Modern pollen rain in the northwest of the British Isles

Abstract

Modern pollen rain in three unforested regions in the northwest of the British Isles is investigated using surface sediments from 64 small lakes (mean size 1.5 ha). Pollen assemblages from Shetland and the Western Isles accurately reflect the predominance of blanket peat vegetation on the islands and combined frequencies for the three main taxa, Calluna vulgaris, Gramineae and Cyperaceae, exceed 65% at all sites. The proportion of tree and shrub pollen is small (7-24%). Variation in pollen representation is much greater in surface samples from Donegal, Ireland; tree and shrub pollen frequencies range from 12-52% and have a mean of 30.1%. Concentrations and accumulation rates indicate that the pollen production capacity of blanket peat vegetation is comparatively high and is within the range for boreal woodland. Pollen assemblages from remote Scottish islands are not overwhelmed by long-distance inputs; a mean of 11.3% on Shetland and 13.8% on the Western Isles is thought to have originated from off-island sources. Small lakes in a treeless landscape record regional pollen signals and recruit a large proportion of pollen from outside the immediate catchment areas.