Understanding the fate of permafrost‐derived dissolved organic matter (DOM) is critical for unraveling its role in carbon cycling. However, it remains unclear whether the high lability of permafrost‐derived DOM can be attributed to intrinsic chemical properties or elevated carbon concentrations. We investigated the dynamics of permafrost DOM from the Qinghai–Tibetan Plateau using both biodegradation and photodegradation experiments. Biodegradation and photodegradation of permafrost‐derived DOM exhibited distinct qualitative preferences for specific chemical groups (i.e., peptide‐like and aromatics, respectively). Notably, reducing the initial concentration of dissolved organic carbon (DOC) by half and a quarter resulted in shifts in biodegradable DOC content from 11.2% to 11.5% and 8.5%, respectively, accompanied by a corresponding decrease in the biodegradation rate from 0.11 to 0.06 and 0.03. This insight highlights the importance of recognizing the interplay between DOM quality and concentration and bears broader significance for our understanding of the fate of permafrost‐derived DOM in natural ecosystems.

中文翻译：

---

青藏高原多年冻土溶解有机物降解的浓度和成分控制

了解永久冻土衍生的溶解有机物 (DOM) 的命运对于揭示其在碳循环中的作用至关重要。然而，目前尚不清楚永久冻土衍生的 DOM 的高不稳定性是否可归因于内在化学性质或碳浓度升高。我们通过生物降解和光降解实验研究了青藏高原多年冻土 DOM 的动态。永久冻土源 DOM 的生物降解和光降解对特定化学基团（即，分别为类肽和芳香族化合物）表现出不同的定性偏好。值得注意的是，将溶解有机碳 (DOC) 的初始浓度降低一半和四分之一会导致可生物降解的 DOC 含量分别从 11.2% 变化至 11.5% 和 8.5%，同时生物降解率相应从 0.11 下降至 0.06和0.03。这一见解强调了认识 DOM 质量和浓度之间相互作用的重要性，并且对于我们了解自然生态系统中永久冻土衍生的 DOM 的命运具有更广泛的意义。