Hanqin Tian, Chi Zhang, Wei Ren, Guangsheng Chen, Xiaofeng Xu, Mingliang Liu, Hua Chen, Shufen Pan, and Chelsea Nagy. School of Forestry and Wildlife Sciences, Auburn University, 602 Duncan Drive, Auburn, AL 36849
Terrestrial ecosystems in the southeastern United States have experienced a complex set of multiple changes in climate, atmospheric composition, land use and natural disturbances. Little is known about how these multiple changes have affected regional fluxes of methane and carbon dioxide in the southeastern United States. In this study, we have examined how the regional fluxes of methane and carbon dioxide in southeastern United States have changed as a result of multiple stresses/changes and interactions among those stresses including land-cover change, climate variability, atmospheric composition (carbon dioxide and tropospheric ozone), precipitation chemistry (nitrogen composition), and natural disturbances such as fire using factorial simulation experiments with the Dynamic Land Ecosystem Model in conjunction with remotely sensed and field data. For the time period from 1900 to 2000, our analysis suggests that the fluxes of methane and carbon dioxide in this region show substantially interannual and spatial variations. Forest recovery after cropland abandonment and natural disturbances have resulted in an uptake of carbon dioxide, but rapid urbanization and rising tropospheric ozone pollution have led to a significant reduction in carbon storage in the southeast. Our preliminary results indicate that total carbon storage in the terrestrial ecosystems of southeastern US has increased about 4 Pg C or 22% since 1950. Land-use change and intensive management appear to be important controls over regional fluxes of both methane and carbon dioxide.