Vertical and seasonal variations in soil CO2 production in a 55-year-old oriental arborvitae (Platycladus orientalis) plantation in China

The aim of this work was to explore the vertical and seasonal variations of CO 2 within the soil profile based on Fick’s law of diffusion in an oriental arborvitae plantation. We continuously measured the soil CO 2 concentration profile using CO 2 sensors buried at different depths in a coniferous forest in northern China and calculated the CO 2 flux based on the profile measurements using a dynamic model. The diurnal pattern of CO 2 concentration and flux fluctuated during the day and varied less at night. The CO 2 profile had a vertical gradient, with the highest concentrations in the deepest soil layers. The CO 2 flux had a clear seasonal pattern with a maximum in summer and a minimum in winter. The contributions of the H, A, B, and C horizons to the total CO 2 flux were 75.38, 13.52, 7.61, and 3.49%, respectively. Q 10 was 2.668, 4.469, 1.175, and 3.333 in the H, A, B, and C horizons, respectively. The CO 2 flux determined from the concentration profiles agreed well with the CO 2 flux measured by open dynamic chambers, suggesting that this model could be used to successfully measure soil CO 2 emissions and to describe the processes underlying CO 2 efflux.