Determining microbial metabolic limitation under the influence of moss patch size from soil extracellular enzyme stoichiometry

Biological soil crusts (biocrusts) are crucial elements of desert ecosystems, exhibiting patchy distribution patterns across the soil surface and significantly impacting surface soil nutrient dynamics. However, the influence of biocrust patch units, serving as fundamental functional entities, on microbial nutrient restriction remains underexplored. This study conducted measurements on moss crust patches of varying sizes and subcrust soils. Stoichiometric analysis of extracellular enzyme activities (EEAs) related to carbon, nitrogen, and phosphorus was performed, along with vector and redundancy analyses to evaluate microbial nutrient limitation and key influencing factors. The findings reveal that both patch size and soil layer of biocrusts collectively influence soil nutrients and enzyme dynamics, with heightened enzyme activity observed in the crust layer. Vector analysis based on EEA stoichiometry indicates that moss crust patch size insignificantly impacts microbial nutrient restriction within the crust layer. However, microbial nitrogen restriction in the subcrust layer demonstrates a “single-peak” trend, initially increasing before gradually declining. This suggests that microorganisms in medium-sized crust patches exhibit peak activity, intensifying nutrient competition. This research underscores the pivotal role of biocrust patch units as fundamental functional entities, offering comprehensive insights into microbial metabolic constraints under crust cover. The findings underscore the significant implications of enzyme stoichiometric characteristics for desert land management and conservation.