摘要：Microbiota are essential components of the soil, driving biogeochemical cycles. Fungi affect decomposition and biotic interactions with plants across scales. Climate projections suggest that extended dry seasons may transform sensitive rainforests into savanna-like vegetation, with consequent changes in biogeochemistry. Here we compare the impacts of natural seasonality with 14 years of partial throughfall exclusion in an Amazonian rainforest, focussing on soil fungal functional diversity, extracellular soil enzyme activities (EEA) and their implications for nutrient dynamics. Large changes in fungal diversity and functional group composition occur in response to drought, with aconspicuous increase in the abundance ofdark-septate fungi and adecrease in fungal pathogens. The high seasonality of EEA in the control(non droughted) and suppression of seasonality in the drought treatment, together with an increased implied nitrogen demand in the dry season induced by experimental drought, suggest that the changed soil microbiota activity may signal a pending shift in the biogeochemical functioning of the forest. Long-term experimental drought in the Amazon rainforest leads to shifts in soil fungal community composition, soil enzyme activities that indicate nitrogen limitation, and an increase in the relative abundance of drought-resistant dark septate fungi.
