Vascular plants associate with microbial root-symbionts, enhancing resources acquisition and influencing key ecosystem processes that ultimately shape ecosystem resilience and disturbance responses. Root-symbiont associations in the rhizosphere and rhizoplane may be particularly important in tropical ecosystems, where primary production is often limited by belowground resource availability. However, research on root-microbial symbionts has focused largely on the organismal-level, while the role of these symbionts on ecosystem-level functioning and their contribution to ecosystem resilience remains relatively unexplored.

Microbial root-symbionts influence ecosystem processes through their symbiotic relationship with plants, but can also directly influence ecosystem-level processes and traits. Mycorrhizal fungi influence biogeochemical cycling by secreting carbon compounds and extracellular enzymes. Mycorrhizae also affect plant and soil microbial community composition by affecting dispersal, establishment and competition. The predominance of different mycorrhizal groups leads to distinct microbial communities, altering soil carbon transformation rates, nutrient cycling and plant diversity. For example, ectomycorrhizal fungi directly decomposes organic matter, slowing decomposition and lowering nitrogen availability, while arbuscular mycorrhizae dominated environments favor the increase in bacterial biomass that uses inorganic nutrients and decomposes organic matter faster. It remains unknown how the net impacts of mycorrhizal functioning differ in tropical forests compared to temperate ones, where previous research has been based. Root symbionts can also influence plant host’s physiology through increased stress tolerance. Nitrogen-fixing bacteria, though symbionts to only a subset of plants, have large implications for biogeochemical cycling, plant community composition, and restoration rates of tropical ecosystems. There is growing evidence of tripartite relationships among plants, fungi and nitrogen-fixing bacteria that can influence how ecosystems respond to environmental change. Thus understanding the ways in which root-symbionts can influence forest function and how these symbioses are affected by environmental change is critical for understanding ecosystem-level resilience.

We aim to emphasize the effects that tropical root-symbionts have on whole ecosystem processes including nutrient cycles and forest growth, and bridge conceptual and collaborative links between mycorrhizal and nitrogen-fixing symbiont research, to improve understanding of tropical forest function and resilience. The primary goals of our symposium include the exploration of root-microbial symbiont: 1) influence on the connection between below- and above-ground ecosystem function and 2) role in belowground drivers of tropical forest resilience, while highlighting new and emerging evidence for root-symbiont effects on tropical forest resilience. Through this symposium we will promote a collaborative discussion for new future research directions for deepening our understanding of how root-symbionts shape and maintain tropical forest resilience.