Air-dried soils for microbial biogeography

The potential of archived air-dried soil samples to enhance our understanding of long-term microbial community dynamics remains largely untapped due to concerns about their reliability for molecular analyses. While previous studies have investigated air-drying effects on soil microbial analysis, few have examined these effects across diverse environmental gradients, limiting our understanding of archived soil samples in microbial biogeography at large spatial scales. Through a comprehensive regional survey of 244 arable sites in eastern China, we evaluated the impact of air-drying on microbial biogeographical analysis. Our results demonstrate that while air-drying significantly altered community composition and diversity metrics, it preserved broad ecological patterns and environmental relationships. Air-dried samples maintained similar community dissimilarity patterns and environmental drivers as fresh samples, despite showing reduced diversity and shifted taxonomic compositions. Co-occurrence network analysis revealed altered correlation patterns, likely due to differential responses to desiccation stress. These findings establish a framework for leveraging air-dried samples in microbial ecology, particularly for large-scale studies focused on microbial biogeography and environmental relationships, while providing practical guidelines for results interpretation.