中国稻田水稻生长季N2O排放估算

由于土壤水分状况的不同,水稻生长季土壤N2O排放量明显不同于旱地作物。基于多元统计模型,通过多点代面的方法进行尺度扩展,并应用蒙特卡洛方法模拟影响因素的变异程度,模拟了中国稻田水稻生长季的N2O排放情况。所模拟的378个点的水稻生长季N2O排放通量为6.0～74.3μgN.m-2.h-1,其均值接近于原始观测结果;378个点位的N2O排放通量空间分布不均,排放量较高的点位于北纬20°到30°之间;378个点中单季稻、稻-旱轮作中的水稻和双季稻的生长季N2O平均排放量分别占年总排放量的53%、34%和59%。多点代面的尺度扩展结果显示2008年中国稻田水稻生长季N2O排放量均值为22.48Gg,其95%的概率区间为20.5～24.8Gg;化肥氮的N2O排放系数为0.27%,与IPCC缺省值0.3%接近。用秩相关关系表征影响因子对中国稻田水稻生长季N2O排放量的不确定性的贡献,结果表明水分管理类型、有机肥类型、土壤属性、氮用量等对结果均有显著影响。

Estimation of N2O Emissions from Paddy Fields During Rice Growing Season in China

Based on a multivariate statistical model,N2O emission from paddy fields during rice growing season in China was estimated,by considering the variability of influencing factors using Monte-Carlo simulation.The results showed that N2O fluxes from 378 rice paddy sites during rice-growing season ranged from 6.0 to 74.3 μg N m-2·h-1,and the mean of the simulated fluxes was close to that of the observed ones.There was a large spatial heterogeneity in the simulated emissions,with higher emissions occurring between 20° N and 30°N.For single rice,rice-upland crop,double rice cropping system,N2O emissions during rice-growing season accounted for 53%,34%,and 59% of their annual emissions,respectively.Monte-Carlo simulation showed that N2O emissions from paddy fields during rice growing season in China was 24.48 Gg N in 2008,with a 95% uncertainty range of 20.5~24.8 Gg N.The fertilizer-induced N2O emission factor was 0.27%,which was close to default IPCC value of 0.3%.The Monte-Carlo simulation also showed that water management,the type of organic N,the amount of chemical fertilizer N,and soil properties significantly affected the simulated N2O emissions.