Short-term warming shifts microbial nutrient limitation without changing the bacterial community structure in an alpine timberline of the eastern Tibetan Plateau

Abstract

The forest-alpine ecotone is considered susceptible to climate change. Addressing the effects of climate warming on the structure and function of the soil microbial community will provide insights into carbon (C) and nutrient cycling under climate change. A short-term open-top chamber (OTC) experiment was conducted in the alpine timberline of the eastern Tibetan Plateau to test the effects of experimental warming on the soil bacterial community composition, extracellular enzymes, ecoenzymatic stoichiometry and soil physicochemical properties. The results showed that there were no significant changes in the soil bacterial alpha-diversity, composition or community structure in response to soil warming. However, during the early growing season, two carbon-degrading enzymes (β-glucosidase, BG; peroxidase, POD) and microbial carbon limitation decreased with soil warming in the mineral soil layer, which might be a result of an increasing accumulation of soil C. We also observed that C:P enzyme ratios decreased and the relative microbial P limitation increased with soil warming in the organic soil layer. Our db-RDA results demonstrate that both available nutrient pools (dissolved organic carbon and total dissolved nitrogen) and total nutrient concentrations (soil organic carbon and total nitrogen), in addition to soil pH and moisture content, affected soil bacterial communities. These findings suggest that short-term soil warming may change the microbial C and P demand, although bacteria showed temperature adaptability to soil warming.