La sensibilité au climat des arbres forestiers a-t-elle changé au cours du XXe siècle ?

Significant warming already observed in Europe and in France together with predictions made at the end of the 20th century raise questions in the forestry and forest-based community about the sustainability of species and ecosystems in this rapidly changing context. A dendroclimatological approach can be adopted to analyse the response of species to climate, in which inter-annual variations in radial increment are explained using temperature and water climatic factors. This analysis relies on a fundamental principle referred to as “the principle of uniformity” that sets out that the physical and biological processes that govern the growth of trees currently growing are the same as in the past and have the same type of effect. In other words, the response of trees to year-to-year climate variations is assumed to be stable over time. However, for some years now, this principle of uniformity has been challenged by environmental changes that reflect instability of tree response to climate over time. This instability is referred to as “the divergence problem”. This article summarises current knowledge about the sensitivity to climate of forest species and divergence problems encountered in the various northern hemisphere forest ecosystems.