土壤非保护性有机碳对荒漠草原沙漠化的响应

沙化草地的恢复与重建是干旱半干旱区生态建设的重要内容,分析荒漠草原沙漠化过程中土壤非保护性有机碳分配比例的变异规律对于探讨沙化草地恢复机制具有重要的理论价值。以干旱、半干旱地区荒漠草原不同沙化阶段的土壤为研究对象,分析土壤粗颗粒有机碳、细颗粒有机碳、轻组有机碳含量和分配比例的分布特征、土壤非保护性有机碳转化为保护性有机碳的速率。结果表明:荒漠草原发生逆向演替后,土壤细颗粒有碳含量和分配比例表现为固定沙地荒漠草地半固定沙地流动沙地;粗颗粒有机碳含量表现为荒漠草地半固定沙地流动沙地固定沙地,粗颗粒有机碳分配比例表现为流动沙地半固定沙地荒漠草地固定沙地;轻组有机碳含量和分配比例递减。颗粒有机碳、轻组有机碳、土壤有机碳对草地沙漠化的敏感性不同,颗粒有机碳较轻组有机碳和土壤有机碳敏感性强,其中细颗粒有机碳较粗颗粒有机碳敏感性强。随着草地沙漠化程度的增强土壤非保护性有机碳分配比例呈下降趋势,表明草地沙漠化降低土壤质量。荒漠草地退化至流动沙地土壤非保护性有机碳转化为保护性有机碳的速率整体呈上升趋势。

Response of unprotected soil organic carbon to desertification in desert grassland

The restoration and reconstruction of desertification grassland in arid and semiarid region are critical constituents of regional ecological construction. Changes of unprotected soil organic carbon in different desertification stages of desert grassland is important in discussing the mechanism of desertification grassland. The characteristics of the content and proportion of coarse particulate organic carbon (CPOC), fine particulate organic carbon (FPOC), light-fraction organic carbon (LFOC) and the rate constant for C transferring from the unprotected to the protected soil pool (k) in different desertification stages of desert grassland in arid and semiarid region were studied. The results demonstrated that during the desertification process of desert grassland, the rank of the content and proportion of FPOC was fixed dunes >grasslands > semi-fixed dunes > mobile dunes, the rank of the CPOC content was grasslands > semi-fixed dunes > mobile dunes > fixed dunes; and the rank of the CPOC proportion was mobile dunes > semi-fixed dunes > grasslands > fixed dunes. The LFOC content and proportion decreased gradually during the desertification process of desert grassland. Particulate organic carbon (POC) was more sensitive to desertification grassland than LFOC and SOC, and FPOC was more sensitive than CPOC, LFOC and SOC. The proportion of unprotected soil organic carbon decreased gradually during the desertification process in desert grassland, which indicated that there was a decrease in soil quality. The rate constant for C transferring from the unprotected to the protected soil pool (k) increased gradually during the desertification process in desert grassland (from grasslands to mobile dunes).