Immediate and potential long-term effects of consecutive heat waves on the photosynthetic performance and water balance in Douglas-fir.
The frequency and intensity of climatic extremes, such as heat waves, are predicted to increase globally, with severe implications for terrestrial carbon and water cycling. Temperatures may rise above critical thresholds that allow trees to function optimally, with unknown long-term consequences for forest ecosystems. In this context, we investigated how photosynthetic traits and the water balance in Douglas-fir are affected by exposure to three heat waves with temperatures about 12°C above ambient. Photosynthetic carboxylation efficiency (Vcmax) was mostly unaffected, but electron transport (Jmax) and photosynthetic rates under saturating light (Asat) were strongly influenced by the heat waves, with lagging limitations on photosynthesis still being observed six weeks after the last heat wave. We also observed lingering heat-induced inhibitions on transpiration, minimum stomatal conductance, and night-time stomatal conductance (gs-night). Results from the stomatal models used to calculate minimum stomatal conductance were similar to gs-nightand indicated changes in leaf morphology, e.g. stomatal occlusions and alterations in epicuticular wax. Our results show Douglas-fir's ability to restrict water loss following heat stress, but at the price of reduced photosynthetic performance. Such limitations indicate potential long-term restrictions that heat waves can impose on tree development and functioning under extreme climatic conditions.
Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research-Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany; The University of Western Ontario, 1151 Richmond St., London, ON, N6A 3K7, Canada. Electronic address: aduarte4@uwo.ca.
André G
AG
Duarte
Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research-Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany; Japan Atomic Energy Agency, Ibaraki, Japan.
Genki
G
Katata
Institute of Sustainable Plant Protection, National Research Council of Italy, Turin, Italy.
Yasutomo
Y
Hoshika
Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research-Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany; The University of Western Australia, Perth, Australia.
Mohitul
M
Hossain
University of Freiburg, Freiburg im Breisgau, Germany.
Jürgen
J
Kreuzwieser
Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research-Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany.
Almut
A
Arneth
Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research-Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany.
Nadine K
NK
Ruehr
D002244:Carbon / Q000378:metabolism*; D006358:Hot Temperature; D010788:Photosynthesis / Q000502:physiology*; D018515:Plant Leaves / Q000502:physiology; D054046:Plant Stomata / Q000502:physiology; D018526:Plant Transpiration / Q000502:physiology*; D028224:Pseudotsuga / Q000502:physiology*; D014197:Trees; D014867:Water / Q000502:physiology*
D014867:Water; D002244:Carbon
Douglas-fir (Pseudotsuga menziesii); Heat waves; Minimum stomatal conductance; Photosynthesis; Recovery; Water balance