The quantitative estimation of the likely impacts of climate changes on tree development and growth and on forest stand processes is clearly important both to projections about the future ecology of regional and global forests and to their role in mitigating climate change. In the extreme, the possibility of trees dying and of extensive forest decline is a matter of global significance. The main aim of the project has been to test the hypothesis that a doubling of the global atmospheric CO 2 concentration, and associated, more local changes in climate predicted from General Circulation Models to occur over the next 100 years, will not be detrimental to European forests. A number of models for predicting stand scale proceses have been compared one with another, and shown good agreement amongst their predictions. These models are now being used to make the projections regarding the likely medium to long-term effects of the rise in atmospheric CO 2 concentration and temperature for a range of species in different climates.
Some key questions remain.
Whilst the parameters in the data base have all been derived from growth experiments lasting several years, with the trees rooted in the ground, i.e. not in pots, no experiments have continued up to and through canopy closure. What is likely to happen then to the responses is difficult both to follow experimentally and to predict. Y-P. Wang, A.Rey and P.G. Jarvis. Carbon balance of young birch trees grown in ambient and elevated atmospheric CO 2 concentrations. Medlyn et al.