Transformation-driven reorganization of cross-domain microbial interactomes reflects multifunctionality loss in alpine wetlands

Abstract

Ecosystem degradation restructures soil microbial interaction networks, yet the mechanistic pathways linking network topology to functional decline remain poorly understood. Here, we investigate how grasslandification, that is, “the conversion of alpine wetland meadows into degraded meadows,” alters cross-domain microbial networks across soil depths and plant root compartments on the Tibetan Plateau. Using integrated network analysis, multivariate modeling, and structural equation models (SEMs), we demonstrate that grasslandification drives a systematic restructuring of network architecture through declining connectivity and environmental filtering via soil chemistry and microbial biomass. These networks progressively lost connectivity and became more modular, indicating fragmentation into isolated functional modules with reduced synergistic interactions. Network robustness declined substantially, rendering degraded communities more susceptible to perturbations. Cross-domain ana-lyses revealed that vertical connectivity between soil layers remained intact despite surface degradation, while plant-associated networks became more sensitive, with disrupted rhizosphere-rhizoplane interactions. Keystone taxa shifted from fungal connectors in pristine meadows to bacterial module hubs in degraded meadows, signifying fundamental changes in community assembly. The SEMs highlighted that grasslandification affected soil multifunctionality mainly through indirect pathways mediated by soil chemistry and microbial biomass, while the direct effects of network topology were comparatively weak. This suggested that network changes represent emergent indicators of ecosystem state transitions rather than principal direct drivers of functional loss. We conclude that microbial network restructuring co-occurs with multifunctionality loss during grasslandification, and that network metrics provide early-warning indicators for ecosystem degradation in alpine regions under environmental stress.

Graphical abstract

Keywords

microbial networks / grasslandification / cross-domain interactions / keystone taxa / multifunctionality / alpine wetlands

Highlight

	● Grasslandification restructured microbial network architecture along the gradient.
	● Networks lost connectivity, became more modular, and reduced interactions.
	● Root associated networks were more sensitive to degradation than the bulk soil.
	● Keystone taxa shifted from fungal to bacterial connectors during degradation.
	● Multifunctionality was affected by soil chemistry and microbial biomass C/N.

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