Abstract

Soil microbial communities exhibit complex interaction patterns that are significantly influenced by environmental factors, particularly soil pH and organic matter composition. This study investigated the co-occurrence networks of soil microbes across different pH gradients and organic matter fractions to understand microbial community assembly and ecological interactions. We analyzed 120 soil samples from agricultural and forest ecosystems using 16S rRNA and ITS gene sequencing, coupled with comprehensive soil chemical analyses. Network analysis revealed distinct microbial co-occurrence patterns across pH ranges, with acidic soils (pH 4.5-5.5) showing higher network complexity and stronger positive correlations compared to alkaline soils (pH 7.5-8.5). Organic matter fractions, particularly dissolved organic carbon (DOC) and particulate organic matter (POM), emerged as key drivers of microbial network topology. Bacterial networks demonstrated greater stability across pH gradients compared to fungal networks, which showed pronounced shifts in community structure. The study identified 23 keystone taxa that maintained network stability across environmental gradients. These findings provide crucial insights into soil microbial ecology and have implications for sustainable soil management practices in agricultural systems.