Atmosphere-biosphere exchange of CO sub 2 and O sub 3 in the central Amazon forest

Journal Article · Thu Sep 20 04:00:00 EDT 1990 · Journal of Geophysical Research; (USA)

OSTI ID:6101111

Fan, Songmiao; Wofsy, S C; Bakwin, P S; Jacob, D J ^[1]

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1. Harvard Univ., Cambridge, MA (USA)

Measurements of vertical fluxes for CO{sub 2} and O{sub 3} were made at a level 10 m above the canopy of the Amazon forest during the wet season, using eddy correlation techniques. Nocturnal respiration of CO{sub 2} by the forest ecosystem averaged 2.57 kgC/ha/h, with about 85% from the forest floor. During the daytime, CO{sub 2} 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{sup {minus}2}), corresponding to fixation of 0.0076 moles CO{sub 2} per mole photons (about 0.017 moles CO{sub 2} per mole of absorbed photons at photosynthetically active wavelengths). The relationship between net ecosystem exchange and solar flux was virtually the same in the Amazon forest as in forests in Canada and Tennessee. The relatively high efficiency for utilization of light (about 30% of the theoretical maximum) and the strong dependence of net CO{sub 2} uptake on solar flux suggest that light may significantly regulate net ecosystem exchange and carbon storage in the tropical forest. Changes in the distribution of cloud cover, associated for example with climatic shifts, might induce globally significant changes in carbon storage. Rates for uptake of O{sub 3} averaged 2.3 {times} 10{sup 11} molecules cm{sup {minus}2} s{sup {minus}1} in the daytime , dropping by roughly a factor of 10 during the 14 hours from dusk to dawn. The mean O{sub 3} deposition velocity at 40 m was 0.26 cm s{sup {minus}1} in the night and 1.8 cm{sup {minus}1} in the day. Diurnal variation of O{sub 3} deposition was regulated both by stratification of the atmospheric boundary layer and by stomatal response to light and water deficit. The total flux of O{sub 3} to the forest was limited largely by supply from the free troposphere above. Deposition of O{sub 3} to the forest canopy appears to be a regionally, and perhaps globally, important sink for tropospheric O{sub 3}.

• OSTI ID: 6101111
• Journal Information: Journal of Geophysical Research; (USA), Journal Name: Journal of Geophysical Research; (USA) Vol. 95:D10; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540110*
540210 -- Environment
Terrestrial-- Basic Studies-- (1990-)
AIR-BIOSPHERE INTERACTIONS
AMAZON RIVER
ATMOSPHERIC CHEMISTRY
BOUNDARY LAYERS
BRAZIL
CANADA
CANOPIES
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON DIOXIDE FIXATION
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
CHEMISTRY
CLOUDS
COMPARATIVE EVALUATIONS
DAILY VARIATIONS
DEPOSITION
DEVELOPING COUNTRIES
EARTH ATMOSPHERE
ECOLOGICAL CONCENTRATION
FEDERAL REGION IV
FORESTS
LATIN AMERICA
LAYERS
MEASURING METHODS
NORTH AMERICA
OXIDES
OXYGEN COMPOUNDS
OZONE
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHESIS
RADIATIONS
RESPIRATION
RIVERS
SEASONAL VARIATIONS
SOLAR RADIATION
SOUTH AMERICA
STELLAR RADIATION
STREAMS
SURFACE WATERS
SYNTHESIS
TENNESSEE
TROPOSPHERE
UPTAKE
USA
VARIATIONS