Pedunculate Oak Woodland in a Severe Environment: Black Tor Copse, Dartmoor

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Abstract
Black Tor Copse is one of 3 small oakwoods growing in isolated positions among granite blocks on steep slopes at > 250 m altitude on Dartmoor, an upland area of moorland in southwest England. The trees of these oakwoods are distinctive in growth form and height. Some are procumbent, while upright trees are from 2-12 m tall. Most are of gnarled and twisted appearance. Historical records show that grazing by cattle, sheep and horses of the moorland surrounding Black Tor Copse was intense for at least 700 yr, and that the woodlands have had much the same appearance for at least 400 yr. Tree growth outside Black Tor Copse is probably limited primarily by soil waterlogging and only secondarily by grazing. There is no evidence of management as a timber source. Grazing has probably limited the distribution of trees within the edaphically suitable area. Analyses of tree size, age and density suggest that different parts of Black Tor Copse have arisen during different periods of regeneration, and that competition within dense stands is the underlying cause of mortality. Regeneration from seed takes place only in open sites offering some protection from grazing. Such sites probably arise as a result of a phase of canopy degeneration. There is some evidence of regeneration from old stools after wind-blow. Regeneration is sufficient to sustain the woodland canopy at Black Tor Copse. Year-to-year changes in effects of grazing, stock numbers, tree regeneration and mortality need to be monitored to allow prediction of any major changes in the state of the woodland.