1. ESRM 501
5/7/07
Natural Disturbance
Doug Sprugel

2. “As a consequence of almost universal use and misuse by man, subseres [successional communities developing after disturbance] in possible stage of succession constitute the most abundant of all every communities… In regions long-settled, subseres form practically the entire cover of vegetation” (Weaver and Clements, Plant Ecology, 1938, p. 78)
But
“Before the advent of civilized man, nearly the whole area of each climax was occupied by the [climax] dominant species” (ibid., p. 479)

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9. - lodgepole pine forests in Rocky Mts
- lodgepole pine forests in Rocky Mts. (including Yellowstone) [catastrophic fires]
- mixed conifer forests in the Sierras (e.g. Sequoia Nat’l Park) [surface fires]
- ponderosa pine in Arizona and eastern Washington [surface fires]
- East Coast (esp. Florida and Harvard Forest, Mass.) [hurricanes]
- Northeastern mountains [spruce budworm outbreaks and fir waves]

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19. Take-home message 1. Disturbance is a normal component of most natural ecosystems and exerts a powerful control on vegetation characteristics. Many plants and animals are well adapted to particular kinds of disturbances and often can’t survive without them.

20. Disturbance characteristics: 1. Disturbance type

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22. Disturbance characteristics: Disturbance type1.
2. Intensity
3. Frequency
4. Size

23. Types of disturbance: Surface fire
--examples: ponderosa pine and Sierran mixed conifer forests
--adaptations: thick bark, rapid early growth, absence of low branches, "grass stage" of longleaf pine
--effects of fire suppression—major changes in ecosystem structure and function.

24. Types of disturbance: Stand-destroying or catastrophic fire
--example: lodgepole pine forests; Western Washington Douglas-fir forests
--adaptations: numerous small seeds with dormancy; serotinous cones; shade-intolerant. Seeds able to grow on exposed soil.
--effects of fire suppression--largely insignificant

25. Why should we care? Understanding basic ecology can advise management
Unexpected consequences of fire control
Management of natural areas
Endangered species management
Impacts on planning
Effects of climate change