1. Impacts of Climate Change on Western Forests Dr. Mark Johnston Saskatchewan Research Council and Prairie Adaptation Research Collaborative

2. Projections (broad generalizations) for the future climate of the Prairie Provinces Temperature: increasing, greater in winter than summer, greater at night than during day Precipitation: great uncertainty, annually small increase to significant decrease Evaporation: increased Soil moisture: decreased Growing season: increased Atmospheric CO 2 : increased Extreme events: increased frequency and magnitude Hydrology: increased variability, earlier peak flows

3. Major environmental drivers of change in forests  Temperature Both air and soil temperatures are important  Moisture availability Soil is key  Nutrient Availability Especially nitrogen  Atmospheric CO 2 concentration Interactions with other factors

4. Types of Impacts to Forests  Changes to productivity (growth rates)  Changes to disturbance regimes Forest fires, insect pests  Changes in species composition  Shifts in forest boundaries

5. Dry soils – productivity declines in the future Medium soils – productivity increases, then declines Wet soils – productivity increases in the future Note: Analysis assumes soils fully recharged following snowmelt Dry soils Medium soils Wet soils Source: Johnston 2001

6. Soil warming impacts  Warming will release additional nutrients, especially nitrogen  N is generally limiting in boreal forests so should increase growth  But dependant on water availability

7. Increased CO 2  Often assumed to increase growth  But increases constrained by N availability, water availability  Effect offset by other pollutants, e.g. ozone  Studies have shown transient response – may not be long-lasting

8. 30-50% increase in fire season severity under 2 X CO2 (Flannigan et al. 2001)

9. Insects  Drought increases vulnerability to insect feeding – higher carbohydrate levels in foliage  Jack pine budworm increases under drought conditions  Forest tent caterpillar associated with drought in forest fringe area  Forest fragmentation shown to increase FTC populations

10. Species composition  Changes in environment often lead to new species  But constrained by need to migrate – seed dispersal  Land use activities (roads, agriculture, urbanization) may prevent migration  Rate of climate change greater than species ability to move

11. Future climate? (Hogg and Hurdle 1995)