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Fire Ecology - FOR526
Penny Morgan
Fire ecology of ponderosa pine
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Historically, fires were
frequent (every 2-25 yr)
and predominantly
nonlethal
Droughts are common
Biomass production
exceeds decomposition
Ignition is not limiting:
lightning and people
Fire Ecology - FOR526
Penny Morgan
People have long used
warm, dry forests
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Indians peeled and ate the
inner bark from this tree
Forests were homes, a
source of food for people and
animals, and many sites
were culturally important
Euro-Americans logged,
grazed, and mined these
forests
Fire Ecology - FOR526
Penny Morgan
Biodiversity
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Ponderosa pine forests provide habitat for many
animals (at least 250 species of vertebrates), plants,
invertebrates, and microbes
Many rare, sensitive and declining species, e.g.
northern goshawk and flammulated owl
Habitat alteration and fragmentation affects
invertebrates and soil organisms that are critical to
ecosystem function.
Fire Ecology - FOR526
Penny Morgan
Ponderosa pine forests are
shaped by:
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Frequent surface fires
Episodes of tree
regeneration
Insect infestations
Regional climatic
events, such as
droughts
Human use
Fire Ecology - FOR526
Penny Morgan
Fire effects on trees
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Crown damage
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Foliage dies if crown burns (needles
black or gone)
Scorch (red needles) is caused by
dessication
PIPO can survive up to 75% crown
scorch
Cambium damage
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Bole and roots
Look for pale green, moist inner
bark
Tree can survive damage on up to
50% of circumference
Fire Ecology - FOR526
Penny Morgan
Fire effects
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Fires consume biomass and recycle nutrients
Fires rejuvenate vegetation
Fires influence diversity
Many plants and animals depend on the
forest structures and composition that
develops post-fire
Fire Ecology - FOR526
Penny Morgan
Fire exclusion
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Fire suppression
Roads
Valley settlements
Fewer Indians (many died of introduced diseases
after first white contact); many moved to reservations
Very intensive grazing – in the Southwest grazing
was used to prevent fires
Fire Ecology - FOR526
Penny Morgan
Fire exclusion
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When was the last surface
fire that scarred this tree?
What was the average
number of years between
fires that scarred this tree?
This is from Long Valley
near Flagstaff, Arizona, an
area where fires were once
VERY frequent
Fire Ecology - FOR526
Penny Morgan
Forest structure has changed
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Fewer large trees and snags – these are
ecologically, economically, and socially more
important than small trees
More trees that are less fire resistant
Unnaturally dense stands of suppressed
young trees now threaten the remaining
large trees through competition and by
fueling crown fires
Fire Ecology - FOR526
Penny Morgan
Ecosystem composition changes
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Old-growth is rare
Meadows have shrunk
Many native plants and animals have
declined in abundance due to habitat
alterations
Fire Ecology - FOR526
Penny Morgan
An “outbreak” of Douglas-fir
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In some stands, white fir, Douglas-fire, and
juniper have increased
Fire Ecology - FOR526
Penny Morgan
Fuels accumulate when fires are less
frequent
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Fuels accumulate on the forest floor
(as duff, litter, woody debris) and in the crowns of trees
Increased crown fuel loading
Fuels are more continuous horizontally
Fuels are more continuous vertically
Fire size and intensity increases
Crown fires are more likely
Fire Ecology - FOR526
Penny Morgan
Changed ecosystem processes
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Decreased tree growth
Trees are less vigorous
Organic matter decomposition slows
Nitrogen mineralization declines
Stagnant nutrient cycles
Declining diversity of native flora and fauna
Increased risk of stand-replacing fire
Fire Ecology - FOR526
Penny Morgan
Spatial patterns have changed
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Simpler patterns and processes at all hierarchical
levels, from stand to landscape
Stands are less aesthetically pleasing
Landscapes are more homogeneous
Greater canopy closure
Fire Ecology - FOR526
Penny Morgan
Watershed effects
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Decreased water availability
Decreased total streamflows, peak flows, and
base flows
Post-fire erosion and mass-wasting
increases when fires are more severe
Fire Ecology - FOR526
Penny Morgan
Increasing fire risk
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Dramatically increased vulnerability of warm,
dry forests to destructive crown fires
Threatening people, property, watersheds
and wildlife habitat
More than 39 million acres at risk to
catastrophic fires (GAO 1999) in US – much
is in the warm, dry forests
Fire Ecology - FOR526
Penny Morgan
Human actions have made these forests
less sustainable
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Fire suppression
Livestock grazing
Logging, especially of bigger trees and pines
Road construction
Predator control
Exotic species introductions
Fire Ecology - FOR526
Penny Morgan
Many have called for active
management
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To reduce fire risk, restore ecosystem health,
and to protect people and their property
Some combination of thinning “from below”
(taking smallest trees only) and prescribed
burning
Fire Ecology - FOR526
Penny Morgan
Visualizing alternatives: the next six
slides
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Simulation and visualization using Fire Fuels
Extension of the Forest Vegetation Simulator
Ponderosa Pine State Park near McCall,
Idaho – they have thinned and burned to
reduce fuel risk around visitor center,
campgrounds and other recreation sites
Fire Ecology - FOR526
Penny Morgan
Examples
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Fuels management efforts under the National
Fire plan
Ecological restoration
Fire Ecology - FOR526
Penny Morgan
National Fire Plan
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More money for fire fighting, fire
rehabilitation, fuels management,
community assistance and
accountability
Especially in urban/interface and
in municipal watersheds
Much of the attention is focused
on warm, dry forests, including
ponderosa pine
Read the 2002 overview:
http://www.fireplan.gov/
Skim the Western Governor’s
Association Implementation
Strategy:
http://www.westgov.org/wga/initiati
ves/fire/implem_plan.pdf
Fire Ecology - FOR526
Penny Morgan
Fuels management prescriptions
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Probably, fewer trees need to be cut to
reduce the risk of crown fires than to do
ecological restoration
It should be a goal for both to enhance
sustainability and resilience of ecosystems
Fire Ecology - FOR526
Penny Morgan
Prescribed fire programs
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The scale and intensity of Rx fire programs
are inadequate at a regional scale.
