土壤呼吸的温度敏感性——全球变暖正负反馈的不确定因素

基于模型模拟结果表明,全球变暖与大气CO2浓度增加将形成正反馈关系,这种正反馈效应将明显加速21世纪的气候变暖。然而,这些模拟模型都基于一个重要假设,即不同平均驻留时间的土壤有机质分解具有相同的温度敏感性(Q10)。这一假设与酶动力学理论相悖,而且不同学者对不同质量土壤有机质分解温度敏感性的差异的认识存在严重分歧,所以,全球变暖与大气CO2浓度增加的正反馈关系的显著性仍值得商榷。围绕土壤呼吸的温度敏感性问题进行了讨论和评述,涉及1)土壤有机质分解温度敏感性争论的焦点问题;2)通过经验模型曲线拟合估计Q10值存在的分歧及Q10变异的机理解释;3)实验室土壤培养实验估计Q10值存在的问题;4)土壤培养实验中Q10值计算方法的改进。进一步深化有关土壤有机质分解温度敏感性不确定性的认识,将为今后土壤呼吸及其对气候变化响应的相关研究提供参考。

Temperature sensitivity of soil respiration: uncertainties of global warming positive or negative feedback

Several models indicate that a positive feedback of an increasing atmosphere CO₂ concentration to global warming would occur, which will accelerate the global warming in the current century. However, these models' results largely rely on an important hypothesis: Decompositions of soil organic matter with different mean resident time have the same temperature sensitivity (Q₁₀). This hypothesis, however, is contrary to enzyme kinetic theory. Furthermore, a consensus has not yet reached on whether the temperature sensitivity of soil organic matter decomposition positively, negatively or do not change with different soil organic matter quality. Therefore, the significance of the positive feedback of global warming and the increasing atmosphere CO₂ concentration is still to be explored before this divergence comes to an agreement. In this paper, a review was made on the following issues: 1) controversy issues on the temperature sensitivity of soil organic matter decomposition, 2) disagreement on Q₁₀ estimation based on experiential model curve fitting and the mechanism of Q₁₀ variation, 3) issues resulting from soil incubation experiments, 4) a modified method to calculate Q₁₀ through soil incubation experiments. Deepening understanding of the uncertainties of temperature sensitivity of soil organic matter decomposition is of significance to future research on soil organic matter decomposition and soil respiration response to global warming.