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Improvement of water and light availability after thinning at a xeric site: which matters more? A dual isotope approach

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Giuggiola Arnaud, Ogée Jérôme, Rigling Andreas, Gessler Arthur, Bugmann Harald, Treydte Kerstin,
Project iTREE-Long-term variability of tree growth in a changing environment - identifying physiological mechanisms using stable C and O isotopes in tree rings.
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Original article (peer-reviewed)

Journal New Phytologist
Volume (Issue) 210(1)
Page(s) 108 - 121
Title of proceedings New Phytologist
DOI 10.1111/nph.2016.210.issue-1

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 evapo- ration and might not be beneficial. Detailed knowledge of the short- to long-term physiologi- cal 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 nega- tive water balance and thus foster tree growth, and ultimately the survival of forest trees under drought
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