Vertical Variation in Pollen Abundance in North-Central London

Pollen data from three samplers located at heights of 0.5m, 10m and 55 m were used to investigate vertical differences in pollen abundance in North-Central London. Weekly accumulative counts for all pollen types were collected from February to September 1988. Distinct variations in abundance between the sites were recorded for some pollen taxa. For example,Gramineae recorded greater abundance at the higher sampling position. Other pollen types, includingPlatanus, were recorded at consistently greater abundance at the 10 m height compared to the 55 m level. Significant differences between the pollen counts at these two heights are discussed in relation to pollen source area, the specific gravity of the pollen grain, airflow patterns of the urban area and the weather conditions affecting pollen dispersal. Tracer experiments using Lycopodium spores were employed to investigate dispersal patterns to all three sampling heights. The results from these trials are used to assist in the interpretation of data from the depositional samplers. The study reported in this paper forms part of a wider survey of 14 sampling sites examining spatial variations in pollen abundance.