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How do forest ecosystems respond to environmental change?

How do forest ecosystems respond to environmental change?. Resilience & Ecosystem Feedbacks. Dominant species. Disturbance. Functional traits. Recruitment. Interactions. Competition. Aerial seed bank. Low nutrient cycling. Cold soils. Recruitment on organic soils. Conservative growth.

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How do forest ecosystems respond to environmental change?

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  1. How do forest ecosystems respond to environmental change?

  2. Resilience & Ecosystem Feedbacks Dominant species Disturbance Functional traits Recruitment Interactions Competition

  3. Aerial seed bank Low nutrient cycling Cold soils Recruitment on organic soils Conservative growth Mosses accumulate Resilience Feedbacks Black spruce

  4. Self-replacement of black spruce Asexual regeneration of understory Little compositional change after disturbance Typical successional trajectories

  5. Deep burning fires can shift successional trajectories Is there a threshold of organic soil consumption that has predictable effects on regeneration pathways?

  6. Recruitment declines with organic depth 2-yr recruitment from seeding experiments (Alaska/Yukon) n=4 to 16 (total plots = 60)

  7. Seedling Density Species differences lead to strong effects on post-fire dominance Aboveground Biomass • Burned spruce forest • Alaska 40,000 ha burn • 8 yrs post-fire • n=19 stands

  8. Can we detect thresholds across real landscapes? • Alaska 2004 fires • 3 fire complexes • 90 black spruce sites

  9. Regression Tree pseudo-R2=0.65 Deciduous vs. Spruce Recruitment Natural seedling densities 2 yrs post-fire

  10. Fire & regeneration thresholds • Residual organic layer determines seedbed quality • Differences in species sensitivity lead to strong composition effects • Increased fire severity => crossing threshold of residual organics => shift in successional trajectory

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

  12. Low nutrient cycling X X Conservative growth Resilience Feedbacks Species dominant Organic seedbeds X Interactions Recruitment Mosses accumulate

  13. Critical Research • Moving deeper in time • What are the longer term consequences of variations in fire severity? • Understanding space • Which parts of the landscape are vulnerable to shifts in trajectories, and which aren’t? • Can we test anticipated changes?

  14. Climate response dynamics • Key feedbacks support resilience • Do threshold responses measure the depth of resilience? • At the landscape scale, is this the primary pathway for climate change response?

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