ABSTRACT

The emission rate of isoprene from an oak tree (Quercus serrata) in the field was measured at almost hourly intervals during daytime. The emission showed an marked diurnal variation with a maximum around noontime. More than 80% of daily emission occurred between 10:00 and 14:00. The emission rate correlated with light intensity, and their relationship could be described by a simple hyperbolic function. The daily isoprene emission showed a seasonal variation with a maximum in September. This seasonal variation differed considerably from the one presumed from average monthly temperatures, indicating the need of a check of seasonal variations in the case of the estimation of annual emission rate from vegetation.