A 10-YEAR RECORD OF THE ARBOREAL AIRBORNE POLLEN IN STOCKHOLM, SWEDEN

The daily concentration of airborne pollen has been recorded in central Stockholm during the period 1 March-31 August, 1977-1986, using a Burkard seven-day recording volumetric spore trap placed c. 20 m above ground level. Total annual catches and phenology of arboreal pollen are presented, attaching importance to five frequent deciduous taxa namely Corylus, Alnus, Ulmus, Betula and Quercus. The annual arboreal pollen count is numerically presented in a bar diagram together with non-arboreal, unidentified and estimated missing data. The arboreal count dominates and has varied from 10513 in 1986 to 39552 in 1985. The non-arboreal pollen contribution to the annual sum has varied from 10 to 30% and does not correlate to the rise and fall of the arboreal sum. Annual pollen sums in Betula and Ulmus show a certain tendency towards a two-year cycle while Pinits shows a tendency towards a three-year cycle. The phenology is presented on a decadal (10-day) mean basis and shown as a percentage of the yearly sum for each taxon. The flowering seasons in decadal percentages year by year for Corylus, Alnus, Ulmus, Betula and Quercus is compared to the 10-year decadal average. Rank correlation statistics are used to define within which decade a pollen type dominates the pollen spectrum. Using our study alone, which is based only on pollen concentration calculations, it is not possible to forecast cither the total annual catch or the phenology of the following year. © 1990 Taylor & Francis Group, LLC.