A Case Study of Initial Vegetation Restoration Affecting the Occurrence Characteristics of Phosphorus in Karst Geomorphology in Southwest China

Phosphorus (P) is one of the necessary nutrient elements in the process of plant growth and development. The temporal and spatial distribution characteristics of phosphorus content can not only reflect the soil structure and availability, but also affect the growth of wetland vegetation, the formation of the environment, and the process of vegetation succession. In this paper, taking Guizhou Caohai Nature Reserve as the research object, the temporal and spatial substitution method was used to study the distribution and influencing factors of soil total phosphorus (TP) and soil available phosphorus (AP) under different geomorphological environments (non-karst landforms, karst landforms, and geomorphology after vegetation restoration (5 years)). The results showed that (1) the TP content in the topsoil of the restored vegetation landform was generally higher than that in the topsoil of the karst landform and non-karst landform, and the distribution difference of the AP content in the three areas was slight. At the top, hillside, and foot of the mountain, the contents of TP and AP in the non-karst landform and karst landform decreased with increasing soil depth and accumulated at the foot of the mountain. (2) The results of the correlation analysis showed that the interpretation rates of TP and AP by each soil physicochemical factor were the highest, reaching 64–86%, while the interpretation rate of TP and AP by the combined action of multiple physicochemical factors was relatively small; in addition, there was a significant correlation between environmental factors and soil TP and AP (p < 0.05). (3) Compared with unrepaired karst landforms, in the process of vegetation restoration (5 years), TP content has convergence between geomorphology after vegetation restoration and non-karst landforms, while AP content fluctuates greatly. The analysis showed that the changes in soil TP and AP contents were mainly affected by vegetation communities, while the changes in soil TP and AP contents in mountain areas were also affected by soil organic matter, pH, soil particle size, and climatic conditions