Effects of Changing Restoration Years on Soil Nutrient Traits and Plant Community Diversity in a Phosphate Mining Area

Abstract

The thinning vegetation and soil erosion problems left behind by extractive mining have caused serious environmental pollution, and vegetation restoration is one of the effective strategies to counter them. To study the effects of vegetation restoration on plant community species diversity, soil carbon, nitrogen and phosphorus, and the response of their plant community succession, four communities of different ages (1, 7, 10, 40) and one natural forest (>50 years) in the Kunyang phosphate mine were selected, and the analysis was carried out using the methods and protocols for plant community inventory. The species composition was recorded, and soil was collected from 0–60 cm in each community to determine the response of soil nutrients and plant diversity to the restoration process. The results show that the species richness of the community increases with the restoration year, the species composition at 40 years of restoration is similar to that of the natural forest, and the Shannon–Wiener diversity index in the tree layer at 40 years of restoration is greater than in the natural forest. Soil pH showed a decreasing trend with restoration year, and TP and AP increased with increasing time series. And the linear stepwise regression analysis showed that soil pH, soil organic carbon (SOC), total phosphorous (TP), available phosphorous (AP), and restoration year were the main factors of plant diversity. Compared to restoration of 10 years, TP and AP at the restoration of 40 years increased to 11.9–20.0 g∙kg−1 and 33.4–75.5 mg∙kg−1. The SOC of the community reached a maximum at 40 years of restoration, 1.5, 2.8, and 2.4 times higher at 0–20 cm, 20–40, and 40–60 cm, respectively, than at 1 year. The organic carbon fraction increased with the restoration year in an ‘N’ pattern, and mineral-associated organic carbon (MOC) and unstable organic carbon fraction decreased at 10 years and 40 years of restoration. The SOC of natural forests decreased, but stable organic carbon increased. The soil pH, SOC, and organic carbon fraction of the communities decreased with increasing soil depth, while TP and AP increased with increasing soil depth at the later period of restoration. In general, with extended restoration years, 40 years plant of restoration in phosphate mines can be expected to allow for plant community succession to climax community, and the key influence on plant diversity are the phosphorus and stable carbon fractions. These results are expected to facilitate the future basis for vegetation succession and restore systems during mining area restoration.