DNA-Based Bacterial Community Profiles in Air-Dried Historical Soil Archives Are More Representative than Those from Rewetted Soils.

Recording and tracking the long-term dynamic changes in microbial populations is as essential as monitoring other soil properties for evaluating soil quality and health; however, this area has significantly lagged due to technical constraints and challenges in storing fresh soil samples. Historically archived soil samples offer a unique opportunity to characterize the temporal dynamics of microorganisms over several decades. To determine whether archived air-dried soils can be utilized for this purpose, we compared the structure and composition of bacterial communities across fresh soils, air-dried soil archives stored for varying durations, and their corresponding rewetted counterparts, all sourced from a long-term fertilization experiment on calcareous loess soil. Soil microbial features were characterized using the MiSeq sequencing platform. The results indicated that the similarity of DNA-based bacterial community composition between fresh soil and both archived and rewetted soils followed a downward quadratic curve as archiving time increased. Specifically, the DNA-based community structure of soils air-dried and preserved for one year, as well as those rewetted after eight years of archiving, remained highly similar to that of fresh soil. Regarding taxonomic shifts, the relative abundance of