不同时间尺度径流对植被变化的响应

 植被覆盖对陆地生态系统的水分循环起着重要作用。径流对植被变化在不同时间尺度的响应研究,对区域生态环境建设及水资源管理具有重要的参考价值。该文介绍基于对比流域法,在多年平均、年际、季节等不同时间尺度径流对植被变化响应的研究结果。多年平均尺度上,由植被类型更替引起的径流绝对变化量,湿润区较干旱区大,其相对变化量在干旱区严重;年际尺度上,因植被变化,径流从一种平衡状态到另一种平衡状态的响应时间因抚育措施和地区不同而不同,造林情况下,湿润地区一般需要15～20a,干旱地区约需25a甚至更长,森林自然恢复情况下则需要上百年;季节尺度上,径流对植被变化的响应在季风影响区较四季湿润地区强烈。流量历时曲线研究表明,干旱地区造林,其基流无论在量或发生概率的变化上均较湿润区强烈。

Responses of runoff to vegetation alteration at different temporal scale

Vegetation influences water recycle of land ecological system considerably. Understanding these relationships between vegetation and runoff changes is helpful for regional eco-environmental construction and water resources management. Based on paired catchments and time trend studies a number of studies had been undertaken to establish relationships between vegetation cover and water use. The paper reviews results from that which are focusing on changes at various time scales. At mean annual scale the runoff changes resulted from vegetation alteration can he predicted using Zhang curves. The absolute change of runoff due to vegetation alteration in humid area is larger than that in dry region. While the relative change is reverse. At annual scale, it takes 15 -20 years or longer in arid region for catchments to reach a new equilibrium following afforestation, and under natural restoration, it takes about hundred years. The vegetation changes have a proportionally larger impact on low flow at seasonal scale. For catchments in arid regions, relative changes in low flow section of the flow duration curve will he much more significant compared with that in high flow section, leading to increased number of zero-flow days; however in humid regions, changes in runoff tend to be much more uniform