西南山地流域NDVI变化特征及降水敏感性——以贵州沅江流域为例

归一化植被指数(Normalized Difference Vegetation Index,NDVI)是反映植被生长的重要指标,探究其时空变化特征,对生态保护、退耕还林和灾害防治具有重要意义。选取2000—2015年贵州沅江流域典型年份NDVI,采用重心分析、标准差椭圆、地理加权回归等方法,从干旱视角探究流域NDVI变化和降水敏感性。得出以下结论:(1)2000—2015年贵州沅江流域NDVI总体处于上升趋势,植被正在改善,期间西部植被改善最为明显,退耕还林还草取得较好成果。(2)2000—2015年贵州沅江流域干旱年与正常年NDVI空间变化趋势不一致,干旱程度对植被影响具有区域差异。(3)贵州沅江流域NDVI与降水呈负相关,空间敏感性自西向东递增,降水对流域西部喀斯特山区NDVI影响更明显。(4)2000—2015年贵州沅江流域NDVI时段变化与降水主要为负相关,降水越多NDVI时段变化敏感性越弱,退耕还林还草工程应重点放在负敏感区。研究结果可为退耕还林还草和干旱灾害防治提供科学参考。

Research on NDVI variation characteristics and precipitation sensitivity of the Yuanjiang River Basin in Guizhou Province

Normalized difference vegetation index (NDVI) is an important indicator reflecting the growth of vegetation. Exploring its temporal and spatial variation characteristics is of great significance for ecological protection, returning the grain plots to forestry and grassland and disaster prevention. NDVI characteristics of the Yuanjiang River Basin of Guizhou Province were studied for the period 2000-2015. The study used methods of center of gravity analysis, standard deviation ellipse and geographic weighted regression to explore the NDVI changes and precipitation sensitivity in the basin. The study draws the following conclusions:(1) From 2000 to 2015, the NDVI in the Yuanjiang River Basin is generally on an upward trend, and the vegetation is improving. During the period, the improvement of vegetation in the western region is the most obvious, and the returning the grain plots to forestry and grassland has achieved good results. (2) The spatial variation trend of NDVI between the drought years and the normal years in the Yuanjiang River Basin from 2000 to 2015 is inconsistent, and the degree of drought has regional differences in vegetation impact. (3) The NDVI in the Yuanjiang River Basin is negatively correlated with precipitation, and the spatial sensitivity increases from west to east. The influence of precipitation on NDVI in the western Karst mountainous area is more obvious. (4) Between 2000 and 2015, the NDVI change in the Yuanjiang River Basin was mainly negatively correlated with precipitation. The more precipitation, the weaker the NDVI change sensitivity. The results provide scientific support for identification of farmland areas that could be reforested and where grasslands could be restored.