The paper describes work on soil profiles derived from Lower Palaeozoic sedimentary rocks in an area centred on the Plynlimon (Pumlumon) upland, West Wales. Pollen and spore counts were undertaken on selected soil profiles and the data analysed. Profiles studied include soils of moorland plateaux, the peaty podsols and their variants, as well as soils of sloping land west of, and marginal to, the plateaux. It is suggested that Post-glacial vegetation changes initially exerted a direct control on soil development but that, as soil acidification progressed, edaphic factors assumed greater importance. Evidence suggests that Post-glacial woodland extended to the limits of the study area (c. 600 m) but that exposure imposed local restrictions. The view is put forward that the decline in woodland above about 300 m represented a natural degradation and that the action of Bronze Age man was to destroy secondary woodland rather than a Post-glacial climax formation. The establishment of a raw humus layer in moorland areas is associated with the development and extension of an Ericaceous flora. It is considered that, under these conditions, podsolization was initiated and that this led in many instances to impeded surface drainage and peat formation. Vegetation changes in pasture, woodland, and moorland profiles have been identified and it is considered that the degree of consistency in the records obtained confirms that the vertical pollen distribution in soil is essentially a function of time. THE WORK of G. W. Dimbleby (1957, 1962) demonstrates how soil pollen analysis can be used to reconstruct the outlines of vegetational and land-use history for given sites. Furthermore, the comparison of site evidence permits inferences to be drawn regarding regional vegetation distributions. Dimbleby has concentrated on the British heathlands, and many of the sites he examined had already yielded an archaeological datum, which assisted in the interpretation of the pollen records. It is evident that pollen analysis applied to soils allows a much greater variety of sites to be studied than in the case of pollen analysis restricted to peats. There has been little detailed work on the extraction and interpretation of pollen from soils of upland Britain, particularly above 300 m, although C. B. Crampton (1963, 1965) has studied selected localities in South Wales. The area with which the present paper is concerned centres on a part of Cardiganshire which has advantages in terms of relatively undisturbed soils and uniform lithology. An attempt is made to reconstruct Post-glacial changes in soil profiles from a consideration of vegetation changes and other empirical methods. In all, twenty-seven sites have been analysed (R. T. Smith, 1969). The area includes a series of upland planation surfaces. The Plynlimon (Pumlumon) mass surmounts the highest surface; from this core, valleys radiate northward to the River Dovey (Dyfi) and westward to Cardigan Bay. The local rocks consist of Ordovician and Silurian shales and grits (greywackes). Frequently, the shales are identified at the surface by smoother gentler relief, while the occasional grit bands give rise to sharper knolls and ridges. Pleistocene glacial
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Jan 1, 1978
Anne I Woosley + 1
