As global temperatures continue to rise, a key uncertainty of terrestrial carbon (C)–climate feedback is the rate of C loss upon abrupt permafrost thaw. This type of thawing—termed thermokarst—may in turn accelerate or dampen the response of microbial degradation of soil organic matter and carbon dioxide (CO₂) release to climate warming. However, such impacts have not yet been explored in experimental studies. Here, by experimentally warming three thermo-erosion gullies in an upland thermokarst site combined with incubating soils from five additional thermokarst-impacted sites on the Tibetan Plateau, we investigate how warming responses of soil CO₂ release would change upon upland thermokarst formation. Our results show that warming-induced increase in soil CO₂ release is ~5.5 times higher in thermokarst features than the adjacent non-thermokarst landforms. This larger warming response is associated with the lower substrate quality and higher abundance of microbial functional genes for recalcitrant C degradation in thermokarst-affected soils. Taken together, our study provides experimental evidence that warming-associated soil CO₂ loss becomes stronger upon abrupt permafrost thaw, which could exacerbate the positive soil C–climate feedback in permafrost-affected regions.

随着全球气温持续上升，陆地碳（C）-气候反馈的一个关键不确定性是永久冻土突然融化时碳的损失率。这种类型的解冻（称为热喀斯特）可能会反过来加速或抑制土壤有机质的微生物降解和二氧化碳 (CO ₂ ) 释放对气候变暖的反应。然而，实验研究尚未探讨此类影响。在这里，通过实验性地加热一个高地热岩溶地点的三个热侵蚀沟壑，并结合来自青藏高原上另外五个受热岩溶影响的地点的土壤，我们研究了土壤CO ₂释放的变暖响应在高地热岩溶形成时将如何变化。我们的结果表明，变暖导致的热喀斯特地貌中土壤CO ₂释放量的增加比邻近的非热喀斯特地貌高出约5.5倍。这种较大的变暖响应与受热喀斯特影响的土壤中较低的基质质量和较高的微生物功能基因丰度有关，这些基因可促进碳的顽固降解。总而言之，我们的研究提供了实验证据，表明与变暖相关的土壤CO ₂损失在永久冻土突然解冻时变得更强，这可能会加剧受永久冻土影响地区的土壤C-气候正反馈。