

25 Fir-Spruce 

30 Pines 

35 Mixed Softwoods 

44 Nonstocked 

45 Alder 

50 Mixed Hardwoods 

77 Other Softwood Forest 

88 Other Hardwood Forest 

1, PACIFIC NORTHWEST - EASTSIDE 

07 Pinyon-Juniper 

21 Ponderosa Pine 

40 Douglas-Fir 

43 True Fir 

44 Nonstocked 

46 Lodgepole Pine 

50 Hardwoods 

77 Other Softwood Forest 

88 Other Hardwood Forest 

2, PACIFIC SOUTHWEST 

07 Pinyon-Juniper 

23 True Fir 

27 Redwood 

28 Hardwoods 

40 Douglas-Fir 

41 Ponderosa Pine 

44 Nonstocked 

49 Mixed Conifers 

77 Other Softwood Forest 

88 Other Hardwood Forest 

ROCKY MOUNTAINS

 (NORTH-3 and SOUTH-4) 

01 Douglas-Fir 

02 Ponderosa Pine 

03 Fir-Spruce 

04 Lodgepole Pine 

05 Hardwoods 

06 Nonstocked 

07 Pinyon-Juniper 

08 High Elevation 

77 Other Softwood Forest 

88 Other Hardwood Forest 

5, NORTH CENTRAL - PLAINS STATES 

01 Pines 

02 Oak-Pine 

03 Oak-Hickory 

04 Lowland Hardwoods 

05 Maple-Beech-Birch 

09 Nonstocked 

88 Other Hardwood Forest 

6, NORTH CENTRAL – LAKE STATES 

01 Jack Pine 

02 Red Pine 

03 White Pine 

04 Spruce-Fir 

05 Swamp Conifer 

06 Oak-Hickory 

07 Lowland Hardwoods 

08 Maple-Beech-Birch 

09 Aspen-Birch 

10 Nonstocked 

77 Other Softwood Forest 

88 Other Hardwood Forest 

7, NORTHEAST 

01 White-Red-Jack Pines 

02 Spruce-Fir 

03 Loblolly Pine-Shortleaf- 

 Pine-Oak-Gum-Cypress 

04 Oak-Pine 

05 Oak-Hickory 

06 Elm-Ash-Red Maple 

07 Maple-Beech-Birch 

08 Aspen-Birch 

09 Nonstocked 

77 Other Softwood Forest 

88 Other Hardwood Forest 

SOUTH

 (SOUTH CENTRAL-8 and SOUTHEAST-9) 

01 Planted Pine 

02 Natural Pine 

03 Oak-Pine 

04 Upland Hardwoods 

05 Bottomland Hardwoods 

09 Nonstocked 

77 Other Softwood Forest 

88 Other Hardwood Forest
49

Appendix G. Glossary

Age class – Age range assigned to a forest stand based on the number of years

since establishment or the average age of dominant trees. Each class spans 10

years (5 years in the south). There are 18 age classes beginning with age-class 0

representing stands aged 0 to 9 years (0 to 4 years in the south). All stands older

than age class 17 are assigned to it. 

Area loss – Loss of acreage in a management unit (MU) since the previous

period; may be due to land moving to a nonforest use/cover or to another MU

(representing a change in forest type or kind of management).

ATLAS – The Aggregate Timberland Assessment System, a timber projection

model developed by the USDA Forest Service. 

Biomass – All organic material, either from living or formerly living sources,

present in an ecosystem or ecosystem component.

Carbon density – The amount of carbon per area, such as in tonnes per hectare.

Carbon stock change – The difference between carbon stocks at two points in

time. When the movement of carbon into or out of an ecosystem or ecosystem

component is measured directly, such as when using an eddy covariance tower,

the change in carbon is called flux.

Carbon sequestration – Increasing carbon within an ecosystem; by atmospheric

scientists’ convention, often expressed as a negative value indicating that carbon

is being reduced in the atmosphere and carbon in forest components is increasing.

Clear cut – A method of timber harvesting by which all the trees are removed

from a stand. This is the most commonly assumed method modeled in

FORCARB2.

Coarse tree roots – Roots with a diameter greater than a particular threshold,

generally in the range of 0.2 to 0.5 cm depending on the source.

d.b.h. – Diameter of a tree measured at breast height (4.5 feet above the ground). 

This is the standard height at which diameter is measured.

Down dead wood – Woody material on the ground larger than 3 inches (about

7.5 cm) in diameter, consisting of the sum of the two subpools of logging residue

including stumps and the coarse roots of stumps, and fallen trees and branches

from mortality. 

Emitted – A category of disposition of carbon from harvested wood in which

either combustion or decay of the harvested wood occurs without concomitant

energy capture. Emissions are from decay of logging residue; they do not include

emissions from machinery to harvest, transport, or process the wood.
50

Energy – A category of disposition of carbon from harvested wood in which

emissions occur during combustion and resulting energy is captured.

Fine tree roots – Roots with a diameter smaller than a particular threshold,

generally in the range of 0.2 to 0.5 cm depending on the source.

FORCARB2 – An updated version of the U.S. Forest Carbon Budget Model,

which estimates carbon stocks and stock change within and between the various

components of an ecosystem, including live tree, standing dead tree, understory,

forest floor, soil, and woody residue.

Forest floor – A forest-carbon pool that includes all organic material in the layer

of the forest directly above the mineral soil, including fine woody debris less than 

3 inches (7.5 cm) in diameter, tree litter, humus, and fine roots.

Forest products – The various end uses for which harvested wood may be used,

including residential and nonresidential construction, wooden containers, paper

and paper products, and fuelwood.

