Fire Ecology - FOR526 Penny Morgan Fire ecology of ponderosa pine Historically, fires were frequent (every 2-25 yr) and predominantly nonlethal Droughts

Fire Ecology - FOR526Penny Morgan

Fire ecology of ponderosa pine

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


People have long used warm, dry forests

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


Biodiversity

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.


Ponderosa pine forests are shaped by: Frequent surface fires Episodes of tree

regeneration Insect infestations Regional climatic

events, such as droughts

Human use


Fire effects on trees Crown damage

– 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– Bole and roots– Look for pale green, moist inner

bark – Tree can survive damage on up to

50% of circumference


Fire effects

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 exclusion

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 exclusion

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


Forest structure has changed

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


Ecosystem composition changes

Old-growth is rare Meadows have shrunk Many native plants and animals have

declined in abundance due to habitat alterations


An “outbreak” of Douglas-fir

In some stands, white fir, Douglas-fire, and juniper have increased


Fuels accumulate when fires are less frequent

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


Changed ecosystem processes

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


Spatial patterns have changed

Simpler patterns and processes at all hierarchical levels, from stand to landscape

Stands are less aesthetically pleasing Landscapes are more homogeneous Greater canopy closure


Watershed effects

Decreased water availability Decreased total streamflows, peak flows, and

base flows Post-fire erosion and mass-wasting

increases when fires are more severe


Increasing fire risk

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


Human actions have made these forests less sustainable

Fire suppression Livestock grazing Logging, especially of bigger trees and pines Road construction Predator control Exotic species introductions


Many have called for active management

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


Visualizing alternatives: the next six slides

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


Examples

Fuels management efforts under the National Fire plan

Ecological restoration


National Fire Plan 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/initiatives/fire/implem_plan.pdf

http://www.fireplan.gov/


Fuels management prescriptions

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


Prescribed fire programs

The scale and intensity of Rx fire programs are inadequate at a regional scale.

Penny Morgan

The call for restoration


Restoration

Strong consensus that need exists Heated public and scientific debates about

the relative risks and tradeoffs of different approaches


Ecological restoration

Reintroduce fire Thin trees from below Reduce tree densities, especially small trees Reestablish understory vegetation Alter forest structures: increase spatial

heterogeneity


One approach and a critique

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


Reference conditions 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


Strengths of this approach

Clear methods Readily quantifiable Scientifically based Concrete


Challenges to the approach 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


Multiple incremental treatments are an alternative

A search for ecological integrity and sustainability for the future

Addresses these issues– Any particular moment in time may be unique in the long-

term history of an ecosystem– Climate of the late 20th century is unprecedented in last

1,000 years


Multiple incremental treatments

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


Successful restoration projects

Address issues: natural heterogeneity, wildlife and biodiversity

Accommodate our imperfect understanding of these complex systems

Require political, financial, and social support Scientifically sound


Principles of ecological restoration of Southwestern ponderosa pine forests

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

(from Allen et al. In Press)


More principles

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


More principles

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


Other considerations

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


Given uncertainties, act conservatively 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)


Goal

Move toward natural range of variability Allow or use natural processes, such as fire,

to reestablish natural structure and function

Documents

Fire Ecology - FOR526 Penny Morgan Fire ecology of ponderosa pine Historically, fires were frequent (every 2-25 yr) and predominantly nonlethal Droughts