L3 Flashcards
What are the 3 conditions needed for wildfires?
Dry weather
Fuel load (dry plant biomass)
Ignition
Dry weather is due to:
Dry season
Dry years
Fuel load (dry plant biomass) is due to:
Productivity
Fire suppression
Ignition is due to:
Lightning
Humans
Fire in ecosystems:
- 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)
What are the three types of fire?
Crown fires
Surface fires (Savannas)
Ground fires (Moorland)
Crown fires
- Climb up into tree canopies, everything burns
- Hot
- Many mature trees die (lethal)
Surface fires (savannas)
- 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
Ground fires (moorland)
- Organic matter smoulders underground
- Often occur in peatland
- Burn slowly over a long period
- Produces high particulate
- Tough to identify if one is occurring
Global importance of fire
- 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
There is less biomass change after a fire in dry or wet areas?
Less in drier areas
Frequency and burned area of fires is greatest in…?
Surface fires eg savanna and grassland
Global ‘pyromes’ analogous to biomes
- Fires that have different characteristics can classify vegetation according to fire regime
- Mapping biomes according to fire characteristics - frequency, intensity, size
Plant regeneration strategies
- Kills competitors (more sunlight)
-Burns plants (releases nutrients)
What are the two strategies for plant establishment?
Seeder strategy
- Seed release or germination triggered by fire
Sprouter strategy
- Resprouting of surviving plants after fire
What are the two seeder strategies?
Refractory seeds
Serotiny
Refractory seeds
- 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)
Serotiny
- 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
Three methods of sprouter strategy?
- Sprouting from belowground stores
- Lignotubers
- Sprouting from the crown: Epicormic buds
Sprouting from belowground stores
- Chamaerops humilis
- Quercus coccifera
Lignotubers
- 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
Sprouting from the crown: Epicormic buds
- If the crown is scorched but not killed
- Protected underneath the tree bark
- Resprout and reconstruct the canopy
Quercus suber
Eucalyptus pulchella (Aus)
FIre in ecosystems
- Factors necessary for wildfires, and different types of wildfires
- Plant adaptations - regeneration strategies
Plant flammability strategies
- Flammable vs inflammable
- Of the flammable plants: Hot vs cool (fast) flammable