Atmosphere-biosphere exchange of CO₂ and O₃ in the central Amazon forest

Nocturnal respiration of CO₂ by the forest ecosystem averaged 2.57 kgC/ha/h, with about 85% from the forest floor. During the daytime, CO₂ was taken up at a mean rate of 4.4 kgC/ha/h. Net ecosystem uptake of carbon dioxide increased with solar flux by 0.015 (kgC/ha/h)/(W m^-2), corresponding to fixation of 0.0076 moles CO₂ per mole photons (about 0.017 moles CO₂ per mole of absorbed photons at photosynthetically active wavelengths). Rates for uptake of O₃ averaged 2.3×10¹¹ molecules cm^-2s^-1 in the daytime (10 hours, 700-1700 hours), dropping by roughly a factor of 10 during the 14 hours from dusk to dawn. The mean O₃ deposition velocity at 40 m was 0.26 cm s^-1 in the night and 1.8 cm s^-1 in the day. -from Authors