© 1992 Heron Publishing—Victoria, Canada
Modeling shoot water contents in high-elevation Picea rubens during winter
Richard L. Boyce, Andrew J. Friedland and Vanessa N. Macdonald
Environmental Studies Program, Dartmouth College, 6182 Murdough Center, Hanover, NH 03755, USA / Received January 27, 1992
Summary
During the winter of 1990–1991, a meteorological tower was established at an 880-m elevation site within the spruce–fir zone
on Mt. Moosilauke, New Hampshire, USA. Hourly means of air, needle and trunk temperatures, wind velocity, relative humidity
and solar radiation were recorded. On a weekly basis, shoots that had elongated during the preceding growing season were collected
from four red spruce (Picea rubens Sarg.) trees and their relative water contents (RWC) determined. Cuticular resistances of needles from these shoots were
measured four times during the winter.
Measured meteorological parameters were used in a previously developed model to simulate changes in red spruce shoot RWC during
the winter. The modeled results were compared to measured shoot RWCs. The predictive power of the model was improved when
it was modified to include measured values of cuticular resistance and needle and trunk temperatures. The new version of the
model accurately predicted RWC from late December 1990 to the beginning of April 1991, after which spring recharge appeared
to occur. We conclude that water lost from foliage was easily replaced by stored reserves and that uptake of water by the
roots was not required to maintain an adequate foliar water content during the winter.
