Soil organic carbon (SOC) fractions play a crucial role in the carbon cycle of alpine wetland ecosystems and regional climate regulation. In the last decades, alpine marshes at Tibetan Plateau have undergone increased degradation. The effects of marsh degradation on soil labile and recalcitrant organic carbon fractions and on SOC stability remain unclear. In this study, we investigated changes in SOC fractions with different biochemical recalcitrance and stability in the marsh ecosystems with various levels of degradation in the Zoige Wetland, Eastern Qinghai-Tibet Plateau. Soil samples of relatively pristine marsh (RPM), lightly degraded marsh (LDM), moderately degraded marsh (MDM), heavily degraded marsh (HDM) and severely degraded marsh (SDM) were collected and analysed using the acid hydrolysis method. Compared with RPM, the concentrations of SOC labile fraction I (non-cellulosic polysaccharides), SOC labile fraction II (cellulose) and recalcitrant organic carbon (ROC) in degraded marshes decreased significantly: 29–97, 38–95 and 32–99%, respectively, except for the LDM. The SOC recalcitrance index (RIc) in the HDM and SDM was significantly lower than that in RPM by 11–35 and 15–47%, respectively; compared with RPM, the stability of organic carbon was significantly lower in the HDM and SDM. Additionally, the marsh degradation increased vertical variation in the concentrations of SOC fractions. The degradation of alpine marshes decreases the capacity for carbon (C) sequestration via decreasing the resistance of SOC to biodegradation, indicating that the alpine marsh degradation may weaken the carbon sink capacity of the Zoige Plateau, thus aggravating the global greenhouse effect.

中文翻译：

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若尔盖青藏高原东部若尔盖高寒湿地退化土壤有机碳组分和稳定性的响应

土壤有机碳 (SOC) 组分在高寒湿地生态系统的碳循环和区域气候调节中起着至关重要的作用。在过去的几十年里，青藏高原的高山沼泽地退化加剧。沼泽退化对土壤不稳定和顽固的有机碳成分以及对 SOC 稳定性的影响尚不清楚。在这项研究中，我们调查了青藏高原东部若尔盖湿地不同退化程度的沼泽生态系统中具有不同生化逆向性和稳定性的 SOC 组分的变化。收集相对原始沼泽 (RPM)、轻度退化沼泽 (LDM)、中度退化沼泽 (MDM)、严重退化沼泽 (HDM) 和严重退化沼泽 (SDM) 的土壤样品，并使用酸水解法进行分析。与RPM相比，降解沼泽中 SOC 不稳定部分 I（非纤维素多糖）、SOC 不稳定部分 II（纤维素）和顽固有机碳 (ROC) 的浓度显着下降：分别为 29-97、38-95 和 32-99%，除了对于 LDM。HDM 和 SDM 中的 SOC 顽固指数 (RIc) 分别显着低于 RPM 中的 11-35% 和 15-47%；与 RPM 相比，HDM 和 SDM 中有机碳的稳定性显着降低。此外，沼泽退化增加了 SOC 组分浓度的垂直变化。高山沼泽的退化通过降低 SOC 对生物降解的抵抗力降低了碳（C）的固存能力，表明高山沼泽的退化可能削弱若尔盖高原的碳汇能力，