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104 Cards in this Set
- Front
- Back
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Most common source of naturally caused fires |
lightning |
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how many thunderstorms at given time? How many strikes a day? per second? |
2000 thunderstorms 8 billion strikes per day 100 strikes per second |
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How often to lightning strikes cause fire in dry areas? |
.1-1% of the time
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What kind of lightning causes big fire outbreaks? |
dry lightning |
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What does a normal thundercloud charge look like? |
Positive charge at the top, negative charge at the bottom |
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What charge does normal lightning have? |
negative charge |
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Return charge of lightning: How many amps? Superheats to what temperature? how many watts? |
100,000 amps 30,000 degrees C 10^12 watts of energy |
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What are hybrid flashes? |
small but continuous current that can sustain for 1/2 second. |
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Hybrid flashes result in air temps of how hot? |
6000-12000 degrees C |
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How often are hybrid flashes? |
one in every 3 to 5 flashes |
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What percent of positive flashes are capable of starting fires? |
95% |
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When do you see positive flashes? |
near the end of the thunderstorm |
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What percent of flashes are positive flashes? |
5-10% |
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What is another source of naturally ignited fire? |
Volcano |
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What temperature does lava run at? |
600-1100 C |
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What percent of ignition is caused by humans? What percent is the area burned by these fires? |
humans cause 89% of all fires, burning 43% in 2000 |
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What are sources of accident and negligence fires? (8) |
discarded cigarettes, trash burning, heavy equipment, chainsaws, powerlines, cars, hauling, campfires |
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What are the reasons for arson? |
pyromaniacs, to create work, malicious destruction of property |
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How does distance and size of fuels affect how they burn? |
larger fuels need to be closer together to maintain combustion through heat exchange
smaller fuels need to be relatively spaced to allow for airflow |
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is it easier to spread fire along vertical gaps (to the canopy) or horizontal gaps (between spaced shrubs)? |
Vertical gaps |
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what are three important aspects of arrangement of fuel on the landscape? |
1) how close the pieces are to each other 2) continuity on the landscape 3) amount of fuels |
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How do volume and size of fuel matter? |
fine fuels ignite easier large fuels produce more energy large green fuels don't often ignite, form energy sink instead |
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How much litterfall in a conifer forest? |
3 tons/ ha |
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How much litterfall in a deciduous hardwood forest? |
6 tons/ha |
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How much litterfall in tropical forests? |
7-9 tons/ha |
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What conditions make litter decompose quickly? |
warm and humid |
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what conditions make litter accumulate (rather than decompose?) |
Cold or dry |
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How much litter in grasslands? |
2-10 tons/ha |
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How much litter in logging slash? |
70-150 tons/ha |
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How does a windstorm affect fuel load? |
deposit huge amounts of litter on the ground quickly |
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What kinds of disturbances can cause fuel buildup? |
insect attacks, wind storms |
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what kind of fuel is mostly consumed? |
fine, dry fuels |
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what kind of fuel is mostly left unburnt? |
large fuels
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How do deciduous systems burn? Speed/ intensity, season? |
slower, less intense fires with hotter spring fires than summer fires |
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how does a steeper slope affect fire behavior? (3) |
convective heating preheats fuels drier due to increased drainage breaks in fuels |
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how does aspect affect fire behavior? |
south facing slope is typically drier (solar intensity) alters fuel type and loading |
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How does the time of day affect upslope winds? |
upslope during the day, downslope at night |
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where do narrow canyons radiate their heat? |
opposite sides |
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How does night affect temperature? |
decreases at night |
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how does night affect relative humidity? |
increases at night |
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how does night affect wind? |
usually decreases at night |
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What are three seasonal variations that affect fire? |
weather, fuel 'greenness', and difference in fire affects (dormant vs growing season) |
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What affects the spatial patterns on landscape? |
complex mix of fuels and ignition sources |
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Temporal patterns of fire: How much fuel buildup for short intervals, and how does it burn? |
less, patchier |
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temporal patterns of fire: how much fuel buildup for longer intervals, how does it burn? |
more fuel buildup, more uniform vegetation patterns |
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how can we reconstruct fire history in an area? |
fire scars |
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on history of 90 giant sequoias: average number of scars/tree? how far back does the record go? |
64 scars/tree 2000 yr history |
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besides fire scars, what is a way to find out fire history? |
charcoal and pollen in pond sediments |
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What are three difficulties in figuring out within fire perimeters? |
(1) unburnt patches (2) varying severity (3) burout/backfire amount |
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3% of the fires burned account for how much of the area burned? |
97 % |
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Fire regime I return interval/severity: |
0-35 years, low-mixed severity |
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Fire Regime II Return interval/severity: |
0-35 years, high severity |
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Fire regime III return interval/severity |
35-100+ years, mixed-severity |
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fire regime IV, return interval/severity |
35-100+ years, high severity |
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Fire regime V, return interval/severity |
200+ years, high severity |
