Quantifying GHG emission from paddy field in China under climate change: based on the coupling of DNDC, DSSAT and AEZ models

Niu, Y. (2015). Quantifying GHG emission from paddy field in China under climate change: based on the coupling of DNDC, DSSAT and AEZ models. IIASA Report. IIASA, Laxenburg Austria: Young Scientists Summer Program Report

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Abstract

Climate change and food security are critical issues to the world, and have aroused the interest of scientists, policymakers, and ordinary people. Rice is the major food in the Chinese diet, the Chinese government and scientists had put great efforts on improving the rice production to guarantee the food security, but rice paddy field also emits great amount of greenhouse gases (GHGs) to the atmosphere. So it is necessary to study how to reduce the GHGs emission while enhance the food security. In this research, a process-based model, Denitrification-Decomposition model (DNDC), is used to simulate rice growing and GHG emission in rice fields in China. However, DNDC is a site-level agroecosystem model that lacks rice cultivar parameters to represent crop diversity in China. In order to update and up-scale the DNDC model to evaluate the GHG emission from paddy field in China, Decision Support System for Agro-technology Transfer (DSSAT) and Agro-Ecological Zones (AEZ) models are used to provide abundant and detailed cultivar parameters and a more reliable upscaling method. By using the Generalized Likelihood Uncertainty Estimation module in DSSAT and reclassification of cropping zone map, which is based on original cropping zone map in AEZ, rice cultivar parameters and input data of each grid are translated into DNDC successfully. Then the updated DNDC model is applied at both site and regional scale. The site-level simulation result shows that new cultivar parameters improves the performance of the DNDC model greatly in each station. Furthermore, the application of nitrogenous fertilizer is higher than actual crop requirement by 5% to 35%. If the application of nitrogenous fertilizer is reduced to a balanced level, the N2O emission will decrease significantly, the result shows an average reduction of 36% in nine stations. The regional-level result shows that the spatial distribution of rice yield loss and N2O emission reduction are consistent with the site-level result in most regions. In the northeast area of China, less fertilizer application will reduce N2O emission as well as rice yield. The balanced level of fertilizer application may decrease under A1B scenario in the future. The more advanced management practices should be considered and applied to find a scientific approach to mitigate CH4 emission. Furthermore, crop rotation and different climate scenario datasets should be studied in the future.

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