Linear responses of soil microbiomes, metagenomic and metabolomic functioning across ecosystems along water gradients in the Altai region, northwestern China

Abstract

Abstract Background To investigate microbial communities and their contributions to carbon and nutrient cycling along water gradients can enhance our comprehension of climate change impacts on ecosystem services. Results We conducted an assessment of microbial communities, metagenomic functions, and metabolomic profiles within four ecosystems, i.e., desert grassland (DG), shrub-steppe (SS), forest (FO) and marsh (MA) in the Altai region of Xinjiang, China. Soil total carbon (TC), total nitrogen, NH4+, and NO3- increased linearly, but pH decreased with soil water gradients. Microbial abundances and richness also increased with soil moisture except the abundances of fungi and protists being lowest in MA. Within prokaryotes, the relative abundances of Proteobacteria and Acidobacteria increased, whereas those of Actinobacteria and Thaumarchaeota decreased along water gradients. In fungi and protists, Basidiomycota and Mortierellomycota, Evosea and Endomyxa became dominant in FO and MA, respectively, but the relative abundance of Cercozoa decreased along soil moisture gradients. The β-diversity of microbiomes, metagenomic and metabolomic functioning were linearly distributed along soil moisture gradients, significantly associated with soil factors of TC, NH4+, and pH. For soil metagenomic functions, the metabolic genes related to Carbohydrate (CO2 fixation, Di- and oligosaccharides, Fermentation, and One-carbon metabolism), Iron (Iron acquisition in Vibrio and Campylobacter iron metabolism) decreased with soil moisture, while genes related to the metabolisms of Nitrogen (Ammonia assimilation, Denitrification, Nitrogen fixation, and Nitrosative stress) and Potassium (Potassium homeostasis) increased linearly along water gradients. Additionally, MA harbored the most abundant metabolomics dominated by lipids and lipid-like molecules (Erucic acid, Hypogeic acid, and Kojibiose, etc.), and organic oxygen compounds (Maltotetraose, Quinone, Sucrose, and Trehalose, etc.), except certain metabolites showing decline trends along water gradients, such as N'-Hydroxymethylnorcotinine and 5-Hydroxyenterolactone. Conclusions Our study suggests that future ecosystem succession facilitated by changes in rainfall patterns will significantly alter soil microbial taxa, functional potential and metabolite fractions.