Saldivar-Diaz, ManuelManuelSaldivar-DiazBarra, Patricio J.Patricio J.BarraMerino, CarolinaCarolinaMerinoLarama, GiovanniGiovanniLaramaRodriguez, RodrigoRodrigoRodriguezRumpel, CorneliaCorneliaRumpelRómulo Oses PedrazaDuran, PaolaPaolaDuran2026-07-062026-07-062026JOURNAL OF SOIL SCIENCE AND PLANT NUTRITION (2026). https://doi.org/10.1007/s42729-026-03244-20718-9508https://hdl.handle.net/20.500.12740/24554Purpose Biological soil crusts (biocrusts) regulate carbon (C) and nitrogen (N) cycling, but microbiome functional convergence across Chilean pedoclimatic settings remains unclear. We tested whether Chilean biocrusts spanning the hyperarid Atacama and cold Patagonia share a small cross-site core of amplicon sequence variants (ASVs) and show limited convergence in inferred functions. Methods We measured biocrust physicochemical variables and sequenced bacterial 16S rRNA gene (V3-V4) and fungal ITS2 amplicons from four sites (n = 12). We quantified cross-site shared core and site-exclusive ASV fractions using prevalence-based occurrence criteria, related community composition to edaphic variables using distance-based redundancy analysis (dbRDA) and inferred bacterial and fungal functional profiles from taxonomic annotation. Results Physicochemical profiles distinguished alkaline-saline Atacama from acidic Patagonia with higher Al-related metrics. dbRDA was significant (16S: p = 0.001, adjusted R-2 = 0.756; ITS2: p = 0.002, adjusted R-2 = 0.457) and tracked cation exchange capacity versus aluminum saturation and total nitrogen. The cross-site core comprised 10.4% (16S) and 11.8% (ITS2), whereas site-exclusive fractions dominated (67.4% and 70.6%). Aerobic chemoheterotrophy was the dominant inferred bacterial function (23.5-48.8% of ASVs); hydrocarbon degradation peaked in PAI (21.4%) and N fixation in LUN (12.0%). Fungal guilds were site-biased (higher Endophyte-Plant Pathogen in Patagonia; parasitic categories in Atacama). Conclusions Biocrust microbiomes across Atacama and Patagonia are taxonomically distinct, with a small shared ASV core and large site-exclusive fractions, and inferred functions showed limited convergence. These patterns suggest that biocrust-derived inocula should prioritize local provenance and site-specific edaphic and climatic matching.PDFCreative Commons Attribution 4.0 International (CC BY 4.0)https://creativecommons.org/licenses/by/4.0/Biological soil crustsExtreme environmentsMacrogeographic variationMicrobial diversityAmplicon sequencingFunctional inferenceMULTIPLEPRECIPITATIONSETSArticulohttps://doi.org/10.1007/s42729-026-03244-2