基于RUE和NDVI的三江源区草地生态评价

为评价三江源区草地生态退化和恢复状况,基于降水利用效率(RUE)和归一化植被指数(NDVI)的综合评价指标体系,利用三江源区15年(2001~2015)的生长季最大NDVI数据(NDVImax)及同期65个气象站的年降水量数据为基础数据,计算每个像元的RUENDVI及其变化趋势,综合评价三江源区草地生态退化、改善趋势和空间分布。结果表明:(1)近15年三江源区草地生态呈明显好转态势,草地退化面积仅占三江源区总面积的5.85%;(2)从空间分布上地退化主要分布在三江源区中东部,呈明显的西北—东南条带状分布。在三江源区东部,草地退化呈点状分布格局;(3)三江源区RUENDVI与年降水量呈显著负相关关系,与NDVImax呈极显著正相关关系。研究基于RUE和NDVI的综合评价指标体系简单易获取,具有较强的可行性和可靠性,避免了仅利用RUE变化趋势指标引起的误判,研究结果为三江源区草地生态管理和进一步的生态建设提供了科学依据。

RUE and NDVI based ecological evaluation on grassland in the Three-River Source Region,China

In order to evaluate the ecological degradation and restoration of grassland in the Three-River Source Region,China;a comprehensive evaluation index system was established based on rainfall use efficiency (RUE) and normalized difference vegetation index (NDVI).The RUENDVI for each pixel and its changing trend was calculated with the maximum NDVI data for growing season (NDVImax) and the annual precipitation data of 65 meteorological stations in research area for the past 15 years (2001～2015),and then the ecological degradation,improvement trend and spatial distribution of grassland were comprehensively evaluated.The results showed that:1) In the past 15 years,the grassland vegetation has been obviously improved,and the degraded area of grassland accounts for only 5.85％ of the total area;2) The degraded grassland is mainly distributed in the middle and eastern part from the spatial distribution,showing a distinct northwest-southeast striped area.In the eastern part,grassland degradation shown a dotted pattern;and 3) RUENDVI shown significant negative correlation with annual precipitation (P＜0.05) and a significant positive correlation with NDVImax (P＜0.01).It could be concluded that the comprehensive evaluation index system based on RUE and NDVI is simple and easy to be obtained,has strong feasibility and reliability,and also could avoid the misjudgment caused by the misuse of RUE trend index alone.