COS 104-3 - Drought mediates how fungal communities respond to wildfire in two Californian ecosystems.

Abstract: There is a knowledge gap surrounding how fungal decomposition will be altered under changing environmental conditions, such as drought and wildfire. More specifically, previous research has shown contradictory results regarding whether fungal decomposition rates change when exposed to prolonged drought or wildfire events. We assessed response and recovery of fungal guilds after a severe wildfire burned a long-term drought experiment in a California grassland and coastal sage scrubland. We predicted that wildfire would immediately reduce fungal richness and eliminate any significant differences in richness between the ambient and drought adapted communities. We also predicted that the differences in richness between the drought and control treatments would increase significantly across collection dates as an indication of post-fire recovery. We measured the richness of fungal guilds and conducted a series of pairwise comparisons to assess fungal community response across treatment and collection date. The fire did not immediately reduce richness, regardless of treatment, in either ecosystem. Ambient and drought adapted communities in the grassland had similar richness at the first collection, but later diverged to be significantly different thereafter. The shrubland displayed an opposite trend, as fungal richness differed significantly between control and drought treatments at the first collection, but not for others. Overall, we conclude that drought mediates how fungal communities respond to wildfire in the long term, however the direction of the drought effect may differ across ecosystems.