黄土高原植被覆盖时空变化及原因

Dynamic Changes of Vegetation Coverage on the Loess Plateau and Its Factors

研究黄土高原地区植被覆盖动态变化及其与人类活动和气象因子的关系对评价区域生态环境质量及生态过程具有重要意义。以黄土高原1982—2018年NDVI(1982—2011年GIMMS NDVI和2000—2018年MODIS NDVI)数据为基础,利用像元二分模型对植被覆盖度进行估算,借助植被绿度、相关分析和多元回归残差法分析了黄土高原植被覆盖度时空变化规律及其对人类活动和气象因子的响应特征。结果表明:(1)过去37年,黄土高原春、夏、秋和生长季植被覆盖度呈现升高趋势,且各季节FVC增加速率逐年升高,尤其以夏季和生长季增加速率的变化最为明显;(2)空间上,春、夏、秋和生长季FVC呈由西北向东南递增的趋势,且大部分地区呈显著上升趋势,植被呈现改善趋势的面积要大于呈现退化趋势的面积;(3)春、夏、秋和生长季人类活动对FVC主要以正面影响为主,且夏季人类活动对于FVC影响更为显著。在气象因素方面,FVC与平均气温在夏季和生长季呈现显著正相关的区域面积占比较大,FVC与总降水量在春季和秋季呈现显著正相关的区域面积占比较大。退耕还林(草)等生态工程的实施,使得黄土高原植被状态得到明显改善,但是城市扩张使得部分地区植被覆盖度呈现退化现象。

Study of the dynamic changes of vegetation cover in the Loess Plateau and its relationship with human activities and meteorological factors is of great significance for evaluating regional ecological environment quality and ecological processes.Based on the data of the Loess Plateau NDVI from 1982 to 2018(GIMMS NDVI from 1982 to 2011 and MODIS NDVI from 2000 to 2018),we used the dimidiate pixel model to estimate the vegetation coverage,and the temporal and spatial variation of vegetation coverage in the Loess Plateau and its response characteristics to human activities and meteorological factors were analyzed with the help of vegetation greenness,correlation analysis,multiple regression and residual method.The results show that:(1)in the past 37 years,the vegetation coverage in the spring,summer,autumn and growing seasons of the Loess Plateau had shown an increasing trend,and the increase rate of FVC in each season had increased year by year,especially in the summer and the growing season;(2)spatially,the FVC in spring,summer,autumn and growing seasons showed an increasing trend from northwest to southeast,and most of the areas have a significant increasing trend,and the area with improved vegetation cover is larger than that with degraded vegetation cover;(3)human activities in spring,summer,autumn and growing seasons mainly had positive effects on FVC,and human activities in summer had more significant impact on FVC.In terms of meteorological factors,the area where FVC and average temperature showed a significant positive correlation in summer and growing season accounted for a relatively large area,and the area where FVC and total precipitation showed a significant positive correlation in spring and autumn accounted for a relatively large area.The implementation of ecological projects such as returning farmland to forest(grass)had significantly improved the vegetation status of the Loess Plateau,but urban expansion had caused the degradation of vegetation cover in some areas.