© 1991 Heron Publishing—Victoria, Canada
Seasonal changes in shoot water relations of Picea rubens at two high elevation sites in the Smoky Mountains
Christian P. Andersen and Samuel B. McLaughlin
Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6034, USA / Received August 25, 1988
Summary
Seasonal changes in water relations of current-year shoots of red spruce (Picea rubens Sarg.) were examined in relation to climatic conditions in trees growing at elevations of 1720 and 1935 m on Clingman’s Dome,
Tennessee, USA, where increment core data have shown that red spruce decline increases with elevation. Relative height growth
of trees at 1720 m was 68% greater than in trees at 1935 m. Following two weeks in July with only traces of precipitation,
trees at both sites showed decreased saturated osmotic potentials. The magnitude of the reduction was greater in trees at
the high elevation site than in trees at the low elevation site. However, during August and September, shoot water relations
of trees at both sites were similar. Precipitation patterns and water relations measurements suggested that, at both sites,
trees experienced water stress only briefly during the growing season and to a degree that could not account for the lower
growth rates of trees at the high elevation site.
During the period of cold hardening in October and November, trees at the low elevation site exhibited saturated osmotic potentials
that were lower by 0.2 MPa and solute accumulation (osmol kgdw–1) that was 48% greater than in trees at the high elevation site.
