Soil microbial and nematode community responses associated with aerial thiacloprid spraying history in Pinus tabulaeformis forests of the Qinling Mountains

BACKGROUND: Aerial insecticide application is an important component of pine wilt disease vector control, yet few studies have examined whether belowground communities across multiple taxa differ consistently among forests with contrasting management histories. We compared unsprayed Pinus tabulaeformis forests (Control) with forests last sprayed with thiacloprid approximately 2 years (AST-2) or 4 years (AST-4) before sampling in the eastern Qinling Mountains. Soil was collected at 0-10 and 10-20 cm depth from three independent plots per category. Amplicon sequencing was used to compare community composition, diversity and ordination patterns. RESULTS: Bacterial communities were dominated by Acidobacteriota, Pseudomonadota and Actinomycetota, whereas Ascomycota and Basidiomycota predominated among fungi. Bacterial and fungal communities showed clearer separation among spraying-history categories in ordination space than the overall nematode community, which overlapped more extensively. Plant-parasitic nematodes showed some separation among categories. Bacterial and nematode Shannon diversity showed no consistent increase or decrease across spraying histories, whereas fungal Shannon diversity was generally higher in AST-2. CONCLUSION: Differences among forests with contrasting spraying histories were expressed primarily in community composition, with contrasting patterns among nematode feeding guilds. These findings can inform the monitoring of belowground communities in forests subject to chemical pest management.