Tempo-spatial changes and main anthropogenic influence factors of vegetation fractional coverage in a large-scale opencast coal mine area from 1992 to 2015

The surface soil and vegetation had been destroyed by opencast mining, leading the decrease of the vegetation fractional coverage, which caused a severe damage to the mining area and ecosystems. However, land reclamation in mining area minimized the damage to the environment and was an important part of mine production and construction to improve the vegetation fractional coverage and restore the local ecological balance. To analyze the effects of anthropogenic activities on vegetation, the vegetation fractional coverage (VFC) and vegetation index (VI) of the whole Pingshuo opencast coal mine area from Shanxi province of China and four individual reclaimed dumps in this coal mine area were calculated respectively based on remote sensing images. The spatial distribution of vegetation fractional coverage was analyzed using Moran's Index. From 1992 to 2015, the vegetation fractional coverage of the whole coal mine area increased from 0.31 to 0.53, showing a benign development trend with significant change from 2000 to 2015, and it was the lowest in 2009. Moreover, The vegetation fractional coverage transformed from extremely low coverage, low coverage, to middle coverage, middle high coverage, and high coverage during 23 years, which was improved clearly. The long reclamation period is conducive to vegetation restoration, and the reclamation project has a direct effect and significance for the restoration of the ecological environment of the mining area. The vegetation fractional coverage of four dumps in the study area were the lowest at the initial reclamation time, and increased with increasing reclamation time. The vegetation coverage of the Southern dump, Western A dump, Inner dump and Western B dump increased from 0.29 to 0.68, 0.34 to 0.59, 0.5 to 0.76, and 0.46 to 0.54, respectively. The increase of the global Moran's Index from 0.80 to 0.91 indicated that the spatial agglomeration was greatly influenced by anthropogenic activities from 1992 to 2015. The local Moran's Index showed that the vegetation fractional coverage of the whole stage was mainly high-high clustering and low-low clustering in 2015, and the vegetation fractional coverage of the dumping sites changed from the original low-low clustering to high-high clustering from 1992 to 2015. The area was heavily affected by both mining and reclamation, the vegetation fractional coverage of the dump site was significantly improved after reclamation.