退耕还林（草）工程实施前后黄河中游生境质量时空变化分析

It is of great practical significance for the ecological protection, rehabilitation, and high- quality development of the middle reaches of the Yellow River to analyze the spatial and temporal characteristics of habitat quality and its development trend. On the basis of the land cover data of the European Aeronautics and Space Administration from 1992 to 2020, the InVEST model was used to estimate the habitat quality. Sen+MK test and Hurst index analysis methods were applied to explore the spatial and temporal changes and development trends of the habitat quality in the middle reaches of the Yellow River before and after the implementation of the Grain for Green Project. Results showed that the habitat quality in the middle reaches of the Yellow River was good overall in recent 29 years, with the average habitat quality index of 0.652. However, a slight downward trend was observed (a drop of 0.004 per decade). Meanwhile, the habitat quality in the Grain for Green area showed an upward trend (an increase of 0.174 per decade), of which the most significant reached 0.656 recorded from 2011 to 2020. The spatial and temporal changes of habitat quality in the middle reaches of the Yellow River from 2001 to 2020 mainly showed an obvious decrease trend. In terms of the development of different time periods, the area with good habitat quality in 2011-2020 increased compared with that in 2001-2010. This finding was reflected in the improvement of habitat quality in the Grain for Green area. In the future, the temporal and spatial changes of habitat quality in the middle reaches of the Yellow River will be dominated by obvious decrease and obvious increase trends, respectively, and the sustainability will be strong. The significantly reduced areas will be mainly distributed in the Fenwei plain and the urban centralized development areas, and the significantly increased areas will be mainly located in the border areas of Shanxi Province, Shaanxi Province and Inner Mongolia Autonomous Region.