Disturbance-Based Management

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Disturbance-Based Management

• Landscape-Level

• Pattern and complexity
• Stand age class distributions
• Patch distributions type, size,
• shape, and continuity
• Habitat representation
• Historic range of variability

• Stand-Level

• Vertical structure
• Horizontal structure
• Cohorts
• Tree age class distributions
• Biological legacies

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Structural Change Through Stand Development
Figure adapted from Franklin and Spies (1991).
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Recovery facilitated by biological legacies at
Mount St. Helens
Photos courtesy of Jerry F. Franklin, University
of Washington
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Large-scale Windthrow Hurricanes
Fine-scale Windthrow
Ice Storms
Insect and Pathogens Outbreaks
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Coarse Woody Debris in Northern Hardwood Forests

• Habitat
• Nitrogen Fixation
• Soil organic matter
• Mycorrhizal fungi
• Nurse logs
• Erosion reduction
• Riparian functions

Even-aged
Single-tree Selection
Old-Growth
Figure from McGee et al. (1999)
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Teakettle Ecosystem Experiment
Forest Ecosystem Research Network
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Variable Retention Harvest System
0
20
80
Retention at Harvest
20
100
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Removal at Harvest
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Entries per Rotation
2 - 3
4 or more
Even-aged (1 class)
Multi-aged (2-3 classes)
Age Classes
Uneven-aged (4 or more classes)
Figure from Franklin et al. (1997)
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Demonstration of Ecosystem Management Options
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Weyerhaeuser Co. Variable Retention Adaptive
Management (VRAM) Experiment
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Weyerhaeuser Co. Variable Retention Forestry in
B.C.
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VRAM
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Year 0
Year 15
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Long-Term Implications ?
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What have we learned about natural disturbance
effects?

• Scale and frequency of disturbance

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Mimicking scale and frequency of disturbances
Figures from Seymour et al. 2002
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Historical Range of Variability
HRV
Figure from Aplet and Keeton (1999)
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Hurricane
Scale Small Watershed
HRV
Hurricanes
Scale Drainage Basin
HRV
HRV
Scale Region
Source Aplet and Keeton (1999)
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Historical Range of Variability
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0.9
0.8
0.7
0.6
0.5
Proportion of Landscape in Early-Succession
0.4
0.3
0.2
HRV
0.1
0
1300
1350
1400
1450
1500
1550
1600
1650
1700
Year
Figure modified from Aplet and Keeton (1999)
using data from Cogbill (2000)
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What have we learned about natural disturbance
effects?

• Coarse-woody debris snags and downed wood

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Coarse Woody Debris in Northern Hardwood Forests

• Habitat
• Nitrogen Fixation
• Soil organic matter
• Mycorrhizal fungi
• Nurse logs
• Erosion reduction
• Riparian functions

Even-aged
Single-tree Selection
Old-Growth
Figure from McGee et al. (1999)
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What have we learned about natural stand
development?

• Importance of large trees as structural elements

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Crown Release to Increase the Representation of
Large Trees
Partial crown release
Full crown release
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No release
DBH (cm)
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150
300
Age (Years)
Data from Singer and Lorimer (1997)
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What have we learned about natural stand
development?

• Vertical complexity
• Horizontal complexity

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Structural Complexity Index (Zenner 2000)
A)
B)
Ratio of 3D area in A to 2D area in B
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Uneven-aged Forestry

• Single-tree selection
• Group selection

• BDq prescriptions are based on the desired
• residual basal area
• maximum dbh
• q-factor

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Single-Tree Selection Prescription for Mt.
Mansfield Unit 4 q-factor of 1.3, maximum
diameter of 24", and residual basal area of 80
ft2/acre
Stems per Acre
Diameter Class in Inches
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Diameter Distributions
Figure from Goodburn and Lorimer (1999)
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Unbalanced Diameter Distributions

• Density-dependent mortality reduced with fewer
  stems in smaller size classes
• Equal allocation of growing space not found
  consistently

Figure from Goodburn and Lorimer (1999)
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Multi-modal distributions due to old-tree legacy
Figure from Seymour 2005
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Rotated Sigmoid Diameter Distribution

• Often found in old-growth northern hardwoods and
  mixed-woods
• Varies with disturbance history, stand
  composition, and competitive dynamics
• Theoretical silvicultural utility proposed
  (OHara 1999, Leak 2003) tested experimentally
  by Keeton (2005).

of Trees
Shift in basal area allocation to larger size
classes
Diameter Class
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Yield vs. Big Tree Structure in Northern Hardwoods
Selection harvest old-growth structure after
multiple cutting cycles
Maximized volume production
Maximized large sawtimber volume and value growth
50 cm max.
80-100 cm max.
40 cm max.
Data from Hansen and Nyland (1987)
Data from Goodburn and Lorimer (1999)
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An Alternative Multi-aged Silviculture

• Recognizes that reverse J is limiting
• Other stand structures are sustainable
• Ecological functions more closely associated
  with canopy structure
• All-aged stands exceedingly rare in actuality
• Management based on the desired number of
  canopies provides a better alternative
• Set objectives based on canopy strata ?
  two-aged and multi-aged are possibilities

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Multi-aged distributions resulting from multiple
disturbances
Trees/ha
Diameter Class
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Growing space allocation approaches

• Leaf area index
• Stand density index
• MASAM model (OHara 1998)

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Conversion to Multi-Aged or Multi-Canopied
Understory growth
Overstory growth
High
High

• Shift in growing space from one strata to another
  also shifts growth increment

Understory
Overstory
Low
Low
0
50
100
Overstory growing space occupied ()
Figure from OHara (1998)
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Managing for Canopy Strata

• Fewer and longer cutting cycles
• Management across multiple spatial scales
• Need combination of single and multi-layered
  stands to maximize biodiversity potential

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Modelling elements
Initial dynamic conditions
Intial static conditions
Productive
Unproductive
Marginal
Geology
Hydrology
Topography
Meteorology
Climate
Mode of deposition
GPM type
Independant
Geomorphology
Forested land
Dynamic processes
Scale
Fire
Epidemics
Windthrow
Landscape
Watershed
Size, Intensity, Frequency
Size, Intensity, Frequency
Size
Stand
Natural disturbances
Sustainable forest management
Management scenarios
Imposed
Soils
Regeneration
Biodiversity
Aquatic
Harvesting scenarios
Constraints expressed in terms of indicators
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Indicators of biodiversity

• Crit1 Maintenance of ecosystem diversity
• Ind1.1 Age structure of the forest (P)
• Ind1.2 Forest species composition (P)
• Ind1.3 Configuration of the forest (P)
• Crit2 Maintenance of species diversity
• Ind2.1 Road density (P)
• Ind2.1 Monitoring bird populations (M)

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100 year forest rotation
100 year fire cycle
Proposed age class distribution for managed
forest
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Extended Rotations
300
Mean annual increment
Cubic ft./acre/year
Periodic annual increment
0
10
100
Stand age
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• Advantages of extended rotations
• Reduced land area in regeneration and
  early-development stages, hence
• Reduced visual impacts
• Lower regeneration and respacing costs
• Less need for herbicides, slash burning, etc.
• Reducing frequency of intense disturbance
• Large tree and higher-quality wood
• Adjust precently unbalanced age distributions
• Higher quality habitat for species associated
  with late-successional forest structure
• Hydrologic benefits
• Increased carbon stock associated with increased
  net biomass/larger growing stock
• Preservation of options for future adaptive
  management

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Landscape Management System (LMS)
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Simulated landscape based on individual stand
structures important features (e.g. roads,
streams, etc.)