Fuel treatment effectiveness depends on forest type and fire weather conditions

Photo Credit

Forest Service photo by Mike Battaglia

A combination of stand density reduction followed up by prescribed fire is an effective approach to reduce fire severity in frequent fire forest systems. 

Forest treatments with prescribed fire or previous low to moderate severity wildfire show reduced burn severity across most forest types, even during extreme burning conditions. Forest treatments done without fire, such as tree removal and surface fuel reduction, have had mixed effectiveness at reducing burn severity and depended upon forest type and wildfire burning conditions.

Treatments in frequent fire forests, such as ponderosa pine, have reduced burn severity, but in the infrequent fire forests like spruce-fir and lodgepole pine, treatments without fire were ineffective during extreme events.

Understanding which types of fuel treatments are effective under a range of fire weather conditions provides managers with the ability to design better treatments. Based on this research, we found that fire (previous low to moderate severity wildfire or prescribed fire) is an effective tool to reduce future burn severity across frequent fire forest types.  

If fire is not an option, then mechanical treatments that include reducing surface fuels are key to reducing burn severity in frequent fire forests. However, in high elevation forests, mechanical removal and surface fuel reduction reduce burn severity only under moderate fire conditions.  More work is needed to understand which combination of treatments would reduce burn severity in high elevation forests. 

This project examined various combinations of fuel reduction treatment activities to understand how burn severity is altered when challenged with wildfire. It’s unique in that it examined this across the elevational gradient of forest types along the Front Range of the southern Rocky Mountains.