Sitka spruce (Picea sitchensis) forests in Atlantic Europe: changes in forest management and possible consequences for carbon sequestration

Sitka spruce (Picea sitchensis (Bong.) Carr.) was introduced in Atlantic Europe in the nineteenth century. Forests of this species are the major forest type in the United Kingdom and Ireland, with substantial areas in Norway, France and Denmark. Most forests are managed under a patch clearfelling regime on comparatively short (35-50 years) rotations. However, forest policies in a number of countries seek to increase the structural and species diversity of Sitka spruce forests: such measures are also proposed to help adapt to projected climate change and management of climate risk. Datasets from 26 experimental plots in Atlantic Europe representing existing and alternative management approaches showed high carbon stocks under current management and lower stocks in all alternatives. In addition, there was little evidence of Sitka spruce being grown successfully in long-term intimate mixture. Thinning is required to increase the diversity of Sitka spruce forests, but this can result in increased risk of wind damage, and hence reduction in carbon stocks, other than on the most sheltered sites. Such risks will be higher with the wetter soils anticipated from greater winter rainfall. Future management of Sitka spruce forests for carbon sequestration should focus both on improvement of current management (e. g. use of higher-yielding genotypes) and on developing wind-stable stands through careful thinning to act as long-term carbon stores.