Atmospheric carbon dioxide is strongly influenced by both on-going and historic land management. Yet, the precise rates at which carbon is taken up by some forests, fields, and residential areas, and released by others, are not well quantified. This lack of precision can be attributed to an absence of field experiments that monitor carbon for more than a few years, and to a shortage of studies examining carbon stored deeply in the soil (>1 ft). This proposed research builds on a 50-year record of carbon sequestration in trees, litter, soil, and large wood at the Calhoun Experimental Forest in South Carolina, one of the world's longest running forest studies of its kind. Because deep tree roots appear to have sequestered significant amounts of soil carbon, we now plan to look more deeply belowground, inventorying roots and soil to 6 ft in depth. Field research will be linked with computer exercises to evaluate the potential regional and global significance of carbon sequestration. The new project will greatly expand the ability of one of the world's finest long-term ecological studies to address the pressing issue of carbon cycling. The research will include undergraduate and graduate students and scientists at Duke University and Woods Hole Research Center. The research will also involve high school educators via collaboration with the renowned North Carolina-based Kenan Fellows Program that promotes science-teacher retention. The data may prove critical for improving land management for carbon sequestration and will be broadly distributed in the technical and public scientific literature.