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.