Density- and age- dependent influences of droughts and intrinsic water use efficiency on growth in temperate plantations

•High-density younger trees were less sensitive to droughts than low-density trees.•Droughts increased water use efficiency for low-density old trees.•High-density younger trees had a more balance carbon uptake per water loss.•Droughts reinforce stomatal closure to reduce carbon uptake in low-density old age stands.•High-density young-age trees had high resistance but low recovery to drought.