Presentation on theme: "Historical Creation of Early Seral Habitat: Fire, Wind, Bugs …"— Presentation transcript:
1Historical Creation of Early Seral Habitat: Fire, Wind, Bugs … Fred SwansonUSDA Forest ServicePacific Northwest Research Station
2Early seral – definition issues And we thought we have problems with old growth definitions!Easy to talk about the archtypeDimensions for definition:Precursor systemTemporal - persistenceSpatial – patch size, location in environmental gradientsDisturbance regime context
3Creating early seral Many disturbance types Few types commonly create big patchesMany processes create fine patterns
4Controls on disturbance effects Selective of vegetation structure classSelective of speciesSpatial heterogeneity – of disturbance process, of affected ecosystemSpecies dominating post-disturbancePersistence of effects of disturbance – biotic legacies, dispersal, soil properties change
5Disturbance processes in PNW Big patchFireForest cuttingVolcanic – tephra vs.lava flowsSmall patchLandslides – fastLandslides – slowWindBugsRoot rot
6Non-forest openings Wildfire Patch size largeMount St. HelensBlast zone – plantedMount St. HelensBlast zone - unplantedMount St. HelensPrimary succ. zoneLavaflowsPatchsizeWildfireClearcutsfast (Yang et al) slowXericmeadowsMesic meadowsCanopygapsmall50100Persistence of early seral (yrs)tropics
8Root rot, wind, bugs Part of ecosystem disturbed Species ready to occupy the siteAfter Phellinus weiri Holah et al. (1997) observed:Coast Range – shrubs dominate siteCascades – hemlock dominates siteAfter Bull Run windthrow – hemlock dominates(Sinton et al 2000)
13Stand-Replacing Disturbance in Western Washington, 1972-2004 Fires HarvestsVolcanic eruption
14Age Class Distributions in Coastal Oregon Early seralRelative 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.Source: various CLAMS analyses (Spies et al. 2007)
15What we don’t know Character of pre-management early seral habitat Character of current plantations we might call early seral
16“Real”, complex early seral – More or less? Probably less! Lack of cultural burningFire suppressionReduced federal harvestForest encroachment in mesic meadowsPractices to hasten conifer canopy closureRegime-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?
17Closing thoughts Next steps: Synthesize existing knowledge of early seral condition and functionConfer about management options and impedimentsIntegrate thinking/management across landscapes and all age classesAddress geographic variationWhat are the similarities/differences with development of old-growth science, policy, and management?