Seasonal and Annual Variation Over 5 Years in Contemporary Airborne Pollen Trapped at a Cumbrian Lake

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Abstract
Airborne pollen catches from unroofed Tauber traps floating in the center of a small lake in the English Lake District were counted every 4-6 wk for 5 yr. Fresh pollen input to the traps followed the seasonal flowering pattern of the plants in the vicinity of the lake, but some refloated pollen was also caught. Total annual catches of tree pollen and of non-tree pollen varied between years by factors of up to .times. 6.8 and .times. 3.2, respectively. Consideration of weather records suggested that this variation was due to annual differences in pollen production (which is determined partly by climatic factors), rather than to the relative efficiency of pollen dispersal each year. Annual pollen input to the floating traps was significantly lower than to additional unroofed traps put out in woodland, reedswamp and pasture, where high input of pollen from local plants was recorded. Percentages of pollen caught annually in the air traps were compared, by means of multivariate analyses, with pollen percentages from lake sediment and from annual catches in traps submerged in the lake and in an inflowing stream.