Diurnal pattern of soil CO₂ efflux in a pinus densiflora forest measured using an open-flow chamber system

This study was conducted to investigate the diurnal pattern of soil CO₂ efflux (R_S) using an open-flow, closed-chamber system for a 70- to 80-year-old Pinus densiflora forest in the Gwangneung Experimental Forest in central Korea. The daily mean R_S rate (g CO₂ m^-2 h^-1) was 0.486 in September, 0.073 in April, and 0.169 in May 2010. Although R_S exhibited a diurnal pattern that was similar to the soil temperature pattern, the pattern varied seasonally. The Q₁₀ value was 4.57 and 4.26 for day and night time, respectively. The annual R_S rate was estimated as 6.16 t C ha^-1 y^-1 by the relationships between R_S and soil temperature using continuous measurements, but as 6.73 t C ha^-1 y^-1 by using the 11:00 h mid-morning point measurements. Our study results demonstrate the necessity of measuring the diurnal pattern of R_S throughout the whole year in order to obtain an accurate estimate of annual R_S using an open-flow, closed-chamber system.