Effects of land use change on soil carbon cycling in the conterminous United States from 1900 to 2050

We developed matrices representing historical area transitions between forest and other land uses. We projected future transitions on the basis of historical transitions and econometric model results. These matrices were used to drive a model of changes in soil and forest floor carbon stocks. Our model predicted net carbon emission from 1900 until 1982, then sequestration until 2030, with little subsequent change. However, the northeast region showed substantial carbon sequestration from 1900 to the present. From 1990 to 2004, afforestation caused sequestration averaging 17 Tg C yr−1: 6 Tg C yr−1 in soil and 11 Tg C yr−1 in forest floor. Deforestation caused emission averaging 12 Tg C yr−1: 3 Tg C yr−1 from soil and 9 Tg C yr−1 from forest floor. However, these effects were only 5% of the total change in carbon stocks in all forestland.