Holocene blanket peat development in south west Scotland : the roles of human activity, climate change and vegetation change
Flitcroft, Catherine Esther
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This thesis examines the role of autogenic and allogenic forces in determining the timing and development of blanket peat initiation and how the occurrence and growth of blanket peat subsequently constrains human activities. A number of factors involved in the formation of blanket peat have been defined in the literature, in particular the roles of climate change, soil processes and anthropogenic effects, tested in this thesis from a typical peat-covered upland in south west Scotland. Tests are developed from a multi-proxy approach and by comparing peat-stratigraphic and palaeoecological records from a series of nine 14C dated peat profiles from a single hillside. A detailed examination of the sequence and timing of blanket peat initiation in the Holocene Epoch is presented from a case study from the head of the Glen App valley, Lagafater, south west Scotland. The evidence was taken from a total of nine peat transects at 215m OD, 300m OD and 400m OD where agricultural, hydrological and micro-climatic effects are expected to have differed and had different impacts on soils and vegetation. Samples were retrieved from the top, middle and bottom of a gently undulating slope at each altitude. This has allowed a localised picture of peat initiation to be obtained from each locality and with changes in altitude, allowed for an analysis of the factors responsible up and down slope and the identification of synchronous autogenic forces. A number of analytical techniques have been used. Pollen analysis was undertaken as the principal method of vegetation reconstruction at all sites, particularly through the initiation horizon. Variations in mire-surface wetness, determined through dry bulk density and humification analysis, were also employed to generate a record of probable changes in effective precipitation and the effect these may have had on the accumulation rate of the blanket peat. In order to attempt to answer the question of when blanket peat was initiated and to establish the synchroneity of changes, twenty nine AMS 14C dates were obtained. The evidence suggests that blanket peat developed during the Mesolithic period, through to the early Bronze Age. It substantiates an anthropogenic forcing factor for palaeohydrological changes, with early landscape management and cereal cultivation accelerating the process of blanket peat initiation. With progressive changes in precipitation interacting with factors such as weathering of bedrock and vegetation cover, the local landscape at Lagafater was covered by blanket peat by the early Bronze Age. The radiocarbon chronology obtained from the multi-proxy records allowed the synthesis of these data sets and the definition of Holocene vegetation change, climate change and the history of human impact throughout the early prehistoric era across this landscape.