风蚀对中国北方脆弱生态系统碳循环的影响

IMPACT OF WIND EROSION ON CARBON CYCLE OF FRAGILE ECOSYSTEM IN NORTHERN CHINA

风蚀是中国北方脆弱生态系统土壤质量退化和沙漠化的关键因素。文章基于土壤剖面普查和土壤侵蚀遥感调查数据,计算出风蚀土壤有机碳的侵蚀量和空间分布,并与风蚀区的净第一性生产力(NPP)比较。结果发现土壤风蚀区的一个显著特征是表层土壤有机质含量较小,并且随着土壤风蚀强度的增加,相应的表层土壤平均有机质含量和NPP基本上逐渐减小,而相应的土壤有机碳的侵蚀量却明显增大。在中国北方严重风蚀的脆弱生态区,土壤有机碳的侵蚀量超过了NPP,风蚀影响了生态系统的正常碳循环。

In arid and semi-arid area of northern China, one serious problem is soil degradation and expanding desertification due to wind erosion. Based on the soil profile survey data and remote sensing investigation of wind erosion, this paper calculates soil carbon erosion caused by wind. Moreover, annual net primary production (NPP) of terrestrial ecosystem in China is calculated using CASA (Carnegie-Ames-Stanford Approach) NPP model and is compared with annual soil carbon erosion by wind. Then the distribution of soil carbon erosion by wind and its difference with NPP are analyzed respectively to uncover the impact of wind erosion on carbon cycle of fragile ecosystem in northern China.The result indicates that when local wind erosion intensity increases, soil organic content decreases. Consequently when local wind erosion intensity increases, losses of soil carbon increase dramatically, and meanwhile NPP declines in the same area. For instance, in weak erosion area, organic carbon erosion of surface soil is only 2.3g·C/m2·a and NPP is 243 .9g·C/m2·a. However, in intense erosion area, organic carbon erosion of surface soil reaches to 61.6g·C/m2·a and NPP is only 30.7 g·C/m2·a. So it is obvious that NPP and carbon erosion of surface soil have a negative relationship.In addition, an index is used to indicate the impact of wind erosion on fragile ecosystem, which is defined by soil carbon erosion by wind and NPP. This index increases when local wind erosion intensity increases. In weak erosion areas, such as the middle and east part of Inner Mongolia, NPP is higher than soil carbon erosion by wind. However, in heavy wind erosion areas, such as Xinjiang, Qinghai, Gansu, and the west part of Inner Mongolia, soil carbon erosion by wind often surpasses annual NPP. This situation accelerates the erosion rate of organic carbon of the fragile ecosystem and deteriorates the function of carbon cycle of the fragile ecosystem in northern China.