Limitations of the Q10 Coefficient for Quantifying Temperature Sensitivity of Anaerobic Organic Matter Decomposition: A Modeling Based Assessment
Limitations of the Q10 Coefficient for Quantifying Temperature Sensitivity of Anaerobic Organic Matter Decomposition: A Modeling Based Assessment
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DOI：
10.1029/2021jg006264
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发表时间：
2021-08
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影响因子：
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通讯作者：
Qiong Wu;R. Ye;S. Bridgham;Q. Jin
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作者：
Qiong Wu;R. Ye;S. Bridgham;Q. Jin
Q10系数是在两个相隔10°C的温度下反应速率的比率，并且已被广泛应用于量化有机物分解的温度敏感性。然而，地球化学家和生态学家早就认识到，恒定的Q10系数并不能准确地描述有机物分解的温度敏感性。为了检验Q10常数假设的后果，我们建立了一个模拟美国密歇根州上半岛泥炭地厌氧有机物分解的非地球化学反应模型，并将模拟结果与Q10系数的预测结果进行了比较。通过考虑胞外酶、中温发酵和产甲烷微生物的反应及其温度响应，微生物化学反应模型再现了先前实验室培养实验的观察结果，包括溶解有机碳、乙酸盐、二氢、二氧化碳和甲烷浓度的时间变化，并证实发酵限制了厌氧有机物分解的进展。模拟结果说明了在恒定的Q10假设和假设如何破坏了厌氧有机物分解的动力学预测固有的过于简单化。特别是，该模型预测，在5°C和30°C之间，分解速率几乎随温度的升高而线性增加，这与Q10系数给出的指数关系形成鲜明对比。因此，恒定Q10方法往往低估了Q10值确定的温度范围内的有机物分解速率，并高估了温度范围外的速率。研究结果还表明，地球化学反应模型，结合实验室实验，可以帮助揭示潜在的催化机制所产生的有机物分解的温度敏感性。
The Q10 coefficient is the ratio of reaction rates at two temperatures 10°C apart, and has been widely applied to quantify the temperature sensitivity of organic matter decomposition. However, biogeochemists and ecologists have long recognized that a constant Q10 coefficient does not describe the temperature sensitivity of organic matter decomposition accurately. To examine the consequences of the constant Q10 assumption, we built a biogeochemical reaction model to simulate anaerobic organic matter decomposition in peatlands in the Upper Peninsula of Michigan, USA, and compared the simulation results to the predictions with Q10 coefficients. By accounting for the reactions of extracellular enzymes, mesophilic fermenting and methanogenic microbes, and their temperature responses, the biogeochemical reaction model reproduces the observations of previous laboratory incubation experiments, including the temporal variations in the concentrations of dissolved organic carbon, acetate, dihydrogen, carbon dioxide, and methane, and confirms that fermentation limits the progress of anaerobic organic matter decomposition. The modeling results illustrate the oversimplification inherent in the constant Q10 assumption and how the assumption undermines the kinetic prediction of anaerobic organic matter decomposition. In particular, the model predicts that between 5°C and 30°C, the decomposition rate increases almost linearly with increasing temperature, which stands in sharp contrast to the exponential relationship given by the Q10 coefficient. As a result, the constant Q10 approach tends to underestimate the rates of organic matter decomposition within the temperature ranges where Q10 values are determined, and overestimate the rates outside the temperature ranges. The results also show how biogeochemical reaction modeling, combined with laboratory experiments, can help uncover the temperature sensitivity of organic matter decomposition arising from underlying catalytic mechanisms.