Post-Neolithic Vegetation Changes in the Western Rhinogau, Gwynedd, North-West Wales

Abstract

This paper reports evidence of prehistoric and historic vegetation changes and is based on a comparative analysis of soil-pollen and peat-pollen records in relation to available archaeological and historical evidence. The sites selected for investigation were regarded as broadly representative of the upland topography of the western Rhinogau, Gwynedd, in north-west Wales. The operation of in situ controls, such as slope, soil and the activities of man, on the vegetation succession is differentiated from the broader impact of climatic change. The timing and scale of local vegetation change is shown to deviate from the palaeochronologies established for other parts of the British Isles. The view that Neolithic/Bronze Age man removed a woodland already modified by a preceding phase of natural soil degradation is corroborated. The legibility of soil-pollen records is affirmed, the cumulative change in the pollen record with depth of soil profile being interpreted as a function of time. Correction factors are introduced for the interpretation of pollen assemblages, and pollen transfer models are used to distinguish between local and regional pollen influx. The meso-scale approach to site selection is advocated since a combination of both soil and peat profiles avoids the crude extrapolation over extensive inorganic terrain which is inevitable when peat-bog sections only are used. THIS study collates and interprets palynological evidence derived from several soil profiles and one upland peat site in a distinctive montane habitat of the Rhinogau in north-west Wales (Fig. i). The objective is to identify the nature and extent of human interference with the vegetation succession in the area since the Neolithic period. It emerges that vegetation change may be locally triggered by in situ environmental or cultural factors as well as responding generally to major climatic oscillations. The extent and pattern of regional and altitudinal deviations from the standard British palaeochronology are revealed. A meso-scale approach to site selection is followed (Smith, 1970; Pennington, 1970; Taylor, 1973) which avoids macro-scale extrapolation from specialized, unevenly distributed, and, quite possibly, unrepresentative sites (Godwin, 1956 and 1975; Smith, 1965). Emphasis is placed on the value of combining palaeo-evidence derived from a close network of soil and peat sites, and of correlating such evidence, so far as possible, with data from environmental and archaeological/historical sources. The study area The Rhinogau comprise an upland area above 300 m (maximum elevation 754 m) positioned north of the Mawddach estuary and east of Harlech (Fig. I). The pollen sites shown, with the exception of Dolfrwynog, occur on slopes lying west of the major north-south watershed. Four sites are located on an interfluve extending westwards from Rhinog Fawr (SH 656290) and three sites to the south of Cwm Nantcol. The area, with predominantly moderate slopes, is in marked contrast to the rugged central ridge and the well-marked Trawsfynydd basin lying to the east.