Monitoring photosynthetic activity and ozone stress by laser induced fluorescence in trees

After a general introduction the relations between photosynthesis and chlorophyll fluorescence are explained. Subsequently a brief review is presented of earlier work in the field of remote sensing of chlorophyll fluorescence. The objective of the LIFT project is to investigate the possible use of laser induced fluorescence (LIF) for observing and monitoring vegetation stress due to air pollution. The instrumentation and set-up is briefly described and measuring results are presented. Changes in LIF and air pollution are found to be strongly related. The results can be explained in terms of ozone stress, possibly enhanced by SO⊂2⊂. These effects appear at low concentrations of ozone, i.e., below the concentration limit of 30 ppb, recommended in the Netherlands. It is concluded that this new remote sensing technique has a strong potential in the field of environmental mapping and monitoring.