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What is Fire Severity?

 

Fire Severity is an ambiguous word. It is difficult to find one concrete definition. We have defined Fire Severity using a three pronged approach. There are Fireline Intensity, first-order fire effects, and second-order fire effects. Fireline intensity is simply the rate of energy or heat release per unit length of fire front, regardless of its depth (Scott). Burn Severity takes into account what comes after the fire is out. Burn Severity and, more specifically, first-order fire effects are what we are researching. First-order fire effects are determined by how much a fire has affected the immediate ecology. This could be injury to organisms or immediate mortality, fuel consumption, smoke production, or soil heating (Smith). On the other hand, second-order fire effects are how the ecosystem recovers.  This includes soil erosion, delayed plant and animal mortality, changes in site productivity, plant regeneration, and succession (Smith).

 

Burn Severity is determined by two factors: Fireline Intensity and how resistant the ecosystem is to fire. For example, if a fire with the same fireline intensity hit some trees with thin bark then the amount burned would be greater than if the same fire hit trees with thick bark (Agee).

 

References

Agee, J.K. 2007.Fire Severity. In: FireWords: Fire Science Glossary [electronic]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer).

Scott, Joe. 2007.Fireline Intensity. In: FireWords: Fire Science Glossary [electronic]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer).

Smith, Jane Kapler. 2007.First-Order Fire Effects. In: FireWords: Fire Science Glossary [electronic]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer).

Smith, Jane Kapler. 2007.Second-Order Fire Effects. In: FireWords: Fire Science Glossary [electronic]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer).