L3 Flashcards

1
Q

What are the 3 conditions needed for wildfires?

A

Dry weather

Fuel load (dry plant biomass)

Ignition

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2
Q

Dry weather is due to:

A

Dry season

Dry years

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3
Q

Fuel load (dry plant biomass) is due to:

A

Productivity

Fire suppression

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4
Q

Ignition is due to:

A

Lightning

Humans

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5
Q

Fire in ecosystems:

A
  • Dry weather in a particular location causes fire
    • Typically fire prone ecosystem occur in locations with a dry season
    • Fuel load increases in places where human management suppress fires
    • Fires have been in ecosystems a long time (most are human lit today)
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6
Q

What are the three types of fire?

A

Crown fires

Surface fires (Savannas)

Ground fires (Moorland)

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7
Q

Crown fires

A
  • Climb up into tree canopies, everything burns
    • Hot
    • Many mature trees die (lethal)
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8
Q

Surface fires (savannas)

A
  • Burn fuel on ground surface (grass or litter)
    • Cool
    • Many mature trees survive, doesn’t get up into tree canopy
    • Immature trees have to start again as they are not at escape height
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9
Q

Ground fires (moorland)

A
  • Organic matter smoulders underground
    • Often occur in peatland
    • Burn slowly over a long period
    • Produces high particulate
    • Tough to identify if one is occurring
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10
Q

Global importance of fire

A
  • Satellite data
    • Heat satellites, surface reflectance
    • We can look at different characteristics of fire
    • Large shifts in biomass, particularly in forests. In drier areas there is less biomass change
    • The frequency and burned area of fires is greatest in surface fires eg savanna and grassland
    • Consume less fuel
    • Tropical forest fires are very infrequent
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11
Q

There is less biomass change after a fire in dry or wet areas?

A

Less in drier areas

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12
Q

Frequency and burned area of fires is greatest in…?

A

Surface fires eg savanna and grassland

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13
Q

Global ‘pyromes’ analogous to biomes

A
  • Fires that have different characteristics can classify vegetation according to fire regime
    • Mapping biomes according to fire characteristics - frequency, intensity, size
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14
Q

Plant regeneration strategies

A
  • Kills competitors (more sunlight)
     -Burns plants (releases nutrients)
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15
Q

What are the two strategies for plant establishment?

A

Seeder strategy
- Seed release or germination triggered by fire

Sprouter strategy
- Resprouting of surviving plants after fire

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16
Q

What are the two seeder strategies?

A

Refractory seeds

Serotiny

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17
Q

Refractory seeds

A
  • When seeds are heated they germinate
  • Heat cue
  • Chemicals in smoke that can be detected in soil can trigger germination
  • Acacia (Australia)
  • Adenostoma fasciculatum (California)
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18
Q

Serotiny

A
  • Fruiting bodies that hold onto seeds
  • After fire fruiting bodies open up and release seeds
  • Leucospermum conocarpodendron
  • Banksia
  • Pinus halepensis - cones open up after fire
19
Q

Three methods of sprouter strategy?

A
  1. Sprouting from belowground stores
  2. Lignotubers
  3. Sprouting from the crown: Epicormic buds
20
Q

Sprouting from belowground stores

A
  • Chamaerops humilis
    • Quercus coccifera
21
Q

Lignotubers

A
  • Woody structures that grow close to surface and store starch (energy)
    • Used to start regrowing a tree after a fire
    • Adenostoma can resprout and seed
22
Q

Sprouting from the crown: Epicormic buds

A
  • If the crown is scorched but not killed
    • Protected underneath the tree bark
    • Resprout and reconstruct the canopy

Quercus suber

Eucalyptus pulchella (Aus)

23
Q

FIre in ecosystems

A
  • Factors necessary for wildfires, and different types of wildfires
    • Plant adaptations - regeneration strategies
24
Q

Plant flammability strategies

A
  • Flammable vs inflammable
    • Of the flammable plants: Hot vs cool (fast) flammable
25
Non- flammable plants
- Mature trees - Protective bark - Thick insulating layer around trunk - Eg Cork and Coastal redwood - Growing cells in wood are between wood and bark (tree tries to protect these cells and epicormic buds)
26
How does thick bark protect the vascular cambium?
- As bark thickness increases cambium temperature decreases - Time to kill the cambium increases with bark thickness - Flameproof bark works against surface fires but not crown fires (high mortality) - Protects trunk of tree at surface level
27
Fast flammable grass example
Savanna grasses
28
Fast flammable strategy
- Plant ignites easy - Plant burns fast low heat release - Minimises damage to meristems - Sprouting regeneration
29
Savanna grasses post fire
- Sprout rapidly post fire - Burned plants recover in a few months - Resources below ground so can capture these and resprout
30
What promotes frequent fires that burn fast in Savanna?
- Rate at which they burn depends on biomass accumulation - Fire grasses tend to be large with high biomass
31
Hot flammable strategy
Eg crown fires - Fine, dense biomass burns slowly (trees and leaves) - High heat release - Fires typically lethal - Seeding regeneration Mature plants are killed
32
Plant flammability strategies
- Must be linked to particular regeneration strategies - Eg hot flammable must be coupled with re-seeding - Adaptive under particular fire regimes
33
How are savanna ecosystems structured by fires?
- Open woody plant cover, C4 grass- dominated ground layer - Fast flammable grasses and non-flammable trees - Sprouting strategy in response to fire and herbivory - Both trees and grasses tend to resprout after fire - Savanna existence relies largely upon fires
34
What would happen if there was no fire in savanna ecosystems?
- C4 savanna is replaced by forest
35
Agriculture in savannas
- Expansion and intensification of agriculture in savannas leads to fewer and smaller fires - No allowance for fuel accumulation
36
Mediterranean type ecosystems
- Cool wet-winters and hot- dry summers - Crown fires most frequent and diversity of strategies eg: - Hot flammable/seeders and non-flammable/ sprouters - Refractory seeds/serotiny or thick bark/ epicormic buds
37
Temperate forest ecosystems
- Often have fires and are fire adapted - Surface fires, thick litter fuel - thick bark and serotinous cones - Dry summer leaf litter can be susceptible to fire - Cones drop and open during fire
38
Mismanagement of fire prone ecosystems
- Fire suppression causes fuel accumulation, stops trees establishing - Mismanagement caused a thick layer of leaf litter fuel - Stopped seedlings accumulating as there was too much leaf material
39
Western US redwood fire regimes
- Climate change and fire suppression have altered western US redwood fire regimes- greater risk of crown rather than surface fires - More fire weather - Fires can climb into canopy instead of burning on the ground - Greater risk of crown fires than surface fires - Mature trees have fireproof trunks but not fireproof canopies
40
Can plant traits influence the fire regime?
Yes - Boreal forest (North) - Different trees species on different continents have different plant flammability strategies - Despite them all being boreal species
41
North America boreal forest
- Hot flammable trees "fire embracers" - Branches close to ground - Flammable needles - Thin bark (tree dies) - Serotinous cones (allow for reproduction) Eg black spruce, jack pine - Tend to be crown fires
42
Eurasia boreal forest
- Non-flammable trees "fire resisters" - Self-pruning branches - Moister needles - Thick bark Eg Siberian larch, scots pine - Tend to be surface fires
43
Satellite fire regime data
- North America has hotter fires (crown) - Change in surface albedo after fires - North American fires increase surface albedo due to hotter fire burning more trees so there is more snow cover - Eurasia results in tree covering snow - Interconnection to feedback on climate - High albedo = higher reflectance back to space (this is good for climate)