lecture #12- Wildfires

Question 1

How do wildfires start?

Answer 1

From lightening and Volcanic eruptions

Question 2

What happens after a fire?

Answer 2

The vegetation completes its life cycle form early colonizing to mature ecosystem

Question 3

Which trees are have fire resistant bark?

Answer 3

redwoods and Oak

Question 4

Why are we seeing an increase in wildfires through geologic time?

Answer 4

Warmer and dryer climate

Increased use of fire by human for clearing land and for heat, cooking etc

Question 5

What are the requirements for a wildfire?

Answer 5

Fuel, O2, heat

-if anyone of these are lost, it will dissipate

Question 6

What is the relationship between plants (CO2) and fires?

Answer 6

Plants take in and store CO2 from the atmosphere, so when they get burned they release it back into the atmosphere

Question 7

What are the 3 phases of wildfires?

Answer 7

Pre-ignition
Combustion
Extinction

Question 8

What is the pre-ignition phase?

Answer 8

Vegetation reaches a tem at chic it can ignite

-water leaves vegetation

Question 9

What is pyrolysis?

Answer 9

chemical process describing the degradation of a large hydrocarbon molecule into smaller ones
-occurs in the presence of heat

Question 10

What is the combustion process?

Answer 10

Phase begins with ignition
Ignition is not a single process, it can occur repeatedly as the fire moves
-pyrolysis and pre-heating results in fuel

Question 11

What is Flaming combustion?

Answer 11

The rapid, high temp conversion of fuel into heat

-flames and large amounts of unburned material

Question 12

What is smouldering Combustion?

Answer 12

Occurs in areas with burned material and ash that covers new fuel

Question 13

What are the 3 transfers of heat?

Answer 13

Conduction (molecule to molecule)
Radiation (invisible waves)
Convection (liquid or gas)

Question 14

What happens to air as its heated?

Answer 14

it rises and become less dense and rising air moves heat from the zone of flaming and is replaced with fresh air to fuel the fire

Question 15

what is the extinction phase?

Answer 15

Time when the combustion has ceased

-no longer sufficient fuel

Question 16

What kind of fuel burns easily?

Answer 16

Dead or diseased organic material

Question 17

Which orientation of the sun causes the slopes to be drier than others?

Answer 17

South

Question 18

Which orientation of the wind causes the slopes to be drier than others?

Answer 18

West

Question 19

Why is wind bad?

Answer 19

Can help pre heat material

Can cary embers to other places, spreading the fire

Question 20

Which geographic region is most at risk of wild fires?

Answer 20

Changes form year to year depending on the weather and which areas are experiencing the most drought

Question 21

YellowStone 198 Case study

Answer 21

• Had a policy to let natural fires burn out
• really hot summer and public pressure to put the fire out
• it couldn’t be controlled by the crews and burned for months because of the previous policy to put out all fires
• Revitalized the ecosystem

Question 22

What is a Surface fire?

Answer 22

They travel close to the ground and burn shrubs leaves twigs grasses
-move relatively slow

Question 23

What is a crown fire?

Answer 23

Move rapidly through the forest canopy by slamming combustion

• fed by surface fires that move up limbs or tree trunks
• driven by strong winds
• can have intermittent (can consume tops of trees in an area) or continuous crown fires (can consume tops of all trees)

Question 24

What kind of layer do fires leave behind?

Answer 24

hydrophobic layer

• caused by the accumulation of chemicals from burning vegetation
• increases surface run off and erosion
• can persist for several years

Question 25

How can climate change increase wildfires?

Answer 25

Can increase drought = more fuel and higher chance of fires

Question 26

What is the Mountain Pine beetle?

Answer 26

responsible for destroying forests

-warmer temps increase the time that the beetles can effect the trees

Question 27

What are some impacts of wildfires?

Answer 27

• evacuates large areas, and highways and can close airports
• exposure to smoke and haze can effect health
• Aquatic species feel the effects the most

Question 28

What are some natural service functions of wildfires?

Answer 28

• Reduces competition for sun for a time being
• Triggers the release of seeds
• Can remove microorganisms from the soils that could be parasites
• remove surface litter
• Remove was or diseased trees
• Create grass lands for grazing

Question 29

What is pioneer vegetation?

Answer 29

1st species to appear after a wild fire

Question 30

What is the ideal fire management?

Answer 30

allowing them to burn enough to benefit the ecosystem but keeping it so that humans and their property arent harmed

Question 31

What is a fire regime?

Answer 31

The potential for wildfires in an area

Question 32

how do we suppress fires?

Answer 32

Create fire breaks

-these can be natural or artificial

Question 33

What are prescribed burns?

Answer 33

one way in which to counter the buildup of fuel

- controlled fired that are purposely ignited to reduce the amount of fuel