Pieter Bruegels, Hunters in the Snow

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Pieter Bruegels, Hunters in the Snow
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1895
1980
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Disturbance
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Disturbance any relatively discrete event in
time that disrupts ecosystem, community, or
population structure and changes resources,
substrate availability or the physical
environment. (Pickett and White)
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QUANTIFYING DISTURBANCE   Frequency - number of
occurrences of the disturbance in a specified
area per unit time.   Size - area over which the
event occurs   Intensity - amount of energy
involved in the event (e.g., fire temperature,
wind speed).   Severity - degree to which the
event influences the biota (e.g., percent of
canopy trees killed)   Duration - length in time
of each occurrence   Timing - time of year or
phenological stage at which the event
occurs.   Return interval Time between
disturbances.   Rotation period Mean time
needed to disturb and area equivalent to a
defined study area.   A "disturbance regime" is
the mean and variance in the above for a
specified area over a specified time.
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Frequency none
Frequency 250-500 yrs Severity high Size large
Frequency 50-90 yrs Severity low Size small
Fire Disturbance Regimes in the PNW
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Clearcutting and Wildlife in GYE
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frequency
size
frequency
severity
severity
size
size
Depicting disturbance regimes in three dimensions
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Wildfire and Logging (1, 2) disturbance regimes
expressed in three dimensions.
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Disturbance and Landscape Pattern
How does disturbance influence landscape pattern?
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Disturbance and Landscape Pattern
How does disturbance influence landscape pattern?

• May alter abiotic factors in disturbance patch
• May reset community to early seral stage
• Over time, creates a mosaic of abiotic patches
  and seral stages across the landscape

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Landscape Position and Disturbance
Does susceptibility to disturbance vary with
landscape position?
Fire in Northern Rockies? Hurricane damage in New
England? Landslides in streams?
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Landscape Pattern and Spread of Disturbance
How does vegetation pattern across the landscape
influence spread of disturbance?
Franklin and Forman 1987
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Succession - the non-seasonal, directional and
continuous pattern of colonization and
extinctions on a site by species
populations. Primary succession - succession
following disturbance that removes all biotic
material from the site.
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Yellowstone Conifer Forests
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Yellowstone Conifer Forests
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Secondary succession - succession following a
disturbance that leaves well-developed soil,
seeds, and/or organisms on the site. Biological
legacy - organisms, propagules, and organic
materials that survive disturbance.
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Goal Review how concepts in landscape ecology
can help us restore modern landscapes
Topics

• Principles derived from pre-European settlement
  fire dynamics
• Changes in forest ecosystems during fire
  exclusion period
• Restoring fire to modern landscapes

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Fire Disturbance Key For Developing Concepts in
Landscape Ecology and Management

• Landscape heterogeneity.
• Shifting steady state mosaic.
• Natural range of variation.
• Minimum dynamic area.

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Greater Yellowstone
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Natural Fire Concepts
Fire Frequency and Forest Dynamics
Vegetation
Old Growth Conifer
Aspen
Intense Fire
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Natural Fire Concepts
Spatial Pattern Landscape Heterogeneity
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Natural Fire Concepts
Biodiversity
Natural fire regime maintains the variety of
seral stages and landscape patterns required by
native species.
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Natural Fire Concepts
Shifting Steady-State Mosaic
From Turner et al. 2001
Shifting Steady-State Mosaic - A landscape where
the characteristics of individual patches are out
of phase but the collective behavior of patches
displays equilibrium.
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Natural Fire Concepts
Natural Range of Variation
Vegetation
Old Growth Conifer
NRV
Aspen
Intense Fire
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Natural Fire Concepts
Minimum Dynamic Area
Nature reserve
Minimum Dynamic Area Smallest landscape where a
collective behavior of individual patches
displays equilibrium.
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Natural Fire Concepts
Minimum Dynamic Area
Nature reserve
Minimum Dynamic Area Smallest landscape where a
collective behavior of individual patches
displays equilibrium.
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Natural Fire Concepts
Fire Varies with Biophysical Setting
200-250 years
20-30 years
10-15 years
Fire Frequency
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Natural Fire Concepts
Fire Varies with Biophysical Setting
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Natural Fire Concepts
Summary

• Many pre-European landscapes were in some
  equilibrium as maintained by natural disturbance.
• Principles derived this natural condition have
  been used to guide modern management.

