phoD-harboring bacterial community assembly and co-occurrence in soil aggregates during roadside slope restoration

Soil organic phosphorus (OP) mineralization plays a vital role in the ecological restoration of roadside slopes. However, the changes in the functional bacterial (phoD-harboring) community involved in OP mineralization in soil aggregates during slope restoration are still unknown. In this study, a space-for-time substitution was conducted to compare the differences in the phoD-harboring bacterial community structure and assembly in soil aggregates of four particle sizes (<0.053, 0.25–2, 0.053–0.25, and >2 mm) at different slope restoration ages (7, 11, and 14 years). The results showed no significant differences in the phoD-harboring community diversity and structure among soil aggregates in the same restoration year. Community structure dissimilarity increased with restoration time. Species replacement dominated slope soils restored for 7, 11, and 14 years, accounting for 78.40 %, 79.68 %, and 68.96 % of the total β-diversity, respectively. Community assembly processes shifted from coexisting deterministic (68 %) and stochastic (32 %) processes in the 7-year restoration slope soil to dominantly deterministic (98 % and 91 %) processes in the 11- and 14-year restoration slope soils, respectively. Dominant phoD-harboring bacteria tended to shift from r-to K-strategies as slope restoration progressed, and the C:P ratio significantly correlated with both community structure and assembly. The increasing C:P ratio over restoration time stimulated phoD-harboring bacteria to secrete alkaline phosphatase to improve P availability, enhancing the complexity and stability of the network. This study elucidates the changing patterns of phoD-harboring bacteria in soil aggregates and provides a theoretical basis for the management of soil P during roadside restoration.