Xh. Lee et al., CARBON-DIOXIDE EXCHANGE AND NOCTURNAL PROCESSES OVER A MIXED DECIDUOUS FOREST, Agricultural and forest meteorology, 81(1-2), 1996, pp. 13-29
This paper reports the results of the analysis of CO2 exchange from a
one-month experiment conducted at a mixed deciduous forest, Camp Borde
n (80 degrees 65'W, 44 degrees 19'N), Canada, in the summer of 1993. T
he mid-day CO2 flux from the forest under clear sky conditions was aro
und -1.0 mg m(-2) s(-1), the average light and water use efficiencies
13 mmol CO3(mol photon)(-1) and 7.95 mg CO2(g H2O)(-1), and the averag
e nocturnal respiration rate 0.21 mg CO2 m(-2) s(-1). We observed diff
erent flow features at heights of 34.5 (14.5 m above the canopy) and 2
2.4 m at night. Wavelike structures were frequently encountered at z =
34.5 m. Depending on the phase angle between the vertical velocity an
d CO2 concentration time series, they could act to enhance the co-grad
ient (upward) flux or to create counter-gradient (downward) flux of CO
2. We speculate that the wave events were limited to isolated regions
in the upwind direction. Near the tree-tops (z = 22.4 m), the strong w
ind shear was able to maintain turbulence. Inverse temperature ramp st
ructures were very common and flux of sensible heat was well behaved (
directed downward).