In alpine environments, the decomposition rate of soil organic carbon (SOC) is controlled by several biotic and abiotic factors, which mostly change simultaneously and often lead to freezing and thawing cycles. However, it is highly uncertain whether the temperature sensitivity of decomposition around the freezing point of water is similar as in higher temperature ranges. In this study, we conducted a full factorial incubation experiment using soil samples from a grassland site in the Tibetan Plateau. A manipulative freeze-thaw cycle was imposed to these soils by continuously changing temperature, from −5 to 10 °C. Additional treatments included 4 levels of soil moisture at 15, 30, 60 and 90% of water-filled pore space (WFPS), and two levels of O₂ concentration at 0 and 20%. We fitted the Arrhenius equation into the flux data to estimate the activation energy (E_a) and base flux rate (A) for each treatment level. Then, we predicted the dependence and sensitivity of decomposition rate (k) by implementing the Dual Arrhenius and Michaelis-Menten (DAMM) model using a Bayesian optimization approach. While soil temperature had the strongest control on SOC decomposition rate at all soil moisture and O₂ levels, its intrinsic temperature sensitivity (Δk/ΔT) remained nearly constant across the entire temperature range except around 0 °C. We found that E_a was higher in nearly dry or anoxic conditions, suggesting that in these extremes more energy is required for microbial activity to take place. These intrinsic sensitivities revealed that temperature (energy) is the main factor that limits decomposition in cold environments provided that moisture and oxygen are sufficiently available. Intrinsic sensitivities with respect to soil moisture and oxygen concentration were only relevant at very narrow ranges, when soils were almost dry or partially anoxic, and small changes within these narrow ranges may lead to very strong changes in decomposition rates.

在高寒环境中，土壤有机碳 (SOC) 的分解速率受多种生物和非生物因素的控制，这些因素大多同时变化，并经常导致冻融循环。然而，在水的冰点附近分解的温度敏感性是否与在较高温度范围内相似，这是高度不确定的。在这项研究中，我们使用来自青藏高原草地的土壤样本进行了全因子孵化实验。通过不断改变温度（从 -5 到 10 °C），对这些土壤施加了人工冻融循环。其他处理包括 15%、30%、60% 和 90% 的含水孔隙空间 (WFPS) 的 4 个水平的土壤水分和两个水平的 O ₂浓度为 0% 和 20%。我们将 Arrhenius 方程拟合到通量数据中，以估计每个处理水平的活化能 ( E _a ) 和基本通量率 ( A )。然后，我们通过使用贝叶斯优化方法实施 Dual Arrhenius 和 Michaelis-Menten (DAMM) 模型来预测分解率 ( k )的相关性和敏感性。虽然土壤温度对所有土壤水分和 O ₂水平的SOC 分解速率的控制最强，但其固有的温度敏感性 (Δ k /Δ T ) 在整个温度范围内几乎保持不变，除了 0 °C 左右。我们发现，Ë_一在几乎干燥或缺氧的条件下更高，这表明在这些极端条件下，微生物活动需要更多的能量。这些内在敏感性表明温度（能量）是限制寒冷环境中分解的主要因素，前提是水分和氧气充足。当土壤几乎干燥或部分缺氧时，与土壤水分和氧气浓度相关的内在敏感性仅在非常窄的范围内相关，而这些窄范围内的微小变化可能会导致分解速率发生非常强烈的变化。