Arbuscular mycorrhizal fungal communities in forest plant roots are simultaneously shaped by host characteristics and canopy-mediated light availability

The majority of terrestrial plant species associate with arbuscular mycorrhizal (AM) fungi, to exchange carbon compounds with nutrients. However, the factors that determine the composition of AM fungal communities in individual plant roots remain poorly understood. We hypothesized that AM fungal communities are simultaneously influenced by environmental conditions, such as light availability, and the photosynthetic capacity of host plant species. We sampled individuals of shade-tolerant and shade-avoidant plant species, growing in the presence and absence of forest canopy, representing conditions of low and high light availability. We recorded photosynthetic parameters, shoot biomass and root AM fungal colonisation of these plant individuals and used 454-sequencing to characterise AM fungal communities in the roots of these plants. Shade-avoidant plant species increased their photosynthetic capacity more than shade-tolerant plant species as a response to increased light availability due to canopy removal. Root AM fungal colonisation of all plants was higher when the forest canopy was absent, but canopy status had little influence on AM fungal richness in plant roots. The composition of AM fungal communities associating with shade-tolerant plants was significantly influenced by canopy status, while a less pronounced difference was observed among shade-avoidant plants. We suggest that both environmental conditions and the ability of plant species to exploit available resources determine the dynamics of mutualistic associations between host plant species and AM fungal taxa.