Arbuscular mycorrhizal fungi in changing mountain grassland ecosystems: a challenge for research

Abstract

Even though arbuscular mycorrhizal fungi (AMF) are present from foothills to all alpine habitats, research on their role in mountain ecosystems remains incomplete. Here we provide a literature review of the ecology and functioning of AMF in mountain ecosystems, as well as their response to global change. We investigated how AM fungal abundance, community composition, and fungal traits are studied under field conditions and are affected by altitude, habitat patchiness, succession, host identity, seasonality, and interaction with other living organisms. The effects of climate change, nutrient enrichment, land-use change, and their interactions are also addressed in this review, as well as the possible applications of AMF for grassland restoration. We show that altitudinal effects on AMF are blurred by other environmental gradients and by host-plant identity. The benefits to plants and possible facilitation effects by AMF in mountain ecosystems have not yet been identified. Based on the stress-gradient hypothesis, the symbiosis between plants and AMF should become more mutualistic with increasing environmental stress. We propose a working hypothesis for the functioning of the AMF–plant interaction along altitudinal gradients by grading it along the mutualism–parasitism continuum, considering current and global climate and environmental change conditions. We conclude by suggesting further research directions.