Study on the influence of mining disturbance on the variation characteristics of vegetation index: A case study of Lingwu Mining Area

The vegetation growth environment has been seriously affected by the high-intensity mining of coal resources in ecologically fragile mining areas in the Western China. To understand the spatial and temporal variation characteristics of vegetation index in mining area is the precondition of exploring the protective mining methods of surface vegetation. Based on the Landsat-8OLI and Sentinel-2A remote sensing image data from 2016 to 2020, the SBAS-InSAR technology and Arcgis spatial anal-ysis tool were employed in this study; the spatial-temporal evolution of normalized differential vegetation index (NDVI) was analyzed from the mining area scale by regression slope and correlation coefficient. The 10 mm subsidence contour range on the typical working face was extracted as the mining disturbance range. At the scale of the working face, the influence law of mining technical parameters and occurrence conditions on surface vegetation index was revealed. The results show that: (1) Lingwu mining area has relatively low surface vegetation coverage, which conforms to the partial normal distribution; the average NDVI in the southwest of the mining area is greater than that in the northeast. (2) The vegetation growth process in the mining area presents a phenological pe-riodic variation trend, and mining activities have a certain negative impact on the growth of surface vegetation. However, after regional vegetation restoration, the NDVI in the mining area shows a fluctuating growth trend. (3) In the pre-mining stage of the working face, the NDVI change trend of vegetation in the mining area is basically the same; in the mining stage of the working face, the mining influence is relatively small due to the lagging effect of mining subsidence; in the post-mining stage (1-2 years after mining), the growth of vegetation is seriously damaged, and NDVI of the mining area decreases significantly. (4) The mining area of working face is positively correlated with the decline scope of NDVI; the ratio of mining depth to mining thickness and bedrock thickness are negatively related to surface subsidence, which slows down the decline of NDVI; the loose layer on the surface has large thickness, which can also effectively slow down the destruction of vegetation in the subsidence area. The research results are of great significance for further understanding the influence of coal mining on surface vegetation elements in ecologically fragile mining areas in Northwest China.