CBM Fire Behavior & Ecology 3 — Questions and Answers
Question 1: What does 'torching' describe in the context of fire behavior?
- The act of lighting a prescribed fire with a drip torch
- Ignition of an individual tree or small group of trees from base to crown (Correct answer)
- Wind-driven fire running through surface fuels at high speed
- Complete consumption of all organic matter in the soil
Correct answer: Ignition of an individual tree or small group of trees from base to crown
Torching occurs when surface fire ignites the foliage of individual trees or small tree groups, creating tall flame columns that can promote spotting.
Question 2: In fire ecology, 'fire return interval' (FRI) refers to:
- The time required for a fire to return to its origin point
- The average number of years between successive fires at a given location (Correct answer)
- The seasonal window during which fire can be reintroduced
- The rate at which burned areas recover their pre-fire fuel load
Correct answer: The average number of years between successive fires at a given location
Fire return interval is the average or median time between fire events at a specific location, reconstructed from fire scars or charcoal records.
Question 3: Which fuel moisture category has the SLOWEST response time to changes in atmospheric humidity?
- 1-hour timelag fuels
- 10-hour timelag fuels
- 100-hour timelag fuels
- 1000-hour timelag fuels (Correct answer)
Correct answer: 1000-hour timelag fuels
1000-hour timelag fuels (logs and large woody debris >3 inches diameter) take approximately 1000 hours to reach equilibrium with ambient humidity conditions.
Question 4: The 'smoke column' produced by a prescribed fire can affect fire behavior by:
- Reducing fuel moisture through condensation around the fire perimeter
- Creating convective updrafts that can influence wind patterns and spotting distance (Correct answer)
- Filtering UV radiation and reducing atmospheric instability near the fire
- Suppressing ember transport by increasing air density above the flame
Correct answer: Creating convective updrafts that can influence wind patterns and spotting distance
A strong convection column creates intense updrafts that loft firebrands and can alter local wind patterns, sometimes drawing air inward and increasing fire intensity.
Question 5: What is 'pyrodiversity' and why is it ecologically valuable?
- The use of multiple ignition methods to achieve complete combustion
- Variation in fire frequency, severity, and seasonality that creates a mosaic of habitat types (Correct answer)
- Genetic diversity within fire-adapted plant species populations
- The diversity of fire management tools used by burn crews
Correct answer: Variation in fire frequency, severity, and seasonality that creates a mosaic of habitat types
Pyrodiversity refers to heterogeneity in fire history across a landscape, which promotes biodiversity by creating varied structural habitats used by different species.
Question 6: During a prescribed burn, an 'escape fire' situation is most likely when:
- Fuel moisture is slightly above the prescription maximum
- Wind shifts cause the backing fire to become a head fire (Correct answer)
- Relative humidity rises above the prescription minimum
- Fire intensity is lower than predicted
Correct answer: Wind shifts cause the backing fire to become a head fire
A wind shift that reverses fire direction can instantly transform a slow backing fire into a fast-moving head fire, potentially overwhelming containment lines.
Question 7: Which ecological role does fire play in shortgrass prairies and grassland ecosystems?
- It eliminates all invasive species permanently
- It promotes woody plant encroachment by removing grass competition
- It recycles nutrients, stimulates grass growth, and prevents woody encroachment (Correct answer)
- It reduces soil organic matter to levels that prevent future fire
Correct answer: It recycles nutrients, stimulates grass growth, and prevents woody encroachment
In grasslands, fire returns nutrients to the soil, removes accumulated thatch, promotes vigorous grass re-growth, and suppresses shrub and tree establishment.
CBM Fire Behavior & Ecology 3
What does 'torching' describe in the context of fire behavior?