Methane emission and production from wetlands as influenced by water table - a process-based model

Natural wetlands are considered to be the major source of the global atmospheric methane(CH4). An one-dimensional process-based model has been developed for investigating the influence of hydrological cycle on the methane emission from wetlands. Three processes involved in the methane emission: production, reoxidation in aerobic region, and three transport pathways (diffusion across water-air or soil-air interface, ebullition, and diffusion through plant), were implemented as influenced by soil property, plant growth, water table, temperature and any external input (e.g. fertilizer) in this model. Water table was considered as a primary parameter in this study to control all the three processes. The model was used to simulate the seasonal variation of the methane emission from a rice field in Hunan, China where intensive data set on the methane emission, production and three transport pathways are available. The simulation with the fluctuation of the water table not only changed the magnitude of the methane production rate and furthermore the emission, but also affected its vertical profile. The seasonal variation of the methane production and emission, the ratio of the emitted methane to the atmosphere to the produced methane in the soil, and the seasonal change of the role of the plant in transporting methane to the atmosphere were captured by the model as compared to the observed data. This study provides a framework for the further development of the model coupled with the climate and hydrologic models and driven by the spatially distributed variables (e.g. the water table, soil temperature and vegetation) in the large-scale study.

Global Geochemical Cycle, in review, 1998.

8/26/98