RELATIONSHIP BETWEEN RECENT POLLEN DEPOSITION AND AIRBORNE POLLEN CONCENTRATION

In the reconstruction of past or recent vegetation the study of deposi ted pollen plays an important role. As reference value, very often the pollen content of moss polsters (''moss cushions'') is assessed to es timate the pollen deposition (''influx'') from the air. Recently, the data from moss-polster sampling and from sedimentation-trap sampling h ave been compared, showing both similarities and inconsistencies in th e two sets of data. Whether the relative pollen presence in moss polst ers is in accordance with airborne pollen concentrations as assessed b y continuous volumetric air sampling has been studied rather scarcely. This relationship between recent pollen deposition and airborne polle n concentration has been studied also in Leiden by comparing the perce ntages with which 28 frequent pollen types were represented in a conti nuous volumetric air sampler over a period of 9 years, with the percen tages with which they were extracted from moss polsters collected at t hree sites in the vicinity of the air sampler. It appears that some ty pes are relatively strongly under-represented in moss polsters, especi ally Urtica. Consequently, a number of other types are relatively over -represented in moss polsters. This finding should have consequences f or the interpretation of the results of observations on sub-fossil and more recent pollen deposition in relation to vegetation reconstructio n.