Temporal variation in CO2 efflux from soil and snow surfaces in a Japanese cedar (Cryptomeria japonica) plantation, central Japan

CO(2) efflux from soil and snow surfaces was measured continuously in a Japanese cedar (Cryptomeria japonica D. Don) forest in central Japan using an open dynamic chamber system. The chamber opens and closes automatically and records measurements based on an open-flow dynamic method. Between May and December, mean soil CO(2) efflux ranged from 1,529 mg CO(2) m(-2) h(-1) in September to 255 mg CO(2) m(-2) h(-1) in December. The seasonal change in CO(2) efflux from the soil paralleled the seasonal pattern of soil temperature. No marked diurnal trends in soil CO(2) efflux were observed on days without rainfall, whereas significant pulses in soil CO(2) efflux were observed on days with rainfall. In this plantation, soil CO(2) efflux frequently responded to rainfall. Measurements of changes from litter-covered soil to snow-covered surfaces revealed that CO(2) efflux decreased from values of ca. 250 mg CO(2) m(-2) h(-1) above soil to less than 33 mg CO(2) m(-2) h(-1) above snow. Soil temperature alone explained 66% of the overall variation in soil CO(2) efflux, but explained approximately 85% of the variation when data from two anomalous periods were excluded. Moreover, we found a significant correlation between soil CO(2) efflux and soil moisture (which explained 44% of the overall variation) using a second-order polynomial function. Our results suggest that the seasonality of CO(2) efflux is affected not only by soil temperature and moisture, but also by drying and rewetting cycles and by litterfall pulses.