With increasing temperature and changing precipitation regimes in the Midwestern United States due to climate change, temperate forest trees will have to adapt to new climatic conditions or shift ranges to track historic climates. Root associated microbes may aid tree survival and evidence suggests that temperate forest tree populations can adapt to local microbial communities. Specifically, different mycorrhizal fungal symbioses associated with forest trees may impact tree seedling success when facing a changing climate. We tested whether microbial communities sourced from locations local or foreign to tree seedling source populations influence tree seedling tolerance of drought. We grew seedlings of two species of forest trees, one an arbuscular mycorrhizal fungi (AM) associated tree, Acer negundo, and the other an ectomycorrhizal fungi (EM) associated tree, Quercus rubra, in both a greenhouse setting where temperatures and precipitation were manipulated and in the field where precipitation was reduced. We inoculated the tree seedlings with live soil either from the same site as population of the tree seedling (local) or from five sites foreign to the tree seedling population as a novel microbial community.
Results/Conclusions
We measured seedling growth and survival, and characterized the microbial populations using ITS metabarcoding to investigate how AM and EM species respond to different microbial taxa under different climate conditions. During year 1 we found that imposing warmer temperatures and drought increased the effect that microbial community source had on greenhouse grown Acer negundo tree seedling biomass and found a positive correlation between fungal diversity and greenhouse grown Acer negundo tree seedling biomass. We did not see this trend with greenhouse grown Quercus rubra tree seedlings; however, we repeated the experiment in year 2 and found significant variation in growth among the populations of greenhouse grown Quercus rubra tree seedlings within our greenhouse treatments. These results reveal the differences EM and AM associating trees may have in their response to their local microbial communities as climates change.