How the ecology of conifers determines an environmental issue
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How the ecology of conifers determines an environmental issue Forest fires in natural ecosystems Yellowstone National Park 1988 Human Concerns: economics, timber reserves, continuing public access, nature conservation.

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How the ecology of conifers determines an environmental issue

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How the ecology of conifers determines an environmental issue

Forest fires in natural ecosystems

Yellowstone National Park 1988

Human Concerns: economics, timber reserves, continuing public access, nature conservation.

Can we develop a policy toward fire that takes into account the biology of forest species and the ecology of forests?

Forest Fires in the United States

Note the frequency and distribution of lightning caused fires

Lightning never strikes twice?

An estimated 16 million thunderstorms occur each year on earth, causing some 100 lightning strokes to the ground per second.

Only a small fraction ignite fires, but suppose 0.1% of the 3,153,600,000 strikes do, that gives 3 million lightning fires/year.

Between 50 and 80 percent of forest fires in western North America are lightning caused. There are some 4,871 lightning fires per year on federally-owned land in the US.

Fires burning on 18 August 2001

in Washington and Oregon

High incidence of fire on the eastern slopes of the Cascade Mountains

The total area classified as being on fire is 341, 669 acres

The Icicle fire

A series of fires of different sizes started following multiple lightning strikes. The fires shown are on the tops of ridges and are difficult to access. Most fires are small.

Yellowstone 1988

More than 25,000 firefighters served in the Yellowstone area and represented the largest firefighting effort in U.S. history

At its height, the Greater Yellowstone Unified Fire Command fielded 336 fire engines, 57 helicopters, 41 bulldozers, and numerous retardant bombers.

"How do you put out the Yellowstone fires? Pour a hundred million dollars on it and wait for it to snow."

Forest fires are a natural events

Forest fire is a natural event

Conifer species in the western USA form largely ‘dry’ land forests

Many conifer species are adapted to withstand fire and/or regenerate following fire


Different types of forest ecosystems and their relationship with fire

Lodgepole pine: the ‘Yellowstone type’. Dense stands that burn completely but usually with a high frequency.

Ponderosa pine: ground fires burn with high frequency and maintain a stand of widely spaced mature trees.

Douglas fire on the west side of the Cascades: Large old-growth forests that burn at infrequent intervals (400+years).

8 years after the Yellowstone fire

The burnt lodgepole pine trees remain standing.

Lodgepole pine bears serotinous cones that require heat before they open.

Fire in ponderosa pine forest

Prior to 1900 low elevation ponderosa pine forests burned every 5 to 30 years

Most fires burned only the forest floor reducing fuel and killing small trees

This produced open stands of large trees with grassy understories, some shrubs and occasional thickets of young trees.

After fire in Ponderosa pine

450+ year old-growth Douglas-fir type forest

What would happen if this forest burned?

Why are forest fires a problem?

Human requirements from forests of timber, recreation and dwelling space are at odds with fire

Fire suppression has resulted in the accumulation of high fuel loads

Effects of fire exclusion in Ponderosa pine

Fire exclusion has produced a dense understory of young Douglas fir

Deep woody debris and duff give hotter longer lasting fires and poor germination

Since the advent of fire fighting some forests have missed 8 to 10 fire rotations

The consequences of fire protection in Ponderosa pine

These photos were taken at Lick Creek in the Bitterroot Valley of Montana over an eighty-year period. Notice how the old growth ponderosa pine stand is replaced by dense Douglas-fir after fire suppression begins in the 1920s.

Exit PowerPoint

Pinus palustris

The longleaf pine, or Pinus palustris grows in warm, wet temperate climates in the south east US characterized by hot summers and mild winters.

A healthy longleaf pine forest needs fire. Without it hardwoods and other pines encroach. Thick bark of mature trees makes them fire resistant. Its seedlings are resistant to grass fires.

Prescribed fire in the Okefenokee Forest

Controlled burning

Ground fire

East side of the Cascades set in late fall

What conditions of fuel load, moisture content, temperature and wind produce a fire that burns the excess undergrowth and small trees without burning the dominant trees?

The effect of a controlled burn


The effect of a controlled burn

in a Pinus ponderosa forest


Crater Lake, lower elevation forest burnt in early spring

Has sufficient material been removed to prevent a major conflagration?

Research and Policy Problems


establishing a prescribed burn procedure for forests that are overstocked and with greater fuels loads than usual in a fire regime,

establishing effective regimes for different fire types.


gaining acceptance for a prescribed burning policy,

the ‘smoke’ problem,

defining regulations for ‘urban forestry’.

Is there such a thing as a “natural” forest?

If we define “natural” as not influenced by humans


wherever there has been an effective fire suppression policy is it reasonable to conclude that forests there are not natural?

If we define “natural” as a forest that is in equilibrium with its environment then, because fire suppression has altered that equilibrium, is it reasonable to establish a prescribed fire regime to restore that equilibrium as much as possible?

Sections you need to have read

17.9, 34.17, 36.6 & 36.7

Courses that deal with this topic

ESC322 Forest Ecosystems

ESC320 Natural Resource Issues: Old-growth and Forest Management

FM324 Forest Health and Protection

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