Abstract. Severe droughts are expected to become more frequent and persistent. However, their effect on autumn leaf senescence, a key process for deciduous trees and ecosystem functioning, is currently unclear. We hypothesized that (I) severe drought advances the onset of autumn leaf senescence in temperate deciduous trees and that (II) tree species show different dynamics of autumn leaf senescence under drought. We tested these hypotheses using a manipulative experiment on beech saplings and three years of monitoring mature beech, birch and oak trees in Belgium. The autumn leaf senescence was derived from the seasonal pattern of the chlorophyll content index and the loss of canopy greenness using generalized additive models and piece-wise linear regressions. Drought did not affect the onset of autumn leaf senescence in both saplings and mature trees, even if the saplings showed a high mortality and the mature trees a high leaf mortality (due to accelerated leaf senescence and early leaf abscission). We did not observe major differences among species. Synthesis: The timing of autumn leaf senescence appears conservative across years and species, and even independent on drought stress. Therefore, to study autumn senescence, seasonal chlorophyll dynamics and loss of canopy greenness should be considered separately.
A R2R3-MYB GeneLfMYB113is Responsible for Autumn Leaf Coloration in Formosan sweet gum (Liquidambar formosanaHance)
