| Summary: | The distribution and variation in vegetational composition of dry heath is investigated. The scope of the investigation is limited to those heaths which contain the two species Calluna vulgaris and Arctostophylo ouveural. Three sets of workers have independently recognized an association on subjective grounds which contains these two dwarf-shrube and which is character used by being species-rich, Huir Fraser (1940), McVean and Rateliffe (1962), Gininghen (1964). Mcveen and Rateliffe have named the association artctaphyleto-callunetun. Using objective techniques interest has centred on a study of Onllune arctestpaphylob heathe with a view to identifying the major directions of variation, and in an attempt to see if objective techniques produce an association which can be termed arctostaphylete-Calluntum. A study of Dinnet Moor indicates that the burning regime and the nature of the surface soil are the most important feature affecting vegetational composition. The Arctostaphylote-Collnnetum appears to form part of a continnum. In a wide-scale study of the Collune-Arctostanhyloo heaths of north-east Scotland, attention was limited to heaths which had not been burnt for 12-15 years, and soil-type was found to be the major factor affecting the vegetation. The compbined use of association-analysis and principal components analysis produced a unit of stands which can be termed arctostaphyleto-Callunctum. The basis on which this unit was originally described to examined. A brief survey of the oalluris-Arctostaphylos communtion of north-west Scotland indiestes that they probably form a continuum with these of the north-east. Due to Geographical discontinuity between the areas sompled in the cast and west, this can only be postulated. Giminghan (1968) has pointed out the need for studies making use of British and Continontal data for heaths in an attempt to eelueidate the relationships between them. Data collection in sondinevia combined with the date from north-east Scotland. It was possible to demonstrate a close relationship between the herb-rich calluna-Arctostaphylos heaths of north-east Scotland and the Calluna-Frice cinerea heaths of south-west Norway. The application of a new objective classificatery technique known as group analysis to two sats of data resulte in two elightly different versions of the association arctostephyleto-Callunetum being produced. Thus the objective methods of association-analysis and group analysis support the existence of an abstract unit which has been terned aretoeslaphyleto-osllunetum. The stands so classified are shown to form part of a continuum in heathland vegetation using principal components analysis.
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