In Situmeasurement of soil respiration rate by a dynamic method

Abstract

Abstract In this paper, various problems relating to the in situ measurement of soil respiration rate by a dynamic method in which CO2 was directly measured by an infrared gas analyzer were discussed. The rate of soil respiration increased with increasing air flow rate in the dynamic method. However, the rate of CO2 diffusion from soil to the atmosphere inside the chamber was approximately constant regardless of the air flow rate and was almost equal to that under natural conditions (without a chamber). Based on these results, it is suggested that the process of mass flow by the air flow contributed to soil respiration, that is, the suction of soil air (high CO2 content) from soil into the chamber caused by the air flow resulted in increase of the rate of soil respiration. The rate of soil respiration measured by the dynamic method was compared with that obtained by the static method which employed an alkali solution (NaOH) to trap CO2. The soil respiration rate as determined by the static method was 58% of that determined by the dynamic method at an air flow rate of 1.0 liter/min. The difference in the values between the two methods may be due to the decrease in the absorption efficiency of NaOH and the decrease in the rate of CO2 diffusion and mass flow in the static method.