Subtask 1.22 - Microbial Cycling of CH4, CO2, and N2O in a Wetlands Environment

[摘要] Soil microbial metabolic activities play an important role in determining CO{sub 2}, CH{sub 4}, and N{sub 2}O fluxes from terrestrial ecosystems. To verify and evaluate CO{sub 2} sequestration potential by wetland restoration in the Prairie Pothole Region (PPR), as well as to address concern over restoration effects on CH{sub 4} and N{sub 2}O emissions, laboratory and in situ microcosm studies on microbial cycling of CO{sub 2}, CH{sub 4}, and N{sub 2}O were initiated. In addition, to evaluate the feasibility of the use of remote sensing to detect soil gas flux from wetlands, a remote-sensing investigation was also conducted. Results of the laboratory microcosm study unequivocally proved that restoration of PPR wetlands does sequester atmospheric CO{sub 2}. Under the experimental conditions, the simulated restored wetlands did not promote neither N{sub 2}O nor CH{sub 4} fluxes. Application of ammonia enhanced both N{sub 2}O and CH{sub 4} emission, indicating that restoration of PPR wetlands may reduce both N{sub 2}O and CH{sub 4} emission by cutting N-fertilizer input. Enhancement of CO{sub 2} emission by the N-fertilizer was observed, and this observation revealed an overlooked fact that application of N-fertilizer may potentially increase CO{sub 2} emission. In addition, the CO{sub 2} results also demonstrate that wetland restoration sequesters atmospheric carbon not only by turning soil conditions from aerobic to anoxic, but also by cutting N-fertilizer input that may enhance CO{sub 2} flux. The investigation on microbial community structure and population dynamics showed that under the experimental conditions restoration of the PPR wetlands would not dramatically increase population sizes of those microorganisms that produce N{sub 2}O and CH{sub 4}. Results of the in situ study proved that restoration of the PPR wetland significantly reduced CO{sub 2} flux. Ammonia enhanced the greenhouse gas emission and linearly correlated to the CO{sub 2} flux within the experimental rate range (46-200 kg N ha{sup -1}). The results also clarified that the overall reduction in global warming potential (GWP) by the PPR wetland restoration was mainly contributed from reduction in CO{sub 2} flux. These results demonstrate that restoration of currently farmed PPR wetlands will significantly reduce the overall GWP budget. Remote sensing investigations indicate that while the 15-meter resolution of the imagery was sufficient to delineate multiple zones in larger wetlands, it was not sufficient for correlation with the ground-based gas flux measurement data, which were collected primarily for smaller wetland sites (<250 meters) in the areas evaluated by this task. To better evaluate the feasibility of using satellite imagery to quantify wetland gas flux, either higher-resolution satellite imagery or gas flux data from larger wetland sites is needed.

[发布日期] 2008-12-31 [发布机构] University of North Dakota

[关键词] Population Dynamics;Wetlands;Greenhouse Effect;Remote Sensing;Terrestrial Ecosystems