Effects of mining activities and vegetation restoration methods on soil organic matter content and enzyme activities in the alpine meadows of Gannan

Studying the effect of revegetation is important for the successful restoration of the soil and the ecological environment in a mining area. However, very few studies have been undertaken on the ecological restoration in the mined areas in the Qinghai-Tibet Plateau. In this study, we focused on the gold mining area in the Gannan alpine meadow (located to the north east of the Qinghai-Tibet Plateau) and explored the changes in the soil organic matter content and enzyme activity after five years of revegetation with herbs and woody plants. The results showed that, subsequent to mining activities, the soil organic matter content and enzyme activities decreased significantly (P < 0.05). The organic matter content and urease activities in sites planted with herbs increased significantly after five years of recovery (P < 0.05), but neither of these increased significantly in sites that were revegetated with Picea crassifolia. There was a positive correlation between soil organic matter content and enzyme activity in the restored plots and in those that were not. There was no significant difference in the soil organic matter content and enzyme activity across the soil profile (between 0 – 10 cm and 10 – 30 cm soil depths; P < 0.05). In the early stage of vegetation restoration, compared to sites with Picea crassifolia as the dominant species, the grassland community with Elymus nutans showed higher input of litter and root exudates, which could improve soil quality quickly. Thus, restoration using woody plants should ensure that the chosen tree species provide large litter inputs that are easily decomposed.