A palaeoecological study of Cors Gyfelog and Tre'r Gof: lowland mines of north west Wales

Abstract

This study investigates post-Glacial development of Cors Gyfelog and Tre'r Gof - lowland mires in north west Wales - and the vegetational history of the region over the same period. Using existing hydroseral theories, possible future successions are predicted, their desirablility from conservation viewpoints, and whether management might be considered necessary.
Peat stratigraphy records vegetational changes at the two sites, supported by pollen analysis, which also reveals regional developments. Additionally, correlations are attempted between variations in peat chemistry and mineral content, and mire vegetational changes shown by the other techniques.
Results from Cors Gyfelog indicate central parts of the mire were of early post-Glacial lacustrine origin, but terrestrialisation followed quickly. The wetland area expanded during the Atlantic period. Pollen and biostratigraphy indicate fluctuations between poor-fen and alder carr until the sub-Atlantic, when there was reedswamp and incipient valley bog, before general succession to sedge fen. Latterly, probably following minor drainage attempts, conditions have become drier, and large areas are now dominated by Molinia or Salix.
Tre'r Gof history spans the post-Glacial. Until c.4000 B.P., conditions were lacustrine, with calcareous waters deriving from shelly Irish Sea till. Surrounding wet meadow succeeded to carr. With terrestrialisation, the mire became rich fen. Southern parts of the mire have recently been affected by drainage, leaving drier grassland areas and small patches of carr, although with some very wet patches.
Whilst research on British mires suggests that eventual domination by Sphagnum mosses is normal, this does not appear to be happening here. Drainage attempts, however, could raise surface vegetation above the water table, away from nutrient-rich waters, and allow ombrotrophic Sphagnum growth. Alternatively, carr may spread and dominate, particularly at Cors Gyfelog. It is suggested that neither would be desirable, so frequent monitoring should be conducted, unwanted carr removed, and water levels manipulated to prevent excessive drying.