基于NDVI的农牧交错区植被覆盖度变化研究——以宁夏盐池县为例

Study on the Change of Vegetation Fraction in Agro-pastoral Transition Area Based on NDVI——A Case Study in Yanchi County,Ningxia

为了解农牧交错区植被覆盖度变化，以宁夏盐池县为例，基于NDVI和植被覆盖度遥感定量模型，提取了植被覆盖等级图。在此基础上对盐池县1989年、1999年、2003年的植被覆盖度等级图进行对比分析，结果表明两个时间段的植被盖度都呈增加趋势，后期（1999～2003年）年均变化明显高于前期（1989～1999年）年均变化，这主要归功于荒漠化治理措施（包括退耕还林、禁牧封育等）以及降水增加等多种因素。与此同时，在生态环境建设过程中，原有中、高覆盖度植被发生退化。因此，今后的治理工作应该加大对中、高盖度植被地区的保护工作。

In order to understand the change of vegetation fraction in agro-pastoral transition area, Yanchi county , Ningxia was taken as an example. Based on NDVI and quantitative remote sensing model on vegetation fraction,the grade map of vegetation fraction is extractcd. Based on the analysing of the grade map of vegetation fraction in 1989,1999,2003, the results show that the vegetation fraction is increasing in this two period. The annual average change in later period（1999～ 2003）is more than that in early period （1989 ～ 1999）. It mainly attributes to desertification controlling measure（by converting cropland to forests,closing and fencing and discontinuing farming and letting go out of cultivation）and increasing rainfall. Meanwhile, in the process of ecological environment construction, the middle and high grade vegetation fraction degraded. So, more attention should be paid to the protection of the region with middle or high grade vegetation fraction.