中国农田表土有机碳含量变化特征——基于国家耕地土壤监测数据

通过对299个国家级耕地土壤监测点20余年数据的统计分析，评价了我国农田表土有机碳含量变化情况和固碳潜力。结果表明，全国约80％试验点有机碳年平均相对增长率（Average relative annual increment，ARAI）在-1．5％～7．5％。中国农田表土有机碳含量整体呈上升趋势。东北、华北等6个地理区域分析得出，华北、华东、西南农田表土有机碳含量显著增加；华东地区有机碳增加的农田面积占全国农田比例最大，东北最小。旱地和水田有机碳含量增加显著；水田有机碳增加的试验点所占比例大于旱地；对ARAI与初始有机碳含量进行相关分析得出，我国旱地和水田有机碳潜在储存能力估计值分别为17．2和27．7g·kg^-1。农田土壤类型中水稻土和褐土有机碳含量增加显著；黑土有机碳含量下降样本所占比例最高。对我国各典型种植制度分析得出，双季稻、麦-稻、麦-玉、单季小麦种植制度下农田有机碳有了显著增加；麦玉轮作较其他种植制度的农田有机碳年平均相对增长率高。

Changes in Topsoil Organic Carbon of China＇s Cropland Evidenced from the National Soil Monitoring Network

Soil organic carbon（ SOC ） is the critical parameters not only soil fertility but environmental safety also. Understanding changes in organic carbon of cropland will be needed for assessing the Carbon sequestration potential of China＇s croplands. In this study, we used data of topsoil SOC content from the national monitoring network to analyze the SOC dynamics and the sequestration status in China＇croplands. The data set comprises 299 observations across mainland China. Topsoil SOC of China＇s cropland was in a general trend of accumulation with a frequency of 79.1%, which were mainly distributed in North, East and Southwest China＇s cropland. The difference of land use effect on soil carbon sequestration was significantly, the SOC content of paddy soils was higher significantly than that of dry croplands and the frequency of increasing SOC was also greater than that of dry cropland. The SOC content of paddy soils and cinnamon soils increased significantly; the frequency of decreasing SOC from black soils was greatest. Furthermore, topsoil SOC was greatly increased under the cropping systems of double rice, rice-wheat, wheat-corn and wheat, with the wheat-corn being the highest. Therefore, topsoil SOC storage in China＇s croplands had been affected profoundly by the land use type, Cropping and rotation, and the dynamics and the overall sequestration capacity would be greatly masked by the land managements and agro management practices.