基于不同土壤数据单元法的DNDC模型对太湖地区水稻土CH4排放模拟研究

利用农业土壤痕量气体排放模型DNDC(DeNitrification-DeComposition),以整个太湖地区37个县234万hm2水稻土为例,分析了3种不同土壤数据单元法对CH4排放模拟的影响.其中,1∶5万图斑单元法土壤属性来自1∶5万土壤数据库,图斑为最小模拟单元;1∶5万"县级"单元法土壤属性也取自1∶5万土壤数据库,"县"为最小模拟单元;1∶1 400万"县级"单元法土壤属性取自国内同类研究使用最多的1∶1 400万土壤图和《中国土种志》,"县"为最小模拟单元.结果表明,虽然1∶5万图斑单元法大多数县的CH4排放量都在1∶5万"县级"单元法最大与最小值范围之间,但整个地区总排放量(以C计,下同)相差达到1 680 Gg;而1∶1 400万"县级"单元法CH4排放量与1∶5万图斑单元法相比,尽管整个地区总排放量只相差180 Gg,但各"县级"单元之间的估算差异却很大,这一方面说明了土壤数据的详细程度是保证地球生物化学模型模拟精度的重要因子,另一方面也说明在区域CH4排放量估算模拟中使用更详细的土壤资料是非常必要的.

Simulation of Methane Emissions from Rice Fields in the Taihu Lake Region, China by Using Different Unit of Soil Database with the DNDC Model

Application of a biogeochemical model, DeNitrification and Decomposition or DNDC, was discussed to assess the impact of CH, emissions on different soil database from rice fields in Taihu Lake region of China. The results showed that CH_4 emissions of the polygon-based soil database of 1:50 000, which contained 52 034 polygons of paddy soils representing 1 107 paddy soil profiles extracted from the latest national soil map (1:50 000), were located within the ranges produced by the county-based soil database of 1:50 000. However, total emissions of the whole area differed by about 1 680 Gg CH_4-C. Moreover, CH_4 emissions of the polygon-based soil database of 1:50 000 and the county-based soil database of 14 000 000, which was the most popular data source when DNDC model was applied in China, have a big estimation discrepancy among each county-based unit in spite of total emissions of the whole area by a difference of 180 Gg CH_4-C. This indicated that the more precise soil database was necessary to better simulate CH_4 emissions from rice fields in Taihu Lake region using the DNDC model.