1999—2018年黄河流域NDVI时空变化及驱动力分析

为了探究黄河流域NDVI时空变化及其驱动力,基于SPOT NDVI遥感数据,采用趋势分析、空间转移矩阵分析了1999—2018年黄河流域NDVI时空变化特征,并采用地理探测器模型对黄河流域NDVI空间分异特征与驱动力进行解释。结果表明:(1)从NDVI像元尺度的时间变化趋势来看,1999—2018年黄河流域NDVI变化趋势以极显著缓慢增长为主,占整个流域面积的53.12%,整体变化趋势向好,但可持续性不强; 极显著较快增长和快速增长的区域占15.47%,主要位于山西西部吕梁山脉和陕西北部黄土高原。(2)从NDVI空间变化特征来看,20 a间,植被覆盖度保持稳定的区域占31.6%,持续增加的占65.99%。(3)黄河流域的NDVI空间差异主要由年平均降水量、湿润指数、干燥度、土壤类型所决定,其因子解释力均超过30%,这表明气候因素仍然是影响黄河流域NDVI的主导因素。绝大多数驱动因子间交互呈现相互增强或非线性增强,交互解释力最强的是年平均降水量和土地利用,q值为0.704。只有年平均降水量与土地利用类型交互及高程与人口密度的交互是相对独立的。

Analysis of Spatiotemporal Variations and Driving Forces of NDVI in the Yellow River Basin During 1999-2018

In order to explore the temporal and spatial variation of NDVI and its driving forces in the Yellow River Basin,based on SPOT NDVI remote sensing data,trend analysis,spatial transfer matrix and barycentric transfer model were used to analyze the spatial-temporal variation characteristics of NDVI in the Yellow River Basin from 1999 to 2018,and geographic detector model was used to explain the spatial differentiation characteristics and driving forces of NDVI in the Yellow River Basin.The results show that:(1)from the perspective of the time variation trend of NDVI pixel scale,the NDVI variation trend of the Yellow River Basin from 1999 to 2018 was dominated by an extremely significant slow growth,accounting for 53.12%of the whole basin area;the overall change trend was good,but the sustainability was not strong;the areas with extremely significant and rapid growth accounted for 15.47%,which mainly located in the Lüliang Mountains in the west of Shanxi and the Loess Plateau in the north of Shaanxi;(2)from the spatial variation characteristics of NDVI,during the 20 years,31.6%of the areas had stable FVC,while 65.99%had continued to increase FVC;(3)the spatial difference of NDVI in the Yellow River Basin was mainly determined by average precipitation,wetness index,dryness degree and soil type,and the explanatory power of all factors was more than 30%,indicating that water was still the dominant factor affecting NDVI in the Yellow River Basin;most of the interactions among the driving factors were mutually or non-linearly enhanced,with the strongest interaction explanatory power being average precipitation and land use,with a q value of 0.704;only the interaction between average annual precipitation and land use type and the interaction between elevation and population density were relatively independent.