Soil Microbial Biomass Carbon and Freeze‐Thaw Cycles Drive Seasonal Changes in Soil Microbial Quotient Along a Steep Altitudinal Gradient

Understanding seasonal changes in soil microbial quotient (qMB, i.e., the MBC-to-SOC ratio) along altitudinal gradients and their dominant drivers is essential for determining effects of environmental on organic carbon pool. A 3-year situ core incubation experiment was thus conducted a dry valley shrub, valley-mountain ecotone forest, subalpine coniferous an alpine meadow across 2,431-m gradient eastern Qinghai-Tibetan Plateau. Soil qMB layer (OL) mineral (ML) measured at five critical periods. The average significantly higher than other sites, with no significant difference among sites. this region less global value (1.2%), indicating that pool local ecosystem has stability lower mineralization potential ecosystems globally. Seasonal variations differed gradient. Significant increases during were mainly observed OL altitudes, implying increased sensitivity to changes. Microbial biomass freeze-thaw cycles factors pattern qMB. regime under climate change scenarios will alter balance between SOC assimilation maintenance respiration demands, affecting biogeochemical cycling mountainous ecosystems.