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.
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?
Note the frequency and distribution of lightning caused fires
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.
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
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.
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 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
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).
The burnt lodgepole pine trees remain standing.
Lodgepole pine bears serotinous cones that require heat before they open.
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.
What would happen if this forest burned?
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
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
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.
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
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
in a Pinus ponderosa forest
Crater Lake, lower elevation forest burnt in early spring
Has sufficient material been removed to prevent a major conflagration?
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’.
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?
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