土壤异养呼吸的测定及其温度敏感性影响因子

Measurement methods of soil heterotrophic respiration and key factors affecting the temperature sensitivity of the soil heterotrophic respiration

土壤异养呼吸主要指土壤中微生物分解有机质释放CO2的过程,是陆地生态系统中土壤碳的主要净输出途径,土壤异养呼吸与净初级生产力的差值是决定生态系统碳源/汇的关键。本文介绍了土壤异养呼吸的测定方法———室内培养的去根土壤样品培养和原状土柱培养,以及野外原位测定的根排除法、环割法和同位素法等操作方法的优缺点以及适用范围。在土壤异养呼吸的研究方面,土壤异养呼吸温度敏感性(Q10)是碳循环研究的重要方面之一,温度、水分以及土壤呼吸底物是影响Q10的主要因子,一般情况下,随着温度的升高,Q10下降;土壤含水量过低或过高时,Q10降低;土壤有机碳的有效性影响着土壤异养呼吸对温度变化的响应程度,当有效性降低时Q10下降,不同周转时间的有机碳的温度敏感性也不相同,活性有机碳的温度敏感性较惰性有机碳的温度敏感性低。

Soil heterotrophic respiration can indicate the CO2 efflux from the decomposition of soil organic matter, the major pathway of soil carbon into atmosphere. The difference between soil heterotrophic respiration and ecosystem net primary productivity is crucial to determine whether the ecosystem is a carbon source or sink. In this paper, the operations, merits, and drawbacks of the methods used to measure soil heterotrophic respiration, including those of laboratory incubation （incubation with root-removal soil or soil core） and in situ investigation （root-exclusive method, stand girdling method, and isotopic method）, were introduced. The dependence of soil heterotrophic respiration to temperature has received considerable interest in studying the carbon cycle and its potential feedbacks to climate change. Temperature, soil moisture, and the availability of soil organic carbon are the major factors affecting the temperature sensitivity of soil heterotrophic respiration （Ql0）. Under normal condition, the Q10 value decreases with the increase of temperature. When the desiccation stress happens or the soil water content is far above the field capacity, the dependence of soil heterotrophic respiration to temperature will be weakened. The availability of soil organic carbon also affects the sensitivity of soil heterotrophic respiration to temperature change. The Q10 decreases with decreasing availability of soil organic carbon. The temperature sensitivity of soil heterotrophic respiration differs when soil organic carbon has different turnover rate, and this respiration has a lower sensitivity to labile organic carbon than to inert organic carbon.