MODELING METHANE EMISSIONS FROM RICE PADDIES

The quantification of methane (CH4) emissions from global rice paddies is still highly uncertain. The extrapolation of CH4 release rates from point measurements to regional level or empirically correlating methane emission rates with a few factors (e.g., temperature and rice primary production) is unlikely to yield reliable results. Reducing the uncertainties in estimates of current CH4 emission and predicting its future change require a process model to simulate CH4 emissions from various paddyland environments. CH4 emission is an ecosystem process closely coupled to plant growth and soil organic matter decomposition. In this study a methane emission model was developed based on supplies of carbon substrate for methanogens by rice primary production and soil organic matter degradation, direct environmental controls on methanogenesis, and the balance between CH4 production and consumption by methanotrophic oxidation. A validation of the model indicated its reasonable ability to calculate CH4 emission rates and their seasonal variations. The model, when coupled with supporting data sets, would complement spatial and dynamic analysis of CH4 emissions from rice paddies in the framework of climate-plant-soil interactions.