Climate change legacies contrastingly affect the resistance and resilience of soil microbial communities and multifunctionality to extreme drought

Soil microbial communities largely determine the ability of soils to provide multiple functions simultaneously (i.e. soil multifunctionality; multifunctionality hereafter). However, a major research challenge is understanding how soil microbial communities and associated multifunctionality resist and recover from extreme climate events such as droughts, and how the legacy of past climatic conditions may constrain such responses. Here, we used soils subjected to 7 years of reduced rainfall (~35% reduction), warming (3°C temperature increase) and their combination to assess climate change legacies on the resistance and resilience of both soil fungal and bacterial communities and multifunctionality to a subsequent extreme drought event (2 weeks at 3% water-holding capacity). At the end of the extreme drought, and 1, 15 and 60 days after rewetting, we assessed bacterial and fungal community composition, richness and abundance, as well as a multifunctionality index based on eight functions related with soil carbon (C), nitrogen (N) and phosphorous (P) cycling. Climate change legacies influenced the resistance and resilience of bacterial and fungal abundance to extreme drought, but not those of community composition, richness and multifunctionality. The resistance of bacterial and fungal abundance showed opposite responses to warming and reduced rainfall. Specifically, climate change legacies increased the resistance of fungal abundance, whereas they reduced that of bacterial abundance. The resistance and resilience of multifunctionality to extreme drought were not related to the resistance or resilience of bacterial and fungal communities. Yet, the resistance of multifunctionality was related to that of Chytridiomycota, whereas its resilience was related to that of Proteobacteria. Overall, our results indicate that climate change legacies affected the resistance and resilience of soil bacterial and fungal abundance to a subsequent extreme drought event, but not those of their community composition, richness and multifunctionality. Our results provide new insights on how climate change legacies contrastingly influence the resistance and resilience of soil microbial communities and multifunctionality. Furthermore, our findings highlight the role that specific microbial taxa play in maintaining soil multifunctionality and recovering from extreme drought events predicted under anthropogenic climate change. A free Plain Language Summary can be found within the Supporting Information of this article.