Potential impacts of climate change on winter survival of perennial forage crops in the QuÉbec region of Canada

The predicted increase of 2 to 6°C in average winter temperature by 2050 in Québec will likely affect seasonal factors responsible for winter survival of forage crops. To assess the impact of climate change on the risk of winter injury to perennial forage crops, we identified causes of winter damage during fall and winter and developed specific agro-climatic indices expressing the risk of damage associated to each cause. Fall indices describe temperature and precipitation conditions during cold hardening. Winter indices integrate the impact of cold intensity and duration with the protective action of snow cover, assess the loss of cold hardiness due to warm temperatures, and estimate potential damage to roots by soil heaving and ice encasement. Twenty climate stations were selected within the agricultural regions of Québec. Temperatures and precipitation for the periods 2010-2039 and 2040-2069 were estimated for each station by adjusting daily weather data from the 1961-1990 period with climate change scenario data from the First Generation Coupled Canadian General Circulation Model. Estimated mean indices of the future periods were compared to current climate values.

By 2040-2069, the reduction of the hardening phase (5 d) and the warming of fall temperatures are expected to result in a decrease in cumulative cold degree days (CDD) below 5°C from the current 87 to 67 CDD. Rainfall during the hardening phase of forage crops will decrease from the current 66 to 47 mm. The rate of rainfall during the cold period, i.e. the period of exposure to temperatures equal or below 15°C, will increase from the current 0.54 to 0.76 mm/d. The annual minimum temperature will increase by 5.1°C, the length of the cold period will decrease by 14.5 d and the number of days with a snow cover will be reduced by 35.5 d. Consequently, cumulative cold degree days below 15°C will decrease from the current 156 to 68 CDD, daily degree days (DD) above 0°C will increase from the current 0.18 to 0.51 DD/d, and the period with a protective snow cover during the cold period will be reduced by 21 d. Although winters in Québec are expected to be warmer in the future, preliminary results indicate that the risk of winter injury to perennial forage crops is likely to increase because of sub-optimal cold acclimation conditions during fall, but mostly because of the predicted lack of a sufficient protective snow cover during the cold period.