title: Improvement of water and light availability after thinning at a xeric site: which matters more? A dual isotope approach.
abstract: Thinning fosters individual tree growth by increasing the availability of water, light and nutrients. At sites where water rather than light is limiting, thinning also enhances soil evaporation and might not be beneficial. Detailed knowledge of the short- to long-term physiological response underlying the growth responses to thinning is crucial for the management of forests already suffering from recurrent drought-induced dieback. We applied a dual isotope approach together with mechanistic isotope models to study the physiological processes underlying long-term growth enhancement of heavily thinned Pinus sylvestris in a xeric forest in Switzerland. This approach allowed us to identify and disentangle thinning-induced changes in stomatal conductance and assimilation rate. At our xeric study site, the increase in stomatal conductance far outweighed the increase in assimilation, implying that growth release in heavily thinned trees is primarily driven by enhanced water availability rather than increased light availability. We conclude that in forests with relatively isohydric species (drought avoiders) that are growing close to their physiological limits, thinning is recommended to maintain a less negative water balance and thus foster tree growth, and ultimately the survival of forest trees under drought.
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, CH-8903, Birmensdorf, Switzerland.|Forest Ecology, Department of Environmental Systems Science, ETH Zürich, CH-8092, Zürich, Switzerland.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Giuggiola
authors.affiliation: INRA, UMR 1391 ISPA, 71 l'Avenue Edouard Bourlaux, 33140, Villenave d'Ornon, France.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Ogée
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, CH-8903, Birmensdorf, Switzerland.
authors.forename: Andreas
authors.initials: A
authors.lastname: Rigling
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, CH-8903, Birmensdorf, Switzerland.
authors.forename: Arthur
authors.initials: A
authors.lastname: Gessler
authors.affiliation: Forest Ecology, Department of Environmental Systems Science, ETH Zürich, CH-8092, Zürich, Switzerland.
authors.forename: Harald
authors.initials: H
authors.lastname: Bugmann
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, CH-8903, Birmensdorf, Switzerland.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Treydte
mesh_terms: D002247:Carbon Isotopes; D002980:Climate; D005843:Geography; D007553:Isotope Labeling / Q000379:methods*; D008027:Light; D008954:Models, Biological; D010103:Oxygen Isotopes; D041605:Pinus sylvestris / Q000502:physiology* / Q000528:radiation effects*; D018515:Plant Leaves / Q000502:physiology; D012621:Seasons; D012984:Software; D013557:Switzerland; D013997:Time Factors; D014197:Trees / Q000502:physiology / Q000528:radiation effects; D014867:Water / Q000378:metabolism*; D052584:Xylem / Q000502:physiology
chemical_list: D002247:Carbon Isotopes; D010103:Oxygen Isotopes; D014867:Water
keywords: MuSICA model; assimilation; light; stable isotopes; stomatal conductance; thinning; tree rings; water