Lecture 10: Wildfires

Question 1

Pre-Ignition Phase

Answer 1

vegetation reaches temp. it can ignite at, loses water

Question 2

Pyrolysis

Answer 2

Chemical process of breaking large hydrocarbons down into smaller ones

Question 3

Combustion Phase

Answer 3

ignition of the pre-heated fuel

Question 4

Flaming Combustion

Answer 4

rapid, high-temperature conversion of fuel into heat

-contains flames and unburned fuel

Question 5

Smouldering Combustion

Answer 5

-occurs in areas with burned material, ash covering fueled

Question 6

Conduction

Answer 6

molecule to molecule contact to transfer heat

Question 7

Radiation

Answer 7

transfer ofheat through invisible waves

Question 8

Convection

Answer 8

Transfer of heat through movement of liquid or gas

Question 9

Extinction Phase

Answer 9

combustion ceased due to lack of fuel/heat

Question 10

Weather conditions for Wildfires

Answer 10

-drought and dry thunderstorms (rain evaporates before hitting the ground, lightning ignites)

Question 11

Surface Fire

Answer 11

travel close to ground, burn surface fuel

-slow

Question 12

Crown Fire

Answer 12

move rapidly through canopy with flaming combustion
intermittent: consume some canopy
Continuous: consume all of canopy

Question 13

Effects of Wildfires

Answer 13

• hydrophobic layer can form on surface of burned soil due to chemicals burning: increases run off and lowers soil permeability, persists for years
• increase particles in the atmosphere, “haze”

Question 14

Linkages to Climate Change

Answer 14

• increase in drought severity increases wildfire severity
• grasslands replace forests, forests go pole-ward
• insect infestations can make forests more vulnerable to wildfires

Question 15

Mountain Pine Beetle

Answer 15

80% of mature mountain pines are infested

• threatens Alberta pine forests and Jack pine in Boreal
• warmer temp. makes them last through the winter

Question 16

Impacts of Wildfires

Answer 16

• fires lead to evacuation of towns, road/airport closure, property loss
• smoke/haze has ocular/respiratory impacts
• ON ANIMALS
• large animals outrun, rodents can hide underground
• opens up grazing grounds
• increase in sedimentation from run off+erosion impacts aquatic ecosystems

Question 17

Natural Service Functions of Wildfires

Answer 17

• temporarily lower competition for sunlight and water
• surviving/new species can thrive at forest floor
• triggers release and opening of flowers or seeds in some species
• remove parasites from soil
• remove surface litter to allow more moisture infiltration
• removes diseased trees to limit beetle infestation

Question 18

Pioneer Vegetation

Answer 18

first species to appear after a wildfire

-aspen, lodgepole pine, wire weed

Question 19

Yellowstone NAtional Park Wildfire

Answer 19

• policy allows natural fires to burn
• fire suppression policies in past allow fuel to build up too much
• lightning caused 50 fire in 1988, all merged
• eventually caused political pressure and 10 000 firemen called in
• eventually revitalized the park

Question 20

Fire Break

Answer 20

Area with no fuel. steer fire here

• can create artificial break by clearing land with bulldozer
• this causes accumulation of fuel though

Question 21

Prescribed Burns

Answer 21

• controlled fires purposely ignited to lower fuel in forests
• difficult to predict weather/ fuel amount that’s easy to control