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Examines the various forms of evidence used to establish the history and scale of environmenal changes during the Quaternary. The evidence is extremely diverse, ranging from landforms and sediments to fossil assemblages and isotope ratios, bringing the book fully up to date since its last publication.

The overall aim of the TIGGER IIb project is to increase our understanding of the manner and rates by which ecosystems responded to climate changes during the Last Glacial-Holocene transition. Success in this venture requires better constrained palaeoenvironmental reconstructions than have been achieved thus far, and the TIGGER project focused, in particular, on three main aims: (1) off-setting the limitations of conventional radiocarbon dating, in order to provide a more secure chronology of events: (2) increasing the resolution and precision of palaeoclimatic reconstructions; (3) widening the scope of site-specific palaeoecological investigations. In this paper we focus on the first of these strategies, and describe the progress made in developing a more coherent timescale for the climate history of the Lateglacial period. This has been achieved by using a number of independent methods, including calibration of AMS radiocarbon dates obtained from terrestrial plant macrofossils, MCR estimates of summer temperatures based on coleopteran records, analysis of stable carbon isotope ratios in terrestrial plant macrofossils and tephrochronology. Following Bjorck et al.'s 1998 recommendations, we integrate the new results to construct a provisional event stratigraphy for the Last Glacial-Holocene transition in the British Isles, which is based on a sequence of features that are believed to be time-parallel. This approach is considered to provide a more coherent framework for direct comparison of the palaeo-environmental evidence from Britain with that from elsewhere.

Pollen-stratigraphic investigations are described from a site on the northern slopes of the Brecon Beacons, South Wales, in which over 5.0 m of Devensian Late-glacial and early Flandrian sediments have accumulated. Relative (percentage) pollen concentration, and deteriorated pollen diagrams were constructed and these data were augmented by radiocarbon dates from the major stratigraphic boundaries. The evidence shows that relatively mild conditions characterized the Late-glacial Interstadial, but these were succeeded at c. 10600 B.P. by the markedly colder phase of the Loch Lomond Stadial during which a severe periglacial climatic regime prevailed in the area. Climatic amelioration at c. 10000 B.P. led to a rapid sequence of vegetational changes and the establishment of a birch-hazel woodland on the lower slopes of the Brecon Beacons, possibly in the space of 1000 years. Of particular interest in the profile are fluctuations in both pollen percentages and pollen concentration values during the Late-glacial Interstadial which are interpreted as reflecting major landscape changes around the site. Possible explanations for the fluctuations, which may well have been climatically-induced, are discussed in the context of other Late-glacial records from Wales, Highland Britain and north west Europe.

Pollen-stratigraphic data supported by four radiocarbon dates are presented from a site on Hirta in the St Kilda archipelago, western Scotland. The pollen spectra in the basal sediments reflect an open tundra environment and are considered to be of Loch Lomond (Younger Dryas) Stadial age. Although no evidence of early Flandrian vegetation is preserved in the stratigraphy, the middle and upper levels of the profile contain a record of landscape changes throughout the middle and late Flandrian. During the period from about 6000 B.P. to the present, wood and scrub cover on the island was minimal and the vegetation consisted of a mosaic of grassland and heathland communities. Changes in the composition of the vegetation, involving in particular the role of maritime plant communities, are discussed principally in terms of regional climatic changes in the north-west Atlantic province.

Pollen-stratigraphic evidence is presented from three sites in Glen More on the Isle of Mull, Inner Hebrides, Scotland, which spans the time interval from the wastage of the Loch Lomond Advance glaciers to the virtual disappearance of woodland from the island in the Late Flandrian period. Radiocarbon dates suggest that the Isle of Mull was deglaciated by about 10 000 B.P., and palynological evidence from the base of the profiles implies time-transgressive deglacial retreat of the ice that occupied Glen More. Wastage of the last glaciers on the island was followed by the expansion of Empetrum heath and juniper scrub, the latter being widespread by about 9600 to 9500 B.P. At that time birch woodland may have been present in the lowlands and in sheltered localities along the coastal fringes, but the spread of Betula into the hills of central Mull appears to have occurred some 200 to 300 years later. Corylus avellana became widely established around 8800 B.P. and was followed by mixed woodland genera including Quercus, Ulmus, Pinus and Alnus. The relatively low representation of arboreal pollen in all three profiles suggests, however, that woodland was never widespread on Mull during the Flandrian due principally, it would seem, to exposure to strong westerly winds. The expansion of grassland and Calluna-dominated heaths during the Late Flandrian reflects a change to wetter climatic conditions, but may also be partly a consequence of anthropogenic activity, particularly in lowland areas.

