Abstract:
The range of vegetation disturbance by open-pit mining is of theoretical and practical significance for the ecological management and restoration of mining areas. The current researches mainly focus on a single coal mine or several coal mines, and the conclusions obtained only reflect the characteristics of particular coal mines, lacking of the investigation of general patterns of mining disturbance for a large number of open-pit coal mines at a regional scale, which is difficult to be promoted and used in practice. In terms of above problems, four types of OD-NDVI(Orientation Distance-Normalized Difference Vegetation Index) curves for open-pit coal mines are defined based on the distribution characteristics of adjacent coal mines and the type of ecological disturbance, including “negative independent curve”,“negative dense curve”,“positive independent curve” and “positive dense curve”. Also, a distance extracting method for vegetation disturbance by mining based on the OD-NDVI curves is proposed, which includes four main steps: data pre-processing, OD-NDVI curve extraction, curve classification and mining disturbance distance identification. In a case study, all mining disturbance distances were extracted and statistically analyzed with 106 open-pit coal mines in the Shendong coal base, which revealed the general statistical patterns of vegetation disturbance range by open-pit mining in the study area. The results are as follows:(1) The Shapiro-Wilk for significance test shows that the mining disturbance distance of the open-pit coal mines in the Shendong coal base obeys a normal distribution(R
2=0.95),with most of the mining disturbance distance around the mean value of 1 214 m, and 68.26% of the mining disturbance distance is distributed in the range of 939.05 m, 1 488.71 m(within the mean value with one time of the standard deviation).(2) There are bounded characteristics of mining disturbance distances in open-pit coal mines by using the box plot statistics, with a maximum value of 2 025 m and a minimum value of 600 m, and only 0.13% of mining disturbance distances are greater than 2 038.37 m(above the mean value with three times of the standard deviation).(3) Through analyzing the coefficient of variation of mining disturbance distances in eight directions in open pit coal mines, a significant directional heterogeneity has been observed in the directional mining disturbance distances of the open-pit coal mines, with strong or moderate directional heterogeneity in 70.7% of the mines and weak directional heterogeneity in only 29.3%.(4) A significant logarithmic relationship is found between the mining disturbance distance and the actual annual coal production(R
2=0.613) via fitting modeling analysis, which increases logarithmically as the annual coal production increased, but after the annual coal production increases to 2.32 million tons, the annual coal production has no significant effect on the disturbance distance. The results of statistical analysis based on a large sample of open-pit coal mines have stronger general applicability and fineness, which are expected to provide scientific guidance for hierarchical zoning management, precise restoration, and production scheduling optimization in arid and semi-arid coal mining areas.