Forest and moorland in the South Pennine uplands in the mid-Flandrian period. II. The hillslope forests

• Published in: The Journal of ecology 1990-12, Vol.78 (4), p.857-883
• Main Authors: Tallis, J.H, Switsur, V.R
• Format: Article
• Language: English
• Subjects: altitude; altitudinal zones; botanical composition; Earth sciences; Earth, ocean, space; Exact sciences and technology; fire effects; fires; forest trees; forests; heathlands; Highlands; hill land; Lowland forests; Lowlands; Montane forests; northern england; Paleobotany; paleoclimatology; paleoecology; Paleontology; Peat; plant ecology; Pollen; spatial distribution; Taxa; Timberlines; Trees; Vegetation
• ISSN: 0022-0477; 1365-2745
• DOI: 10.2307/2260940

(1) A simple model of pollen influx to an upland sampling site near the altitudinal treeline is described. In the model, influx derives from four successive altitudinal zones (called lowland forest, upland forest, scrub and moorland), and declines stepwise and exponentially with increasing distance downslope and upslope from the sampling site. An approximation of the spatial distribution of the four vegetation zones on the hillslope can be achieved if the pollen contributions from the four zones are expressed as percentage of total influx and are logarithmically transformed. (2) Three separate lines of evidence are used to determine the main pollen taxa contributing to the influx from these four vegetation zones in the South Pennines in the early and mid-Flandrian period. It is suggested that Alnus, Tilia and perhaps Fraxinus pollen comprised the lowland forest influx; Pinus, Quercus and Ulmus pollen comprised the upland forest influx; and Betula, Corylus and Salix pollen comprised the scrub zone influx. (3) The pollen-influx model is used to examine a pollen record from deep peat at 500 m a.s.l. on Robinson's Moss. Derbyshire, covering the time-period from about 9000 B.P. to 4500 B.P. The Robinson's Moss data are summarized as a logarithmic plot of the percentage contributions of pollen of moorland, lowland forest, upland forest and scrub taxa. Supplementary pollen information from two other upland sites is used to identify the environmental processes operating over that period in the South Pennines. (4) Four processes are highlighted: a rapid temperature rise in the early Flandrian; repeated burning at and near the treeline; soil deterioration and blanket peat formation; and a reversion to a colder and perhaps wetter climate between c. 5300 and 4000 B.P. (5) At Robinson's Moss an altitudinal zonation of forest and scrub communities developed gradually on the hillslopes during the early Flandrian, and had achieved a position of approximate stability by 6700-6800 B.P. These forest and scrub communities continued to expand upslope for several hundred years after they had become established in the lowlands. (6) Fluctuating non-arboreal pollen values throughout the period 9000-4500 B.P. indicate that the uppermost scrub communities were very sensitive to environmental perturbation. Changes attributable to climatic, edaphic and biotic factors are identified and discussed. (7) Mesolithic hunting bands may have had a major impact on the upland scrub in many part