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本文讨论了用动态方法原位测定土壤呼吸强度的有关问题,在该方法中,用红外气体分析仪直接测定CO_2浓度。在动态测定法中,土壤呼吸强度随气体流速增大而增大。但是,不论气体流速大小如何,CO_2从土壤中向采样圆筒内扩散的速率却是大致稳定的,且几乎与自然条件(无采样圆筒)下的扩散速率相等。这些结果揭示出气体流动引起的质流过程对土壤的呼吸是有影响的。也就是说,因气体流动而使土壤空气(CO_2含量高)从土壤向采样圆筒的抽吸导致了土壤呼吸强度的增大。对动态方法和静态方法[用碱性溶液(NaOH)吸收CO_2]测得的土壤呼吸强度进行了比较,当气体流速为每分钟1升时,静态方法测得的结果是动态法的58%,两种方法测定值之间存在的差异可能是因为静态法中NaOH的吸收能力、CO_2的扩散率和质流速度的降低。
In this paper, the problems related to the in situ determination of soil respiration intensity using a dynamic method are discussed, in which CO 2 concentration is measured directly with an infrared gas analyzer. In the dynamic method, soil respiration intensity increases with gas flow rate. However, the rate of diffusion of CO 2 from the soil into the sampling cylinder is approximately constant regardless of gas flow rate, and is almost equal to the diffusion rate under natural conditions (without sampling cylinder). These results reveal that the mass flow induced by gas flow has an effect on soil respiration. That is, as the gas flows, suction of soil air (high CO 2 content) from the soil to the sampling cylinder results in an increase in soil respiration intensity. The soil respiration intensity measured by the dynamic method and the static method [CO 2 absorbed with alkaline solution (NaOH)] was compared. When the gas flow rate was 1 liter per minute, the static method measured 58% of the dynamic method, The difference between the measured values of the two methods may be due to the absorption capacity of NaOH in the static method, the diffusivity of CO 2 and the decrease of mass flow velocity.