Microbial metabolic limitation response to experimental warming along an altitudinal gradient in alpine grasslands, eastern Tibetan Plateau

Alpine grassland is an important carbon (C) pool in terrestrial ecosystems, and the response of microbial metabolism to warming along an altitudinal gradient is essential for soil C stabilization. However, the patterns and drivers of soil microbial metabolism in the alpine grassland at different altitudes under warming remain poorly understood. Here, according to soil enzymatic stoichiometry, we observed that microbial metabolism was limited by C and phosphorus (P) in the alpine grassland ecosystem, eastern Tibetan Plateau, and microbial C limitation increased with altitude from 3800 to 4200 m despite the topsoil (0-5 cm) or subsoil (5-10 cm). Experimental warming significantly decreased microbial C limitation in the topsoil, but not the subsoil. The significantly negative correlation between microbial C and P limitation in both topsoil and subsoil suggests that the alleviation of C limitation after warming may aggravate the microbial P limitation. Furthermore, the contents and ratio of nutrients and microbial biomass mainly affected microbial C and P limitation in the alpine grassland, respectively. Our results indicated that climate warming could modulate microbial metabolic limitation in alpine grassland soils and thus soil C sequestration by regulating nutrient availability and microbial biomass. This study provides an insight into the microbial regulation of nutrient cycles global warming, which is helpful for ecosystem C cycling in alpine grassland.