煤矿排土场复垦干扰指数构建及其时空分异

排土场复垦后受干扰情况影响重建生态系统的稳定性,直接关系煤矿区生态修复成败,针对长期恢复过程的干扰状况评价尤其重要。该文在MODIS全球干扰指数的基础上,将地表温度与增强型植被指数相结合,构建基于Landsat影像的排土场复垦干扰指数(dump reclamation disturbance index, DRDI),并计算山西平朔安太堡露天矿排土场28 a间的干扰指数及其时空分异特征。结果表明:复垦初期干扰强烈区呈现较强空间聚集特性,植被结构和功能恢复至自然水平的平均时长约为10a,单个排土场受干扰面积可下降至1.32%～17.76%之间。平朔安太堡露天煤矿4个排土场在稳定时限和干扰分布特征上呈现典型差异,受排矸方式、复垦方向、年限及地形地貌等因素驱动。DRDI可评估复垦排土场重建生态系统稳定时限,有效识别重建生态系统因干扰造成植被退化的空间范围和严重程度,应用于排土场复垦效果评价将为优化复垦模式、提高复垦效率提供参考。干扰指数对自然及人为因素响应的定量分析是未来研究重点。

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.