Temperature-driven deterministic assembly processes facilitate the coexistence of photoautotrophic communities in greenfield biocrusts across China

Aims: Soil photoautotrophic microorganisms, including cyanobacteria and eukaryotic microalgae, play important roles in ecosystem functioning through carbon fixation, nutrient cycling, and the enhancement of soil stability. Understanding their distribution and driving factors is vital for maintaining soil health and environmental sustainability amid climate change. Currently, knowledge about the geographic distribution, community assembly, and environmental drivers of soil photoautotrophic microorganisms remains limited. Methods: In this study, we used environmental DNA (eDNA) analysis to collect photoautotrophic microbial data in greenfield biocrusts, followed by statistical analyses including linear regression, generalized dissimilarity model, co-occurrence network analysis, the Sloan neutral community model, and structural equation model. These methods enabled a comprehensive examination of the distribution patterns and assembly processes of photoautotrophic microorganisms across 57 greenfield biocrusts in China. Results: Our results revealed a strong positive correlation between the diversity of photoautotrophic microorganisms and mean annual temperature. In particular, the α-diversity of cyanobacteria, eukaryotic algae, and the total photoautotrophic community showed a significant decrease from southeast to northwest. Temperature emerged as the primary environmental factor influencing both the α- and β-diversity of these microorganisms. Furthermore, rising temperatures were associated with an increase in deterministic assembly processes, which in turn significantly enhanced species coexistence. These findings suggest that temperature-driven deterministic processes promote higher species coexistence and biodiversity. Conclusions: Our results establish links between environmental temperature, biogeographic patterns, community assembly processes, and species coexistence mechanisms within photoautotrophic communities. Future research could extend upon these findings by investigating additional environmental factors and their interactions with photoautotrophic microbial communities.