Dissertation Research: Effects of Carbon Fertilization and Temperature on Methane Cycling

9311143施莱辛格拟议的研究利用了北卡罗来纳州沿海平原上相当不寻常的淡水沼泽生态系统，由于潮汐强迫，该湿地每天被淹和排干两次。在这些森林中，洪涝灾害基本上与土壤变暖的季节模式无关。我建议在一年的时间里现场监测甲烷的主要循环路径，以确定源和汇是否对高温做出同样的反应。季节性研究很少同时考虑甲烷的产生和氧化。现场数据将与实验室确定的甲烷生产和氧化的温度响应特征进行比较。这项研究将表明，氧化的温度限制步骤是酶促的，意味着随着土壤变暖而大幅增加，或者O2扩散意味着较小的反应。最后，我建议确定二氧化碳施肥和温度升高通过增加根系生产力和根系分泌物来协同增加甲烷通量的潜力。这种正反馈对于模拟各种气候变化情景下的痕量气体排放具有重要意义。%有理由担心，大气中二氧化碳浓度的升高会增加湿地的甲烷排放量。二氧化碳浓度升高可能直接通过增加植物产量或间接通过提高土壤温度来促进甲烷的产生。***

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. ***