Construction and spatiotemporal variation of dump reclamation disturbance index

Dumps in coal mine occupy huge areas of land and cause many problems, therefore, dumps reclamation become an important issue in ecological restoration. The reconstructed ecosystem of the reclamation dump is affected by various disturbance factors, which causes it to be unstable and prone to degradation. The disturbance influences the stability of reconstructed ecosystem and decides the success or failure of the ecological restoration in coal mine. Therefore, it is important to evaluate the recovery process of the reconstructed ecosystem. Based on the MODIS global disturbance index (MGDI) and vegetation disturbance index, which are based on MODIS data, we constructed the dump reclamation disturbance index (DRDI) by combing land surface temperature (LST) and enhanced vegetation index (EVI) using Landsat data. DRDI can provide higher spatial resolution than MGDI and VDI. EVI indicates the vegetation structure, and LST indicates the function of vegetation. The best status of reconstructed ecosystem is estimated by the maximum EVI and minimum LST, which is compared with the status of every year. DRDI is used to measure the vegetation recovery process and the degree of disturbance of vegetation in dumps. This study calculated the disturbance index of Antaibao opencast coal mine dump in Shanxi province, China for 28 years. This study combined remote sensing analysis with field validation data to analyze the spatial and temporal dynamics of characteristics for reconstructed vegetation restoration and interference. The results indicated that: in the early stage of reclamation, the areas with great disturbance showed highly spatial aggregated. The areas with disturbances had been gradually decreasing and took about 10 years for the vegetation structure and function to recover to the natural state in the reclamation dump, when the disturbed area could be reduced to the degree between 1.32% and 17.76%. DRDI could reflect the reclamation process and reveal spatial heterogeneity. The four dumps in Antaibao coal mine showed different stability periods and distribution characters of disturbance, which were influenced by dumping (coal gangue), reclamation strategy and vegetation reconstruction mode, as well as topography. Due to the spontaneous combustion of coal gangue, South Dump was more unstable than other dumps. Inner Dump began to reclaim later than other dumps but has entered a stable state relatively quickly, which was because of fine topography condition. The Western dump and its expansion area showed a degradation and great disturbance, where the surface vegetation covers mostly wasteland, grassland and cultivated land. DRDI can effectively identify the spatial extent and severity of disturbances for vegetation in reclamation dumps. DRDI is intuitive, effective and easy to implement. Its data can be easily obtained, and the calculation method is simple. It can effectively monitor the restoration properties of the reconstructed ecosystem for post-review evaluation of land reclamation. The quantitative analysis between influencing factors and disturbance index will be a key point in future research. Applying DRDI in evaluating the effect of reclamation in dumps will provide references to optimizing reclamation strategy and improving the efficiency of reclamation. For future research, DRDI can be combined with VDI to distinguish the causative factors of restoration character.