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Improvement of water and light availability after thinning at a xeric site: which matters more? A dual isotope approach
Author(s) -
Giuggiola Arnaud,
Ogée Jérôme,
Rigling Andreas,
Gessler Arthur,
Bugmann Harald,
Treydte Kerstin
Publication year - 2016
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.13748
Subject(s) - deserts and xeric shrublands , thinning , stomatal conductance , environmental science , limiting , ecology , biology , botany , habitat , photosynthesis , mechanical engineering , engineering
Summary 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.