Estimates of methane emissions from Chinese rice fields using the DNDC model

Abstract

Methane (CH4) emissions from rice fields across China were estimated using the DNDC (DeNitrification-DeComposition) model. The results showed that the CH4 emissions from Chinese rice fields in 2012 were estimated to be 8.20 Tg CH4 yr−1 (ranging from 4.80 to 11.40 Tg CH4 yr−1); the values from early, late, and single cropping rice were 1.12, 2.86, and 4.23 Tg CH4 yr−1. Rice fields in AEZ (agricultural ecosystem zoning) 7 (southeastern China) and AEZ 6 (central and southwestern China) were the two major sources, accounting for 92% of the total CH4 emissions in China. The CH4 emissions in AEZ 7 mainly originated from double cropping rice fields, while single cropping rice fields dominated the CH4 emissions in AEZ 6. The CH4 emission hotspots were in the Sichuan Basin of AEZ 6B (southwestern China), AEZ 6A (central China, except for Henan Province), AEZ 7 (except parts of Fujian and Zhejiang Provinces), and Heilongjiang Province. At the national scale, water management (positive correlation), air temperature (positive correlation), and the soil clay content (negative correlation) were the three dominant factors controlling the CH4 fluxes in paddy fields. These results provide an understanding of the spatial distribution of CH4 emissions from paddy fields and will help the government formulate policies to control CH4 emissions at a regional scale.