Forest inventory data, models, and assumptions for monitoring carbon flux

Estimates from forest inventories indicate that U.S. forest ecosystems are a net sink for C, currently removing 0.2 to 0.3 Pg C yr(-1) from the atmosphere. Estimates of C storage in forest biomass are based on comprehensive forest inventory data collected periodically by the USDA, Forest Service. Estimates of C storage in forest soils (including mineral soil, litter and coarse woody debris) are based on intensive ecosystem studies and models relating soil C to climate variables, forest type, and land use history. Estimates of C storage in wood products are based on comprehensive models of biomass utilization, recycling, and disposal. Opportunities to improve the estimation process include better estimates of soil C responses to land use and environmental changes, and the need for more comprehensive data to estimate C flux on remote forest lands that are not significantly influenced by human activities.