作者：Deng, Y., Li, X., Wang, Z., Zhao, S. & Shi, F.

Thermokarst lakes (TLs) induced by permafrost thaw can disturb soil carbon and nitrogen cycling, creating positive feedbacks to climate warming. However, active-layer soil organic carbon (SOC) and total nitrogen (TN) dynamics across TL succession stages, as well as relative contributions of factors across spatial scales, remain unknown on the Tibetan Plateau (TP). For the first time, we investigated the expanding, stable, drying, and drained TLs on the TP, each with distinct microfeatures. We found that these TLs predominantly caused SOC and TN losses, peaking at the drying and drained stages; this divergence from the carbon accumulation in the Arctic is possibly due to the TP's warm-dry climate. At the landscape scale, microfeatures, sand, soil water (SW), pH, and aboveground biomass explained over 50% of the variance in SOC, TN, and C:N at most sites, among which the local SW effect shifted from positive at water-limited sites (likely via mitigating water stress) to negative at water-sufficient sites (likely by exacerbating erosion). Regionally, background factors (climate, grazing, soil, and vegetation properties) explained over twice the variance in carbon and nitrogen metrics compared to within-landscape factors, with the background SW exhibiting the strongest effect. Projections incorporating climate-driven cascading effects through SW and pH showed that while future trajectories varied by TL stage, historical TL-induced C and N losses were likely irreversible under SSP climate scenarios. Our study demonstrates the need to incorporate fine-scale thermokarst processes (i.e., microfeatures and key hydroclimatic drivers) into Earth System Models to constrain uncertainty in projecting permafrost carbon-climate feedbacks.

冻土融化诱发的热喀斯特湖（TLs）会扰动土壤碳氮循环，形成对气候变暖的正反馈。然而，在青藏高原（TP），活动层土壤有机碳（SOC）与全氮（TN）在热喀斯特湖不同演替阶段的动态，以及各因子在不同空间尺度上的相对贡献，仍属未知。研究首次调查了青藏高原上处于扩张、稳定、干涸与疏干四个阶段、且各具独特微地貌特征的热喀斯特湖。研究发现：这些热喀斯特湖总体上导致SOC与TN的损失，且损失量在干涸与疏干阶段达到峰值；这与北极地区碳累积的格局相悖，可能归因于青藏高原暖干的气候特征。在景观尺度上，微地貌、砂粒含量、土壤水（SW）、pH及地上生物量解释了大多数样点SOC、TN与C:N变异的50%以上；其中，土壤水的局部效应在水分受限样点表现为正效应（可能通过缓解水分胁迫），而在水分充足样点转为负效应（可能通过加剧侵蚀）。在区域尺度上，背景因子（气候、放牧、土壤与植被属性）对碳氮指标方差的解释量是景观内因子的两倍以上，其中背景土壤水的影响最强。纳入气候通过SW与pH传导的级联效应的预估显示：尽管未来轨迹因热喀斯特湖演替阶段而异，但在SSP气候情景下，历史上热喀斯特湖诱导的碳氮损失很可能不可逆转。本研究表明，需将精细尺度的热喀斯特过程（即微地貌与关键水文气候驱动因子）纳入地球系统模型，以约束冻土碳—气候反馈预估中的不确定性。

（来源：Journal of Hydrology 2026  DOI: 10.1016/j.jhydrol.2026.135940）