2001—2020年黄河流域水源涵养区植被覆盖变化及其对气候变化和人类活动的响应

Dynamic changes of vegetation in water conservation area of the Yellow River Basin and its response to climate change and human activities during 2001-2020

植被覆盖变化对黄河流域水源涵养区水源涵养功能和生态环境变化具有重要影响。本文利用Google Earth Engine(GEE)云平台,选取2001—2020年MODIS数据,采用一元线性回归和Hurst指数分析研究区植被覆盖时空变化,并基于地理探测器和Pearson偏相关分析探究各因子对植被覆盖空间分布的影响。结果表明:2001—2020年,研究区植被指数(NDVI)总体呈现波动上升趋势,多年平均NDVI值为0.42,增长速率为0.023/10a,NDVI具有显著的区域差异,整体表现为由东南向西北递减。2001—2020年间植被覆盖呈现改善趋势面积(82.47%)大于退化趋势面积(4.97%),未来持续性改善面积(62.63%)大于持续性不变(5.78%)和持续性退化(3.69%)面积,说明植被覆盖度将继续保持增长趋势。降水量对NDVI空间分布影响力最大,达到0.502,其次为相对湿度(0.418)、高程(0.374);降水量(77.16%)、气温(71.82%)与NDVI空间分布正相关,日照时数(77.94%)、相对湿度(62.70%)与NDVI空间分布负相关。NDVI变化受气候变化和人类活动共同影响,气候暖湿化和人类活动导致的低NDVI土地利用类型向高NDVI土地利用类型转移共同促进了植被覆盖向好发展。该研究有助于厘清研究区植被覆盖时空变化及其影响因素。

Vegetation cover change has an important impact on water conservation function and ecological environment change in the water conservation area of the Yellow River Basin.Based on Google Earth Engine(GEE)cloud platform,MODIS data from 2001 to 2020 were selected to analyze the spatial-temporal changes of vegetation cover in the study area by one-dimensional linear regression and Hurst index.The effects of various factors on the spatial distribution of vegetation cover were explored based on geodetector and Pearson partial correlation analysis.The results showed as follows:(1)From 2001 to 2020,NDVI in the study area showed a fluctuating upward trend.The annual average NDVI value was 0.42,and the growth rate was 0.023·every decade.NDVI showed significant regional differences,decreasing from southeast to northwest.(2)From 2001 to 2020,the area with improvement trend(82.47%)was larger than the area with degradation trend(4.97%),and the area with future continuous improvement(62.63%)was larger than the area with no change(5.78%)and the area with continuous degradation(3.69%),indicating that the vegetation coverage will continue to maintain an increasing trend.(3)Annual precipitation had the greatest influence on the spatial distribution of NDVI,reaching 0.502,followed by relative humidity(0.418)and altitude(0.374).Precipitation(77.16%)and air temperature(71.82%)were positively correlated with NDVI spatial distribution,while sunshine hours(77.94%)and relative humidity(62.70%)were negatively correlated with NDVI spatial distribution.(4)The change of NDVI is jointly affected by climate change and human activities,and the shift from low NDVI land use types to high NDVI land use types caused by climate warming and human activities jointly promote the better development of vegetation cover.This study is helpful to clarify the temporal and spatial changes of vegetation cover and its influencing factors in the study area.