Lecture 4 - DA

Question 1

What are the 2 most important determinants of what plants will grow in a given region?

Answer 1

Moisture

Fire

Question 2

What kind of rainfall do fire prone regions have?

Answer 2

Low rainfall.

Question 3

How can one tell if an area is a fire prone region?

Answer 3

By looking at rock layers, and the presence of ash layers.

Question 4

At what annual rainfall level would a region stop catching fire?

Answer 4

> 2000mm

Question 5

Does a high annual rainfall level always mean a region is safe from catching fire?

Answer 5

No, it only takes at least one period of low moisture content to catch fire.

Question 6

What two things can add to fire intensity?

Answer 6

High fuel load due to breakdown of litter

Presence of flammable species with oils/resins

Question 7

What percentage of Australia burns every year?

Answer 7

4-10%. Some of this is deliberate.

Question 8

What are the causes of fires in percentage?

Answer 8

50% lightning strikes
20% control burnings gone wrong
Rest is due to arson, accidents etc.

Question 9

How can a fire boundary be seen? What happens to this boundary over time if there is no fire?

Answer 9

It is a divide between plants that are resistant to fire, and those that arent. Clearly visible after a fire.
After periods of no fire, the boundary will shift as the resistant plants encroach past the boundary, progressively taking over.

Question 10

When did fires become prevalent in Australia?

Answer 10

When it broke from Antarctica.

Question 11

What happened to Australia as it migrated north?

Answer 11

Became drier.

Question 12

Australia was once covered in rainforests. What percentage remains?

Answer 12

5%.

Question 13

Which of the following are tolerant and intolerant to fires:

• Tropical/temperate rainforest
• Tropical/temperate sclerophyll forest
• Heathland
• Grassland

Answer 13

Intolerant
-Tropical/temperate rainforest
Tolerant
-Tropical/temperate sclerophyll forest
-Heathland
-Grassland

Question 14

Can intolerant plant communities (like a rainforest) re-establish after a fire? What about tolerant ones?

Answer 14

Intolerant cant, but tolerant will.

Question 15

Can a plant be a reseeder and a resprouter?

Answer 15

Yes, but not always.

Question 16

Do eucalypts dominate rainforests (both temperate and tropical)?

Answer 16

No.

Question 17

Name 4 ways the Aborigines used fire as a tool.

Answer 17

For hunting
Controlling grassland
Clearing forests
Managing forests for food

Question 18

What 3 factors caused a massive loss in rainforests?

Answer 18

Drying (Australia moving north)
Numerous fires
Massive expansion of fire resistant vegetation

Question 19

Are both natural and induced fires a threat to fire tolerant plant communities?

Answer 19

Natural fires arent, but induced fires can lead to degradation.

Question 20

What induced fire method occurs on a large scale in most tropical rainforests? What 3 factors heavily influence the clearance of forests?

Answer 20

Slash and burn.

High pressure from humans, an increasing population, expansion, and economic pressure.

Question 21

Does altitude affect fire intensity and readiness?

Answer 21

High altitudes have less oxygen and fires dont start as readily and arent as intense.

Question 22

What is the main variable in fire intensity?

Answer 22

Fuel.

Question 23

What is the main variable in fires starting?

Answer 23

Heat.

Question 24

What does fuel accumulation increase?

Answer 24

Fire intensity.

Question 25

Which tends to accumulate more fuel, forests or woodlands?

Answer 25

Forests.

Question 26

What does high windspeed contribute to in the context of fires?

Answer 26

Higher rate of spread of fire.

Question 27

When a fire begins, what is the temperature like, and how does it develop over time?

Answer 27

Temperature peaks quickly, but will also decrease quickly as fuel runs out.

Question 28

If the fire temperature is taken in a given region annually (assume it burns at the same time annually), what happens to the recordings?

Answer 28

Increases every interval, and the fire also lasts longer.

Question 29

How does soil depth affect temperature?

Answer 29

Temperature decreases with soil depth.

Question 30

What 2 nutrients (name the element) leave after fires? What do they become? What happens to these nutrients if fires are prevalent?

Answer 30

Sulphur - becomes sulphur dioxide
Nitrogen - becomes nitrogen dioxide
Both are gaseous
A deficiency occurs in these elements if fires are prevalent.

Question 31

What happens to organic matter after a fire?

Answer 31

Becomes mineralised.

Question 32

What happens to pH after fires?

Answer 32

Increases.

Question 33

How is the massive loss in nitrogen from soil replaced?

Answer 33

N fixation, carried out by plants like wattles, which thrive after fires.

Question 34

Are fires always necessary to germinate the seeds of resprouters?

Answer 34

Not necessarily, may sometimes require the ingredients of smoke rather than heat. Smoke water can have similar effects.

Question 35

What is ultimately responsible for fixing nitrogen, and what keeps them alive?

Answer 35

Rhizodium fixes nitrogen, kept alive by photosynthesis of the plant whose roots they live on.

Question 36

Between resprouters and reseeders, which do better in areas of frequent fires? Why is this so?

Answer 36

Resprouters do better. Reseeders need time to mature. If the fire is too frequent, they will not mature quick enough.

Question 37

Are reseeders or resprouters always at a disadvantage if fire frequency is short? What about if the frequency becomes longer?

Answer 37

Reseeders are always at a disadvantage if fire frequency is short.
However, they will dominate as fire frequency becomes longer.