Differences in Soil Inorganic Phosphorus Availability and pqqC-Harboring Bacterial Communities Between Long-Term Vineyards and Adjacent Uncultivated Soils

Soil phosphorus (P) availability is critical for vineyard productivity, and pqqC-harboring bacteria contribute to inorganic P (Pi) mobilization. However, knowledge of the coordinated responses of Pi partitioning and pqqC-harboring bacteria to prolonged grape cultivation remains limited. Here, soils from 20-year-old grape orchards (Y20) and adjacent uncultivated soils (CK) were compared to explore the relationships among Pi fractions, pqqC-harboring communities, and edaphic characteristics. Relative to CK, Y20 showed significantly lower pH and higher concentrations of labile and moderate labile Pi fractions. Although the pqqC gene abundance declined significantly in Y20, the Shannon diversity of pqqC-harboring communities increased, and community composition differed markedly between the two land-use types. Soil pH and labile Pi were the main factors shaping community composition. Network analysis revealed strong associations between pqqC-harboring taxa and soil P fractions, with Azospira serving as a key connector. Pearson correlation analysis further showed that labile and moderately labile Pi fractions were negatively correlated with soil pH and pqqC gene abundance, while NaHCO3-Pi was positively correlated with the Shannon diversity. Overall, long-term grape cultivation redistributed soil Pi toward more bioavailable forms, closely associated with soil acidification and shifts in the abundance and diversity of pqqC-harboring communities.