Annual carbon fluxes via soil and root respiration were estimated in a cool-temperate deciduous forest to evaluate the importance of root respiration in the forest's overall carbon balance. Total soil respiration rates were measured during the snow-free season in 2000 and 2001 using an open-flow gas-exchange system with an infrared gas analyzer. To determine the annual carbon emission from the soil, we constructed a polynomial multiple-regression model that included two variables (soil temperature and soil water content) and that used hourly data for soil respiration rates. To estimate root respiration, we used data on the seasonal changes in the contribution of root respiration to the soil respiration rate that were determined in a previous study. The annual root respiration rate was estimated to be 4.8 t C ha-1 year -1, which corresponds to 45% of the annual total soil respiration (10.6 t C ha-1 year-1). Thus, root respiration contributed about half of the total annual soil respiration in the cool-temperate forest. The importance of root respiration in determining a forest's carbon balance is discussed in relation to data on net ecosystem production by the same forest.
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