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

Abstract

Soil aggregates offer diverse habitats for microorganisms, which can be characterized by variations in the microbial 16S rRNA gene operon (rrn) copy number. The rrn copy number is considered a functional trait that is indicative of microbial growth rates and organic matter availability, which is linked to soil fertility, nutrient cycling, and ecosystem health. However, the impact of soil aggregate fraction on microbial functional traits, such as the rrn copy number, remains unclear. This study revealed that microbial taxonomic composition differs significantly according to the soil aggregate fraction, with a higher community-level rrn copy numbers in microaggregates, potentially indicating the prevalence of microbial r-strategists, compared to macroaggregates and silt+clay fractions. Additionally, the strong positive correlation between soil organic carbon and community-level rrn copy number suggested that the rrn copy number is a meaningful functional trait of soil organic carbon availability. Overall, this study provides new insights into how soil aggregate fractions may shape the life-history strategies of microbial communities, soil organic matter content and promote soil health.