A simulation model for the annual frost hardiness and freeze damage of scots pine

The changes in the frost hardiness of Scots pine were modelled by a dynamic model where the input variables were temperature and photoperiod and the phase of annual development. The damage caused by freezing wits described by the sigmoidal relationship between the relative needle damage and Freezing temperature. The model simulations were carried out 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 climatic warming were also simulated by increasing temperature of the long-term 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 requirement had a stronger effect on the amount of damage in the warmed climate than in the present climate. A large variation between years was found in the level of damage.