With global warming, droughts in the 21st century will set in more rapidly, last longer and be more intense. Because forests store the majority of terrestrial carbon and are primary drivers of global evapotranspiration, feedbacks between rising temperature, extended periods of reduced precipitation, and forest functioning could have major implications on climate regulation. Acclimation to climate variability is a particularly important process for long-lived organisms like trees, as some may persist and experience climatic conditions in 100 years. However, how trees may acclimate on various time scales to a changing climate, and whether this plastic ability can be inherited by future generations is not well understood. The objectives of this project are (i) to assess the impacts of climate change on short- and long-term mechanisms of tree acclimation, (ii) to compare acclimation potential gained from transgenerational epigenetic effects vs. local adaptation, and (iii) understand the limits of acclimation and the tipping points leading to progressive tree decline to predict mortality trajectories. To reach these objectives, we apply stable isotope approaches, together with metabolite analyses and the assessment of physiological and morphological leaf and canopy traits affecting CO2 and water fluxes.