Lecture 4 - RH

Question 1

What are features of fire prone areas?

Answer 1

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)

Question 2

How much vegetation is burned per year in Australia?

Answer 2

4 - 10%

Question 3

What is the most common cause of fires?

Answer 3

> 50% of the time due to a lightning strike

<20% are due to ‘control’ burning going out of control

Question 4

What happens to rainforests when fires become more frequent?

Answer 4

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

Question 5

How are flora adapted to fire?

Answer 5

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

Question 6

What are the strategies used for re-establishing fire-tolerant species?

Answer 6

Re-sprouters and re-seeders (seed regenerators)

Question 7

Which species is never dominant in fire-intolerant rainforests?

Answer 7

Eucalypts

Question 8

What do fossil and pollen records indicate about Australian flora?

Answer 8

Rainforests preceded eucalypt forests

Question 9

How long have fires been documented for?

Answer 9

Since the earliest written records

Question 10

What are some features of fire-prone areas?

Answer 10

Low moisture content for at least a single period

High fuel load (due to low breakdown of litter)

Flammable species (oils, resins, etc)

Question 11

How much of Australia’s vegetation is lost to fires annually?

Answer 11

4 - 10% (32 - 80 million hectares/year)

Question 12

What causes fires?

Answer 12

Lightning (>50%)

Control burning going out of control (<20%)

Other

Question 13

What are some adaptations used to protect a species during fires?

Answer 13

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.

Question 14

What are plants that depend on reseeding to survive fires called?

Answer 14

Obligate seed regenerators (eg. Callitris)

Question 15

Why did aboriginal tribes use fires?

Answer 15

To lure animals out of the forest

To create new, edible, vegetation

Question 16

How long has the practice of burning been done by aboriginal tribes?

Answer 16

50000 years

Question 17

What was the result of burning lots of rainforests?

Answer 17

The loss of rainforest vegetation and expansion of fire-resistant vegetation

Question 18

What does control burning lead to?

Answer 18

Degradation

Question 19

What are some pressures that humans have that influence fires in the world?

Answer 19

Population expansion (fertility rate 4 - 5/female)

Economic development (wood, cattle, export, etc)

Question 20

What is the rate of vegetation loss per year?

Answer 20

78 million hectares per year (1 football field/second)

Question 21

What factors influence the rate of spread of a fire?

Answer 21

Fire frequency

Fuel load

Fuel accumulation

Question 22

Which litter accumulates more quickly; tree litter or grass litter?

Answer 22

Tree litter

Question 23

How does wind speed affect the rate of spread of a forest fire?

Answer 23

Wind speed is a big factor in the acceleration of fire’s spread and can cause control burning to go out of control.

Question 24

What happens to fire temperature if more time passes from previous fire?

Answer 24

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.

Question 25

What happens to soil during a fire?

Answer 25

Heat sterilizes the soil until approximately 6 cm of depth for the average fire. Hotter fires that are above 500 degrees transmit heat to a greater depth.

Question 26

What is the ash bed effect?

Answer 26

The effect where nutrients from the ash seep into the soil. Sulfur and Nitrogen are lost due to becoming gas.

Higher pH in the soil due to accumulation of Potassium.

Question 27

How do plants use the ash bed effect?

Answer 27

Resprouters use the nutrients to establish themselves

Question 28

How does smoke affect seeds?

Answer 28

Many seeds need fire to germinate

ingredient found in smoke is used to stimulate germination

Question 29

What effect does biodiversity have on length of time of the fire?

Answer 29

More Biodiversity = Longer fire

Question 30

How do species change after a fire?

Answer 30

Resprouters are the first to return and then over time the reseeders take over.