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Historical Creation of Early Seral Habitat: Fire, Wind, Bugs …

Historical Creation of Early Seral Habitat: Fire, Wind, Bugs …. Fred Swanson USDA Forest Service Pacific Northwest Research Station. Early seral – definition issues. And we thought we have problems with old growth definitions! Easy to talk about the archtype Dimensions for definition:

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Historical Creation of Early Seral Habitat: Fire, Wind, Bugs …

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  1. Historical Creation of Early Seral Habitat: Fire, Wind, Bugs … Fred Swanson USDA Forest Service Pacific Northwest Research Station

  2. Early seral – definition issues And we thought we have problems with old growth definitions! Easy to talk about the archtype Dimensions for definition: • Precursor system • Temporal - persistence • Spatial – patch size, location in environmental gradients • Disturbance regime context

  3. Creating early seral • Many disturbance types • Few types commonly create big patches • Many processes create fine patterns

  4. Controls on disturbance effects • Selective of vegetation structure class • Selective of species • Spatial heterogeneity – of disturbance process, of affected ecosystem • Species dominating post-disturbance • Persistence of effects of disturbance – biotic legacies, dispersal, soil properties change

  5. Disturbance processes in PNW Big patch • Fire • Forest cutting • Volcanic – tephra vs. lava flows Small patch • Landslides – fast • Landslides – slow • Wind • Bugs • Root rot

  6. Non-forest openings large Mount St. Helens Blast zone – planted Mount St. Helens Blast zone - unplanted Mount St. Helens Primary succ. zone Lava flows Patch size Wildfire Clearcuts fast (Yang et al) slow Xeric meadows Mesic meadows Canopy gap small 0 50 100 tropics Persistence of early seral (yrs)

  7. Root rot, wind, bugs • Part of ecosystem disturbed • Species ready to occupy the site After Phellinus weiri Holah et al. (1997) observed: • Coast Range – shrubs dominate site • Cascades – hemlock dominates site After Bull Run windthrow – hemlock dominates (Sinton et al 2000)

  8. Big, homogeneous disturbance – fine-scale complexity

  9. Stand-Replacing Disturbance Fires

  10. Stand-Replacing Disturbance Fires Harvests

  11. Stand-Replacing Disturbance in Western Washington, 1972-2004 Fires Harvests 1972-1977 1977-1984 1984-1988 1988-1992 1992-1996 1996-2000 2000-2002 2002-2004 Volcanic eruption

  12. Early seral Age Class Distributions in Coastal Oregon Source: various CLAMS analyses (Spies et al. 2007)

  13. What we don’t know • Character of pre-management early seral habitat • Character of current plantations we might call early seral

  14. “Real”, complex early seral – More or less? Probably less! • Lack of cultural burning • Fire suppression • Reduced federal harvest • Forest encroachment in mesic meadows • Practices to hasten conifer canopy closure • Regime-scale effects – is there cumulative loss of structural complexity and biotic diversity over multiple cuttings? But, does harvest do the early seral creation job? Do we have more wildfire?

  15. Closing thoughts Next steps: • Synthesize existing knowledge of early seral condition and function • Confer about management options and impediments • Integrate thinking/management across landscapes and all age classes • Address geographic variation What are the similarities/differences with development of old-growth science, policy, and management?

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