9311143 Schlesinger The proposed research makes use of a rather unusual freshwater swamp ecosystem on the North Carolina coastal plain which is flooded and drained twice- daily due to tidal forcing. In these forests, the flooding regime is essentially uncoupled from seasonal patterns of soil warming. I propose to monitor the major cycling pathways for CH4 in situ over a one-year period to determine if sources and sinks respond equally to elevated temperatures. Seasonal studies have rarely considered both production and oxidation of CH4. The field data will be compared to the temperature response characteristics of methane production and oxidation as determined in the laboratory. This study will show if the temperature-limited step for oxidation is enzymatic, implying a large increase with soil-warming, or O2 diffusion implying a smaller response. Finally, I propose to determine the potential for CO2-fertilization and elevated temperature to synergistically increase methane flux through increased root productivity and root exudation. Such positive-feedbacks have important implications for modelling trace gas emissions under various climate change scenarios. %%% There is legitimate concern that elevated CO2 concentrations in the atmosphere will increase CH4 emissions from wetlands. Elevated CO2 may stimulated methanogenesis directly by increasing plant production or indirectly by increasing soil temperature. ***
