"1. The effect of climate change on forest biodiversity will be evaluated through better understanding of the ecological processes that shape species composition and are particularly sensitive to climate conditions. Forest species composition will correspond to the assemblage of tree species and both symbiotic and antagonistic species that can drive tree species composition. Climate conditions will include both average and extreme values of climatic variables (e.g. temperature, humidity and wind). 2. The relationships between forest biodiversity and functioning will be deciphered through better understanding of the respective role of tree species richness and composition and by focussing on the biotic interactions between species. As the fundamental ecological hypothesis behind the diversity – productivity relationship is the optimal use of resources, we will analyse the energy flow (i.e. resources production and consumption) across different trophic levels (trees and symbiotic organisms as producers, herbivores and pathogens as consumers). 3. In a final step we will aggregate the information from the first two steps to predict the effect of climate change on forest productivity through changes in tree species composition. The prediction will be expressed as a risk of dysfunction, in particular the risk of forest productivity loss. Traditionally, the risk for a given system is a function of hazard probability and system vulnerability to this hazard. In this case, hazards will be changes in average and extreme climatic conditions. Vulnerability will be the vulnerability to climate change of forest species that both shape forest composition and are the main drivers of forest biomass productivity. In each step, we will focus on fundamental ecological processes at work so that to deliver more generic scientific outcomes that will allow easier generalization to diverse types of European forest or forest managers expectations than a case by case approach."