Wei Ren1, Hanqin Tian1, Mingliang Liu1, Xiaofeng Xu1, Jerry Melillo2, and John Reilly3. (1) School of Forestry and Wildlife Sciences, Auburn University, 602 Duncan Drive, Auburn, AL 36849, (2) The Ecosystems Center, Marine Biological Laboratory, Woods Hole, MD 22543, (3) , Massachusetts Institute of Technology, Joint Program on the Science and Policy of Global Change, 77 Massachusetts Avenue, Cambridge, MD 02139
We have developed the Agricultural Ecosystem Model (AEM), which fully couples major biogeochemical cycles with hydrological cycles at a daily time step and multiple spatial scales, as a tool for investigating how changing climates, land management, fertilization and irrigation have affected crop productivity and exchanges of trace gases (CO2, CH4 and N2O) between agroecosystems and the atmosphere. The AEM has been calibrated against field data from both China and USA. We have used this calibrated AEM to examine how crop productivity and carbon storage have changed as a result of multiple stresses and interactions among those stresses including climate variability, atmospheric composition (carbon dioxide and tropospheric ozone), precipitation chemistry (nitrogen composition), and agronomic practices. We applied the model in both site and regional levels and the preliminary results show substantial year-to-year variations in crop yield as a result of seasonal and interannual climate variability. Irrigation and fertilization are primary controls over trace gas emission. Tropospheric ozone could lead to a 10-20% mean reduction of crop yield. Our simulated results indicate that the improvement of air quality and land management could enhance the capacity of agroecosystems in sequestering carbon dioxide, and reduce trace gas emissions from agroecosystems to the atmosphere.