Early‐and Mid‐flandrian Environmental History of the Brecon Beacons, South Wales

Abstract

SUMMARY Pollen‐stratigraphic data are described from two sites on the northern face of the Brecon Beacons escarpment in South Wales, U.K. Pollen percentage, pollen concentration and deteriorated pollen diagrams are presented which contain details of vegetational changes in this part of Britain from the time period immediately following the wastage of the Loch Lomond Advance glaciers around 10000 radiocarbon years ago, until the establishment of oak and alder woodland in the mid‐ Flandrian some 4000 years later. An initial phase of juniper scrub was followed by the expansion of birch woodland over much of the area, and these forests were subsequently invaded by large numbers of hazel. Quercus, Ulmus and Pinus were present throughout the mid‐Flandrian, but increasing climatic wetness, possibly beginning around 7000 radiocarbon years ago, led to the decline of elm, pine and birch as woodland components in this part of South Wales, and to the expansion of Quercus and particularly Alnus. These vegetational changes are discussed in terms of vegetational developments at other sites in upland Wales and western Britain.

The Holocene vegetation history of the Arfon Platform, North Wales, UK

“…Pinus was common at higher altitudes (Hibbert & Switsur 1976;Walker 1978) but not in low lying areas (Botterill 1988;Watkins 1991;Chambers 1998), perhaps because there was no opportunity for it to compete within a closed canopy forest as its seedlings are light demanding (Carlisle & Brown 1968). This supports Walker (1982), who suggested that there was considerable variation in the local and regional distribution of Pinus in North Wales. Moore (1972) suggested that this was because of variations in edaphic conditions, but at Llyn Cororion frequent charcoal records indicate that fire may have been instrumental in creating and maintaining an ecological niche for Pinus to exploit.…”

PALAEOECOLOGY OF ALNUS (ALDER): EARLY POST‐GLACIAL RISE IN A VALLEY MIRE, NORTH‐WEST WALES

“…Borth Bog (Moore, 1968) Llyn Mire (Moore & Beckett, 1971;Moore, 1978) Maesgoleu (Slater, 1966) Tregaron Bog (Hibbert & Switsur, 1976) Cefn Gwernffrwd (Chambers, 1982a) Rhosgoch Common (Bartley, 1960) Cledlyn Pingoes (Handa & Moore, 1976) South Wales Llangorse Lake (Chambers, 1985) Llanllwch (Thomas, 1965) Waen Ddu (Trotman, 1963) Cwmllynfell (Trotman, 1963) Coed Taf C (Chambers, 1983) Ffos ton Cenglau (Hyde, 1940) • Protracted rise of Alnus also noted at two cirque basins in the Brecon Beacons, investigated by Walker (1982). rapid rise of Alnus at lowland Llangorse Lake (150 m O.D.)…”

Pleistocene deposits of the South Wales Coalfield and their engineering significance

“…As to the length of time during which periglacial conditions prevailed in the South Wales coalfield area, work by Trotman (1963) near Swansea and Walker (1980, 1982a, 1982b in the Brecon Beacons, on pollen profiles, has shown that late Devensian climatic changes in South Wales were similar to those determined by Coope (1977) for lowland central Britain. A very rapid warming occurred at the end of the main Devensian glaciation, but was followed by a return to several hundred years of very low temperatures (Younger Dryas or Loch Lomond Stadial) before final rapid warming at the beginning of the Holocene.…”