© 1988 Heron Publishing—Victoria, Canada
Water relations of Eucalyptus pauciflora near the alpine tree line in winter
P. M. Cochrane and R. O. Slatyer
Research School of Biological Sciences, Australian National University, GPO Box 475, Canberra, ACT 2601, Australia / Received November 23, 1987
Summary
Water potential measurements were made, over three winter seasons, on Eucalyptus pauciflora Sieb. ex Spreng. at four elevations extending up to 200 m above the natural tree line in the Snowy Mountains area of southeastern
Australia.
Shoot water potentials were lowest in winter but never approached lethal levels. Contrary to expectations, there was no gradient
of water potential with elevation. This was attributed primarily to the absence of a gradient of soil temperatures once snowpack
had developed. Lowest water potentials were observed at air temperatures several degrees above zero, suggesting that transpiration
and
absorption may be differently affected, with temperatures above and below these values causing higher water potentials. The
results suggest that shoot dieback in winter, which is a common phenomenon at alpine tree lines, is not caused by low water
potentials in southeastern Australia.
