三江源地区草地退化对土壤含水量的影响

【目的】研究草地退化对青海三江源地区土壤含水量的影响,为草地生态系统的综合监测与评估提供科学参考。【方法】根据遥感解译数据,得到20世纪70年代以来三江源地区草地退化的时空特征,结合不同土壤类型、不同退化等级下的孔隙度实测数据,利用空间分布替代时间演替的方法得到不同时段土壤饱和含水量的时空变化,分析该区草地退化与土壤饱和含水量的关联程度。【结果】20世纪70年代中后期至2004年,三江源地区草地退化现象持续发生; 2004―2012年,该区草地得到了一定程度的恢复。20世纪70年代中后期至2004年,三江源地区草地土壤饱和含水量减少了45.58亿m3; 2004―2012年,草地土壤饱和含水量减少了1.50亿m3。【结论】尽管草地退化情况略有减轻,但草地土壤饱和含水量表现出持续减少的现象。植被退化是三江源地区土壤退化的直接原因,由其引起土壤理化性状的改变,进而影响土壤持水性。
Abstract: 【Objective】Influences of grassland degradation on soil saturated moisture content in the Three-River Headwaters Region, Qinghai Province, could provide certain scientific reference for comprehensive monitoring and assessment of grassland ecosystem.【Method】Based on remote sensing data, we analyzed the temporal and spatial characteristics of grassland degradation since the middle and late 1970s. According to the measured porosity data for different soil types and different degradation grades, we analyzed the temporal and spatial variation of saturated moisture content of grassland soil in order to analyze their relational degree.【Result】Grassland degradation occurred continually from the middle and late 1970s to 2004. In contrast, the degraded grasslands exhibited a degree of recovery from 2004 to 2012. The saturated moisture content of grassland soil decreased by 4.558 billion m3 and 0.150 billion m3 in these two periods, respectively.【Conclusion】Although the degraded grassland had shown a slight recovery since 2004, the saturated moisture content of grassland soil showed a declining phenomenon. Vegetation degeneration was the direct cause of soil degradation in the study area. Such degeneration could change the soil physical and chemical properties, further affecting soil water retention in grassland ecosystem