The call for restoration
Penny Morgan
Fire Ecology - FOR526
Penny Morgan
Restoration
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Strong consensus that need exists
Heated public and scientific debates about
the relative risks and tradeoffs of different
approaches
Fire Ecology - FOR526
Penny Morgan
Ecological restoration
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Reintroduce fire
Thin trees from below
Reduce tree densities, especially small trees
Reestablish understory vegetation
Alter forest structures: increase spatial
heterogeneity
Fire Ecology - FOR526
Penny Morgan
One approach and a critique
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Continue with this powerpoint for an
overview
Then continue with the case study to see
more about this approach, critiques of it, and
alternatives, as well as ongoing research
Fire Ecology - FOR526
Penny Morgan
Reference conditions
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Covington, Moore, Fulé and others at the Ecological
Restoration Institute at Northern Arizona University
Substantial efforts to reconstruct and reestablish the
tree density and spatial pattern that existed just prior
to the date of cessation of the natural fire regime
Test the effects of treatments on ecosystem
components
Restore surface fires
Fire Ecology - FOR526
Penny Morgan
Strengths of this approach
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Clear methods
Readily quantifiable
Scientifically based
Concrete
Fire Ecology - FOR526
Penny Morgan
Challenges to the approach
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Intensive – many trees are cut at once
Integrates structure, but what about composition and
ecosystem processes?
Need an adaptable method
Because of lagged response of forest structure to
climate variation, the precise replication of past plant
densities and spatial arrangements may not
maximize future ecosystem resilience
Post-settlement tree regeneration pulses would
occurred to some degree
Fire Ecology - FOR526
Penny Morgan
Multiple incremental treatments are an
alternative
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A search for ecological integrity and sustainability for
the future
Addresses these issues
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Any particular moment in time may be unique in the longterm history of an ecosystem
Climate of the late 20th century is unprecedented in last
1,000 years
Fire Ecology - FOR526
Penny Morgan
Multiple incremental treatments
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Use a combination of thinning and fire
Thin only enough to allow prescribed fire
More conservative and justifiable
Potentially allows more extensive treatments
Identify thresholds where fire alone will be
enough
Fire Ecology - FOR526
Penny Morgan
Successful restoration projects
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Address issues: natural heterogeneity,
wildlife and biodiversity
Accommodate our imperfect understanding
of these complex systems
Require political, financial, and social support
Scientifically sound
Fire Ecology - FOR526
Penny Morgan
Principles of ecological restoration of Southwestern
ponderosa pine forests (from Allen et al. In Press)
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Reduce vulnerability to crown fires
Integrate process and structure
Site-specific reference conditions
Multiple conservative interventions
Build upon existing forest structure
Restore ecosystem composition
Retain trees of significant size or age
Fire Ecology - FOR526
Penny Morgan
More principles
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Incorporate demographic processes
Control and avoid introducing exotics
Protect and enhance sensitive communities
and regional heterogeneity
Prioritize treatment areas Consider
cumulative effects
Protect from overgrazing
Monitor and do research
Use ongoing adaptive management in a
diversity of approaches
Fire Ecology - FOR526
Penny Morgan
More principles
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Retain some dead, deformed and diseased trees
Keep some clumps of large trees with interlocking
crowns
Maintain important food and nesting habitat
Maintain genetic diversity
Use opportunities to increase habitat heterogeneity
and biodiversity
Fire Ecology - FOR526
Penny Morgan
Other considerations
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Pay attention to vulnerable and irreplaceable
ecosystem elements
Leave some areas untreated as refuges for
sensitive species
Adjust future treatments
Maintain future flexibility
Avoid creating uniform stand and landscape
conditions
Fire Ecology - FOR526
Penny Morgan
Given uncertainties, act
conservatively
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Limited understanding of ecosystem function
We know more about past fire frequency than about
past fire size, severity, and spatial pattern
Uncertain reconstruction of fire regimes and past
structure and composition due to missing evidence
and sampling bias
Use reconstructed overstory tree densities
conservatively (as minimum rather than maximum values)
Fire Ecology - FOR526
Penny Morgan
Goal
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Move toward natural range of variability
Allow or use natural processes, such as fire,
to reestablish natural structure and function