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ERS 234 Final > Lecture 8 - Forest Fires > Flashcards

Lecture 8 - Forest Fires Flashcards

1
Q

What is the largest cause of forest fires in terms of number and area burned?

A

Humans!

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2
Q

What are the natural causes of forest fires?

A
  • dry weather
  • lightning
    (b/c some ecosystems depend on fire)
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3
Q

What can be evidence of fires from the past?

A
  • lake sediments
  • fire resistant trees with burn scars
  • forest floor charcoal layer
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4
Q

How often does lightning lead to fires?

A
  • there are approximately 500,000 lightning strikes daily of which 10% lead to forest fires (frequency varies globally)
  • causes round 10,000 fires/year in the USA
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5
Q

Where are fires started by lightning most commonly and uncommonly found?

A
  • leading fire cause in western NA (30-60% of fires)

- uncommon in tropical rainforests and in moist temperate forests (western Europe and eastern NA)

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6
Q

How many fires can a single lightning strike start?

A

upwards of 50 fires

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7
Q

Lightning accompanied by rain makes fires:

A
  • sluggish
  • smouldering for days/weeks in leaf litter or trees
  • can break out in fire once the weather is dry and windy
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8
Q

Lightning in the absence of rain:

A
  • starts fires immediately

- is known as dry lightning

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9
Q

How does the adaptation of species after a fire vary?

A
  • some species have light seeds that can be easily dispersed after fire by wind
  • others have serotinous cones (like jack pine, black spruce, and lodgepole pine) that once they are opened by fire, rapid germination of the seeds occurs and will also produce seeds at a young age
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10
Q

What does a natural fire look like?

A
  • frequent, low-intensity fires
  • keeps forests open and are common in grass/pine areas
  • discourages invasion of shade tolerant species
  • prevents outbreaks of large conflagrations (out of control fires)
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11
Q

What does a suppressed fire look like?

A
  • high severity
  • trees have flammable foliage (Ex. conifers)
  • there is a high fuel buildup
  • 50 to 400 year fire rotation
  • dominated by even-aged stands/species adapted to fire
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12
Q

Human intervention with fire has always occurred. How have ancient cultures used it?

A
  • improve hunting
  • aid in land clearing
  • reduce insect/snake populations
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13
Q

How is fire used in tropical forests?

A
  • the practice of slash and burn agriculture is common. which can cause forest fires
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14
Q

Why did NA natives use fire?

A
  • to make the land more passable/usable
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15
Q

How did European settlers in NA use fire? How did this turn out?

A
  • used it to clear the land
  • usually resulted in infernos/uncontrollable fires
  • caused the implementation of forest fire suppression policies
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16
Q

What is fire management?

A

It is strategies used to suppress fires or to conduct prescribed burning. The strategy used depends on fire behaviour, like direction of travel, rate of spread, and intensity

17
Q

What is the start and spread of fire dictated by?

A

The fire triangle.

  • flammable fuels
  • sufficient heat energy to ignite fuel
  • adequate oxygen
18
Q

What is a surface fire?

A
  • requires dry fuel (litter and dead branches)
  • lush understory vegetation deters fires
  • fuel buildup creates more intense and difficult to control fires
19
Q

What is a ground fire?

A
  • common in areas with peat accumulation (as it is the fuel)
  • spreads slowly with low intensity and can smoulder for months
  • difficult to judge whether the suppression is successful due to smouldering
  • it requires lots of water to suppress these fires
20
Q

What is a crown fire?

A
  • not very common
  • sweeps through the canopy and covers large areas
  • conifers are more susceptible to these fires b/c of the low moisture levels in their foliage
  • most start as surface fires and the reason for transition is unknown
  • usually causes heavy or complete mortality
21
Q

How do weather conditions impact fire behaviour?

A
  • weather regulates fire as atmospheric moisture and winds play a key role
  • the amount/duration of moisture in fuel and relative humidity are factors
  • the wind influences the rate of fire spread/intensity and shapes the pattern of fire as it can change the direction
22
Q

How does topography impact fire behaviour?

A
  • fire burns quicker up a steeper slope because the heat generated at the front of the fire decreases moisture (and heat is directed towards ground surface)
  • S/SW facing slopes are warmer and drier so they experience more intense fires frequently
  • rugged mountains induce turbulent winds, making it difficult to predict fire patterns
23
Q

How are blow up fires created?

A
  • when fires are undergoing an abrupt transition from a low to high intensity fire, a convection column with upward rising gases and smoke is created (known as blow up fire)
  • caused by sudden change in wind speed
24
Q

What can be the result of a blow up fire?

A
  • erratic behaviour
  • potential wind speeds of >300km/h
  • many new fires can be created
  • can only be extinguished by rain or snow
  • human control efforts are only successful by stopping lateral spread
25
Q

The prediction of forest fires has become a:

A

science!

  • through experiments and developing equations, the National Fire Rating System was developed (rates danger of forest fire)
  • there are many fire prediction models (ex. American computer model ‘BEHAVE’ helps to predict shape and spread pattern)
26
Q

How was fire prevention methods spread to common knowledge

A
  • through fire prevention campaigns (radios, posters, signs, magazines, news/media)
27
Q

How are unhealthy forest fires started?

A
  • through the accumulation of fuel due to fire suppression

- number has increased

28
Q

In relation to forest fires, what is the issue with urban sprawl?

A
  • many communities are built in areas that have highly flammable vegetation causing an interference
  • this places many people and their homes at risk
29
Q

What are some solutions for controlling unhealthy fires?

A
  • mechanical thinning of forest stands
  • salvage cutting (removing trees that have been damaged by fire)
  • extensive prescribed burning
30
Q

What are the steps of fire control?

A
  1. Detection: the use of fire lookout towers (most effective), planes, infrared scanners (not effective on cloudy days)
  2. Suppression: through the removal of fuel, oxygen, or heat; ground suppression through using water or bulldozers to create ditches; and aerial suppression through water bombs
31
Q

What is prescribed burning?

A

The controlled use of fire (ignited aerially or on the ground) to accomplish specific objectives

32
Q

Why initiate prescribed burning?

A
  • reduction of logging debris for replanting
  • preparation of seedbeds for replanting species that require exposed mineral soil
  • reduction of fuel accumulation
  • control of understory vegetation
  • control of diseases
  • improvement of range land for livestock grazing
  • restoration of prairie habitat
33
Q

Why does prescribed burning require careful planning?

A
  • can easily cause out of control fires
  • increases air pollution
  • there is a limited window with suitable conditions
34
Q

What are the negative and positive views on fire by forest managers?

A
  • for a long time, it has a negative association for forest managers
  • currently more positive outlook b/c they’ve realized the importance of fire in maintaining forest ecosystems and that many factors influence the outcome of the fire on the landscape
35
Q

What are the environmental impacts of fire?

A
  • erosion: exposes bare soil due to burning of forest floor; reduces soil porosity, increasing surface runoff; and changes the soil structure
  • influences soil fertility: nutrients are lost to the atmosphere during intense fires (ex. N), but low intensity fires release nutrients in the soil for tree uptake
  • influences wildlife populations: habitats are modified, some species are killed if they can’t get away fast enough
  • affects air quality: increases concentration of atmospheric pollutants

ERS 234 Final (9 decks)

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