生态退化与恢复对三江源区土壤保持功能的影响

目的]探讨生态退化与恢复对土壤保持功能的影响及其作用机理,为三江源区生态保护与建设决策提供一定依据。方法]通过构建土地覆被状况等来表征三江源区宏观生态系统变化,定量分析生态系统变化对土壤保持功能的影响,并探讨其主要机制。结果]三江源地区从2000—2010年的生态系统经历了显著的退化和恢复过程。不同覆被类型下土壤保持能力依次为:林地耕地高覆盖度草地中覆盖度草地低覆盖度草地湿地未利用地。在研究区生态退化及恢复的过程中,2000—2010年的单位面积潜在流失量从1.25×10~4 t/hm~2增加到1.50×10~4 t/hm~2,单位面积实际流失量从2000年的3 200t/hm~2增加到2005年的3 500t/hm~2,至2010年持续增加到3 800t/hm~2。在生态恢复过程中,三江源区高覆盖度草地及湿地面积增加,从一定程度上减轻生态系统退化的趋势,三江源区单位面积土壤保持量从2000年的9 300t/hm~2,增加到2005年的1.03×10~4 t/hm~2,直至2010年三江源区单位面积土壤保持量为1.11×10~4 t/hm~2。结论]土地覆被类型及植被覆盖程度对土壤保持功能有重要影响,三江源的生态退化与恢复过程与源区土壤保持功能变化联系紧密。

Effects of Ecological Degradation and Restoration on Soil Conservation Function in Three Rivers Headwater Region

Objective] To explore the effect of ecological degradation and restoration on soil conservation function and its mechanism, and to provide a certain basis for decision making regarding ecological protection and construction in Three Rivers Headwater Region.Methods] By building indices such as land cover condition to characterize the macro-ecosystem changes in headwater region, we quantitatively analyzed the effect of ecosystem changes on soil conservation function, and discussed its main mechanism.Results] The ecosystems in headwater region experienced significant degradation and recovery process from 2000 to 2010. Soil conservation capacity of different types ranked as:forest land > cultivated land > high coverage grass > medium coverage grass > low coverage grassland > wetland > unused land. In the process of ecological degradation and recovery in the study area, the potential loss per unit area increased from 1.25×10⁴ t/hm² to 1.50×10⁴ t/hm² during 2000-2010, The actual loss per unit area increased from 3 200 t/hm² in 2000 to 3 500 t/hm² in 2005, and to 3 800 t/hm² in 2010. In the process of ecological restoration, the areas of high coverage grassland and wetland in Three Rivers Headwater Region increased, alleviating the trend of ecosystem degradation to some extent. Soil conservation quantity per unit area in Three River Headwater Region increased from 9 300 t/hm² in 2000 to 1.03×10⁴ t/hm² in 2005, and to 1.11×10⁴ t/hm² in 2010.Conclusion] The types of land cover and vegetation coverage had important effects on soil conservation function, the ecological degradation and restoration of Three Rivers Headwaters Region were closely related to the change of soil conservation function.