Short-term microbial community responses to an intense simulated precipitation pulse in the hyperarid Atacama Desert soil

Understanding how microbial communities from hyperarid environments respond to sporadic water availability is crucial for predicting ecosystem responses to unpredicta-ble precipitation related to climate change. Here, we experimentally simulated a short-term precipitation pulse (50 mm) in soils from the hyperarid Atacama Desert to evaluate shifts in microbial community composition, diversity, and functional potential, as well as changes in soil physicochemical properties. Using a microcosm experiment with time-structured sampling and high-throughput amplicon sequencing, we found that changes in soil properties after precipitation do not significantly influence micro-bial community composition. However, carbon dynamics exhibit significant variation. Actinobacteria and Proteobacteria dominated bacterial communities, exhibiting func-tional stability over time, which suggests high resilience. In contrast, fungal communi-ties, primarily composed of Ascomycota, displayed greater temporal variation in both taxonomic and functional profiles, particularly during intermediate hydration stages. Notably, fungal functional richness increased despite a limited taxonomic change, in-dicating lower redundancy and, thus, potentially higher community fragility. Our findings highlight distinct microbial strategies for coping with hydration pulses in ex-treme drylands, underscoring the role of fungi in nutrient cycling, decomposition, and soil structure, while also revealing their increased vulnerability to environmental fluc-tuations. Our results reinforce the importance of microbial dynamics in maintaining ecosystem functioning in pulse-reserve systems under ongoing climatic changes.