Strong and rapid responses of soil microbial respiration to pulses,such as those from available soil organic matter (SOM) or water input from precipitation (especially in arid areas),are common.However,how soil microbes utilize new SOM inputs and the effects that temperature may have on their activities are unclear owing tothe limitation in the application of traditional isotopic techniques at minute scales.In the present study,we developed a system of measuring 12CO2 and δ13C minutely and synchronously under controlled incubation temperatures,i.e.,for 48 h at 7,10,15,20,and 25 ℃,to explore the carbon utilization strategies of soil microbes.We measured the respiration rates of soil microbes in response to different carbon sources,i.e.,added glucose (Rg) and initial SOM (Rs),as well as the total respiration rate (Rt).All responses were rapid and characterized by unimodal curves.Furthermore,the characteristic values of these curves,such as the maximum of rate (R-max),the time required to achieve R-max,and the ratio of the duration of R-max to that of 1/2 R-max,were all dependent on incubation temperature.Interestingly,temperature greatly influenced the strategy that microorganisms employed to utilize different carbon sources.The effects of temperature on the intensity of the microbial respiratory response and the ratio of Rg/Rs are important for evaluating the effect of land-use changes or variations in seasonal temperature on SOM turnover and should be considered in ecological models in future studies.%降雨事件使土壤水分快速变化从而引起土壤微生物会产生强烈而又快速的脉冲效应,是自然界中普遍存在的现象,该过程对土壤有机质周围具有很重要的作用.然而,由于传统测定技术的限制,土壤微生物如何快速利用新输入的有机质,以及温度是否影响其过程,依然不甚了解.本研究运用自主研发的全自动变温土壤微生物呼吸δ13C连续测定装置,以中国北方暖温带针阔混交林样地土壤为对象,通过设置了7、10、15、20、25℃C五个温度梯度,探讨了模拟降水脉冲事件中,在分钟尺度上和不同温度状况下土壤呼吸速率和δ13C值.实验结果表明,葡萄糖呼吸速率(Rg)、土壤有机质呼吸(Rs)、土壤总呼吸速率(Rt)均为呈现出单峰曲线,而且这些曲线的特征值,例如呼吸速率最大值、到达最大值的时间,以及最大值到1/2最大值的持续时间,都与培养温度密切相关,意味着温度直接控制着降水脉冲事件中微生物对新输入碳的使用策略.温度会影响了土壤微生物对不同碳源的利用策略,将对评价土地利用变化或季节温度变化对土壤有机质分解的影响具有重要意义,甚至在未来生态模型中也应考虑这种温度效应.
展开▼
