Soil microbial community abundance responses to plant residue inputs assessed by quantitative PCR

Soil organic matter (SOM) dynamics are closely linked to the abundance of microbial soil communities, which regulate key carbon and nitrogen transformation processes in agroecosystems. This study assessed microbial community abundance in contrasting cropping systems differing in plant residue input and diversity using quantitative PCR (qPCR). Soil samples were collected from different treatments, and microbial abundance was estimated by quantifying bacterial 16S rRNA, archaeal 16S rRNA, and fungal 18S rRNA genes. Archaeal communities consistently predominated across all systems, suggesting soil conditions favorable to microorganisms adapted to stable environments and closely associated with SOM processing. No significant differences in total microbial gene abundance were detected among treatments, indicating limited short-term effects of management on overall community abundance. However, systems with higher biomass input and greater crop diversity showed increased variability in microbial abundance, reflecting enhanced spatial heterogeneity and the formation of distinct microbial niches. These findings indicate that increased organic inputs may reorganize the spatial distribution of microbial communities rather than promote uniform increases in abundance. The qPCR approach proved effective in detecting subtle abundance patterns related to SOM inputs and supports integrative analyses of microbial community organization and soil organic matter dynamics.