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.

Stratigraphic records from four sequences in Britain that span the Last Glacial-Holocene transition (c. 15.0-11.5 cal ka BP) are summarized and compared using a calibrated timescale. Palaeoclimatic changes are defined using temperature estimates based on coleopteran data at two of the sites, and chironomid assemblages at the other sites. An attempt is made to distinguish between the timing of (a) climate shifts and (b) ecosystem responses at all four sites. The British data are compared with the GRIP ice-core record, recently advocated by Bjorck et al. as the type-sequence for the Last Termination in the North Atlantic region. There is a degree of compatibility between the British and GRIP palaeoclimatic records. The clearest climatic signals in the British lake records are (a) a period of warm conditions (a thermal maximum) between 15.0 and 14.5 cal ka BP, which equates approximately with GRIP zone GI-le; (b) the onset of climatic cooling, which appears to have commenced during GRIP zone GI-le, at c. 14.5 cal ka BP; (c) a period of marked climatic instability from 14.4 to 12.7 cal ka BP, the regional effects of which are difficult to resolve using the evidence presently available: (d) further climatic cooling, which commenced at around 13.0 cal ka BP, after which the lake biota, catchment soils and vegetation cover, at least in some parts of Britain, did not recover until the onset of the Holocene; (e) continued climatic cooling, with the most severe impact on lake ecosystems occurring during the period c. 12.6 to 11.5 cal ka BP.

This paper presents the results of further investigations into the early Postglacial environmental history of Rannoch Moor, Scotland. Detailed pollen analyses were carried out at four sites in the eastern and northern parts of the Moor, and radiocarbon dates were obtained from three of the profiles. The pollen stratigraphic and radiocarbon data lend considerable support to conclusions reached from previous research in the Rannoch Moor area. The evidence suggests that glacier ice of the Loch Lomond Advance had disappeared completely well before 10 000 BP by which time a dwarf shrub heath vegetation had become firmly established locally. Birch woodlands were widespread in the Rannoch Moor area by c. 9800 BP, and were succeeded by a forest cover of birch, hazel, pine and alder. The close similarities between the pollen records from all the sites on Rannoch Moor suggest that apart from minor local variations there was very little regional differentiation in vegetation composition throughout this area of the Grampians during the Postglacial period. This in turn suggests that the regional pollen assemblage zones (R-zones) defined here can be used for the correlation of ecological changes within the Rannoch Moor area.

Pollen stratigraphic investigations are described from two sites in the central Grampian Highlands, Scotland. At Loch Etteridge, which is situated beyond the presumed maximal extent of Loch Lomond Readvance ice, the basal deposits are of Late Glacial age, with the pollen spectra indicating a milder Interstadial followed by a harsher Stadial phase. The overlying sediments are Postglacial in age. Four radiocarbon dates were obtained from the Late Glacial deposits, the basal date being in excess of 13,000 B.P. The second site is located on the Drumochter Pass within the mapped Loch Lomond Readvance limits, and contains only Postglacial sediments. Data from the two sites are used to reconstruct the Late Glacial and Early Postglacial vegetational history of the central Grampian Highlands, and also as an aid in the establishment of a Late Devensian glacial chronology for the area.

Pollen stratigraphic investigations are described from three sites on Rannoch Moor in the western Grampian Highlands of Scotland. The profiles are broadly similar and provide a detailed record of vegetational and environmental change in the Rannoch Moor area during the early and mid-Postglacial periods. Radiocarbon dates from the base of one profile suggest that glacier ice of the loch Lomond Readvance had disappeared completely from Rannoch Moor well before 10 000 BP, and that by that time dwarf shrub heaths of Empetrum and Juniperus had become firmly established throughout the region. This heathland vegetation cover was replaced first by birch, then by birch-hazel woodland, and subsequently by forests of pine and birch, and pine and alder. Deteriorating climatic conditions which resulted in accelerated rates of leaching, the growth of acid blanket peat, and a marked increase in areas of waterlogged ground, led to the gradual decline of trees and the progressive evolution of the present-day landscape of blanket peat and heather moor.