Fred Swanson - Historical Creation of Early Seral Habitat: Fire, Wind, Bugs...


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Fred Swanson - Historical Creation of Early Seral Habitat: Fire, Wind, Bugs...

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  • Relative to HRV in the coast range, we have no shortage of early-seral forest in current landscape. Slide compares age-class distributions in current landscape (‘initial’, 1996) with HRV (300 years pre-Euro-settlement) and 100 years from now (CLAMS simulation – ignore for now). ~30% of current forest is early seral, vs. 3-12% historically.
  • Fred Swanson - Historical Creation of Early Seral Habitat: Fire, Wind, Bugs...

    1. 1. Historical Creation of Early Seral Habitat: Fire, Wind, Bugs … Fred Swanson USDA Forest Service Pacific Northwest Research Station
    2. 2. Early seral – definition issues <ul><li>And we thought we have problems with old growth definitions! </li></ul><ul><li>Easy to talk about the archtype </li></ul><ul><li>Dimensions for definition: </li></ul><ul><li>Precursor system </li></ul><ul><li>Temporal - persistence </li></ul><ul><li>Spatial – patch size, location in environmental gradients </li></ul><ul><li>Disturbance regime context </li></ul>
    3. 3. Creating early seral <ul><li>Many disturbance types </li></ul><ul><li>Few types commonly create big patches </li></ul><ul><li>Many processes create fine patterns </li></ul>
    4. 4. Controls on disturbance effects <ul><li>Selective of vegetation structure class </li></ul><ul><li>Selective of species </li></ul><ul><li>Spatial heterogeneity – of disturbance process, of affected ecosystem </li></ul><ul><li>Species dominating post-disturbance </li></ul><ul><li>Persistence of effects of disturbance – biotic legacies, dispersal, soil properties change </li></ul>
    5. 5. Disturbance processes in PNW <ul><li>Big patch </li></ul><ul><li>Fire </li></ul><ul><li>Forest cutting </li></ul><ul><li>Volcanic – tephra vs. </li></ul><ul><li>lava flows </li></ul><ul><li>Small patch </li></ul><ul><li>Landslides – fast </li></ul><ul><li>Landslides – slow </li></ul><ul><li>Wind </li></ul><ul><li>Bugs </li></ul><ul><li>Root rot </li></ul>
    6. 6. Non-forest openings Patch size Persistence of early seral (yrs) 0 50 100 small large Mount St. Helens Blast zone – planted Canopy gap Mount St. Helens Blast zone - unplanted Mesic meadows Xeric meadows Lava flows Mount St. Helens Primary succ. zone Clearcuts fast (Yang et al) slow Wildfire tropics
    7. 8. Root rot, wind, bugs <ul><li>Part of ecosystem disturbed </li></ul><ul><li>Species ready to occupy the site </li></ul><ul><li>After Phellinus weiri Holah et al. (1997) observed: </li></ul><ul><li>Coast Range – shrubs dominate site </li></ul><ul><li>Cascades – hemlock dominates site </li></ul><ul><li>After Bull Run windthrow – hemlock dominates </li></ul><ul><li>(Sinton et al 2000) </li></ul>
    8. 9. Big, homogeneous disturbance – fine-scale complexity
    9. 11. Stand-Replacing Disturbance Fires
    10. 12. Stand-Replacing Disturbance Fires Harvests
    11. 13. 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. 14. Age Class Distributions in Coastal Oregon Source: various CLAMS analyses (Spies et al. 2007) Early seral
    13. 15. What we don’t know <ul><li>Character of pre-management early seral habitat </li></ul><ul><li>Character of current plantations we might call early seral </li></ul>
    14. 16. “ Real”, complex early seral – More or less? Probably less! <ul><li>Lack of cultural burning </li></ul><ul><li>Fire suppression </li></ul><ul><li>Reduced federal harvest </li></ul><ul><li>Forest encroachment in mesic meadows </li></ul><ul><li>Practices to hasten conifer canopy closure </li></ul><ul><li>Regime-scale effects – is there cumulative loss of structural complexity and biotic diversity over multiple cuttings? </li></ul><ul><li>But, does harvest do the early seral creation job? Do we have more wildfire? </li></ul>
    15. 17. Closing thoughts <ul><li>Next steps: </li></ul><ul><li>Synthesize existing knowledge of early seral condition and function </li></ul><ul><li>Confer about management options and impediments </li></ul><ul><li>Integrate thinking/management across landscapes and all age classes </li></ul><ul><li>Address geographic variation </li></ul><ul><li>What are the similarities/differences with development of old-growth science, policy, and management? </li></ul>