Abstract:

The large scale topsoil stripping and land acquisition during open-pit mining lead to destructions of land surface, vegetation, and underground water systems as well as alteration of landscape patterns, causing a series of ecological environmental problems. Open-pit mining in the desert area of northwestern China, an important successor mining location in China’s future coal resources strategy, can severely threaten the country’s land and ecological securities if there are no targeted countermeasures for ecosystem restoration. In this study, seven typical open-pit coal mines in the northwest desert area were selected for the landform remodeling, gravel layer reconstruction, and desert vegetation restoration studies through field investigation, empirical analysis, remote sensing imaging, and comparative analysis. The results are as follows: (1) The seven open-pit mines caused a variety of land disturbances. Among all mines, the land destruction in Baishihu is most severe, reaching 1190.3 hm²; the occupied land in Wucaiwan is the largest at 2251.0 hm²; the land excavation in Jungjun Gobi is most severe, reaching 1007.3 hm²; the bare land area in Dananhu is the largest at 20164.2 hm²; the vegetation around Yili is most abundant at 343.3 hm²; and the traffic land around Xiheishan is the largest, reaching 194.3 hm². (2) The area of the gravel layer in Wuheishan, the most representative open-pine mine selected for gravel layer study, decreased from 60.12% in 2000 to 31.28% in 2010, then increased to 42.75% in 2017. (3) For the Wucaiwan mine, the estimated biomass was 12.53 g/(m²·a); the landscape diversity index was 0.2193; the landscape dominance was 1.7807; and the landscape evenness was 0.1097. This area has insufficient ecological carrying capacity, weak resistence to ecological disturbance, and low ecological integrity. (4) The vegetation coverage of the Wucaiwan mining area showed an upward trend from 2000 to 2005, reaching 7.72% in 2005, followed by a downward trend from 2005 to 2015, reaching 3.89% in 2015. It can be concluded that the desert open-pit mining area in northwestern China has suffered relatively severe ecological damage. Therefore, the reconstruction of gravel curtains in this area is most urgent, and human support and guidance should be adopted to improve the rate and effectiveness of natural ecological restoration, so that the damaged habitats can spontaneously shift towards recovery and virtuous cycle through active self-feedback.

Key words: northwest desert, open-pit coal mine, ecological restoration, gravel cover, vegetation coverage