A Preliminary Study of Some Environmental Variables in an Upland Ecosystem: Cader Idris, Merionethshire

Abstract

The assumption of a close, if not genetic, relationship between slope, soil and vegetation has often been useful in ecological surveys. This relationship is sometimes expressed in the idea of 'site'-a slope facet uniform in surface inclination, regolith, drainage and soil type (Bourne 1931). Each site is occupied by a plant assemblage or 'community'; dependent upon the aims of the survey, the characteristics of the site or the community, or both, can be used as a basis for mapping and classifying broad ecosystem patterns. In upland Britain, two major site groupings can be recognized; those of colluvial slopes, and those of scree and moraine/blockfield areas. Although areas mostly devoid of soil and vegetation ('rock dominant') are important in the general hydrological and topographical relations of an upland ecosystem, they can be regarded as a minor site-grouping. Colluvial slopes are mantled by variable hillwash or 'head' deposits consisting of stony fragments bedded in a clay or loam matrix (Tivy 1961; Ball 1966). Occupying areas of less than 26? angle of slope, above which they grade into screes, these slopes have a more