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Recent studies have shown the significant effects of environmental selection and possible dispersal limitation on soil fungal communities. However, less is known about the role of soil depth in fungal community assemblages, especially under soil environments that are intensely cold, infertile and water-deficient. In Ngari drylands of the Asiatic Plateau, we studied fungal assemblages at two soil depths, using Illumina sequencing of the ITS2 region for fungal identification (0–15 cm as the surface soil and 15–30 cm as the subsurface soil). Fungal diversity in the surface soil was much higher than that in the subsurface soil ( P < 0.001), and communities differed significantly between the two layers ( P = 0.001). Neither soil properties nor dispersal limitation could explain variation in the surface-soil fungal community. For the subsurface, by contrast, soil, climate and space explained 27% of variation in fungal community. Collectively, these results point to high dispersal rates and absence of edaphic effects in the surface-soil fungal community assemblage in Ngari drylands. It also suggests that for soil fungi with highly effective dispersal, regional distributions may fit with Bass-Becking's paradigm that ‘Everything is everywhere’. [ABSTRACT FROM AUTHOR]

Microbial necromass carbon (MNC) is key to soil organic carbon (SOC) storage. However, mechanisms regulating MNC accumulation on large scales are poorly understood. Here we provide the first batch of regional-scale MNC data based on amino sugars for the Qinghai-Tibet Plateau alpine grasslands. We show that Qinghai-Tibet grasslands have similar microbial biomass carbon (MBC) but lower MNC concentrations in SOC than Mongolian and other grasslands. The low contribution of MNC to SOC is mainly attributed to high aridity and low net primary productivity of the Qinghai-Tibet grasslands. Our findings highlight climatic and plant influences on MNC accumulation at regional scales. • Qinghai-Tibet grasslands have lower microbial necromass carbon (MNC) in SOC. • The MNC content of grasslands is regulated by aridity at global scale. • Low MNC in Qinghai-Tibet grasslands is attributed to the low NPP and high aridity. [ABSTRACT FROM AUTHOR]