Natural restoration of degraded karst vegetation shifts soil microbial phosphorus acquisition strategies.

Aims: Soil phosphorus (P) cycling in karst regions is mainly regulated by microbial activities. Natural restoration has been widely adopted in the degraded karst regions of southwest China. However, the response of functional genes and microbial communities involved in soil P cycling to revegetation has not been well characterized. Methods: We used metagenomic sequencing to investigate the genes and microorganisms related to soil P cycling derived from natural restoration stages (shrubbery, TG; secondary forest, SG; old-growth forest, OG) in the southeast of Guizhou Province, China. Results: Natural restoration affected the composition of soil P cycling genes. When TG restored into OG, the relative abundance of organic P (OP) mineralization genes increased from 45.78% to 48.38%, while the genes related to inorganic P (IP) solubilization decreased from 27.19% to 25.03%. The effect of soil nutrients on the relative abundance of OP and IP genes was greater than that of aboveground plant diversity. Structural equation modeling further indicated that soil nutrients directly drove the increase in the relative abundance of OP genes and indirectly impacted the relative abundance of IP genes. The results show that Proteobacteria (38.97%–52.72%) and Actinobacteria (13.44%–29.34%) are the main contributors to soil OP and IP cycling genes, but their contributions vary in different restoration stages. Conclusions: Natural restoration of the degraded karst vegetation changes the acquisition strategy of soil microbial P by enhancing OP but decreasing IP cycling potentials. This study investigate the regulation of P cycling in the ecological restoration of degraded karst regions from microbial perspective. [ABSTRACT FROM AUTHOR]