宁夏农牧交错区植被覆盖时空变化及成因分析

厘清人类活动和气候变化对宁夏农牧交错区植被覆盖度变化的共同影响对指导宁夏农牧交错区植被恢复具有重要的现实意义。基于Google Earth Engine(GEE)云平台，以宁夏农牧交错区1990-2020年陆地卫星地表反射率数据为基础，采用像元二分模型估算区域植被覆盖度并分析其时空变化规律，通过计算累积植被覆盖度的斜率变化率和残差分析确定人类活动对植被覆盖度的影响，运用相关分析法明确气候因素与植被覆盖度的相关性。结果表明，1)1990-2020年研究区年均植被覆盖度增加，增速为0.58%/a(P<0.05)。其中，1990-2000年年均植被覆盖度无显著变化(P>0.05),2000-2020年年均植被覆盖度显著增加(P<0.05),增速达到1.04%/a。2)空间上，研究区年均植被覆盖度由北向南逐渐递增，植被覆盖度恢复的区域面积大于退化面积，城镇的建城区是植被覆盖度显著降低的主要区域。3)人类活动是研究区植被覆盖度增加的主要影响因素，气象因素次之；气象因素中降雨量对植被覆盖度变化起主要作用。

Spatio-temporal Variation and Driving Force Analysis of Fractional Vegetation Coverage in Agro-pastoral Ecotone of Ningxia

It is of great practical significance to clarify the joint effects of human activities and climate changes on fractional vegetation coverage (FVC) change in agro-pastoral ecotone of Ningxia for guiding vegetation restoration in this area.Based on the cloud platform of Google Earth Engine (GEE) and the surface reflectance data of land satellite from 1990 to 2020 in Ningxia farming-pastoral ecotone,the pixel dichotomy model was used to estimate the FVC in the region and to analyze its temporal and spatial variation.The influence of human activities on FVC was determined by calculating the slope change rate and residual analysis of cumulative FVC.The correlations between climatic factors and FVC were determined by correlation analysis.The results showed that 1) the average annual FVC in the study area increased by 0.58 %/a (P<0.05) from 1990 to 2020,and the average annual FVC increased significantly (P<0.05) from 2000 to 2020,and the growth rate reached 1.04 %/a.2) Spatially,the average annual FVC in the study area gradually increased from north to south,and the area of FVC restoration was larger than that of degradation.The built urban area of the town was the main area where the FVC significantly decreased.3) Human activities were the main influencing factors of FVC increase in the study area,followed by meteorological factors.Rainfall played a major role in FVC change in meteorological factors.