陆地生态系统土壤有机碳分解温度敏感性研究进展

A review on the temperature sensitivity of soil organic carbon decomposition in terrestrial ecosystem

在全球变化背景下,土壤有机碳的分解及其温度敏感性在陆地生态系统碳循环中的重要性备受关注。温度敏感性指数(Q_(10))微小的变化都可能导致未来土壤碳库大小评估的巨大偏差,充分了解土壤有机碳分解温度敏感性的调控机理对预测未来土壤碳变化具有重要意义。笔者对国内外已有研究进行分析,比较培养温度模式、底物质量、物理化学保护和微生物属性对土壤有机碳分解温度敏感性的影响。结果发现:(1)与传统的恒温模式相比,变温培养模式更好地克服了土壤微生物对恒定培养温度的适应性以及不同培养温度下底物消耗不均的缺点,能够更加准确地估算Q_(10)。(2)较多的研究发现难分解有机碳的Q_(10)大于易分解有机碳的Q_(10),但也有研究发现难分解有机碳的Q_(10)并不比易分解有机碳的Q_(10)高,这主要是由于土壤有机碳库的异质性造成的。(3)团聚体和矿物吸附保护通过改变底物有效性或者反应位点的底物浓度来影响土壤有机碳分解的温度敏感性。(4)微生物的生理特性、群落组成和结构也会对温度敏感性造成影响,温度变化会造成土壤微生物群落组成及其相关生理特征的变化,进一步引起相关功能基因丰度的改变,从而改变有机碳分解的温度敏感性。土壤有机碳分解及其温度敏感性是全球气候变化对碳循环影响研究中很重要的一部分,对它的精确估算有利于完善全球气候变化模型,对准确预测未来全球气候变化具有重要意义。

The importance of the decomposition of soil organic carbon(SOC)and its temperature sensitivity(Q_(10))in terrestrial ecosystem carbon(C)cycling have been widely recognized,especially under climate change.A small change in the Q_(10)of SOC decomposition may result in a large effect on the global C cycle.Therefore,the identification of critical driving factors of Q_(10)is needed for accurately predicting soil CO;efflux and its feedback to climate change under a continuously warming scenario.By reviewing the published literatures,we explored how different incubation approaches,substrate quality,physicochemical protection and microbial properties affect Q_(10).We found that:(1)Varying temperature incubation largely overcomes the issues of substrate depletion and microbial adaption that occur using constant temperature incubation,and provides a more accurate and rapid estimation of Q_(10).(2)While the results of some studies have shown that the Q_(10)value of recalcitrant C is higher than that of labile organic C,others have also found that the Q_(10)of recalcitrant C is not necessarily higher than that of labile C,which is mainly due to the heterogeneity of SOC pool.(3)The protection of soil aggregates and minerals on organic matter can affect Q_(10)by changing the substrate availability or concentration at reaction microsites.(4)Physiological characteristics and community composition and structure of microorganisms also influence the Q_(10).Microbial communities and physiological characteristics in warmed soils possess a varying relative abundance of key functional genes involved in the degradation of SOC.the SOC decomposition and its Q_(10)are the essential aspects of the global C cycle.A better understanding of Q_(10)could contribute to the development of the global change models and accurate projection of future climate.