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Ecosystems and sustainability in a changing world > L3 > Flashcards

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
Q

Non- flammable plants

A
  • 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
Q

How does thick bark protect the vascular cambium?

A
  • 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
Q

Fast flammable grass example

A

Savanna grasses

28
Q

Fast flammable strategy

A
  • Plant ignites easy
  • Plant burns fast low heat release
  • Minimises damage to meristems
  • Sprouting regeneration
29
Q

Savanna grasses post fire

A
  • Sprout rapidly post fire
  • Burned plants recover in a few months
  • Resources below ground so can capture these and resprout
30
Q

What promotes frequent fires that burn fast in Savanna?

A
  • Rate at which they burn depends on biomass accumulation
  • Fire grasses tend to be large with high biomass
31
Q

Hot flammable strategy

A

Eg crown fires

- Fine, dense biomass burns slowly (trees and leaves)
- High heat release
- Fires typically lethal
- Seeding regeneration

Mature plants are killed

32
Q

Plant flammability strategies

A
  • Must be linked to particular regeneration strategies
  • Eg hot flammable must be coupled with re-seeding
  • Adaptive under particular fire regimes
33
Q

How are savanna ecosystems structured by fires?

A
  • 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
Q

What would happen if there was no fire in savanna ecosystems?

A
  • C4 savanna is replaced by forest
35
Q

Agriculture in savannas

A
  • Expansion and intensification of agriculture in savannas leads to fewer and smaller fires
  • No allowance for fuel accumulation
36
Q

Mediterranean type ecosystems

A
  • 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
Q

Temperate forest ecosystems

A
  • 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
Q

Mismanagement of fire prone ecosystems

A
  • 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
Q

Western US redwood fire regimes

A
  • 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
Q

Can plant traits influence the fire regime?

A

Yes

- Boreal forest (North)

- Different trees species on different continents have different plant flammability strategies

- Despite them all being boreal species
41
Q

North America boreal forest

A
  • 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
Q

Eurasia boreal forest

A
  • Non-flammable trees “fire resisters”
    • Self-pruning branches
    • Moister needles
    • Thick bark

Eg Siberian larch, scots pine

- Tend to be surface fires
43
Q

Satellite fire regime data

A
  • 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)

Ecosystems and sustainability in a changing world (21 decks)

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