Changes in Soil CO2 Concentration Following Experimental Warming in Four Coniferous Species Seedlings.

Soil carbon (C) dynamics is expected to be affected by temperature increase due to climate change. Compared to sporadic manual measurements, continuous measurements of soil CO₂ fluxes provides us with comprehensive understandings of soil C dynamics involving temporal patterns. We aimed to examine the responses of soil CO₂ concentrations of four coniferous seedlings to future temperature increase by conducting an open-field warming experiment. An experimental warming set-up using infra-red heater was built in 2011 and the temperature in warming plots has been regulated to 3^oC higher than that of control plots constantly. The seeds of Pinus densiflora, P. koreansis, Abies koreana, and A. holophylla were planted in each 1 m x 1 m plot (n=3) in Apr., 2012. Soil CO₂ concentrations at 5cm depth were monitored using solid-state CO₂ sensors, GMT-222 (Vaisala, Finland) from Dec., 2011 to Nov., 2012. Soil CO₂ concentrations under the open-field experimental warming throughout a year were decreased for three species and increased only for P. densiflora. Different seasonal patterns were observed according to species. In spring, soil CO₂ concentrations of P. densiflora, A. koreana, and A. holophylla were increased, while those of P. koraiensis were decreased in all seasons. Lower soil water content of warmed plots was reported to cause decreased soil CO₂ concentrations. Soil CO₂ concentrations of P. densiflora in warmed plots were increased although soil water content was decreased. Increased soil CO₂ concentrations might be induced by higher root and microbial respiration derived by higher seedling growth and photosynthetic activity of P. densiflora seedlings. Our results demonstrating different responses of continuous soil CO₂ concentrations according to species and season under experimental warming will contribute to the knowledge of species-specific response of soil C dynamics and to development of model predicting changes in soil C under the future climate regime.