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Condition class I: |
within normal variation of regime |
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condition class II |
moderate departure from normal variation of regime |
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condition class III |
high departure from normal variation from regime |
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Lethal plant temperature: |
60 C or 140 F |
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Adaptations trees have to protect cells from mortality during fire: (3) |
protect vulnerable tissue (bark protects cambium)
protect seeds (serotinous cones, seed bank)
dormancy protections |
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adaptations trees have following fire: (2) |
rapid resprouting
serotinous cones |
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why do some plants not have any adaptation to fire? |
live in systems with infrequent fire |
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what trees protect their cambium? |
Thick bark: ponderosa pine douglas-fir coast redwood |
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which trees have thin bark? |
sitka spruce western redcedar red alder |
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Giant sequoia bark thickness? |
1-3 feet thick |
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How do plants protect apical meristem? (3) |
fast juvenile growth temperatures decline rapidly with height during fire good self-pruning |
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which tree is adapted to protect the apical meristem? |
longleaf pine ('grass phase') |
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where are serotinous cones stored previous to fire? |
high part of tree canopy, away from heat |
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how much seedfall is released from serotinous cones following a fire? |
4 million / ha |
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why is sprouting from serotinous cones successful after a fire? (2) |
bare mineral soil access to light (eliminates competition) |
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varying degrees of serotiny: which trees have weakly serotinous cones? strongly serotinous? |
monterey pine- weakly jack pine- strongly |
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Resprouting: which species are good stump sprouts? |
oaks, manzanita, pepperwoods |
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resprouting: which species are good root suckers? |
quaking aspen, cottonwood, willows |
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Seasonality: what months are the Spring-summer-fall fire season? what elevation/types of forest? |
may-november, low elevation/deserts |
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Seasonality: what months are the summer-fall fire season? what elevation/types of forest? |
july-october, mid elevation, mixed conifer |
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Seasonality: what months are the late summer-fall fire season? what elevation/types of forest? |
september-november, central and south coast, chaparral |
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Fire Return Interval: whole area burns, short return intervals longer intervals convert to different type (type, species) |
Truncated short return interval, oak woodlands, montane meadows, grasslands |
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Fire Return Interval: most of area burns, short return intervals some with longer return intervals (type, species) |
Short return intervals ponderosa pine |
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Fire Return Interval: whole area burns, within a range of intervals outside of range will change intervals (type, species) |
Truncated medium return intervals closed-cone pine and cypress |
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Fire Return Interval: most of area burns, medium intervals some strong deviation (type, species) |
medium fire return interval chaparral, live-oak, upper montane (red and white fir)
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Fire Return Interval: whole area burns, long return intervals (>70 yrs) frequent returns convert to different type not typically adapted to fire (type, species) |
Truncated long fire return interval mountain hemlock, whitebark pine, foxtail pine, sitka spruce |
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Fire Return Interval: most of area burns, long return intervals shorter intervals are isolated (type, species) |
lodgepole pine, singleleaf pinyon, beach pine |
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Fire size: Small |
10 ha (25 ac) |
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Fire size: truncated small Fuel continuity? |
1 ha (2.5 ac) discontinuous fuel |
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Fire size: Medium fuel continuity? |
10-1000 ha (25-2500 ac) patchy fuels or limited size stand (red/white fir forests) |
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Fire size: Large |
more than 1000 ha (2500 ac) grassland, chaparral, oak woodlands |
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spatial complexity: most of area within perimeter is homogenous with few unburned islands |
low complexity |
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spatial complexity: most of area within perimeter has intermediate level of complexity
mosaic of fine and course-grained patterns |
moderate complexity |
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spatial complexity: most of area burns with high complexity patterns
fine grained mosaic pattern
mixed conifer, giant sequoia |
high complexity |
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spatial complexity: two distinct types: complex surface type homogenous crown fire |
multiple spatial complexity |
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Magnitude: Low intensity Flame length kW/m |
<1.2 m (4 ft) 346 kW/m |
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Magnitude: moderate intensity Flame length kW/m |
1.2-2.4 m (4-8 ft) 346-1730 kW/m |
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Magnitude: high intensity Flame length kW/m |
> 2.4 m (>8 ft) >1730 kW/m complete consumption of vegetation |
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Magnitude: multiple intensity |
low surface intensity, high crown fire intensity |
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Fire Severity: most of area burned produces little or no change to vegetation structure |
low severity |
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fire severity: moderate modification of vegetation structure |
moderate severity |
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fire severity: fire kills above-ground parts of most plants |
high severity fire |
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fire severity: stand replacing fires over most of the area |
very high severity fire |
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fire severity: two distinct types, low and high to very high |
multiple severity |
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Fire type: most of area burned is surface fire up to 30% crown burned by torching
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surface fire-passive crown fire
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fire type: surface fire supported by passive and active crown fires active crown fire is synchronous with surface fires |
passive-active crown fire |
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fire type: rare in califoria |
independent crown fire |
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fire type: complex mix under different weather/fuel/topography conditions |
multiple fire type |
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Succession phases: (5) |
bare mineral soil pioneer species gap-phase species shade tolerant (climax species) disturbance |
