Microbial Phosphorus Functional Genes are More Sensitive to Environmental Variation in Temperate Forests than in the Subtropics

Microorganisms play important roles in phosphorus (P) cycling via their regulation of P uptake and transport, P mineralization and solubilization, and the mediation of P deficiency in forest biomes. However, the dynamics of microbial P functional genes and the underlying regulatory mechanisms in different forest biomes (e.g., temperate vs. subtropical) have yet to be sufficiently clarified. In this study, we applied a metagenomics approach to investigate changes in the abundance of three microbial P functional gene groups (P-starvation response regulation genes, P-uptake and transport genes, and P-solubilization and mineralization genes) along a subtropical–temperate gradient of forest biomes (23°N–45°N) in China. Our results revealed that the abundances of P-starvation response regulation genes in temperate forest biomes were significantly higher than those in the subtropics (p < 0.05), although not in the cases of the other two P functional gene types (p > 0.05). Moreover, in both temperate and subtropical forests, Acidobacteria, Actinobacteria, Proteobacteria, and Verrucomicrobia were identified as key phyla associated with P cycling. Furthermore, in both forest biomes, microbial community α-diversity was significantly positively correlated with P-starvation response regulation genes (p < 0.05), whereas α-diversity was significantly positively related to P-uptake and transport genes in temperate forest biomes (p < 0.001), although not in subtropical forests (p > 0.05). In addition, we found that whereas soil substrates showed significant negative relationships with P-solubilization and mineralization genes in temperate forest biomes (p < 0.05), this was not the case in subtropical forests. Collectively, these findings indicate that the responses of microbial P functional genes to the environmental variation in temperate forests are more sensitive than those in subtropical forests, thereby providing a theoretical foundation for further elucidation of the differential regulatory roles of these genes in different forest biomes.