OZONE DEPOSITION ONTO A DECIDUOUS FOREST DURING DRY AND WET CONDITIONS

Results of an experiment conducted to quantify the ozone deposition onto a deciduous forest stand in an acid-precipitation-impacted area of Canada are presented and discussed. The ozone deposition data were obtained above and within the forest canopy. The deposition process was affected by solar radiation, wind speed and ambient ozone concentration. Solar radiation was likely acting through its influence on stomatal opening and wind speed through its effects on bulk boundary layer resistance. Ozone deposition deep in the canopy was negligibly small compared with that in the upper canopy. The difference is ascribed to a larger biological sink for ozone in the upper canopy and to a lack of efficient transport in the lower canopy. Substantial ozone deposition was measured while the forest canopy remained wet with either dew or rain water, during night-time and daytime conditions. This is contrary to assumptions made in some deposition models that ozone uptake is reduced when foliage is wet.