LATE-GLACIAL AND HOLOCENE VEGETATION HISTORY OF WESTERN DONEGAL, IRELAND

The late-glacial and Holocene vegetation history of the western lowlan ds of Donegal has been reconstructed from three lake sediment sequence s, using pollen, charcoal, sediment, and pine stomata analyses. Plant colonisation began between 12,900 and 12,700 BP, and the same patterns of vegetation development, divided into three subzones, are recorded at each site during the late-glacial. Successive expansions of Juniper us, Betula and Corylus mark the beginning of the Holocene. Early woodl ands were invaded by Ulmus, Quercus and Pinus between 9000 and 8200 BP . Closed-canopy mixed woodland developed and persisted in parts of wes tern Donegal until after 5000 BP. In other areas which were marginal f or tree growth, woodland contracted after the diversification phase an d blanket peat spread. Alnus became established between 7200 and 6600 BP. The elm decline (5300-5100 BP) was followed by woodland instabilit y and tree population fluctuations. Pinus expanded and reached its max imum distribution between 5000 and 4500 BP. Disturbance relating to hu man activity increased in the latter half of the Holocene and was the main controlling factor in the final woodland decline. Blanket peat sp read gradually as woodland contracted, and the present treeless landsc ape was in existence 2400-1500 years ago.