Abstract:Under the background of greater temperature increase in high latitude and high elevation areas, the distribution ratio of soil organic carbon fractions in the alpine and subalpine forest and its feedback to temperature increase need to be expounded. On the Tianshan Mountains, there are temperate coniferous forests with Picea Schrenkiana as the monodominant tree species. Furthermore, on the northern slope of the middle Tianshan Mountains at an elevation range of about 1760-2800 m, the zonal and patch distribution of Picea Schrenkiana with an elevation drop of more than 1000 m makes it convenient to exclude the influence of mingled forest to determine the altitudinal distribution ratio of the soil organic carbon (SOC) fractions and the response of the distribution difference to climate change. In this study, the sampling plots were set along the altitudinal gradients, and soils were sampled from different soil layers to determine the altitudinal variation of the total soil organic carbon pool (CSOC), active carbon pool (Ca), slow carbon pool (Cs), passive carbon pool (Cp), and microbial biomass carbon (MBC). Besides, the carbon pool activity (A), carbon pool activity index (AI), carbon pool index (CPI) and soil organic carbon density (SOCD) were also determined to explore the altitudinal variation of SOC fractions on the Tianshan Mountains. The results showed that:(1) As the elevation increased, the ratio of Ca in the Picea Schrenkiana forest soil on the northern slope of the middle Tianshan Mountains grew gradually, while that of Cs and Cp gradually decreased. This indicates a positive feedback of the decomposition and release of soil carbon in the Picea Schrenkiana forest to the regional climate warming, showing an increasing deviation from the equilibrium state. (2) Although both MBC and microbial quotient (qMB) of the forest soil showed bimodal curves as the elevation increased, their peaks were different. The qMB increased significantly at high elevation (2600-2800 m), indicating the stronger soil microbial activity in the high elevation area of the forest. (3) CSOC, Ca, Cs, and Cp showed obvious topsoil aggregation and their value changes showed unimodal curves as the elevation increased. (4) The AI and CPI were the highest in the elevation range of 2400-2600 m, and the A, CPI, and SOCD were at a low level in the elevation range of 2200-2400 m. This study provides scientific reference for the further study of the responses of forest soil organic carbon pool on the Tianshan Mountains to climate warming as well as the management of the soil organic carbon pool in this area.