Which type of fuel transition can cause the rate of spread to triple?

The correct answer is the transition from timber and second growth to grass. This type of fuel transition can significantly increase the rate of spread of fire because grass, once ignited, can spread flames rapidly due to its lower moisture content and more continuous fuel bed compared to denser timber or second growth.

When a fire moves from a more substantial, vertical fuel source like timber, which has varying amounts of moisture, to grass, it encounters a fuel type that ignites easily and burns quickly, allowing the fire to spread at a much faster rate. The horizontal arrangement of grasses also facilitates quicker lateral spread, enabling the fire dynamics to change drastically and potentially triple in speed.

Understanding this transition is crucial for firefighting strategies, as it informs how crews should anticipate the behavior of a wildfire and prepare their tactics accordingly. Recognizing the differences in fuel types and their burn characteristics helps in predicting fire spread and developing appropriate suppression efforts.