A POST‐GLACIAL POLLEN SEQUENCE FROM LOCH A'MHUILINN, NORTH ARRAN: A RECORD OF VEGETATION HISTORY WITH SPECIAL REFERENCE TO THE HISTORY OF ENDEMIC SORBUS SPECIES

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Abstract
Summary: A sequence of lake muds and fen peat deposits from Loch a'Mhuilinn, north Arran, contains evidence for the local vegetation history for parts of the Flandrian Interglacial. The main components of this history are as follows: Sedimentation occurred under open‐water conditions during early Flandrian times. By around 5000 B.P., fen peat was accumulating, and during the 2nd millenium B.P., an unexplained reversion to open‐water conditions occurred.The earliest recorded vegetation immediately predates the Corylus rise and is characterized by Betula‐rich woodland with Juniperus and Salix being present in places. The Corylus rise, occurring at around 8600 B.P., marks the beginning of a period of Corylus‐rich Betula woodland. Subsequent increases of Ulmus, Quercus, Pinus and Alnus pollen represent further forest development. Fluctuations in the composition of this mixed forest are recognized, as can a distinction between areas of Betula‐Quercus, Corylus‐rich and Alnus‐rich woodland.At around 5000 B.P., the vegetational development, previously representing broad regional changes, appears to respond to local processes. Fluctuations in the proportions of trees and Gramineae pollen may reflect vegetational disturbance, although sedimentation processes may be influencing the pollen deposition at this time. This period is followed by apparently greater woodland stability, with minor indications of human activity. By around 4000 B.P., early stages of Calluna‐rich heath are apparent. The development of the heath vegetation is not recorded, but by the 2nd millenium B.P., Calluna heath and grassland appear to be well established in north Arran.The history of Sorbus spp. is examined in as much detail as the fossil evidence allows. By around 6500 B.P., Sorbus aucuparia L. is present in the area, and by around 5400 B.P., evidence for non‐aucuparia Sorbus species is present. This evidence may represent the former presence of 5. rupicola (Syme) Hedl. and/or one or both of the two endemic species 5. arranensis Hedl. and S. pseudofennica E. F. Warb.