Ozone (O-3) duxes, together with detailed multi-height micrometeorolog
ical fluxes of water vapour, sensible heat and momentum, have been det
ermined for a 4 d period above a Sitka spruce canopy using eddy correl
ation techniques. O-3 fluxes increased from -0.2 mu g m(-2) s(-1) at n
ight to between -0.6 and -1.0 mu g m(-2) s(-1) in the early morning an
d then gradually reduced throughout the day. Deposition velocities beh
aved in a similar way, varying from nighttime minima of less than 2 mm
s(-1) to maxima of between 7 and 14 mm s(-1). Canopy resistances for
O-3 were compared to those of water vapour and the rate of uptake of O
-3 was shown to be up to three times that of stomatal deposition. The
enhanced uptake rates were only observed during daylight hours and rea
ched a maximum around midday. These increased fluxes may be caused by
increased transport; however, the leaf cuticles could provide a photoc
hemical sink for O-3 in strong sunlight conditions, a pathway observed
by Rondon (1993). The toxic effects of this pathway remain unclear bu
t this mechanism may have severe consequences for coniferous forests d
uring summertime anticyclonic conditions in Europe when O-3 concentrat
ions may be very high.