Mycorrhizal fungi are ubiquitous symbionts of land plants, are vital for plant growth and have been studied in an ecological context for well over a century. While we have gained tremendous insight into the evolution, physiology and partner identity of these plant-fungal symbioses, we are still lacking synthetic understanding of their role in ecosystems. Conceptual and theoretical frameworks recently developed describe how mycorrhizal fungi influence ecosystem properties and modulate processes within systems. Our organized oral session will highlight some of these recent advances with a core focus on the role of mycorrhizal fungi from an ecosystem perspective in which macroscopic pattern and process emerges from local organism-environment interactions and long-term dynamics of inputs and losses. Our goal is to facilitate discussion and idea exchange among a broad range of ecologists who conduct research in this emerging area. We will focus on biogeochemical consequences of mycorrhizal fungi, including elemental fluxes among plants, soils, atmosphere and hydrosphere, with the recognition that these fluxes are ultimately organized at the level of individual plants and fungi. To motivate conceptual advance, we will discuss processes from fine scales (e.g., gene expression, extracellular enzyme activity, decomposition and nutrient acquisition) to increasingly coarse scales, which capture the importance of trait assembly within mycorrhizal fungal communities and interactions with other soil micoorganisms. Most broadly, we will discuss how mycorrhizal symbioses may give rise to patterns and processes at the scale of ecosystems and biomes, including how the dominance of mycorrhizal types (i.e., arbuscular and ectomycorrhizal symbioses) influence biogeochemical cycling. This synthetic understanding of mycorrhizal fungi across scales is critical for the accurate representation of microbial-plant interactions in Earth system models that simulate the terrestrial carbon cycle and global change.