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: Precursor system Temporal - persistence Spatial – patch size, location in environmental gradients Disturbance regime context

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

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

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

Non-forest openings Wildfire Patch size 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 50 100 Persistence of early seral (yrs) tropics

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)

Big, homogeneous disturbance – fine-scale complexity

Stand-Replacing Disturbance Fires

Stand-Replacing Disturbance Fires Harvests

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

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

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

“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?

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?