Light availability and light demand of plants shape the arbuscular mycorrhizal 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 in AM fungal community structure for experimental bait plant roots and the surrounding soil. Yet, deviation from the surrounding 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' selectivity for specific AM fungi, and promote compatibility with a larger number of AM fungal taxa.

Automated summary

This study found that plants' shade-tolerance influences their root arbuscular mycorrhizal (AM) fungal communities, with shade-intolerant plants showing lower AM fungal beta-diversity in shaded conditions due to preferential carbon allocation to specific AM fungi when plant-assimilated carbon available to fungi was limited. Favourable environmental conditions, such as optimal light availability, reduce plants' selectivity for specific AM fungi and promote compatibility with a larger number of AM fungal taxa.