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Early Seral Ecosystem Creation And Dynamics
 

Early Seral Ecosystem Creation And Dynamics

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Early Seral Ecosystem Creation And Dynamics

Early Seral Ecosystem Creation And Dynamics

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    Early Seral Ecosystem Creation And Dynamics Early Seral Ecosystem Creation And Dynamics Presentation Transcript

    • Early Seral Ecosystem Creation and Dynamics Thomas Spies PNW Research Station
    • Topics
      • What is early seral?
      • Disturbance effects
      • Successional pathways
      • Regional patterns and trends
    •  
    • His ES High Severity Fire Mixed-Severity Fire
    • A Definition
      • An stage in forest succession that is the immediate product of a disturbance that removes most of the canopy cover
        • Less than 20% canopy cover remaining
        • Large enough patch for light-demanding vegetation to establish
        • Contains biological legacies from previous forest
        • Short lived, depending site productivity
    • Components of Early Seral
      • Loss of tree canopy
      • And reduction or loss one or more of following:
        • Standing trees
        • Understory vegetation
        • Forest floor litter
        • Large woody debris
        • Soil organic matter
        • Tree roots
    • Disturbances that create early seral ecosystems vary in their effects on ecosystem structure Structural Element Wind Fire Landslide Clear cut/Burn Canopy foliage X X X X Standing Trees X x X X LWD X X/ x Understory vegetation X X X Forest Floor X X X OM Soil x X x Roots x
    • 0 20 Low Mod High Tree Canopy Closure (%) Dead and Live Biological Legacies Wildfire Windthrow Landslide Early Seral Based on What Remains Retention Systems
    • Blowdown, Bull Run Watershed
    • HOH Fire Tillamook Fire High Severity Wildfire Yacolt Burn
    • Landslides in Coast Range Photo by Rob Pabst
    • Long-lived early seral related to land-use history and site conditions
    • Early Seral on Intensively Managed Forest Land
    • Gap Disturbances
    • Gap Height Diameter/Ht Ratio = 1.0 Diameter/Ht Ratio = 0.5 Gap Size Effect Dense Conifer Forests ES plant species begin to appear ES plant species infrequent
    • Gap diameter/canopy ht ratio Number of Gaps Most natural gaps are too small for early successional conditions
    • Fire as a gap process in dry, fire-prone forests
    • Historical dynamics of fire and succession in Ponderosa Pine R. Van Pelt Time Zero 20 yrs 40 yrs 60 yrs 80 yrs Fire Suppression
    • ES ES ES ESES Successional Pathways ES
    • ES ES ES
    • Early seral creation in the Biscuit Fire
    • Biscuit Fire Crown Damage by Vegetation Cover Class
      • Median crown damage was 74%
        • 96% for shrub/regen
        • 88% for hardwoods
        • 62% small conifers
        • 53% mixed small and large conifers
        • 32% large conifers (>20 inches dbh)
      Thompson and Spies In Press (ES)
    • Historical Range of Variability Oregon Coast Range % of Landscape Early Seral: 10-25% Old Growth: 35-60% % of Landscape Probability
    • Wildfire Conversion of Old Forest to Early Successional 1993-2003 Percent Loss of Older Forest on a Decadal Basis By Province Based on Moeur and Spies et al. 2005 3.1 % ( incl BB and DL) 3.6 % 3 % 9.5 % 2.3 % 0.4 % 0 % 0 % 0 % 1.4 % 0 %
    •  
    • Conclusions
      • All ES Share the same element: Loss of tree canopy cover to low levels (e.g. <20%)
      • Disturbances produce different kinds of ES vegetation
      • A transitory stage that lasts 15 ~ 30 years depending on site productivity and vegetation type
    • Conclusions
      • Gaps have limited capacity to create ES in wetter forests
      • Small disturbance patches are more effective ES in dry forest types than in wetter types
      • ES can arise at any stage in succession
    • Conclusions
      • Rate of ES creation has varied over time
      • Amount of diverse ES is declining in wetter forests across all ownerships
      • ES created by intensive forest management is not the same as that created by natural disturbances
    •