Drought effects on autumn senescence depend on tree species and stand species richness.

With climate change, temperate forests will face more droughts, threathening their important functions in the earth system. To predict future health and productivity of temperate forests, it is crucial to understand how droughts affect senescence timing, as this determines the growing season length and affects annual carbon (C) uptake of deciduous trees. However, there is no consensus, with studies variously reporting delayed, advanced or unaltered autumn senescence after droughts. This suggests that effects dependent on the context, likely including drought severity, drought tolerance of studied species, and, by modulating competition for water, stand species richness. This project will study (i) how drought severity, species identity and species richness affect drought effects on senescence timing and (ii) whether longer autumn C uptake can compensate for drought-induced reduction of summer C uptake. To gain a broad understanding, I will tackle these questions using a sapling- and a forest plantation experiment, mechanistic modeling to estimate annual and autumnal C uptake under experimental conditions, and remote sensing observations of natural forests across Europe. The project combines phenology, ecophysiology and modeling to provide new insights on how droughts affect forest phenology and productivity. It will provide crucial information for forestry stakeholders about the viability of tree species and species mixtures under increased drought.

Keywords:TEMPERATE DECIDUOUS FORESTS, LEAF SENESCENCE, DROUGHT STRESS

Disciplines:Ecophysiology and ecomorphology, Terrestrial ecology, Plant ecology, Forestry sciences not elsewhere classified