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One of the key goals of ecology is to understand how communities are assembled. The species co‐existence theory suggests that community β‐diversity is influenced by species pool and community assembly processes, such as environmental filtering, dispersal events, ecological drift and biotic interactions. However, it remains unclear whether there are similar β‐diversity patterns among different soil microbial groups and whether all these mechanisms play significant roles in mediating β‐diversity patterns. By conducting a broad survey across Chinese deserts, we aimed to address these questions by investing biological soil crusts (biocrusts). Through amplicon‐sequencing, we acquired β‐diversity data for multiple microbial groups, that is, soil total bacteria, diazotrophs, phoD‐harbouring taxa, and fungi. Our results have shown varying distance decay rates of β‐diversity across microbial groups, with soil total bacteria showing a weaker distance‐decay relationship than other groups. The impact of the species pool on community β‐diversity varied across microbial groups, with soil total bacteria and diazotrophs being significantly influenced. While the contributions of specific assembly processes to community β‐diversity patterns varied among different microbial groups, significant effects of local community assembly processes on β‐diversity patterns were consistently observed across all groups. Homogenous selection and dispersal limitation emerged as crucial processes for all groups. Precipitation and soil C:P were the key factors mediating β‐diversity for all groups. This study has substantially advanced our understanding of how the communities of multiple microbial groups are structured in desert biocrust systems. [ABSTRACT FROM AUTHOR]

Aim: Methane oxidation driven by soil aerobic methanotrophs exhibits the largest methane sink capacity in forest ecosystems and plays important roles in the alleviation of global warming. Many studies have revealed the distribution of methanotrophs in forest ecosystems at field scales; however, the biogeographical patterns of methanotrophic communities and related ecological processes and the drivers shaping methanotrophic communities at a large scale remain poorly understood. Location: China's forests. Time period: 2012–2013. Major taxa studied: Methanotrophic communities. Methods: We evaluated the geographical distributions of soil methanotrophic communities across 26 forests along a 4,000‐km north–south transect in China using a MiSeq high‐throughput sequencing technique. The assembly processes and drivers of the methanotrophic communities were evaluated using the phylogenetic null model approach and structural equation modelling, respectively. Results: The results showed that the upland soil cluster α (USCα) and ammonia‐ oxidizing bacteria‐related (AOB‐rel) methanotrophs were the most abundant taxa in forest soils and exhibited contrasting distributions of relative abundance across different climate zones, suggesting that they occupy different environmental niches. The α‐diversity pattern of the soil methanotrophic community followed a hump‐shaped pattern along a large latitudinal gradient. Statistical analyses suggest that aridity and vegetation productivity [here represented with the normalized difference vegetation index (NDVI)] are major drivers of the α‐diversity of the methanotrophic community, whereas soil pH is the key environmental factor shaping the β‐diversity of the methanotrophic community at a large scale. Additionally, the community assembly of the methanotrophs primarily resulted from deterministic processes, among which heterogeneous selection had a greater contribution in shaping the methanotrophic community than homogeneous selection. Main conclusions: Our study provides new insights into the biogeographical distributions, assembly processes and ecological predictors of the methanotrophic community in forest soil at a large scale. These results can be used to improve simulation models for the better prediction of ecosystem functions under predicted global changes. [ABSTRACT FROM AUTHOR]