天山中段北坡森林土壤有机碳库稳定性组分沿海拔的分异规律

在高纬度高海拔区域气温增幅更大的背景下，高山亚高山森林土壤有机碳稳定性组分分配比关系以及由于此差异导致对增温的反馈效应均有待深入阐释。天山森林是以雪岭云杉(Picea Schrenkiana)为单优树种的温带针叶林，在天山北坡中山带(海拔约1760—2800 m)呈垂直落差超过1000 m的带状斑块分布，便于排除混交树种的影响，而量化土壤有机碳库稳定性组分分配比关系沿海拔的分异规律，及其对气候变化的响应情况。沿海拔梯度设置森林样地并分层采集土样，研究各土层土壤总有机碳库(C_SOC)、活性碳库(C_a)、缓效性碳库(C_s)、惰性碳库(C_p)、微生物量碳(MBC)在海拔梯度上的变化特征，通过碳库活度(A)、碳库活度指数(AI)、碳库指数(CPI)、土壤碳密度(SOCD),探讨天山森林土壤有机碳稳定性组分沿海拔的分异特征。结果表明：(1)随着海拔的升高，天山中段北坡云杉森林土壤C_a占比逐步升高，C_s和C_p占比逐步降低，这意味着天山中段北坡云杉...

Altitudinal distribution of the forest soil organic carbon fractions on the northern slope of the middle Tianshan Mountains

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 (C_SOC), active carbon pool (C_a), slow carbon pool (C_s), passive carbon pool (C_p), 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 C_a in the Picea Schrenkiana forest soil on the northern slope of the middle Tianshan Mountains grew gradually, while that of C_s and C_p 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) C_SOC, C_a, C_s, and C_p 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.