A Simulation Model for the Annual Frost Hardiness and Freeze Damage of Scots Pine

The changes in the frost hardiness of Scots pine were modelledby a dynamic model where the input variables were temperatureand photoperiod and the phase of annual development. The damagecaused by freezing was described by the sigmoidal relationshipbetween the relative needle damage and freezing temperature.The model simulations were carried out using temperature datafrom two sites in central Finland—Suonenjoki and Tampere.The validity of the frost hardiness model was tested with measuredfrost hardiness data from Suonenjoki. The effects of climaticwarming were also simulated by increasing temperature of thelong-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 damageincreased as a result of climatic warming, and the differencesin the chilling requirement had a stronger effect on the amountof damage in the warmed climate than in the present climate.A large variation between years was found in the level of damage. Annual development; climatic change; dynamic model; freeze damage; frost hardiness,Pinus sylvestris ; Scots pine