Crown fire development relies on which two factors along with adequate heat transfer?

Crown fire development is influenced primarily by three key factors: the flammability of the crown fuels, the ability of surface fuels to transmit heat to the crown, and the environmental conditions that support combustion. Correctly identifying the interaction between crown flammability and heat transfer is critical in understanding how crown fires initiate and spread.

In the context of this question, adequate surface to crown heat transfer is essential because it determines how effectively heat from ground-level fires can reach the crowns of trees. This heat transfer can occur through direct contact, radiant heat, or convective heat. If the surface fire is unable to generate sufficient heat to ignite the crown, the fire will remain a surface fire and not escalate into a crown fire.

Crown flammability refers to the inherent ability of the crown of a tree to ignite and sustain combustion. This factor is crucial because even with excellent heat transfer, if the crowns are not flammable, crown fire cannot occur. Therefore, both crown flammability and effective heat transfer between surface and crown fuels work in tandem to facilitate crown fire development.

Understanding this interaction helps in assessing fire behavior and potential escalation from surface to crown fires, which is vital for wildfire management and safety planning.