Soil respiration, the major pathway for ecosystem carbon (C) loss, has the potential to enter a positive feedback loop with the atmospheric CO₂ due to climate warming. For reliable projections of climate-carbon feedbacks, accurate quantification of soil respiration and identification of mechanisms that control its variability are essential. Process-based models simulate soil respiration as functions of belowground C input, organic matter quality, and sensitivity to environmental conditions. However, evaluation and calibration of process-based models against the long-term in situ measurements are rare. Here, we evaluate the performance of the Terrestrial ECOsystem (TECO) model in simulating total and heterotrophic soil respiration measured during a 16-year warming experiment in a mixed-grass prairie; calibrate model parameters against these and other measurements collected during the experiment; and explore whether the mechanisms of C dynamics have changed over the years. Calibrating model parameters against observations of individual years substantially improved model performance in comparison to pre-calibration simulations, explaining 79–86% of variability in observed soil respiration. Interannual variation of the calibrated model parameters indicated increasing recalcitrance of soil C and changing environmental sensitivity of microbes. Overall, we found that (1) soil organic C became more recalcitrant in intact soil compared to root-free soil; (2) warming offset the effects of increasing C recalcitrance in intact soil and changed microbial sensitivity to moisture conditions. These findings indicate that soil respiration may decrease in the future due to C quality, but this decrease may be offset by warming-induced changes in C cycling mechanisms and their responses to moisture conditions.

土壤呼吸是生态系统碳 (C) 损失的主要途径，有可能与大气 CO ₂进入正反馈循环由于气候变暖。对于气候-碳反馈的可靠预测，土壤呼吸的准确量化和控制其变异性的机制的识别至关重要。基于过程的模型模拟土壤呼吸作为地下 C 输入、有机质质量和对环境条件的敏感性的函数。然而，针对长期原位测量的基于过程的模型的评估和校准很少见。在这里，我们评估了陆地生态系统 (TECO) 模型在模拟混合草草原 16 年变暖实验期间测量的总和异养土壤呼吸的性能；对照实验期间收集的这些和其他测量值校准模型参数；并探索 C 动力学的机制多年来是否发生了变化。与预校准模拟相比，根据个别年份的观测值校准模型参数大大提高了模型性能，解释了观测到的土壤呼吸变化的 79-86%。校准模型参数的年际变化表明土壤 C 的顽固性增加和微生物的环境敏感性不断变化。总体而言，我们发现（1）与无根土壤相比，完整土壤中土壤有机碳变得更顽固；(2) 变暖抵消了完整土壤中增加 C 抵抗的影响，并改变了微生物对水分条件的敏感性。这些发现表明，未来土壤呼吸可能会因碳质量而减少，但这种减少可能会被变暖引起的碳循环机制的变化及其对水分条件的响应所抵消。