The scheme depicts sampling time points for different experiments during the hydration/desiccation cycle under controlled day and night conditions in a climate chamber. The sampling time points were defined based on preliminary experiments. The biocrusts were hydrated to 75% of their water holding capacity corresponding to 26% water content/wet weight. Overall, eight time points were sampled in five replicates for the metatranscriptome investigations (blue). Triplicates were selected for sequencing based on their water content. For NanoSIMS analysis, biocrusts were incubated in a parallel experiment with 30% deuterium oxide (heavy water) and destructively sampled at four incubation times spanning the first 24 h after hydration (green). To monitor H 2 oxidation and respiration in dry and hydrated conditions, biocrust samples were incubated in triplicates over a period of several months for the dry and up to 24 h for the hydrated biocrusts (yellow). Gray shading indicates night-time incubation conditions.
