© 2000 Heron Publishing—Victoria, Canada
Dependence of winter water relations of mature high-elevation Picea engelmannii and Abies lasiocarpa on summer climate
Richard L. Boyce (1) and Gregg P. Saunders (1)
1. Department of Biological Sciences, University of Denver, Denver, CO 80208, USA / Received September 14, 1999
Summary
Water relations of Engelmann spruce (Picea engelmannii Parry) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) trees growing at an elevation of 3230 m on Mt. Evans, Colorado, USA, were studied during the winters of 1995–1996
and 1996–1997. During both winters, current-year and 1-year-old shoots were collected weekly and their relative water contents
(RWC) determined. Measured meteorological parameters were used in a conifer winter water relations model, WINWAT, to simulate
changes in shoot RWC of P. engelmannii and A. lasiocarpa during the winter. The model failed to predict shoot RWCs in 1996–1997 when calibrated with 1995–1996 data. The cold early
summer of 1995 inhibited xylem formation, which appears to have caused lower rates of water recharge to the needles during
the 1995–1996 winter than during the 1996–1997 winter. We conclude that summer climate strongly affects winter water relations
in these subalpine species, and that changes in both summer and winter climate must be considered when predicting future ranges
of these species.
Keywords:
modeling, conifer, Colorado, Front Range, Rocky Mountains.