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Fire Exclusion Era
Fire Frequency
Fire events in the Soda Butte Creek Watershed
1550-2000. Douglas-fir zone. Littell 2001
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Fire Exclusion Era
Fire Frequency
Fire events on the Yellowstone Plateau
1700-1985. Subalpine fir zone. Romme and Despain
1989
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Fire Exclusion Era
Vegetation Change
Gallant et al. 2003. Vegetation Dynamics under
Fire Exclusion and Logging in a Rocky Mountain
Watershed 1856-1996. Ecol Apps.
East Beaver Creek Watershed
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Fire Exclusion Era
Vegetation Change
Stand Type
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Fire Exclusion Era
Vegetation Change Aspen Distribution
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Fire Exclusion Era
Vegetation Change Conifer Expansion
1871
1981
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Fire Exclusion Era
Vegetation Change Conifer Expansion
Greater Yellowstone
Powell et al. in prep. Monitoring Forest
Response to Past and Future Global Change in
Greater Yellowstone
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Fire Exclusion Era
Vegetation Change Conifer Expansion Change from
Reference Data

Mean 3.68 Stderr 0.49 N 817 T value
7.54 P lt .0001
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Fire Exclusion Era
Vegetation Change Conifer Expansion Change from
Reference Data
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Fire Exclusion Era
Vegetation Change Conifer Expansion Change from
Reference Data
For low elevation class SE9.5
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Fire Exclusion Era
Vegetation Change Conifer Expansion Change from
Satellite Data
1985-1999
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Fire Exclusion Era
Vegetation Change Conclusions for GYE

• Fire has been largely excluded from lower
  elevation forests since the late 1800s.
• Conifer has expanded over aspen, grassland, and
  sagebrush and later seral stages have replaced
  earlier seral stages.
• Rates of change vary with biophysical setting and
  are especially fast at lower treeline.
• Even with the large fires in 1988, conifer
  expansion has offset conifer decrease since 1985.

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Fire Exclusion Era
Vegetation Change Rocky Mountains

• Mast, Veblen, and Hodgson (1997) - found that a
  mean of 35 of four study sites changed from
  grassland to Ponderosa Pine forest between 1937
  and 1988 along the Colorado front range.
• Covington and Moore (1994) - simulated changes in
  Ponderosa pine basal area at 8 northern Arizona
  sites and found a mean increase from 17 ft2/ac in
  1867 to 306 ft2/ac in 2027.
• Dando and Hansen (1990) - quantified a 35
  increase in area of Douglas-fir and Rocky
  Mountain Juniper forest between 1954-1979 near
  Butte, Montana.

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Rural Homes
Bozeman
Billings
Rexburg
Idaho Falls

• Population has increased 55 1975-95
• Rural homes increased 108 1975-99

Jackson
Pocatello
Gude et al. 2006
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Fire Exclusion Era
Consequences Fundamental Rescaling of
Disturbance and Landscape Dynamics?
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Fire Exclusion Era
Consequences Natural Range of Variation?
Vegetation
New Trajectory?
Old Growth Conifer
NRV
Aspen
Intense Fire
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Fire Exclusion Era
Consequences Loss of Dynamic Steady State?
Decline of fire-dependent communities and species.
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Fire Exclusion Era
Consequences Loss of Dynamic Steady State,
Especially in Biodiversity Hotspots?
Hot Spots for Bird, Tree, and Shrub Species
Richness (Hansen et al. 2003).
Deviation from Natural Fire Regime (USFS).
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Fire Exclusion Era
Consequences Rescaling of Fire Regimes to Less
Frequent but More Severe?
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Fire Exclusion Era
Consequences Increased Risk to Homes?
Area of interest
Legend National Park Service Other
federal lands Greater Yellowstone USFS recent
fires Home density
Low High
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Fire Exclusion Era
Consequences Increased Risk to Homes?
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Fire Exclusion Era
Consequences Loss of Minimum Dynamic Area?
1988 Yellowstone Fires
GYE from Space 1972
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Restoring Landscape Patterns
Traditional Logging does not Adequately Mimic
Wildfire More Innovative Silviculture is Needed
Remnant Forest Patches
MPS
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Wilmer 2000
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Restoring Landscape Patterns
Crown Fire is Needed Prescribed Surface fire is
Not Enough
Fire-dependent bird species not accounted for.
Prescribed fire applied
Beaverhead Deerlodge NF Henderson 1998
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Restoring Landscape Patterns
Restoration is Best Tailored to Biophysical
Setting
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Restoring Landscape Patterns
Landscape-Level Zoning is Needed
Heavy-handed fuel control
Prescribed fire
Let-Burn policy
Zoning against new subdivision
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Restoring Landscape Patterns
Guiding Principles

• Natural range of variation is not likely an
  option in many settings due to ecological
  rescaling and social acceptance.
• Active management is required to restore many
  ecosystems
• Manage at appropriate space and time scales to
  achieve ecological objectives.
• Use a combination natural fire, prescribed fire,
  silviculture, and land use planning.
• Integrate management across public and private
  lands.