Effect of avaliable phosphorus on the soil microbial community and diversity

Most studies demonstrated that phosphorus (P) availability affected the soil microbial community in natural systems with low available P (AP). However, the characteristics of the soil microbial community composition and its relationship to soil properties under different levels of soil AP enrichment in agricultural soils are not well understood. Our objectives were to investigate whether AP affect the soil microbial community composition and diversity in high-level AP soils. The microbial community was analyzed through high-throughput sequencing using the Illumina MiSeq platform based on the 16S rRNA gene and ITS gene. Fifteen soils, including barren land, cropland, and greenhouse soils which were sandy loam Fluvisols, were selected and sampled 0-20 cm from different fields in Beijing, China, with AP contents ranging from 5.03 mg kg-1 to 391.45 mg kg-1. The statistical analyses of 16S rRNA genes revealed high AP (> 100 mg kg-1) decreased alpha diversity (Shannon’s index, H’) but not beta diversity of the soil bacterial community. The sequencing of 16S rRNA genes showed that Proteobacteria, Bacteroidetes and Acidobacteria were the dominant phyla in sandy loam Fluvisols. AP, soil organic carban (SOC) and total nitrogen (TN) had synergistic influence on the shift of the bacterial community composition. Moreover, the partial least squares path modeling (PLS-PM) analysis suggested that AP was the main driving factor affecting the soil bacterial community composition compared with other environmental factors. The members of the Proteobacteria, Bacteroidetes, and Actinobacteria belonging to copiotrophic taxa typically increased in relative abundance in high-P soils, while oligotrophic taxa (mainly Acidobacteria) decreased in relative abundance. Our results demonstrated that the bacterial community composition would shift from oligotrophic to copiotrophic with increasing levels of AP. The results of ITS gene showed that Ascomycota, Basidiomycota, Ciliophora and Zygomycota were the dominant phyla, with the phylum Chytridiomycota being dominant in soils with low AP concentrations (< 10 mg kg-1). In addition, both α- and β-diversity had no regular significant difference in soils with significant variations in AP. Correlation analysis results showed that AP could impact the soil fungal composition at the genus level but not at the phylum level. PLS-PM results indicated that the composition of the soil fungal community was significantly influenced by AP concentration. The results of this study suggest that we should reduce the P input and keep appropriate AP level in cultivated soils in order to manage the soil fertility and healthy.