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

小行星9311143 拟议中的研究利用了北卡罗来纳州沿海平原上一个相当不寻常的淡水沼泽生态系统，由于潮汐力，该生态系统每天被洪水淹没和排水两次。 在这些森林中，洪水制度基本上与土壤变暖的季节性模式无关。 我建议监测的主要循环途径，甲烷在原地超过一年的时间，以确定源和汇同样响应温度升高。 季节性研究很少考虑甲烷的产生和氧化。 将现场数据与实验室测定的甲烷产生和氧化的温度响应特性进行比较。 这项研究将表明，如果温度限制的氧化步骤是酶，这意味着一个大的增加与土壤变暖，或O2扩散意味着一个较小的响应。 最后，我建议确定潜在的CO2施肥和温度升高，协同增加甲烷通量，通过增加根系生产力和根系分泌。 这种正反馈对各种气候变化情景下痕量气体排放的建模具有重要意义。 大气中二氧化碳浓度升高会增加湿地的甲烷排放量，这一点值得关注。 CO2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刺激甲烷生成。 ***

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. ***