中国农田土壤有机碳变化：Ⅰ驱动因素分析

Changes in soil organic carbon in croplands of China:Ⅰ Analysis of driving forces

农业不仅是温室气体的主要排放源之一,同时也可能是温室气体的吸收汇。探明中国农田土壤碳库变化趋势以及农田土壤碳库的源、汇功能对农业减缓和应对气候变暖具有重要意义。本文研究根据中国第一次和第二次土壤普查数据,以及大量文献资料中长期定位点试验数据整理分析,对20世纪60年代以来中国农田土壤碳库时空演变格局,以及农田土壤有机碳变化的驱动因素进行了探讨。研究表明,1960～2000年期间中国农田土壤有机碳含量的增减与气候变化的相关性较弱,其间农田用地类型和管理措施的改变是影响农田土壤碳库源、汇功能的主要驱动因素。1960～1980年期间,农田耕层土壤有机碳含量从23 g.kg-1下降到15 g.kg-1;而1980～2000年期间,由于中国农田保护性耕作等措施的实施,农田耕层有机碳含量从15 g.kg-1增长到21 g.kg-1。中国农田耕层土壤有机碳含量的年均变化速率与初始含碳量呈负相关。尽管20世纪80年代后期,中国农田土壤有机碳源转为碳汇,但不可忽视的是自60年代以来中国已有60%农田耕层土壤有机碳含量出现下降趋势。

Based on the first and the second national soil inventory database,and literature reviews from a large number of chinese long-term field experimental studies,this study analyzed the spatial and temporal changes in soil organic carbon（SOC）during periods 1960～2000,and their driving forces.The results showed that the top SOC in croplands of China during periods 1960～2000 was weak related to climate factors,but influenced with the changes in cropland-use and management options.The top SOC in croplands of China decreased 23～15 g·kg-1 during 1960～1980,while it increased 15～21 g·kg-1 during 1980～2000 due to enhanced implementation of conservation practices.The initial top SOC of croplands had a negative relation with its annual change rates.Despite of soil carbon sinks presented during the late 1980s,it could not be neglected that about 60% of cropland areas have showed the declining trend of the top SOC in China since 1960s.