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Boreal forest resilience

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

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Boreal forest resilience

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

  2. 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?

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

  4. Torre Jorgenson

  5. Kenai bark beetle outbreak

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

  7. We can expect more wildfire Rupp

  8. Rural communities have locations fixed by infrastructure

  9. 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

  10. 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

  11. 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

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

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

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

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

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

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

  18. Abrupt ecosystem shifts From Tinner et al. 2008

  19. directional change tundra black spruce deciduous Disturbance & climate interact to alter forest resilience dynamic equilibrium

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

  21. 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

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