The Late Quaternary palaeoecological history of the Great Wold Valley
The paucity of polliniferous deposits on the British chalklands has left something of a vacuum in the known vegetational history of the British Isles. Conflicting ideas of the past landscape of the chalklands have been presented by archaeologists (e.g. Clark, 1936) and botanists (e.g. Tansley, 1939; Pigott and Walters, 1954). The Tansleyan view, i.e. that the chalklands were forested until the Bronze Age, has held sway. Tansley suggested that the dominant species were Quercus and Fraxinus. This was challenged by the view that Tilia may have been a dominant on basic soils (Merton, 1970). Such palaeoecological evidence as exists would suggest that woodlands covered the southern chalklands prior to Bronze Age disturbance, thus vindicating the Tansleyan school.In this thesis data from a site lying on the Yorkshire Wolds are presented. For the first time a broad spectrum of palaeoecological information is presented from a British Flandrian chalkland deposit. Pollen, bryophytes, plant propagules and macrofossil remains, mollusc and insect data form the basis for an environmental reconstruction of the major water catchment area of the Yorkshire Wolds.This is complemented by a study of modern analogue sites where a vegetation survey had been undertaken. Plant propagules, molluscs and bryophytes from the surface soil and modern pollen rain (trapped over a one year period) were collected from each site. These data were incorporated into statistical analyses to compare the changes in the fossil data with the range of known analogue habitats (after Lamb, 1984).Willow Garth, an ancient carr woodland in the Great Wold Valley, yielded fossil-rich deposits from the late-glacial and Flandrian periods. Although the sedimentary history of this site would appear to be incomplete, an exceptionally detailed image of the palaeoecological history of this valley emerges. The transition from the late-glacial fen and tundra to the Pre-Boreal forest occurred at c. 9200 B.P.. However, the progression towards the mixed woodland of the Boreal forests appears to have been interrupted by the activities of Mesolithic man. It is suggested that Mesolithic hunter-gatherers were 'managing' the woodlands to maximise the carrying capacity of their game. One consequence of this activity was to prevent the forest canopy from closing over the chalk grassland. Calcicolous grassland species were present throughout this period suggesting that the local chalk grassland may never have been totally shaded out. If this was the case the chalk grasslands around the Great Wold Valley would be of considerably greater antiquity than is generally supposed.During the late-Neolithic and the Bronze Age there is abundant evidence of anthropogenic disturbance with the presence of agricultural weed taxa and pollen of Cerealia. Chalk grassland species are also represented in both the faunal and floral records from this period. Cattle probably grazed the fen and the local wetland flora reached a peak of diversity. In early Saxon times the fen started to dry out and it is suggested that its land use may have changed from a grazed fen to an osier bed at c. 1200 B.P.