The consensus for mechanisms controlling soil organic matter (SOM) persistence has shifted from traditional views based on SOM recalcitrance to a new paradigm based on SOM stabilization controlled by soil minerals and aggregates. Recent studies indicate that the origin, composition and molecular diversity of SOM are crucial to the decomposition and stabilization of SOM. However, it is not fully understood how the decomposition and stabilization of SOM are controlled at the molecular level. The objectives of this study were to investigate whether soil organic carbon (SOC) contents and mineralization are controlled by the composition, origin and molecular diversity of SOM. Soil samples were collected from contrasting bedrocks with different precipitation levels at tropical alpine grasslands of the Peruvian Andes. We applied a combination of a 76-day soil incubation experiment and pyrolysis-GC/MS assisted by thermochemolysis to investigate SOM decomposition and stabilization at the molecular level. The results indicated that soil samples with high SOC contents (92.6 ± 7.6 g kg⁻¹ soil) and low SOC mineralization had abundant derivates of lignin, polysaccharides and n-alkanes. After the incubation, we observed neither a selective decomposition of any compound groups nor a decline of molecular diversity. In contrast, soil samples with low SOC contents (30.7 ± 2.8 g kg⁻¹ soil) and higher SOC mineralization showed a depletion of plant-derived compounds, an accumulation of microbial-derived compounds and declined molecular diversity after the incubation. Furthermore, the SOC mineralization of these samples was positively correlated to the depletion of unsaturated fatty acids and the decrease in molecular diversity after the incubation. Therefore, we proposed that SOC contents and mineralization in our soils are (1) controlled by selective preservation of SOM molecular groups (e.g. plant-derived compounds), and (2) associated with changes in molecular diversity of SOM during microbial decomposition. Due to the selective preservation of organic compounds under different environmental conditions, we propose that environmental factors should be considered for the management of ecosystem services such as SOC sequestration in the studied region.

控制土壤有机质 (SOM) 持久性机制的共识已从基于 SOM 顽固性的传统观点转变为基于由土壤矿物质和聚集体控制的 SOM 稳定性的新范式。最近的研究表明，SOM 的起源、组成和分子多样性对 SOM 的分解和稳定至关重要。然而，如何在分子水平上控制 SOM 的分解和稳定化尚不完全清楚。本研究的目的是调查土壤有机碳 (SOC) 含量和矿化是否受 SOM 的组成、来源和分子多样性控制。土壤样品是从秘鲁安第斯山脉热带高山草原具有不同降水量的对比基岩中收集的。我们应用了 76 天的土壤孵化实验和热解辅助的热解-GC/MS 的组合，以在分子水平上研究 SOM 的分解和稳定性。结果表明，土壤 SOC 含量较高（92.6±7.6 g kg^-1土壤）和低 SOC 矿化具有丰富的木质素、多糖和正构烷烃衍生物。孵育后，我们既没有观察到任何化合物组的选择性分解，也没有观察到分子多样性的下降。相比之下，具有低 SOC 含量的土壤样品 (30.7 ± 2.8 g kg ^-1土壤）和较高的 SOC 矿化表明植物源性化合物的消耗，微生物源性化合物的积累和孵化后分子多样性的下降。此外，这些样品的 SOC 矿化与不饱和脂肪酸的消耗和孵育后分子多样性的减少呈正相关。因此，我们提出土壤中的 SOC 含量和矿化（1）受 SOM 分子群（例如植物衍生化合物）的选择性保存控制，以及（2）与微生物分解过程中 SOM 分子多样性的变化有关。由于有机化合物在不同环境条件下的选择性保存，