RELATIONSHIP BETWEEN RECENT POLLEN DEPOSITION AND AIRBORNE POLLEN CONCENTRATION

In the reconstruction of past or recent vegetation the study of deposited pollen plays an important role. As reference value, very often the pollen content of moss polsters (''moss cushions'') is assessed to estimate the pollen deposition (''influx'') from the air. Recently, the data from moss-polster sampling and from sedimentation-trap sampling have been compared, showing both similarities and inconsistencies in the two sets of data. Whether the relative pollen presence in moss polsters is in accordance with airborne pollen concentrations as assessed by continuous volumetric air sampling has been studied rather scarcely. This relationship between recent pollen deposition and airborne pollen concentration has been studied also in Leiden by comparing the percentages with which 28 frequent pollen types were represented in a continuous volumetric air sampler over a period of 9 years, with the percentages with which they were extracted from moss polsters collected at three sites in the vicinity of the air sampler. It appears that some types are relatively strongly under-represented in moss polsters, especially Urtica. Consequently, a number of other types are relatively over-represented in moss polsters. This finding should have consequences for the interpretation of the results of observations on sub-fossil and more recent pollen deposition in relation to vegetation reconstruction