Effects of clear-felling versus gradual removal of conifer trees on the survival of understorey plants during the restoration of ancient woodlands

摘要

Plantations of exotic conifers on ancient woodland sites retain many features of high conservation value and in many countries such sites are being actively restored. Clear-felling of the conifer trees is often a straight-forward first step, but recent guidance on restoration advocates gradual removal of the plantation crop to protect vulnerable woodland specialist plants. To date there has been little empirical evidence to support this policy. One hundred and four stands in 39 woodland sites in the UK owned by the Woodland Trust from Cornwall to Inverness-shire were surveyed in 2001 and again in 2009 to assess the survival of woodland flora following restoration by both clear-felling and gradual removal of the plantation crop. On average, there were over seven woodland specialist and ancient woodland indicator species in each of the stands surveyed. Loss of specialist woodland species – the most shade adapted component of the flora - over this time period was strongly correlated with the degree of canopy opening. In contrast, the loss of more light demanding plant species was not related to the intensity of tree removals. This study suggests that a careful assessment and prioritisation of conservation values is needed before restoration. Rapid removal of an exotic species as part of a restoration programme may have an adverse effect on subsequent succession.