O2:CO2 exchange ratios observed in a cool temperate deciduous forest ecosystem of central Japan.

Detailed observations of O₂:CO₂ exchange ratios were conducted in a cool temperate deciduous forest located in central Japan. The exchange ratios of soil respiration and net assimilation were found to be 1.11±0.01 and 1.02±0.03 from soil chamber and branch bag measurements, respectively. Continuous measurements of the atmospheric O₂/N₂ ratio and the CO₂ concentration, made inside the canopy during a summer season, indicated that the average exchange ratio was lower in the daytime (0.87±0.02) than in the nighttime (1.03±0.02) with a daily mean value of 0.94±0.01. The observed average daytime and nighttime exchange ratios were nearly consistent with the corresponding values obtained from a 1-box canopy O₂/CO₂ budget model simulation of net turbulent O₂ and CO₂ fluxes between the atmosphere and the forest ecosystem. Our results suggest that the daily mean exchange ratios of the net turbulent O₂ and CO₂ fluxes depend sensitively on the forest ecosystem processes. [ABSTRACT FROM AUTHOR]