Rainfall-induced microbial resuscitation reveals functional decoupling across biocrust succession

Dryland ecosystems rely on infrequent rainfall pulses to activate soil microbial communities, yet the fraction and identity of microbes resuscitating after hydration remain unclear. We applied bioorthogonal non-canonical amino acid tagging coupled with fluorescence-activated cell sorting (BONCAT-FACS) and 16S rRNA gene sequencing to identify translationally active bacteria in early (L-BSC) and late (D-BSC) successional cyanobacteria-dominated biocrusts subjected to simulated rainfall under light and dark conditions. Our results reveal that only a small subset of the microbial community resumes activity within six hours, with higher active cell abundances in mature crusts. Microbial activity patterns were largely independent of light exposure and showed partial decoupling from total community composition, indicating that presence does not predict short-term function. These findings suggest that biocrust maturity shapes microbial activation dynamics and that functional responses to precipitation pulses are governed by a conserved pool of fast responders, informing predictions of dryland soil microbiome resilience under changing precipitation regimes.