Rhizosphere Soil Properties and Microbial Community Across an Apple Replanting Chronosequence

Apple replant disease originates from rhizosphere microbial dysbiosis, allelochemical accumulation, and soil physicochemical degradation, causing seedling stunting and obstructing aged orchard renewal. Here, rhizosphere soils were sampled from newly planted control (CK) and 2–7-year replanted apple trees (Y2–Y7) arranged in a cross-sectional space-for-time chronosequence. We characterized soil physicochemical traits and profiled bacterial (16S rDNA) and fungal (ITS) communities via relative abundance amplicon sequencing. Soils from Y2–Y7 had significantly lower concentrations of alkali-hydrolyzable nitrogen (AN), available phosphorus (AP), total nitrogen (TN), total potassium (TK), available zinc (AZn), and available copper (ACu) than CK, but higher exchangeable magnesium (Ex-Mg). Sequencing obtained 5883 bacterial and 2063 fungal ASVs. Y2–Y7 soils showed elevated relative abundances of Bacillota and Pseudomonadota; Ascomycota dominated all samples. Bacterial alpha diversity did not differ significantly among treatments, whereas bacterial beta diversity significantly separated long-term replanted (Y5–Y7) soil from CK. Soil nutrients were associated with bacterial community structure; partial Mantel tests for fungi yielded only trend-level associations, consistent with the non-significant overall fungal PERMANOVA (p = 0.08). This study examines the associations among rhizosphere soil properties and microbial composition across a 2–7-year apple replanting chronosequence and provides correlative evidence linking microbial compositional changes to soil nutrient availability, establishing a baseline for understanding rhizosphere microbiome-soil interactions in replanted orchards.