Ground flora and seed banks of woodlands in south west England

Abstract

This thesis examines the ground flora and seed banks of a range of forest and woodland types in south west England. Ground flora surveys were earned out and seed banks investigated by sampling and germination trials. Depletion of both the ground flora and seed banks of conifer plantations and neglected coppice was shown to have occurred after periods of 40-50 years or more. Re-coppicing or clear-felling of such woodlands did not always result in immediate ground flora recovery and subsequent seed bank renewal. After long periods of shade, resulting from neglect or the presence of a dense conifer canopy, the ground flora which develops after felling develops mainly from species which have survived either in the seed bank or in the ground flora. The seeds of many woodland species are poorly represented in the seed bank since they do not survive for long periods in the soil. Since these species are also intolerant of dense shade and they are generally lost from neglected and coniferised woodland. The diversity of the ground flora and hence the seed bank was shown to be limited by site fertility and fewer species were present at sites with acid soils than at those with more base-rich soils. Uneven-aged forestry systems were shown to promote a greater ground flora and seed bank diversity than the even-aged, clear-fell system currently used in most British forests. These alternative systems are particularly appropriate for use in lowland Britain. With declining agricultural profitability, recent changes in forestry policy encourage the expansion of forestry on surplus agricultural land. Since soil fertility is generally high on such land, the introduction of alternative forestry systems could fulfil a dual objective of commercially viable timber production with increased ground flora diversity and hence ecological interest.