Data from: Climatic influences on winter precipitation use by trees in summer

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. The data set
provides information on the sites (e.g., latitude/longitude, site name),
site characteristics (e.g., weather/climate), tree species studied (beech,
spruce and oak), and corresponding observations of stable isotopes of
hydrogen and oxygen in tree xylem water.