Spore traits mediate disturbance effects on arbuscular mycorrhizal fungal community composition and mutualisms

Trait-based approaches in ecology are powerful tools for understanding how organisms interact with their environment. These approaches show particular promise in disturbance and community ecology contexts for understanding how disturbances like prescribed fire and bison grazing influence interactions between mutualists like arbuscular mycorrhizal (AM) fungi and their plant hosts. In this work we examined how disturbance effects on AM fungal spore community composition and mutualisms were mediated by selection for specific functional spore traits at both the species and community level. We tested these questions by analyzing AM fungal spore communities and traits from a frequently burned and grazed (bison) tallgrass prairie system and using these spores to inoculate a plant growth response experiment. Selection for darker, pigmented AM fungal spores, changes in the abundance and volume of individual AM fungal taxa, and altered sporulation, were indicators of fire and grazing effects on AM fungal community composition. Disturbance associated changes in AM fungal community composition were then correlated with altered growth responses of Schizachyrium scoparium grass. Our work shows that utilization of trait-based approaches in ecology can clarify the mechanisms that underly belowground responses to disturbance, and provide a useful framework for understanding interactions between organisms and their environment.