Seasonal variation in soil CO2 efflux in evergreen coniferous and broad‐leaved deciduous forests in a cool‐temperate forest, central Korea

Abstract

AbstractWe measured the soil surface CO2 efflux (RS) from January 2005 to December 2006 in two neighboring stands in Gwangneung Forest, central Korea: evergreen coniferous forest (Abies holophylla, stand A) and broad‐leaved deciduous forest (Quercus‐dominated, stand Q). Regarding seasonal variation, RS rate was low during the winter and early spring months in each stand and peaked in late July [1170 (stand A) and 1130 (stand Q) in 2005, and 1000 (stand A) and 740 (stand Q) mg CO2 m−2 h−1 in 2006]. RS rate was higher in stand A than in stand Q during most of the growing season. The pattern of summer rainfall differed between 2005 and 2006. RS rate for both stands was suppressed significantly by the droughts in June 2005 and September 2006. After the heavy rainfall of July 2006, RS rate was lower than in July 2005 in both stands, but this decrement was much greater in stand Q than in stand A. In midsummer (August) 2006, under higher soil temperature (ST) and lower soil water content (SWC) conditions than in August 2005, RS rate of stand A was lower than that in August 2005, whereas stand Q showed no marked change. The exponential relationship between ST and RS accounted for approximately 91–97% of the RS variability in each stand and in each year. In stand A, the application of a second‐order polynomial function indicated a significant correlation between SWC and RS when the soil was warm (ST > 15°C). Our results suggest that the seasonality of RS is strongly affected by the pattern of summer rainfall even in an Asia monsoon climate regime. In addition, the vegetation type (i.e., evergreen coniferous forest vs. broad‐leaved deciduous forest) plays a significant role in response of RS to various environmental fluctuations such as drought, heavy rainfall, and hot‐dry condition.