Characteristics of CH4 Emission in Double Paddy Field Under Climate Change in Southern China Simulated by CMIP5 Climate Model Projections

Abstract

Methane (CH4) is one of the major agricultural greenhouse gases (GHG) which is mainly emitted from flooded paddy fields. Compared with single rice cultivation double rice cultivation has a longer growing season, which means it needs a longer flooding environment during rice growing, which led to more methane emission. There is a considerable area of double cropping rice in the southern China. Thus, it is necessary to map changes of CH4 emission in the paddy field of double cropping rice area under future climate change scenarios and investigate the sensitivity of CH4 emission from double paddy field to climate change. In this study, we employed Denitrification-Decomposition (DNDC) - a process-based biogeochemistry model- to simulate the CH4 emission from double paddy field and to analysis the influence of climate change on CH4 emission from double paddy field with simulation result. First, we utilized the historical meteorological data (source from Chinese Meteorological Data Center), soil data (source from The Harmonized World Soil Database) and observational data (sowing date, transplant date, harvest date, fertilizing rate, and cultivated area) from agrometeological stations during 1981 to 2010, to calibrate the library of rice varieties in the DNDC model. Then we employed the calibrated model to simulate the CH4 emission from double paddy field during 2041 to 2070(2050s) under RCP45 scenarios from the Coupled Model Intercomparison Project, Phase 5 (CMIP5) climate model projections. Finally, combining Geographic Information System (GIS) technology for regional scale simulation and mapping changes of CH4 emission in the main producing province of double cropping rice. The result indicates that there is a strong relationship between climate change and the CH4 emission. The emission result under climate change scenarios all has shown an increasing trend of methane emissions. Comparing several climate patterns, in Anhui, Hunan and Jiangxi have increased methane emissions by more than 25%; Fujian, Hubei, Yunnan and Zhejiang took second place, and the increase in methane emissions was still as high as 20%. Methane emissions from Fujian, Hubei, Yunnan and Zhejiang increased by more than 20%. Guangdong and Guangxi have increased by 14.5% and 16.5%, The smallest change in Hainan is 6.7%. Furthermore, there is a significant correlation between temperature change and methane emission at the spatial scale, indicating that climate warming has increased methane emissions. In addition, we did not consider the differences in rice varieties and field management between agro-ecological zone. These differences can be increased the uncertainty of the simulation results. We will consider it in the further studies.