The changes in the frost hardiness of Scots pine were modelled by a dy
namic model where the input variables were temperature and photoperiod
and the phase of annual development. The damage caused by freezing wa
s described by the sigmoidal relationship between the relative needle
damage and freezing temperature. The model simulations were carried ou
t using temperature data from two sites in central Finland-Suonenjoki
and Tampere. The validity of the frost hardiness model was tested with
measured frost hardiness data from Suonenjoki. The effects of climati
c warming were also simulated by increasing temperature of the long-te
rm climatic data. Genotypic differences in chilling requirement, which
determines the timing of the reduction of hardening competence, were
included in the simulations. The simulated needle damage increased as
a result of climatic warming, and the differences in the chilling requ
irement had a stronger effect on the amount of damage in the warmed cl
imate than in the present climate. A large variation between years was
found in the level of damage. (C) 1996 Annals of Botany Company