CARBON SEQUESTRATION BY FORESTS OF THE UNITED-STATES - CURRENT STATUS AND PROJECTIONS TO THE YEAR 2040

National-level forest carbon budgets are of interest in relation to understanding the global carbon cycle, comparing anthropogenic and biogenic sources of carbon, and developing possible strategies for conserving and sequestering carbon. In this study, forest carbon pools and flux for timberlands in the conterminous United States were projected over the coming 50 years by coupling a forest economics model, a forest inventory model and a forest carbon model. In the base case scenario, US forests sequestered carbon in the 1990s at a rate of 80 Tg yr(-1) but came close to carbon equilibrium by the 2020s. The dominant factors driving this change were an increasing forest harvest, a decreasing forest land base, and a reduction in average stand age. Scenarios in which alternative forest policy options were implemented related to increased paper recycling and increased afforestation (5x10(6) ha) produced long-term increases in carbon sequestration on the forest land base of up to 15 Tg yr(-1). The carbon sink on the forest land base currently offsets 6% of US fossil carbon emissions but that proportion is likely to decrease over the coming decades.