Growing-stock removals – Removals of trees from the growing-stock inventory

through harvesting, cultural operations, or land-use change. 

Growing-stock volume – Total volume of trees within an area that are classified 

as growing stock includes all live trees of commercial species that meet minimum

merchantability standards. In general, these trees have at least one solid 8-foot

section, are reasonably free of form defect on the merchantable bole, and at least

34 percent of the volume is merchantable (may be less in some locations).

Growth – In ATLAS, this is most often net growth on growing stock, which

refers to addition of tree volume through natural development over a period of

years. The net change has the loss from mortality subtracted.

Harvest – The cutting of trees from a stand which may result in the regeneration

of a new stand. 

Harvest unit (HU) – The area to which harvest volumes are applied. The

coarsest level of aggregation in ATLAS; typically identified by geographic 

region, ownership class, and fiber type (hardwood or softwood), as many as 

65 MUs can be assigned to one HU.

Inventory – A systematic sampling of trees in a given area to determine the basic

composition and/or characteristics of the surrounding forest.

Inventory unit (IU) – A relatively homogenous area for which inventory data

are compiled. The finest level of aggregation used in ATLAS, usually stratified by 

geographic region, owner/land-status category, forest type, and site class. Within

an IU, the inventory area and volume per unit area (often acres and cubic foot

volumes per acre) are stratified by age class.
51

Landfill – A waste management area in which discarded wood and paper (and

its associated carbon) may be stored for a long period and undergo a slow rate

of decay.

Large sawtimber – A size class of harvested timber meeting minimum standards

of length and defect and generally having a minimum diameter of 15 inches.

Logging residue – The unused portions of growing-stock and nongrowing-stock

trees cut or killed by logging activities and which remain on site. FORCARB2

considers both above- and belowground amounts.

Management intensity – In ATLAS, a further level of stratification within an IU 

that may represent specific silvicultural treatments or unusual stand composition 

such that the growth and harvesting parameters in the MU are distinct.

Management unit (MU) – A level of aggregation in ATLAS developed to

represent a group of stands having similar management objectives and growth

characteristics; as many as 10 IUs can be assigned to one MU. MU parameters

used in ATLAS include growth, yield, area change, and harvest rules.

Merchantable volume – See Growing-stock volume

Net area change – Area gained minus area loss. As used here, generally refers

to the difference between timberland or forest land removed from productive

forest and converted to other uses vs. cropland or other lands reverting or planted

to forest.

Owner/land-status category – The grouping of land of a particular IU according

to ownership (such as National Forest and Other Government) or land status

(such as Reserved and low-productivity forest land [Other]). See the description

of coefs_owners.txt above for an owner/land-status category list.

Partial cutting – A method of accounting for harvest in the ATLAS model where

only part of the forest area in an age class is harvested.

Period – The time interval between model estimations of inventory, growth,

acreage, and harvest. It is specified by the user, though the generally accepted 

convention is 10 years (5 years in the Southern United States).

Pulpwood – A size class of harvested timber that does not meet the requirements

for saw logs; generally used in the production of wood pulp, paper, or other

lower grade wood products. In FORCARB2, we emulate pulpwood by defining 

it as age class 4 and younger (40 years and younger; 20 years and younger in

the south). 

Region – An aggregation of U.S. States over which model estimations are

produced. See Figure 2 for the regions used in FORCARB2 and their constituent

States.
52

Removals – Net volume of growing-stock trees removed from the inventory by

harvesting, cultural operations, or inventory lost due to land-use change. 

Saw log – A log meeting minimum standards of diameter, length, and defect

specified by regional standards. Includes logs at least 8 feet long, straight and 

sound, with minimum diameters of 6 inches inside bark for softwoods and

8 inches for hardwoods. 

Sawtimber – A size class of harvested timber meeting minimum standards of

length and defect and generally having a minimum diameter at breast height of

9 inches (11 inches for hardwoods). Sawtimber often is used to indicate size of

trees rather than logs. 

Soil organic carbon – Carbon in the organic portion of soil to a depth of 1 meter

(not including coarse roots).

Standing dead tree – All nonliving woody vegetation at least 1 inch in d.b.h.,

including coarse nonliving roots.

TAMM – Timber Assessment Market Model, a timber sector model that provides

annual projections of volumes and prices in the solid-wood products and

sawtimber stumpage markets, and estimates of total timber harvest and inventory

by geographic region for periods up to 50 years. 

Thinning – The harvesting of trees within a stand generally to improve stand

composition or spacing. 

Understory – All live herbaceous vegetation and woody vegetation less than

1 inch d.b.h. 
Heath, Linda S.; Nichols, Michael C.; Smith, James E.; Mills, John R. 2010. FORCARB2: An updated 

version of the U.S. Forest Carbon Budget Model. Gen. Tech. Rep. NRS-67. Newtown Square, PA: U.S. 

Department of Agriculture, Forest Service, Northern Research Station. 52 p. [CD-ROM].

FORCARB2, an updated version of the U.S. FORest CARBon Budget Model (FORCARB), produces 

carbon stocks and stock change projections for forest ecosystems and forest products at 5-year intervals. 

FORCARB2 includes a new methodology for carbon in harvested wood products, updated initial inventory 

data, a revised algorithm for dead wood, and now covers public forest land, reserved forest land and 

forest land of low productivity. The program is written in FORTRAN and is text based, though virtually 

every parameter is defined by input text-based files that can be modified or built by the user. Instructions 

for running the program, input and output files, and codes used are included, and input files for public 

forest lands of the United States are provided as an example. 

KEY WORDS: carbon sequestration; forest inventory; RPA Assessment; carbon model; FIA

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