2001—2020年新疆伊犁河谷植被主要生长季NDVI时空变化与水热因子关系研究

Spatial-temporal Variation of NDVI during the Main Growing Season and Response to Hydrothermal Factors in Yili River Valley,Xinjiang from 2001 to 2020

利用MODIS-NDVI数据,采用Theil-Sen中值趋势分析、Mann-Kendall检验及变异系数方法,对2001—2020年伊犁河谷植被主要生长季(5—9月)归一化植被指数(NDVI)的时空变化特征进行研究,结合气温降水数据采用相关性分析的方法,探究植被主要生长季的影响因素。结果表明:(1)伊犁河谷植被主要生长季NDVI在空间上存在明显的差异性,NDVI多年均值较高。(2)区域尺度上,NDVI年际变化趋势较为平缓;像元尺度上,微量减少和微量增加的面积占比较大,显著增加与显著减少的区域较集中,占比较小。(3)伊犁河谷生长季植被的稳定性较好,CV≤0.10基本分布在整个区域,0.3<CV≤1分布较集中。(4)伊犁河谷气温呈现上升的趋势,降水量呈现缓慢下降的趋势;NDVI年均值与年降水量显著相关(r=0.7644),与气温无显著相关;NDVI月均值与月气温均值极显著相关,与月降水量相关性不显著。

Based on MODIS-NDVI data,the temporal and spatial variation characteristics of the normalized vegetation index(NDVI)during the main growing season(May-September)in Yili River Valley during 2001-2020 were studied by Theil-Sen median trend analysis,Mann-Kendall test and coefficient of variation method.The influencing factors of vegetation growth season were explored.The results showed that:(1)There was a significant spatial difference in NDVI during the main growing season in Yili River Valley from 2001 to 2020,and the average value of NDVI was higher in multiple years.(2)At the regional scale,the interannual variation trend of NDVI was relatively flat.At the pixel scale,the areas of micro decreases and micro increases were relatively large,while the areas of significant increases and decreases were relatively concentrated and small.(3)Vegetation stability was good in Yili River Valley from May to September(main growing season).Regions with CV≤0.10 were distributed in the whole vally,and regions with 0.3<CV≤1 were concentrated.(4)From 2001 to 2020,the temperature in Yili River Valley showed an increasing trend,while the precipitation showed a slow decreasing trend.The NDVI annual mean had a significant correlation with annual precipitation(r=0.7644),and no significant correlation with temperature;the NDVI monthly mean was strongly correlated with the monthly mean temperature,and weakly correlated with the monthly precipitation.