Lecture 4 - RH Flashcards
What are features of fire prone areas?
Low rainfall/low moisture for at least one period
High fuel load due to low breakdown of litter (branches, leaves, etc)
Flammable species (due to oils/resins)
How much vegetation is burned per year in Australia?
4 - 10%
What is the most common cause of fires?
> 50% of the time due to a lightning strike
<20% are due to ‘control’ burning going out of control
What happens to rainforests when fires become more frequent?
Rainforests get pushed back further and further if fires become more frequent.
For this reason Australia has less rainforests compared to what it had several centuries ago
How are flora adapted to fire?
flora divided sharply along lines of reaction to fire:
Fire-intolerant (tropical/temperate rainforest) these species do not re-establish after fire
Fire-tolerant (tropical.temperate sclerophyll forest, heathland, grassland) these species re-establish after the fire
What are the strategies used for re-establishing fire-tolerant species?
Re-sprouters and re-seeders (seed regenerators)
Which species is never dominant in fire-intolerant rainforests?
Eucalypts
What do fossil and pollen records indicate about Australian flora?
Rainforests preceded eucalypt forests
How long have fires been documented for?
Since the earliest written records
What are some features of fire-prone areas?
Low moisture content for at least a single period
High fuel load (due to low breakdown of litter)
Flammable species (oils, resins, etc)
How much of Australia’s vegetation is lost to fires annually?
4 - 10% (32 - 80 million hectares/year)
What causes fires?
Lightning (>50%)
Control burning going out of control (<20%)
Other
What are some adaptations used to protect a species during fires?
Many plants flower in response to fire and they are known as resprouters (eg. Xanthorrhoea)
Lignotubers which produce more plants after a fire. This is a resprouting strategy
Epicormic shoots which come out of burned stem. They are typically microscopic buds that grow in response to fire. This is a resprouting strategy
Capsular fruit which germinate only when a fire occurs. this is known as a reseeding strategy.
What are plants that depend on reseeding to survive fires called?
Obligate seed regenerators (eg. Callitris)
Why did aboriginal tribes use fires?
To lure animals out of the forest
To create new, edible, vegetation
How long has the practice of burning been done by aboriginal tribes?
50000 years
What was the result of burning lots of rainforests?
The loss of rainforest vegetation and expansion of fire-resistant vegetation
What does control burning lead to?
Degradation
What are some pressures that humans have that influence fires in the world?
Population expansion (fertility rate 4 - 5/female)
Economic development (wood, cattle, export, etc)
What is the rate of vegetation loss per year?
78 million hectares per year (1 football field/second)
What factors influence the rate of spread of a fire?
Fire frequency
Fuel load
Fuel accumulation
Which litter accumulates more quickly; tree litter or grass litter?
Tree litter
How does wind speed affect the rate of spread of a forest fire?
Wind speed is a big factor in the acceleration of fire’s spread and can cause control burning to go out of control.
What happens to fire temperature if more time passes from previous fire?
After 1 year the fire is briefly warm but then becomes cooler. After 7 years The fire is warmer and for a longer period of time.
