Exogenous resources drive convergent successional processes within soil microbial food web in two soil types

Soil microorganisms mediate critical ecosystem processes, including nutrient cycling and climate regulation. However, the extent to which their functional resilience and microbial food web dynamics respond uniformly to organic amendment across two land-use types remain poorly understood.

In this study, we conducted a 30-day microcosm experiment to investigate how exogenous resources addition restructures the assembly of primary microbial functional groups (bacteria, fungi, and protists) in urine-amended soils under contrasting land-use regimes: intensively managed maize fields and natural woodlands. Results showed that straw addition consistently reduced both OTU richness and Shannon diversity of bacteria (by 8% and15%, respectively), fungi (26% and 21%), and protists (21% and 29%) in both soil types, yet enhanced cross-domain microbial interactions. Co-occurrence network analysis revealed variation in trophic interaction based on network parameters: maize soils fostered bacteria-dominated networks, whereas fungal hubs dominated in woodland systems. Deterministic processes predominantly govern bacterial community assembly, contrasting with the stochastic dominance observed in fungal and protist communities. Notably, both land use regimes showed consistent decreases in α-diversity, increased network complexity, and shifts toward similar assembly processes despite initial differences in community structure.

Our findings demonstrate that organic amendments can override land-use legacies in shaping microbial community dynamics, highlighting the integrated impact of availability and biotic interactions in driving soil microbial food web dynamics.