Didier Bert is a Research Engineer in dendroecology at INRA Bordeaux. He studies response of forests and trees to environment with the dendrochronological approach. Tree-rings record the effects of genetics, environment and sylviculture through time. They give the opportunity to understand the present vitality of forest ecosystems by retrospective analysis and, then, to evaluate their most likely evolution in the future. He has addressed the effect of fungi pathogens on the health of Maritime pine, the relationships between climate and growth of European provenances of oaks in common gardens, and the dynamics of a relictual beech forests in South-West of France.