土壤碳循环主要过程对气候变暖响应的研究进展

摘要

目前，土壤呼吸等碳循环过程对气候变暖的响应仍是气候变化预测模型中不确定性的主要来源。本文以土壤呼吸为切入点，首先论述了土壤呼吸对气候变暖的响应及适应机制，并从土壤微生物（土壤呼吸的主体）、土壤有机碳分解的温度敏感性（土壤呼吸的反应底物）两个方面探讨了土壤碳循环过程对气候变暖的响应；随后论述了气候变暖与其他气候变化因子之间、地上与地下部分之间的协同作用对土壤碳循环过程的影响。得到以下主要结论：气候变暖可以影响土壤微生物的生理活性，甚至改变其群落结构，从而使土壤呼吸对增温产生适应；土壤有机碳分解对增温的敏感性由有机碳的化学组成结构、环境因子对其的保护作用、土壤微生物的生理特性等因素决定。并在此基础上提出了未来的研究重点：1）将土壤微生物过程耦合到气候变化模型中；2）积极探索新的土壤微生物研究方法；3）设置长期定位实验，研究多个气候变化因子之间的综合作用；4）加强地上、地下生态过程的系统研究。%Climate warming can directly or indirectly affect soil carbon cycling in a variety of ways.The re-sponse of soil carbon cycling to climate warming has been identified as one of the major sources of uncertainty in model projections of future climate change.In this paper,we discuss the responses and adaptation mecha-nisms of soil respiration to climate warming,and review recent advances on the responses of soil microorgan-isms (reactors of soil respiration)and soil organic carbon (substrate for soil respiration)to climate warming. We also explore the effects of the synergy between climate warming and other climate change factors,and the effects of the synergy between above-and below-ground components on soil carbon cycling.The main conclu-sions are summarized as follows:1)autotrophic and heterotrophic components of soil respiration respond dif-ferently to climate warming.Autotrophic components,especially root respiration,are more sensitive to climate warming because of their dependence on photosynthesis;2)soil respiration initially increases in response to warming and then declines.The decline can be attributed to thermal adaptation,substrate depletion,and nitro-gen or soil moisture constraints;3)the responses to climate warming vary among different kinds of microor-ganisms.Climate warming can induce changes in microbial physiology and even community structure,leading to the adaptation of soil respiration to climate warming;4)soil organic matter decomposition is sensitive to cli-mate warming.The temperature sensitivity of this decomposition is determined by chemical conformation (quality),environmental constraints (physico-chemical protection,drought,flooding,and freezing,which af-fect accessibility),and microbial physiology and enzyme production (efficiency).Finally,we discuss future de-velopments in this research field:1)soil microbial processes should be included in climate change models;2) new molecular biological techniques such as stable-isotope probing and ‘meta-omic’methods should be used for in-depth studies on soil microorganisms;3)long-term experiments and field studies should investigate the com-bined effects of multiple climate change factors on soil carbon cycling;4)there should be further systematic re-search on the interaction between above-ground and below-ground ecological processes.