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 fro m point measurements to regional level or empirically correlating meth ane emission rates with a few factors (e.g., temperature and rice prim ary production) is unlikely to yield reliable results. Reducing the un certainties in estimates of current CH4 emission and predicting its fu ture change require a process model to simulate CH4 emissions from var ious paddyland environments. CH4 emission is an ecosystem process clos ely 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 methanoge nesis, and the balance between CH4 production and consumption by metha notrophic oxidation. A validation of the model indicated its reasonabl e ability to calculate CH4 emission rates and their seasonal variation s. The model, when coupled with supporting data sets, would complement spatial and dynamic analysis of CH4 emissions from rice paddies in th e framework of climate-plant-soil interactions.