Vegetation disturbance analysis in coal mining area with high ground water level based on Landsat time series NDVI data

The eastern mining area of China is an important coal and grain composite production area. Due to the flat terrain and high underground diving level, most of the subsidence caused by mining is perennial or seasonal water, which causes serious land, ecological and environmental problems. As an important part of the ecological environment in mining area, vegetation has dynamic characteristics due to the external disturbance and the change of environmental factors. The normalized difference vegetation index(NDVI) is a common indicator for remote sensing monitoring of vegetation growth. The analysis based on NDVI time series data can effectively reveal the disturbance effect of vegetation. Taking Guqiao Coal Mine in Huainan, Anhui Province as the research object, the temporal and spatial variation characteristics of NDVI values were analyzed based on the classification statistics of Landsat NDVI time series data from 2007 to 2018, as well as hot spot analysis, clustering and outlier analysis, and profile analysis, and then the disturbance effect of coal mining subsidence on the surrounding vegetation was discussed. Results showed that from 2007 to 2018, the vegetation growth in Guqiao Mine was generally good, while the dispersion degree of vegetation cover was increasing. The NDVI distribution in Guqiao Mine has obvious spatial clustering characteristics, both are “High-High” Cluster type or “Low-Low” Cluster type, and there is no abnormal appearance. Under the influence of coal mining, hot spots decreased and cold spots increased, and the conversion of hot spots to cold spots mainly occurred in the area of subsidence water, near the Deshang speedway and Yongxing River. Within a certain range around the subsidence water accumulation area, there was an obvious vegetation disturbance effect, and the initial disturbance of mining was small. With the growth of the water accumulation area and the lapse of time, the disturbance range gradually increased and finally tended to be stable, which showed temporal lag and spatio-temporal accumulation. The results would provide a reference for the determination of ecological influence range and the restoration of ecological environment in coal mining subsidence area.