Phosphorus fertilizer application shifts the rhizosphere bacterial community and their carbon, nitrogen and phosphorus-cycle genes in a Phoebe bournei young plantation

Phosphorus (P) is considered to be one of the most limiting elements in terrestrial ecosystems, especially in the subtropical forests in China. However, little is known about how rhizosphere soil bacterial communities and functions, especially at the level of functional genes abundance, respond to P inputs. Herein we conducted a P addition experiment and treatments included 80 g m−2 yr−1 (P1), 160 g m−2 yr−1 (P2), 240 g P m−2 yr−1 (P3), 320 g P m−2 yr−1 (P4) and the control without any fertilizer application (CK) in the Phoebe bournei young plantations. This study used the quantitative microbial element cycling (QMEC) smart chip technology and 16S rRNA gene sequencing to investigate changes in the relative abundance of C-, N-, and P-cycle genes and rhizosphere soil bacterial community that received various inputs of P nutrients. Soil bacterial diversity showed a progressively decreased trend with increasing of P fertilizer, accompanied by significant differences in bacterial community structure between CK and P4 treatment. The relative abundance of N- and P-cycle genes were increased by P addition, and the highest relative abundance was observed in P3 treatment among the five P addition treatments. The relative abundance of C-cycle genes was significantly enhanced by P4 treatment, promoting C fixation, degradation, and methane metabolism. Random forest model indicated that invertase activity was the most important predictor for the relative abundance of C-, N-, and P-cycle genes. Partial least squares path modeling analysis revealed that the predominant effect of P fertilizer in driving the relative abundance of functional genes was maintained when accounting for multiple abiotic factors (total P, available P, available potassium, soil organic carbon and soil pH) drivers and there was a strong relationship between the relative abundance of functional genes and catalase, invertase and urease activities. Overall, our findings confirm that high P addition significantly altered rhizosphere soil bacterial community composition in the Phoebe bournei young plantations, and significantly enhanced the relative abundance of C-, N- and P-cycle genes. These results suggest that sufficient P fertilizer benefits to improve the nutrients cycle processes mediating by soil bacteria in Phoebe bournei young plantations.