Presentation on theme: "Historical Creation of Early Seral Habitat: Fire, Wind, Bugs …"— Presentation transcript:
1 Historical Creation of Early Seral Habitat: Fire, Wind, Bugs … Fred SwansonUSDA Forest ServicePacific Northwest Research Station
2 Early 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
3 Creating early seral Many disturbance types Few types commonly create big patchesMany processes create fine patterns
4 Controls 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
5 Disturbance processes in PNW Big patchFireForest cuttingVolcanic – tephra vs.lava flowsSmall patchLandslides – fastLandslides – slowWindBugsRoot rot
6 Non-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
8 Root 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)
13 Stand-Replacing Disturbance in Western Washington, 1972-2004 Fires HarvestsVolcanic eruption
14 Age 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)
15 What 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?
17 Closing 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?