Analysis Of Temporal And Spatial Variation Of Vegetation Index In Mining Disturbed Area

Study on the temporal and spatial variation of surface vegetation index in mining disturbed area is conducive to explore the influence of coal mining activities on the growth of vegetation,learn the law and mechanism of ecological destruction in mining area,measure the natural restoration potential of ecological system,guide the reconstruction work of the ecological environment in mining area,and provide a theoretical reference for the sustainable development of the coal mine.According to analyses the current research status of the regional vegetation index change trend in mining disturbed area,this paper aiming at the problem of surface vegetation index change caused by underground mining,using the method of mining subsidence prediction to get the mining disturbed range,selecting eight years’ remote sensing data before and after 2008 in Yicheng mining area,extracting the mean NDVI value of mining disturbed range as the primary data source.By comparing the change trend of NDVI value in non mining disturbance area and mining disturbance area,and analysing the Pearson correlation between rainfall data and NDVI data,it is concluded that the disturbance factors will influence the regional vegetation index.By comparing and analyzing the change trend of the NDVI value under the single factor in mining disturbed area,the influence rule of disturbance factor on the change trend of the regional vegetation index is obtained.Specific results are as follows:(1)In the early stage of mining disturbance,the change trend of NDVI value in Yicheng mining area is mainly affected by rainfall,different surface vegetation types affected by rainfall in different degrees.Farmland and grassland is more sensitive to rainfall,NDVI value of these regions changed with the change of rainfall.Shrub forest is less sensitive to rainfall,the NDVI values range in 2%~7%,after decreased under the influence of rainfall,the recovery time lag about one year,the NDVI value will not immediately increase with the increase of rainfall.(2)In the process of mining,due to the lag of mining influence,the rock damage caused by underground mining is transferred to the surface with delayed effect,large surface damage didn’t happened,vegetation can still maintain growth,NDVI value of Yicheng mining area will not be significantly reduced,the variation range is usually less than 5%,vegetation index change is not obvious.(3)In one to two years after mining,the surface damage in Yicheng mining area is the most serious,the vegetation growing environment is destroyed,the NDVI value declines most.It is easier to produce collapse pits,surface cracks and subsidence basins in the thick loess area,the surface damage is more serious,the decrease of NDVI was greater than that of the non loess area.Within a certain period of time,the area with less bedrock layer is more faster to reach the stable state after mining,vegetation will no longer reduce,the decrease of NDVI is less than that of thick bedrock area.Under the condition of large area mining,the vegetation roots in mining area boundary and surface cracks of big flakiness ratio working face is fractured,unable to regenerate new roots cause vegetation dieback,the inside vegetation can normally grow,the overall NDVI value decreased,the decrease of NDVI value in big flakiness ratio working face is less than that of small area.Two to three years after mining,vegetation growth environment recovered with the stability of surface soil,through rainfall irrigation and local land reclaim work,the vegetation will grow slowly,and finally reach the vegetation index before the mining damage.