Rational eucalypt logging site management patterns enhance soil phosphorus bioavailability and reshape phoD-harboring bacterial community structure

Abstract

Continuous planting of eucalypt plantations negatively affects soil nutrient effectiveness, especially soil phosphorus (P) availability. Therefore, exploring the response characteristics of soil P-mineralising microbial communities and the distribution mechanism of soil P fractions under different transformation patterns on eucalypts logging sites holds great practical significance for improving soil nutrient effectiveness in plantations. This experiment investigated the effects and correlations between four different transformation patterns on soil phoD-harboring bacterial communities, alkaline phosphatase (ALP) activity, and P fractions. Management patterns mainly included non-forest area formed upon eucalypt stump germination suppression after two generations of Eucalyptus afforestation (TWE), the third generation of pure plantation planting (THE), mixing of Eucalyptus with Manglietia glauca (EM), and rotation of pure M. glauca plantation (MM), with previous mixed coniferous and broadleaf forest (CK) as the control. The results showed that, TWE and THE significantly reduced soil (0–10 cm and 10–20 cm) organic carbon (SOC), total nitrogen (TN), bioavailable P, and labile Po, and increased the occluded P and ALP activity compared to CK; however, SOC, TN, bioavailable P, and labile Po indices improved in plantations of EM or MM compared to TWE and THE. Meanwhile, the four management patterns on the logging site caused significant differences in phoD gene community structure and diversity. TWE and THE significantly increased the relative abundances (RAs) of Pseudomonadaceae and Comamonadaceae, which correlated negatively with soil bioavailable P and HCl-P and positively with ALP activity, suggesting a positive effect on Po mineralization and insoluble P mobilization. In contrast, Streptomycetaceae and Oxalobacteraceae were significantly enriched in EM or MM, implying that not all microorganisms carrying phoD genes play important roles in synthesizing ALP. The structure equation model showed that TN, resin-Pi, NaHCO₃-Pi, and HCl-P had indirect effects on ALP through phoD-harbouring bacterial diversity and community composition. These findings provide a basis for understanding the soil P cycling mechanism after eucalypt plantations logging site transformation.