Holocene vegetation history and human impact at Bryn y Castell, Snowdonia, north Wales

Abstract

SUMMARYThree radiocarbon-dafed pollen diagrams are presenfed from Holocene peat and lake deposits in Snowdonia, elose to the Late Iron Age/Romano-Britisb ironworking hill-fort of Bryn y Casfell, Gwynedd, in upland north Wales. This paper discusses pollen, charcoal and peat-stratigrapbic evidence for major local vegetation changes and for tbe development of the surrounding cultural landscape during the last 10000 radioearbon yr. Pollen data from one of the sites (BYC 2) provided a vegetational record for most of the Holocene. The early part of the sequence suggests an oligotrophie lake in a landscape that is being colonized by birch-pine woodland; later, mixed deciduous woodland surrounds an infilling lake basin. Dating of peat deposits at two of tbe sites (BYC, BY'C H) indicated that their pollen records commenced between 5500 and 5000 yr BP. By this time, the lake basin was fringed by alder carr. There followed a gradual and then, c. 2700 yr BP, a more abrupt decline in woodland, such that, by tbe end of the Bronze Age and with the basin largely terrestrialized, the local landscape became dominated by mire vegetation communities, which have persisted to the present. Human activity seems to have been a major factor in the loss of woodland eover. Although there is some circumstantial evidence for earlier phases of human disturbance at BYC 2, human activity becomes increasingly apparent from c. 5000 yr BP. During the mid Holoeene, the impaet of Neolithic and early-to mid-Bronze Age cultures appears to be characterized by temporary woodland clearances, for arable and pastoral agriculture. By c. 2700 yr BP the majority of woodland cover seems to have been permanently removed from the landscape, but as there is scant archaeological evidence for late Bronze Age cultures in this part of Snowdonia, other factors, especially climate change, could be implicated. During the late Holocene, especially during part of the late Iron Age and Romano-British period, remaining local stands of woodland seem to have been exploited for iron smelting, although the overall impact of ironworking was limited.

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

“…The abundance of Juniperus within the early shrub community was perhaps encouraged by the relatively sheltered locality and the slow expansion of Betula. Such high frequencies of Juniperus are not, however, characteristic of other lowlying sites in North Wales, such as Glanllynnau and Tre'r Gof (Simpkins 1974;Botterill 1988) and Llyn Hendref (Watkins 1991), and Juniperus was not recorded at Bryn y Castell (Mighall & Chambers 1995). At higher altitude sites, such as Cwm Idwal (Tipping 1993), Nant Ffrancon (Hibbert & Switsur 1976), Clogwyngarreg (Ince 1996) and Llyn Llydaw (Ince 1983), Juniperus was a dominant component of early postglacial vegetation.…”

“…Seddon 1962;Burrows 1974;Hibbert & Switsur 1976;Ince 1983Ince , 1996Tipping 1993;Mighall & Chambers 1995). These sites illustrate both regional and local postglacial environmental change for upland sites.…”

Dating the introduction of cereal cultivation to the British Isles: early palaeoecological evidence from the Isle of Man

“…Large grass grains of cereal type occur within a disturbance episode at Moel y Gerddi with an interpolated date of ca. 5820 yr BP (Chambers et al, 1988), near to Bryn y Castell (Mighall and Chambers, 1995) with its similar date of ca. 5735 yr BP (Table 2).…”

“…These sites are shown on Fig. 1b and Table 2, which also include slightly younger, between 5600 yr BP and 5800 yr BP, pre-Ulmus decline cereal pollen dates from the British Isles (Pilcher and Smith, 1979;Hulme and Shirriffs, 1985;Hirons and Edwards, 1986;Edwards and McIntosh, 1988;Smith et al, 1989;Mighall and Chambers, 1995), but not several examples closer to the Ulmus decline itself (Edwards, 1988(Edwards, , 1989. For example, cereal pollen that occurs within a well defined clearance phase dated ca.…”

Using mineral magnetism to characterise ironworking and to detect its evidence in peat bogs

“…Pollen data for Llwyn Du confirms that the top of the sequence is missing. Pinus (pine) pollen remains at trace amounts at the site (Mighall and Crew, 2005) and there is no evidence of an increase in Pinus pollen as a result of forestry plantations, which is clearly seen in other pollen diagrams close to Llwyn Du (Walker and Taylor, 1976;Mighall and Chambers, 1995).…”