1. Boreal forest resilience Some initial thoughts BNZ LTER meeting, March 2009 Terry Chapin & Jill Johnstone

3. Is the boreal forest vulnerable to climate change? Is the degree of exposure high?Yes Is it sensitive to changing climate?Yes Does it have the diversity to adapt to change? – Species diversity? – Functional diversity? – Landscape diversity? Roles of local adjustment, migration, and invasion?

4. March-June Average Temperature (C°) Alaska: 1901-2099

5. Torre Jorgenson

6. Kenai bark beetle outbreak

7. Area burned in W. North America has doubled in last 40 years

8. Rupp We can expect more wildfire

9. Rural communities have locations fixed by infrastructure

10. People’s fine-scale relationship with fire has changed over time Pre-contact: Mobile family groups – People adjust to fire regime 1950s: Consolidation in permanent settlements – Fire affects communities

11. Wildfire options in 20-50 years? Maintain same fire regime as today? – ~20-fold increase in cost Maintain current budget for suppression? – Reduce area protected despite rising population Change landscape pattern of fire? – Increase landscape heterogeneity: reduce risk of huge fires – Requires community engagement in fire planning

12. How resilient is the boreal forest to climate change? Does it have the adaptive capacity to adjust? What components will be resilient and what will transform? Can fine-scale change contribute to coarse- scale resilience? – e.g., shift to deciduous dominance maintains fire as a critical forest process

13. Resilience & Ecosystem Feedbacks Dominant species Recruitment Interactions Competition, herbivory Functional traits Disturbance

14. Black spruce dominant Local seed rain Growth & survival FIRE Poor quality seedbeds (organic soil) Slow growth Low competition High moisture High moss Cool soils Resilience cycles in black spruce

15. Black spruce dominant Local seed rain Growth & survival FIRE Poor quality seedbeds (organic soil) Slow growth Low competition High moisture High moss Cool soils Black spruce forests Deciduous dominant Resprouting & seed dispersal Growth & survival High quality seedbeds (mineral soil) Rapid growth High competition Low moisture Rapid cycling Warm soils FIRE Deciduous forests Contrasting plant resilience cycles severe fire long fire interval short fire interval

16. Thick organic layer Cool, moist soils Slow decomposition Slow nutrient turnover High moss NPP Low severity fire High severity fire Long fire- free interval Thick organic layer Shallow organic layer Warm, well- drained soils Rapid decomposition High nutrient turnover High vascular plant NPP High litter production Low moss NPP Shallow organic layer Resilience cycles mediated by soil

17. Time disturbance Hidden changes in resilience yield ecological surprises Relative species dominance Undisturbed trajectory Disturbed trajectory Directional change in recruitment potential

18. Detailed paleo-records are often consistent with resilience thresholds Species abundance 1 Species abundance 2 Species abundance 1 Species abundance 2 1K 5K

19. Abrupt ecosystem shifts From Tinner et al. 2008

20. Disturbance & climate interact to alter forest resilience tundrablack sprucedeciduous dynamic equilibrium directional change

21. Landscapes will have variable resilience Example: Ecosystem sensitivity to surface fuel consumption high resilience low resilience

22. Summary of Points Biotic and abiotic elements interact to determine resilience – What interactions are most critical? – Do we know enough to predict these? – Can we test our predictions? Strong interactions may maintain non-equilibrium ecosystems – “Hidden” changes in resilience – Sudden responses – Possibly (often?) catalyzed by disturbance