Conclusions

Since the late 1980s, researchers in Europe have reported that trees seem to be growing faster. The results of the pan-European project ‘Growth Trends in European Forests’ (Spiecker et al., 1996) indeed showed that the rate of forest growth has increased on many sites in Europe. The causes for this increase have now been investigated in the Recognition project (‘Relationships between Recent Changes of Growth and Nutrition of Norway Spruce, Scots Pine and European Beech Forests in Europe). The results indicate that increased nitrogen nutrition, thought to be mainly driven by the interaction of elevated atmospheric nitrogen deposition and natural recovery of the sites from former devastative land-use practices, contributes most to the observed increases in forest growth. Climatic changes and CO2 fertilization have not been the key factors for forest site productivity changes during the 20th century, but will, according to model predictions, be of increasing importance in the future.