A BIOGEOGRAPHICAL STUDY OF PLANT-COMMUNITIES AND ENVIRONMENTAL GRADIENTS OF SOUTH UIST, OUTER HEBRIDES, SCOTLAND

Plant community types and underlying environmental gradients in the Ou ter Hebrides have not been described in detail, although a number of g eneral accounts of the flora and vegetation exist. Satellite imagery w as used to locate a transect for phytosociological survey across the i sland of South Uist. Species cover and a range of environmental variab les were described for a total of 212 quadrats along this transect. Si xteen plant community types were identified using Two Way Indicator Sp ecies Analysis (TWINSPAN) and the prevailing environmental gradients w ere determined using Canonical Correspondence Analysis (CANOCO). The c ommunities were related to the National Vegetation Classification of t he British Isles and general plant communities previously described fo r the Outer Hebrides. The vegetational history of the transect area wa s also described from pollen analysis of a core obtained from Lake Hel lisdale on the transect. The position of these 16 community types alon g the environmental gradients is discussed as is their relationship to both the palaeoecology/vegetational history of the island and recent human impact. Finally, suggestions are made for further research on se lected aspects of the plant communities of South Uist with a view to t heir conservation and management.