Reduced frost hardiness in temperate woody species due to climate warming: a model-based analysis

The climate warming that has occurred over the past decades may benefit plant growth and development because it reduces the severity of frost events. However, these rising temperatures may also lead to diminished frost hardiness in plants due to their insufficient hardening. Despite climate warming exerting such dual effects on frost damage, how this might change the frost damage of woody plants remains unknown. Here, we conducted a laboratory experiment that used the relative electrolyte leakage method to derive species-specific model parameters for frost hardiness and a damage model. Then we simulated the daily frost hardiness and damage of five typical temperate tree species (Ulmus pumila, Robinia pseudoacacia, Fraxinus chinensis, Salix babylonica, and Armeniaca vulgaris), from 1980 to 2015, in Beijing, China. The root mean square error (RMSE) between observed and predicted frost damage ranged from 3.58% to 7.65%. According to our simulation results, frost hardiness has declined over this 36-year period due to insufficient cold hardening of plants in autumn coupled with rapid dehardening in spring; however, the percentage of frost damage incurred by the five species showed a declining trend because of the reduced frequency and intensity of frost events. Thus, decreased frost severity may, to a large extent, offset the negative effects of diminished frost hardiness such that the frost risk faced by temperate forests may well remain constant or decline with continued climate warming.