Plant-associated fungi can ameliorate abiotic stress in their hosts, and changes in these fungal communities can alter plant productivity, species interactions, community structure and ecosystem processes. We investigated the response of root-associated fungi to experimental drought (66% reduction in growing season precipitation) across six North American grassland ecosystem types and six foundation grass species to determine how extreme drought alters the fungal rhizobiome and which abiotic factors influence fungal rhizobiome composition across grassland ecosystems.
Results/Conclusions
Next generation sequencing of the fungal ITS2 region demonstrated that drought primarily re-ordered fungal species’ relative abundances within host plant species. Grass species whose percent cover decreased due to drought tended to have fungal communities that resisted reordering. Host identity and grassland ecosystem type defined the magnitude of drought effects on community composition, diversity, and root colonization, and the most important factor affecting fungal composition was plant species identity. Across ecosystems, latitude and soil pH were better predictors of fungal diversity than the drought treatment. Drought significantly reduced fungal diversity and evenness only in sideoats grama, Bouteloua curtipendula, and reduced root colonization only in blue grama, B. gracilis. Our results illustrate that predicting the effects of drought on fungal rhizobiomes requires attention to host plant identity and site. By comparing our results to soil microbe responses in the same experiment, we propose the hypothesis that fungi in plant roots are less sensitive to drought than fungi inhabiting soils. The complexity of root-associated fungal communities highlights the importance of studying community-level reordering of fungal composition for understanding plant responses to climate change.