Coniferous-broadleaf mixed plantations reshape phosphorus-solubilizing bacterial communities and enhance soil phosphorus bioavailability in subtropical forests

Mixed-species plantations are proven to enhance phosphorus (P) availability in subtropical forest ecosystems. However, the effect of coniferous-broadleaf mixed plantations on soil P cycling dynamics remains poorly understood. Through a long-term field experiment, the study investigated how mixed plantations influence soil P fractions, <i>phoD</i> and <i>pqqC</i> genes, and associated bacterial communities in bulk and rhizosphere soils. Results showed that compared to monocultures, the introduction of broad-leaved trees significantly increased labile P pools, particularly in the rhizosphere. Amplicon-based community profiling of <i>phoD</i>/<i>pqqC</i> genes demonstrated distinct compositional shifts in P-solubilizing bacterial communities across forest types and soil compartments. The <i>pqqC</i>-harboring bacterial communities were more closely related to the P fractions. More importantly, plant properties were important in explaining bulk soil labile P responses, while in rhizosphere soil, labile P was more strongly associated with soil properties, positively affecting labile P. These findings elucidate the complex interplay between tree diversity, microbial functional traits, and soil P transformations. This study underscores the critical role of mixed plantations in promoting microbial-mediated P mobilization and provides valuable insights for designing sustainable forest management strategies to optimize P utilization in subtropical ecosystems.