Microbial functional trait predicts soil organic carbon across soil aggregates in Northeastern China

Abstract

Soil aggregates offer diverse habitats for microorganisms, characterized by variations in microbial 16S rRNA gene operon (rrn) copy number, a valued functional trait indicative of microbial growth rates and organic matter availability, which is crucial for enhancing soil fertility, nutrient cycling, and ecosystem health. However, the impact of soil aggregate stratification on microbial functional traits, as reflected by rrn copy number, remains unclear. This study revealed that microbial taxonomic composition is significantly different in soil aggregate stratification, with microaggregates favoring higher community-level rrn copy numbers, potentially indicating the prevalence of microbial r-strategists compared to macroaggregates and silt+clay fractions. Additionally, strong positive correlations between soil organic carbon and community-level rrn copy number suggest that rrn copy number serves as a meaningful functional trait reflecting soil organic carbon availability. Overall, this finding provides new insights into how soil aggregate shapes the life-history strategies of microbial communities, soil organic matter content and promote soil health.