Background and aimsClimate and soil-related variables are two major environmental factors contributing to the spatial distribution of organisms. Elevational gradients can be used to better understand the climate impacts on natural systems given their tight relationship with temperature and precipitation. Soil variables can be used to explain elevational discrepancies at fine scales as they are important predictors of species-specific niches. Dryland ecosystems provide a unique opportunity to better understand the spatial distributions especially regarding biocrusts, a collection of ecologically important organisms (e.g. lichens, mosses, and cyanobacteria) that combine with the soil matrix to colonize the soil surface.MethodsWe sampled biocrusts and bulk soil from 31 sites along a 1,700 m elevation gradient between Phoenix and Flagstaff, Arizona, USA. We explored relationships among biocrust cover, elevation, and parent materials including granite, limestone, basalt, and sandstone. We also measured soil respiration and extracellular enzyme activity at each site as an index of potential microbial activity.ResultsLichen crusts were associated with lower elevations whereas higher moss crust cover corresponded with higher-elevation limestone sites. We found that elevation and soil parent material had significant effects on bulk soil enzyme activity, although the direction of the associations differed among enzymes. There was also a significant positive correlation between overall biocrust cover and electrical conductivity.ConclusionOverall, this natural experiment highlights the complexity of uncontrolled studies and the idea of microtopography as a potential source of unexplained variation. It also emphasizes the importance of better understanding variables such as elevation and soil parent material within analyses of biocrust cover and type (i.e., lichens and mosses).