title: Recovery of trees from drought depends on belowground sink control.
abstract: Climate projections predict higher precipitation variability with more frequent dry extremes(1). CO2 assimilation of forests decreases during drought, either by stomatal closure(2) or by direct environmental control of sink tissue activities(3). Ultimately, drought effects on forests depend on the ability of forests to recover, but the mechanisms controlling ecosystem resilience are uncertain(4). Here, we have investigated the effects of drought and drought release on the carbon balances in beech trees by combining CO2 flux measurements, metabolomics and (13)CO2 pulse labelling. During drought, net photosynthesis (AN), soil respiration (RS) and the allocation of recent assimilates below ground were reduced. Carbohydrates accumulated in metabolically resting roots but not in leaves, indicating sink control of the tree carbon balance. After drought release, RS recovered faster than AN and CO2 fluxes exceeded those in continuously watered trees for months. This stimulation was related to greater assimilate allocation to and metabolization in the rhizosphere. These findings show that trees prioritize the investment of assimilates below ground, probably to regain root functions after drought. We propose that root restoration plays a key role in ecosystem resilience to drought, in that the increased sink activity controls the recovery of carbon balances.
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Zürcherstrasse 111, 8903 Birmensdorf, Switzerland.
authors.forename: Frank
authors.initials: F
authors.lastname: Hagedorn
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Zürcherstrasse 111, 8903 Birmensdorf, Switzerland.|Chair of Hydrology, Faculty of Environment and Natural Resources, University of Freiburg, Fahnenbergplatz, 79098 Freiburg, Germany.
authors.forename: Jobin
authors.initials: J
authors.lastname: Joseph
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Zürcherstrasse 111, 8903 Birmensdorf, Switzerland.
authors.forename: Martina
authors.initials: M
authors.lastname: Peter
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Zürcherstrasse 111, 8903 Birmensdorf, Switzerland.
authors.forename: Jörg
authors.initials: J
authors.lastname: Luster
authors.affiliation: Institute of Biochemical Plant Pathology, Helmholtz Zentrum München, German Research Centre for Environmental Health (GmbH), Ingolstaedter Landstrasse 1, 85764 Neuherberg, Germany.
authors.forename: Karin
authors.identifier: 0000-0001-6384-2473
authors.initials: K
authors.lastname: Pritsch
authors.affiliation: Institute of Biochemical Plant Pathology, Helmholtz Zentrum München, German Research Centre for Environmental Health (GmbH), Ingolstaedter Landstrasse 1, 85764 Neuherberg, Germany.
authors.forename: Uwe
authors.initials: U
authors.lastname: Geppert
authors.affiliation: Institute of Biochemical Plant Pathology, Helmholtz Zentrum München, German Research Centre for Environmental Health (GmbH), Ingolstaedter Landstrasse 1, 85764 Neuherberg, Germany.
authors.forename: Rene
authors.initials: R
authors.lastname: Kerner
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Zürcherstrasse 111, 8903 Birmensdorf, Switzerland.
authors.forename: Virginie
authors.initials: V
authors.lastname: Molinier
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Zürcherstrasse 111, 8903 Birmensdorf, Switzerland.
authors.forename: Simon
authors.initials: S
authors.lastname: Egli
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Zürcherstrasse 111, 8903 Birmensdorf, Switzerland.
authors.forename: Marcus
authors.initials: M
authors.lastname: Schaub
authors.affiliation: Research Institute of Forestry, Chinese Academy of Forestry, Xiangshan Road, 100091 Beijing, China.
authors.forename: Jian-Feng
authors.initials: JF
authors.lastname: Liu
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Zürcherstrasse 111, 8903 Birmensdorf, Switzerland.
authors.forename: Maihe
authors.initials: M
authors.lastname: Li
authors.affiliation: Department of Forest Genetics, Dendrology and Botany, Faculty of Forestry, University of Zagreb, Svetošimunska 25, HR-10000 Zagreb, Croatia.
authors.forename: Krunoslav
authors.initials: K
authors.lastname: Sever
authors.affiliation: Chair of Hydrology, Faculty of Environment and Natural Resources, University of Freiburg, Fahnenbergplatz, 79098 Freiburg, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Weiler
authors.affiliation: Laboratory of Atmospheric Chemistry, Ecosystem Fluxes Group, Paul Scherrer Institute (PSI), 5232 Villigen, Switzerland.
authors.forename: Rolf T W
authors.identifier: 0000-0002-0249-0651
authors.initials: RT
authors.lastname: Siegwolf
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Zürcherstrasse 111, 8903 Birmensdorf, Switzerland.|Institute for Landscape Biogeochemistry, Leibnitz Centre for Agricultural Landscape Research (ZALF), Eberswalder Strasse 84, 15374 Müncheberg, Germany.|Berlin-Brandenburg Institute of Advanced Biodiversity Research (BBIB), Altensteinstrasse 6, 14195 Berlin, Germany.
authors.forename: Arthur
authors.initials: A
authors.lastname: Gessler
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Zürcherstrasse 111, 8903 Birmensdorf, Switzerland.|School of Forest Science and Resource Management, Technical University of Munich, Hans-Carl-von-Carlowitz-Platz 2, 85354 Freising, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Arend
mesh_terms: D057486:Carbon Cycle; D055864:Droughts; D029964:Fagus / Q000502:physiology*; D012987:Soil / Q000737:chemistry*; D014197:Trees / Q000502:physiology*
chemical_list: D012987:Soil