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Climatic influences on summer use of winter precipitation by trees
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  • Gregory Goldsmith,
  • Scott T Allen,
  • Sabine Braun,
  • Rolf T.W. Siegwolf,
  • James W. Kirchner
Gregory Goldsmith
Chapman University, Chapman University

Corresponding Author:goldsmit@chapman.edu

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Scott T Allen
University of Nevada - Reno, University of Nevada - Reno
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Sabine Braun
Institute for Applied Plant Biology, Institute for Applied Plant Biology
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Rolf T.W. Siegwolf
Swiss Federal Institute for Forest, Swiss Federal Institute for Forest
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James W. Kirchner
ETH Zurich, ETH Zurich
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Trees in seasonal climates may use water originating from both winter and summer precipitation. However, the seasonal origins of water used by trees have not been systematically studied. We used stable isotopes of water to compare the seasonal origins of water found in three common tree species across 24 Swiss forest sites sampled in two different years. Water from winter precipitation was observed in trees at most sites, even at the peak of summer, although the relative representation of seasonal sources differed by species. However, the representation of winter precipitation in trees decreased with site mean annual precipitation in both years; additionally, it was generally lower in the cooler and wetter year. Together, these relationships show that precipitation amount influenced the seasonal origin water taken up by trees across both time and space. These results suggest higher turnover of the plant-available soil-water pool in wetter sites and wetter years.