The effects of widespread conifer afforestation on the acidity of lakes and
streams in the acid sensitive uplands of the UK has been researched extensively and has
contributed to the development and implementation of national forest management guidelines
(e.g. Forest and Water Guidelines; Forestry Commission, 1993). However, a recent policy
document (Woodlands for Wales; National Assembly for Wales, 2000) has proposed a major
shift in the management of 50% of the Forestry Commission estate in Wales from the current
system of patch clearfelling to Continuous Cover Forestry (CCF). This scale of change is
without precedent in the UK; no studies in the UK forest environment have examined the
likely environmental impacts of CCF. However, the wealth of environmental data from
studies of UK forests managed by patch clearfelling enables an assessment of the impact
of a change to CCF on three issues of particular relevance to surface water acidification
in the uplands; forest harvesting, soil base cation depletion and atmospheric pollutant
deposition. Whilst there is uncertainty as to how even-aged stands will be transformed
to CCF in the UK, guiding principles for CCF on acidic and acid sensitive sites should
focus on those aspects of management which minimise nitrate leaching, encourage base
cation retention within the soil-plant system and enhance base cation inputs from
external (atmospheric) and internal sources (weathering). CCF may provide opportunities
to achieve this by reducing the scale of clearfelling, increasing species diversity,
changing the structure of plantation forests and maintaining uninterrupted woodland cover.
Keywords: acidification, forestry, continuous cover forestry, clearfelling |