Arbuscular Mycorrhizal Fungi as Key Drivers of Plant Resilience: Mechanisms of Stress Adaptation in Saline Environments

Arbuscular mycorrhizal fungi (AMF) play a critical role in mediating plant responses to environmental stress, yet their ecological significance in saline wetland restoration remains underexplored. This greenhouse experiment investigated the effects of salinity, root-zone barrier type (solid, mesh, none), and neighboring species identity on AMF colonization and physiological responses in three native estuarine plants: Carex densa, Juncus patens, and Scirpus microcarpus. Results demonstrated species-specific physiological responses to salinity, with Juncus patens showing greater resilience in maintaining photosynthetic efficiency (Fv/Fm) and percent cover at higher salinity levels, while Scirpus microcarpus exhibited a significant decline. Mesh barriers, which permitted fungal but not root connectivity, were associated with increased AMF colonization and elevated electron transport rates (ETR), suggesting that AMF-mediated facilitation was more effective when direct root competition was excluded. Notably, Juncus patens acted as a suppressive neighbor, significantly reducing the percent cover of Carex densa and Scirpus microcarpus under high salinity. A significant three-way interaction among species, barrier type, and neighbor identity on percent cover and AMF presence underscores the complexity of belowground biotic interactions under stress. These findings support the hypothesis that AMF access enhances plant performance under saline conditions and emphasize the importance of spatial partitioning and plant-plant interactions in wetland restoration strategies. This study provides novel insight into how species-specific and community-level dynamics mediate mycorrhizal benefits, informing adaptive management of tidal wetlands in the face of sea level rise.