Stand Structure and Ecological Restoration

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Stand Structure and Ecological Restoration

• Charles W. Denton
• Ecological Restoration Institute
• John D. Bailey, Associate Professor of Forestry,
  Associate Professor of Forestry, Northern Arizona
  University, School of Forestry

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Todays Topics

• Stand Dynamics and the role of disturbance
• Single vs. multiple species
• Density and basal area
• Even-aged stands
• Multi-aged stands
• Special stand structures, living and dead
• Scaling up spatially
• Temporal variation and planning

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Stand Dynamics

• Regulates
• Age and size distribution
  even-aged vs. multi-aged stands
• Vertical canopy structure/layers
• Horizontal arrangement issues
• Four basic stages
• Stand initiation
• Stand replacing event, growing space
• Stem exclusion (thinning)
• Self-thinning, low diversity, zero g.s.
• Understory reinitiation (transition)
• - shifting mosaic
• Old-growth

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Presettlement Age Distribution in Northern
Arizona
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Mast et al. 1999
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Single vs. Multiple Species

• Mix and ratios based on
• Disturbance type (e.g., fire)
• Shade tolerance
• Initiation vs. transition
• Management preferences
• Spatial arrangement issues

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Presettlement Ponderosa Pine Spatial
Distribution Gus Pearson Natural Area
width of circle indicates age
Covington et. al., 1997
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Current conditions at the Gus Pearson Restoration
site
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Diameter DistributionFort Valley, Arizona
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Kathy Smiths thesis 1999
S10
S9
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Interpreting Density Measures

• Trees per acre
• Little use in multi-aged
• BA and SDI
• Workable, particularly at extremes
• Canopy closure
• Aerial fuels and growing space

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Hypothetical Results of a BDQ 14-50-1.2 Treatment
S9-10 Before Treatment
S9-10 After Treatment
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Implications

• Multi-aged is historically accurate
• Group selection created clumpiness relative to
  individual-tree selection
• Must revisit the sites regularly - the 1919
  cohort is now a real problem
• VSS distribution
• Mistletoe does not have to be a concern

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Special Structural Elements

• Large, old trees
• Not old-growth trees
• Vigorous lower and mid-canopy trees
• True advantage of multi-aged
• Snags and aerial dead wood
• Wildlife habitat value
• Downed, coarse woody debris
• Ecosystem value
• ALL have their limits!

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STIFH Treatment Gradient
Unburned
Burned
Control
Thinned
Wildfire
Thinned and Burned
Disturbance Gradient
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Forest Health Indicators

• Overstory structure and growth/vigor
• Fuel loading
• Understory composition
• Insect diversity
• Soil nitrogen
• Ectomycorrhizal fungi
• Wildlife use

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Scaling up spatiallywelcome to ecosystem
management

• Three fundamental scales for diversity
• Within stand
• Among stands
• Landscapes, watersheds and fragmentation
• Stand inequality is good
• ALL have their role!

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Temporal Scales

• Trees grow
• Disturbance happens
• Trees grow
• Stands change somewhat predictably given stand
  dynamics, but often unpredictably
• Trees grow
• Adaptive Management!

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Fire mortality1999 data collection
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REGENERATION

• Adequate in most decades
• seed tree density and production
• seedbed and germination
• mortality, particularly with fire
• More likely TOO MUCH
• Some decades may be insufficient, but thats OK

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Concluding RemarksStructure and Restoration

• Its ALL about structure
• Multi-aged is often the way, but more complicated
• Promote small trees, too
• Spatial heterogeneity
• Diversity at all three scales