Korean Journal of Soil Science and Fertilizer ISSN:0367-6315(Print) 2288-2162(Online) 한국토양비료학회 학회지

Under the projected global warming, release of carbon as CO₂ through soil organic matter decomposition is expected to increase. Therefore, accurate measurement of CO₂ released from soil is crucial in understanding the soil carbon dynamics under increased temperature conditions. Sodium hydroxide (NaOH) traps are frequently used in laboratory soil incubation studies to measure soil respiration rate, but decreasing CO₂ gas solubility with increasing temperature may render the reliability of the method questionable. In this study, the influences of increasing temperature on the CO₂ capture capacity of NaOH traps were evaluated under 5~35°C temperature range at 10°C interval. Two closed-chamber experiments were performed where NaOH traps were used to capture CO₂ either released from acidified Na₂CO₃ solution or directly injected into the chamber. The sorption of ambient CO₂ within the incubators into NaOH traps was also measured. The amount CO₂ captured increased as temperature increased within 2 days of incubation, suggesting that increased diffusion rate of CO₂ at higher temperatures led to increases in CO₂ captured by the NaOH traps. However, after 2 days, over 95% of CO2 emitted in the emission-absorption experiment was captured regardless of temperature, demonstrating high CO₂ absorption efficiency of the NaOH traps. Thus, we conclude that the influence of decreased CO₂ solubility by increased temperatures is negligible on the CO₂ capture capacity of NaOH traps, supporting the use of NaOH traps in the study of temperature effect on soil respiration is a valid method.

Changes in the CO₂ absorption amount of NaOH solution trap with temperature measured using CO₂ emission-absorption method. Standard error bars are provided and some bars are not depicted due to small error. Different letters on the data bars indicate significant (P<0.05)difference among the treatments (temperature and reaction time).