Mining ecophysiological responses of European beech ecosystems to drought

•Severe droughts reduce European beech GPP and ET annual fluxes by 20%.•Low precipitation limits beech forest productivity much more than heat stress.•Beech forests are sensitive to the timing of drought onset over the growing season.•Future GPP trends depend mainly on precipitation trends simulated by climate models.•Increased WUE in the future will counterbalance negative drought impacts.