Title: Carbon storage and accumulation in United States forest ecosystems
Identifier: CAT93989847 (find matches)
Year: 1992 (1990s)
Authors: Birdsey, Richard A; United States. Forest Service
Subjects: Carbon cycle (Biogeochemistry) United States; Plants Effect of carbon on; Trees Climatic factors United States; Forest ecology United States
Publisher: (Washington, D. C. ?) : U. S. Dept. of Agriculture, Forest Service
Contributing Library: U.S. Department of Agriculture, National Agricultural Library
Digitizing Sponsor: U.S. Department of Agriculture, National Agricultural Library

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Carbon storage was estimated in a four-stage process corresponding to these four major forest ecosystem compo- nents. Separate estimates were generally made at the State level and for major forest types and plantation species in 8 geographic regions (fig. 1). The general approach was to estimate the volume of growing stock from forest inventories, to derive factors from biomass studies and other sources to convert the volume of growing stock to carbon, and to derive estimates for the other ecosystem components from models. Several principal data sources were used to make estimates of carbon storage in forest trees. Statewide forest invento- ries, such as those conducted periodically by the USDA Forest Service, typically involve estimation of timber volume, growth, removals, mortality, and forest biomass for the purpose of analyzing current and prospective timber supplies. Data from these inventories were the basis for estimating carbon storage in forest trees. The data were supplemented by information from a special study to estimate the amount of carbon in tree roots and the conver- sion of volume to carbon (Koch 1989). Because regional forest inventories are based on a statistical sample designed to represent the broad range of forest conditions actually present, estimates of carbon storage in forest trees are representative of the true average values, subject to sampling errors, estimation errors, and errors in converting data from one reporting unit to another. Because of the complexity of making the estimates of tree carbon, the magnitude of the error has not been estimated, but it is likely quite small since the forest inventories used to derive the estimates have very small sampling errors over large areas. Estimates of carbon storage in the soil, forest floor, and understory vegetation were developed through the use of models based on data from forest ecosystem studies. Although these studies include all of the key forest ecosys- tem components, they are valid only for the specific ecosys- tem studied. Uncertainty is introduced into the estimation process by assuming that the results of specific ecosystem studies are representative of regional or national averages without being part of a statistical sample that represents a large geographical area. Therefore, estimates of carbon storage in the soil, forest floor, and understory vegetation are subject to the following errors: bias from applying data from past studies that do not represent all forest conditions, modelling errors (imperfect assumptions), and errors in converting estimates from one reporting unit to another. No attempt has been made to estimate the magnitude of these errors. Details of the modeling and estimation process for estimat- ing carbon storage are presented in appendix 1. Estimates of changes in carbon storage over time were limited to estimating carbon changes in live trees. One could assume that carbon changes in trees are correlated with changes in the whole forest ecosystem, since an increasing quantity of tree biomass is likely associated with an increase in soil and forest floor carbon because litter from trees is one of the main inputs of organic matter to the forest floor and soil (Raich and Nadelhoffer 1989: Vogt and others 1986). Carbon changes in live trees were estimated using the same procedures as in estimating carbon storage, but the starting Pacific Coast Rocky Mountains North Central
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Southeast Figure 1—Broad geographical regions used to report estimated carbon storage,

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