Marine fog is a key non-rainfall water source that sustains microbial activity and transports dissolved nutrients inland, influencing early soil development in hyperarid ecosystems. However, the mechanisms through which sustained fog inputs drive soil surface modification and biocrust formation remain poorly understood. This study evaluated the effects of long-term fog augmentation on soil surface development, biocrust dynamics, and associated microbial communities in the Atacama Desert. We implemented a four-year fog addition field experiment with three sampling times (T0, T24, T48) to assess changes in soil physicochemical properties, biocrust composition, and the integrated multi-diversity of archaea, bacteria, fungi and protist. Sustained fog input transformed bare soils into biological soil crusts, particularly lichen- and moss-dominated stages. This transition was accompanied by increases in soil nitrogen, variations in organic matter accumulation, a shift from alkaline to near-neutral pH, and improvements in soil stability and water retention. Multi-diversity increased over time and was positively associated with ecosystem variables linked to water availability, structural stabilization, and decomposition. These functions, integrated into an ecosystem multifunctionality index, also increased under prolonged fog input, revealing a positive relationship between multifunctionality and multi-diversity. Overall, the results demonstrate that sustained fog input strongly enhances early soil surface development and biocrust establishment, highlighting the ecological importance of marine fog in shaping biodiversity and ecosystem functioning in hyperarid landscapes.

SUMMARY: 1) Herbivores shape multiple facets of biodiversity patterns and ecosystem processes, yet are increasingly threatened by habitat loss and climate change. Here, we use a long-term experiment to examine how excluding herbivores, a proxy for biodiversity loss, restructures dominant plant ecological strategies within and across species. 2) We measured twelve functional traits of four dominant annual plant species in the semi-arid shrublands of Chile. We evaluated changes in trait distributions within and across species and changes in the coordination between above- and below-ground strategies in response to vertebrate herbivore exclusion. 3) Our study reveals three dominant ecological strategies characterizing trait variation within and across species, with an increase in the coordination between above- and below-ground strategies in the presence of herbivores. Our results show that herbivores induce shifts in ecological strategies, leading to conservative resource use, increased herbivore tolerance, reduced collaboration with soil microorganisms, and greater intraspecific diversity, facilitating species coexistence. 4) We empirically demonstrate how herbivores shape ecological strategies within and across species, and demonstrate that the absence of herbivores alters the diversity of adaptation strategies of plants and leads to a decoupling of resource acquisition strategies above- and below-ground. These results advance understanding of annual plant responses to herbivore loss.

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.

Marine fog represents a critical but variable water resource in hyperarid coastal regions, yet its chemical variability at the event scale and meteorological controls remain poorly characterized. This study provides an event-based characterization of fog water chemistry at Alto Patache (~20°S), Atacama Desert, Chile, based on 28 fog events sampled between 2022 and 2024 using a Caltech Active Strand Cloudwater Collector (CASCC) with meteorological monitoring. Seven chemical parameters were measured in situ (alkalinity, hardness, pH, phosphate, ammonium, nitrite, and nitrate), and k-means clustering identified three chemically distinct regimes: dilute (Cluster 0, n = 19), enriched (Cluster 1, n = 6), and buffered (Cluster 2, n = 3), validated by permutation-based analysis (PERMANOVA, p < 0.001). Fog events with higher water yields are associated with better water quality: fog water volume showed the strongest relationship with solute concentration, consistent with a dilution mechanism, with high-yield events showing substantially lower ionic concentrations. Event duration and wind speed exhibited secondary complementary patterns, while wind direction had no clear relationship with fog chemistry. These findings indicate that fog water quality is closely linked to event-scale hydrological processes, with direct implications for fog harvesting management, water quality assessment, and understanding biogeochemical subsidies in fog-dependent ecosystems.