Rare microbial community structure and networks in association with phosphorus forms under soil phosphorus accumulation

Aims: Microbes play a significant role in the biogeochemical cycling of soil phosphorus (P). However, little is known on how P accumulation affects the microbial-driving regulation of soil P forms. Methods: This study investigated soil P forms and microbial community structure in the presence or absence of P accumulation using 31P-NMR spectroscopy and 16S rRNA high-throughput sequencing, respectively. Results: Long-term P accumulation increased available P and orthophosphate, but decreased the proportion of phosphate monoester, phospholipids, DNA-P and pyrophosphate. Meanwhile, the abundant and rare microbial taxa possessed different response to soil P accumulation. As a result, due to the change in soil properties and different sensitivity to soil P content, P accumulation enhanced the alpha diversity indices of microbial community and reduced the relative abundances of Proteobacteria and Actinobacteria. In addition, Bacteroidetes, Firmicutes, Gemmatimonadetes, and Nitrospirae were positively correlated with orthophosphate, but negatively correlated with the P forms of phosphate monoesters, DNA, phospholipids, pyrophosphate, and the abundance of pqqC gene. Among the investigated soil properties, soil organic matter, pH, organic phosphate, and pqqC may dominate the assembly of microbial networks. Conclusions: Under P accumulation, rare microbial taxa may play a more important role in the assemble of microbial networks for soil P cycling than the abundant microbes. These findings may help to optimize soil management for an enhancement of P use efficiency.