Presentation on theme: "How the ecology of conifers determines an environmental issue."— Presentation transcript:
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
An estimated 16 million thunderstorms occur each year on earth, causing some 100 lightning strokes to the ground per second. 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. Lightning never strikes twice? 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.
High incidence of fire on the eastern slopes of the Cascade Mountains Fires burning on 18 August 2001 The total area classified as being on fire is 341, 669 acres in Washington and Oregon
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.
More than 25,000 firefighters served in the Yellowstone area and represented the largest firefighting effort in U.S. history Yellowstone 1988 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 Many conifer species are adapted to withstand fire and/or regenerate following fire Forest fires are a natural events Examples? Conifer species in the western USA form largely ‘dry’ land forests
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
What would happen if this forest burned? 450+ year old- growth Douglas-fir type forest
Why are forest fires a problem? Fire suppression has resulted in the accumulation of high fuel loads Human requirements from forests of timber, recreation and dwelling space are at odds with fire
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
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 consequences of fire protection in Ponderosa pine 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 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? East side of the Cascades set in late fall
The effect of a controlled burn Before After The effect of a controlled burn Has sufficient material been removed to prevent a major conflagration? in a Pinus ponderosa forest Crater Lake, lower elevation forest burnt in early spring
Research and Policy Problems Research: 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. Policy: gaining acceptance for a prescribed burning policy, the ‘smoke’ problem, defining regulations for ‘urban forestry’.
Is there such a thing as a “natural” forest? 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 not influenced by humans then 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 FM324 Forest Health and Protection ESC320 Natural Resource Issues: Old-growth and Forest Management