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19 Cards in this Set
- Front
- Back
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Key Points |
1. Fires have been and will continue to be important drivers of many terrestrial plant comm. 2. Fire has strong effects on individuals, populations, and communities 3. Humans are key players in wildland fire 4. Different fire regimes (including variation in both temporal [succession] and spatial [mosaics] scales) are important in these fire-prone communities |
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Fire distribution |
Natural in CA: -grasslands -woodlands -chaparrals -forests |
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The 'Fire Triangle' |
Fire = oxygen, heat, fuel Mediterranean climates (almost) ideal for fire |
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Effects of Fire |
-Kills plants (erosion) & animals -Triggers regeneration strategies -Changes veg structure -initiates succession -opportunities (requirements) for early and mid-successional species -converts community types -effects fire regimes (feedback) -endangers human values (property and health)
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Paleo-Fire |
Fire = oxygen, heat, fuel -no fires for first 2 billion yrs bc no fuel or oxygen -lots of lightning later on and adaptations to fire -at first there was lightning but still no fire bc of lack of oxygen and no land for fire |
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Humans and Fire |
-Fire has been here since before homo sapiens -Native Americans used fire freely & to their advantage |
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Why burn? |
-Improve wildlife populations, hunting -stimulate regrowth -clear for agriculture -military use -remove unwanted understory -control insects and pathogens -reduce risk of catastrophic fire |
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'Post-Columbian' Fire in CA |
1. Initially continued (&intensified) fire use 2. Era of fire suppression (1900-now) -has left historically burned ecosystems over-full with fuels increasing catastrophic fire events 3. Restoring historic fire regimes -began in 1960s |
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Classification of Fire Regimes |
Temporal a. Season b. Fire return interval (time bw fires) -varies from short to long Spatial a. Size b. Complexity -fires used to be a lot more complicated Magnitude a. Intensity -degrees involved b. Severity -impact of fire -very concerned about this c. Fire Type -surface fires vs crown fires |
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Historic Fire Return Intervals |
Prairie: Frequent?? Oak Woodlands: 5-25 years (high frequency, probs surface) Chaparral: 30-50 years Closed cone forests: >100 years (crown fires, all trees burn) Ponderosa pine woodland: 5-25 years (like oak woodland) Upper Montane (fir) Forests: 50-150 years (grow slower, cooler and wetter) Pine-Juniper Woodlands: 5-15 years (burn fairly readily) |
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Fire Regimes |
Low ignition frequency & Low primary productivity = crown fires -normal in lodgepole pine & chaparral High ignition frequency & high primary productivity = surface fires (non-lethal) surface fires lethal to baby pines, not adults |
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Plant Adaptations |
-Thick bark (trees) -Buried meristems (grasses) -fire kills leaves but it can resprout -Coppicing (sprouting from root crowns) -Serotony = cone opening only after fire -Seed dormancy -Fire-induced germination |
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Disturbance and Succession |
Opportunities for early and mid-successional species Spatio-temporal mosaics = dynamic communities (non-trival to manage and restore) |
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Animal Communities may shift bc of fire |
bc brush mouse is no longer there, kit fox wont be either black backed woodpecker cavity nest |
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Disclimax |
-succession consistently interrupted/arrested at intermediate state -fire and herbivory can cause this -can create and maintain abrupt forest/savanna boundaries, or other types of type conversion |
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Native American Impact |
Their fires opened up forests, creating woodlands, meadows, aspen stands |
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Type Conversion |
-Forest ----> Woodland -elimination of fire-susceptible trees -Less frequent fire? -Wooded ----> Grasslands -elimination of even fire-tolerant trees -more frequent (anthropogenic) fires |
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Deserts & Fire |
-Historically too sparse to carry fire -Recent invasion by annual grasses -Now carries fires that can kill non-adapted species |
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Reintroducing Fire |
-restoring historic fuel loads and stand structure -both fire and mechanical means -restoring historic fire regimes -where and when possible -fire for weed control |
