Network architecture across trophic levels governs ecosystem multifunctionality in subtropical riparian soils

Abstract

Soil multifunctionality in riparian zones regulates the transfer of energy, matter, and biodiversity across landscapes, yet the mechanisms sustaining this multifunctionality remain inadequately understood. Here, we conducted a field investigation across subtropical riparian zones along three major rivers in southeastern China—the Minjiang, Jiulong, and Jinjiang Rivers—to examine the relationships between soil microbial biodiversity, co-occurrence network complexity, and soil multifunctionality (SMF). Our finds revealed that fungal α-diversity, particularly the richness of symbiotrophic and saprotrophic fungi, and soil organic carbon (SOC) content were the primary biotic and abiotic predictors of SMF, respectively. Additionally, fungal richness, niche width, and the stability of the fungal community were significantly correlated with SMF. Structural equation modeling indicated potential trophic linkages within the microbial food web, where greater diversity of higher trophic levels enhanced SMF, likely through cascading effects on the diversity and composition of lower trophic levels. Notably, the complexity of microbial co-occurrence networks, especially among lower trophic levels, exerted a significant positive influence on SMF. Overall, these results highlight the crucial role of multitrophic microbial network structure in sustaining riparian ecosystem functions. These insights provide a mechanistic framework for riparian ecosystem management, emphasizing that conservation of keystone fungal guilds (e.g., symbiotic and saprotrophic fungi) and enhancement of SOC sequestration should be central to riparian restoration efforts.