Dual Mycorrhization or Mixed Associations: A Dynamic Strategy for Plant Resilience to Global Change

Symbiotic mycorrhizal fungi are crucial drivers of ecosystem functioning through their associations with plants. Ecosystems dominated by different types of mycorrhizal fungi, such as ectomycorrhizal fungi (EM) and arbuscular mycorrhizal (AM) fungi, often exhibit variation in plant productivity. However, the mechanisms underlying these differences and their dependence on environmental context remain unclear. Furthermore, the lack of robust, fine-scale evidence linking plant productivity to measurable indicators of mycorrhizal colonization or dominance, together with limited information on environmental variables, constrains accurate global-scale modeling of mycorrhizal effects on ecosystem functioning. In this study, we synthesize existing knowledge on the competitive and complementary interactions between the two dominant mycorrhizal types. Building on this synthesis, we propose a new conceptual framework to describe the context-dependent and often idiosyncratic nature of these interactions. We then present case studies and a meta-analysis spanning local to global scales, examining how vegetation biomass is related to mycorrhizal colonization or dominance under different environmental conditions. Our findings indicate that mycorrhizal types and environmental variables interactively shape ecosystem productivity in a dynamic and resilient manner. This work offers a new foundation for spatially explicit, locally informed assessments of how mycorrhizal influence vegetation productivity across contrasting environmental constraints.