© 1994 Heron Publishing—Victoria, Canada
Frost injury prediction model for Douglas-fir seedlings in the Pacific Northwest
Roger Timmis (1), James Flewelling (2) and Cheryl Talbert (1)
1. Weyerhaeuser Company Technology Center, Tacoma, WA 98477, USA / 2. 26724 51st Place Street, Kent, WA 98032, USA / Received August 16, 1993
Summary
Because simple seed- or breeding-zone guidelines are inadequate for controlling the risk of maladaptation to environmental
stresses, we are developing operational procedures to assess the risk of frost kill to genetically improved families of Douglas-fir
(Pseudotsuga menziesii Mirb. Franco).
We have (1) determined the time course of cold hardening and dehardening of nursery-grown Douglas-fir seedlings over four
winters, by means of controlled freezing tests, (2) fitted curves to relationships between temperature sum and both fall cold
hardening and spring dehardening, (3) applied the temperature sum models to daily temperature records of 80 weather stations
to estimate frequency of years with significant frost kill at those stations, (4) interpolated frost kill probabilities for
tree farms, using a thin plate spline procedure with elevation, latitude and longitude as variables, and (5) prepared a coarse-scale
frost risk map from the resulting grid point estimates.
With the exception of a few high-elevation stations, the most damaging frost at any station in any year occurred in either
the fall (October and November) or late spring (mid-April to mid-May). In general, damaging spring frosts were two to three
times more frequent than fall frosts, and areas in Oregon were at greater risk than areas at similar elevations and longitudes
further north. The spline surface was less precise for predicting spring frost risk than fall frost risk.
Keywords:
breeding zone, chill sum, cold hardening, dehardening, environmental stress, frost damage risk, lethal temperature, temperature
sum.
