Ecological restoration effect of artificial grassland and turf transplantation in alpine mining area on plateau

After years of mining, the local ecosystem in the alpine region on the plateau is seriously damaged, and restoring it to its original state is difficult. This paper focuses on the ecological restoration effect of the mineral resources development project, taking a copper mine in Xizang with an altitude of over 4 300 m located in the southeast margin of the Qinghai-Tibet Plateau as an example. The results showed that: 1) after the ecological restoration of planting grass in the alpine meadow mining area, the average height of the herbaceous layer increased, and the plant coverage decreased, accompanied by the decline of richness index, community diversity index, and evenness index. Compared with the local natural vegetation, self-renewal of vegetation communities appeared in planted grasslands, and degradation of vegetation communities appeared in natural turf-transplanted grassland. 2) The contents of soil organic matter, total nitrogen, available phosphorus, and available potassium in natural grassland of alpine mining areas were high, but the soil nutrient contents decreased after ecological restoration. Compared with natural grassland, the soil organic matter, total nitrogen, available phosphorus, and available potassium of artificial planting grassland decreased by 39.67%, 31.56%, 67.83%, and 14.40%, respectively, and the natural turf transplantation indexes decreased by 72.30%, 72.29%, 61.62%, and 6.77%, respectively. 3) Natural grassland soil was neutral, and the soil was alkaline after ecological restoration in the mining area. The soil pH of artificial planting grassland and natural turf-transplanted grassland increased by 15.71% and 11.43%, respectively. 4) Compared with the local natural vegetation, the content of heavy metals Hg, As, Pb, Zn, and Ni in the natural turf-transplantation grassland soil increased significantly, while the content of each heavy metal element in artificial grassland did not show significant changes. Our results indicate that the ecological restoration measures of turf transplantation have increased the risk of soil heavy metal pollution.