Warming-induced permafrost thaw may stimulate soil respiration (Rs) and thus cause a positive feedback to climate warming. However, due to the limited in situ observations, it remains unclear about how Rs and its autotrophic (Ra) and heterotrophic (Rh) components change upon permafrost thaw. Here we monitored variations in Rs and its components along a permafrost thaw sequence on the Tibetan Plateau, and explored the potential linkage of Rs components (i.e., Ra and Rh) with biotic (e.g., plant functional traits and soil microbial diversity) and abiotic factors (e.g., substrate quality). We found that Ra and Rh exhibited divergent responses to permafrost collapse: Ra increased with the time of thawing, while Rh exhibited a hump-shaped pattern along the thaw sequence. We also observed different drivers of thaw-induced changes in the ratios of Ra:Rs and Rh:Rs. Except for soil water status, plant community structure, diversity, and root properties explained the variation in Ra:Rs ratio, soil substrate quality and microbial diversity were key factors associated with the dynamics of Rh:Rs ratio. Overall, these findings demonstrate divergent patterns and drivers of Rs components as permafrost thaw prolongs, which call for considerations in Earth system models for better forecasting permafrost carbon-climate feedback.

中文翻译：

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多年冻土解冻后土壤自养和异养呼吸的发散轨迹

变暖引起的永久冻土融化可能会刺激土壤呼吸（Rs），从而对气候变暖产生正反馈。然而，由于原位观测有限，目前尚不清楚 Rs 及其自养 (Ra) 和异养 (Rh) 成分如何在永久冻土融化时发生变化。在这里，我们监测了青藏高原多年冻土融化序列中 Rs 及其成分的变化，并探索了 Rs 成分（即 Ra 和 Rh）与生物（例如植物功能性状和土壤微生物多样性）和非生物因素的潜在联系（例如，基板质量）。我们发现Ra和Rh对永久冻土塌陷表现出不同的反应：Ra随着解冻时间的增加而增加，而Rh在解冻序列中呈驼峰状。我们还观察到解冻引起的 Ra 比率变化的不同驱动因素：Rs 和 Rh：Rs。除了土壤水分状况，植物群落结构、多样性和根系特性解释了 Ra:Rs 比的变化，土壤基质质量和微生物多样性是与 Rh:Rs 比动态相关的关键因素。总体而言，这些发现表明随着永久冻土融化延长，Rs 成分的不同模式和驱动因素，这需要在地球系统模型中考虑，以便更好地预测永久冻土碳气候反馈。