根据生态系统服务功能理论,利用RS和GIS技术,以土壤含水量为基础因子,对青藏高原区草地生态系统的土壤水分保持功能及其价值的动态变化过程进行有效评价,以直接的货币形式反映出青藏高原主要草地类型的土壤水分保持功能的大小。通过计算和分析发现:(1)由于草地类型分布面积、单位面积保持量的影响,各种类型草地提供的土壤水分保持功能及其价值贡献率有较大差异,按照大小依次为:高寒草原类、高寒草甸类,高寒荒漠类、高寒草甸草原类和温性山地草甸类;(2)草地对土壤水分保持量及其价值呈现出较强的阶段性变化过程;(3)由于各种草地类型所处地理区域不同、草地本身各种自然特点和整体生态功能的不同,青藏高原草地生态系统提供的土壤水分保持功能及其经济价值呈现出明显的地域分布规律:自西北至东南逐渐降低。应该说,由于青藏高原地域、地理和独特气候等原因所致,本文计算得出的青藏高原草地生态系统土壤水分保持功能及其价值的具体数值不一定十分准确,但是能在一定程度上反映出土壤水分保持功能的强大及其在生长季中随时间变化的动态过程和基本规律(这种规律性结论与前人研究结论一致),这是一种在区域尺度上揭示草地生态系统土壤水分保持功能及其价值动态变化过程的方法尝试,这也是对动态评估生态服务功能的一种有益尝试。
Based on the theory of ecosystem services, this article valuates the capacity of water holding capacity of grassland ecosystem in Qinghai-Tibetan Plateau by using RS and GIS with the factor of water moisture. From the calculation and analysis we can conclude that: ( 1 ) the capacities of holding water and their values vary with the area and unit value, they are as following: Alpine steppe, Alpine meadow, Alpine desert, Alpine meadow steppe and Temperatemontane meadow ; (2) the capacities of holding water and their values vary with growing season and present staggered characters ; (3) the capacities of holding water and their values vary with physically geographical conditions. In general they decrease from the northwest to the southeast gradually. Although this article cannotvaluate all types of grassland with the limitation of data, yet we can say that this method can reveal the value of water holding capacity of grassland in regional scale, and maybe this can be a kind of helpful attemptto the dynamics researchof ecosystem services.