Freeze-thaw (F-T) processes are prevalent and have the inherent potential to alter soil respiration (SR) in cold regions, which are particularly sensitive to climate warming and contribute a large uncertainty to the global carbon budget. However, the impacts of F-T processes on the diel pattern and temperature hysteresis of SR remain unclear. In this study, the Fick's law-based gradient method was employed to obtain high-temporal-resolution SR data, and a four-parameter Gaussian function was used to quantify the diel pattern of SR. The results demonstrate that the magnitude and timing of the daily SR peak exhibit considerable variability across different F-T stages, leading to a delay in the optimal time window for measuring the daily mean SR during the freezing and frozen stages. Furthermore, the daily peak value of SR is primarily regulated by soil temperature (ST) during the thawed period, whereas soil water content (SWC) exerts a more pronounced effect than ST throughout the entire freezing-frozen-thawing period. The diel hysteresis between SR and ST was observed year-round, but its direction was reversed by F-T processes. Additionally, the magnitude of the temperature hysteresis was negatively correlated with SWC. These findings have important implications for understanding the mechanisms driving SR variability and improving the accuracy of annual carbon budget estimates in cold regions.

中文翻译：

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冻融过程改变了青藏高寒草原狄尔土壤呼吸的峰值特性和温度滞后


冻融 （F-T） 过程很普遍，并且具有改变寒冷地区土壤呼吸 （SR） 的内在潜力，寒冷地区对气候变暖特别敏感，并给全球碳收支带来很大的不确定性。然而，F-T 过程对 SR 的 diel 模式和温度滞后的影响仍不清楚。在本研究中，采用基于 Fick 定律的梯度法获得高时间分辨率的 SR 数据，并使用四参数高斯函数量化 SR 的 diel 模式。结果表明，日平均 SR 峰值的大小和时间在不同的 F-T 阶段表现出相当大的可变性，导致在冻结和冻结阶段测量日平均 SR 的最佳时间窗口延迟。此外，SR 的日峰值主要受解冻期土壤温度 （ST） 的调节，而在整个冻冻解期内，土壤含水量 （SWC） 的影响比 ST 更明显。SR 和 ST 之间的 diel 滞后全年都观察到，但其方向被 F-T 过程逆转。此外，温度滞后的大小与 SWC 呈负相关。这些发现对于理解驱动 SR 变化的机制和提高寒冷地区年度碳收支估计的准确性具有重要意义。