Light availability and light demand of plants shape the arbuscular fungal communities in their roots

Plants involved in the arbuscular mycorrhizal (AM) symbiosis trade photosynthetically derived carbon for fungal-provided soil nutrients. However, little is known about how plant light demand and ambient light conditions influence root-associating AM fungal communities. We conducted a manipulative field experiment to test whether plants’ shade tolerance influences their root AM fungal communities in open and shaded grassland sites. We found similar light-dependent shifts shifts in AM fungal community structure for experimental bait plant roots and the surrounding soil. Yet, deviation from the sorrounding soil towards lower AM fungal beta-diversity in the roots of shade-intolerant plants in shade suggested preferential carbon allocation to specific AM fungi in conditions where plant-assimilated carbon available to fungi was limited. We conclude that favourable environmental conditions widen the plant biotic niche, as demonstrated here with optimal light availability reducing plants' se...