Dynamic changes of rhizosphere soil properties and microbial communities across apple replanting years
Introduction: A comparative study of newly planted and replanted apple orchards has revealed differences in rhizospheric soil properties and microbial communities; yet, the failure to identify the key pathogenic and soil factors associated with different replant years has created a disconnect between existing control measures and the actual demands of orchard management.Methods: This study collected rhizospheric soil samples from control (CK, 2-year newly planted) and 2-7-year-old replanted (Y2-Y7) apple trees. Comprehensive analyses were conducted, including the determination of soil physicochemical properties and the profiling of microbial communities through 16S rDNA amplicon sequencing (for bacterial communities) and Internal Transcribed Spacer (ITS) sequencing (for fungal communities).Results: The results demonstrated that the rhizospheric soils of Y2-Y7 apple trees exhibited significantly lower levels of alkali-hydrolyzable nitrogen (AK), available phosphorus (AP), total nitrogen (TN), total potassium (TK), available zinc (AZn), and available copper (ACu) compared to CK, while the content of exchangeable magnesium (Ex-Mg) was notably higher. High-throughput sequencing yielded 5,883 bacterial ASVs and 2,063 fungal ASVs. Comparative analysis revealed that the relative abundance of Bacillota and Pseudomonadota were increased in Y2-Y7 soils compared to other sites, whereas Ascomycota represented the absolutely dominant group across all sampling sites. Alpha diversity analysis indicated no significant differences in bacterial diversity across sampling points. Correlation analysis suggested that environmental factors influenced microbial community composition, with fungal communities being particularly affected by soil nutrient availability. Fungal community variation was primarily regulated by pH and soil nitrogen content, where elevated pH significantly altered community structure.Conclusion: This study characterizes the dynamic changes of rhizosphere soil properties and microbial communities across 2-7 years of apple replanting, providing critical data to decipher microbe-soil nutrient interactionsproviding correlative data on the associations between microbial community composition and soil nutrient availability underlying continuous replanting obstacles, and provides fundamental ecological data for understanding rhizospheric microecological variation in replanted apple orchardsprovides baseline ecological data describing rhizospheric microecological variation across replanting years.