The soil properties and their effects on plant diversity in different degrees of rocky desertification

Rocky desertification is a process of soil erosion and vegetation destruction. On the surface, the landscape of rocky desertification is similar to that of desertification, which has a negative impact on the social and economic development of Southwest China. To clarify the influence of soil properties on plant diversity in rocky desertification areas, three grades of rocky desertification in Southwest Hunan Province were selected: light rocky desertification (LRD), moderate rocky desertification (MRD) and intense rocky desertification (IRD). Soil pH, soil organic carbon (SOC), N, P, K, Ca, Mg were measured, and the species compositions of herbs and shrubs were investigated. The effects of soil properties on plant diversity were studied by using redundancy analysis (RDA). The results showed that except soil pH and Ca, which increased with rocky desertification grade, the soil component contents were MRD > LRD > IRD. The species richness of shrubs was higher than that of herbs, and the difference was significant in MRD. The diversity of herbs first decreased and then increased, and the distribution became increasingly uniform. By contrast, shrub diversity exhibited an opposing distribution trend. RDA analysis showed that the soil nutrient content differed significantly among the rocky desertification grades. Among the nutrients analysed, N, P and K were the main factors affecting species composition in the rocky desertification areas, and their distribution characteristics partly explained the uneven distributions of herbs and shrubs.