Forest stand and site characteristics influence fuel consumption in repeat prescribed burns

Abstract

Prescribed fire is a vital tool for mitigating wildfire hazard and restoring ecosystems in many western North American forest types. However, there can be considerable variability in fuel consumption from prescribed burns, which affects both hazard mitigation and emissions. In the present study, data from replicated, repeat-entry burns following a period of 100+ years of fire exclusion were used to provide a detailed quantification of fuel consumption as it varies by fuel type, size class, stand and prescribed burn number (first, second or third). Using model selection on a series of linear mixed-effects models, it was determined that total fuel load, proportion of overstorey pine, slope, canopy cover, basal area of live trees, burn number and stand influenced fuel consumption at a 0.04-ha scale. Specifically, overstorey pine composition had a positive effect on fuel consumption. Overall fuel consumption across the three burns averaged 45% of pre-burn fuel loads. Overall consumption was highest for the first burn at 65%, decreasing by 15–20% with each successive burn number. Fuel consumption was highly variable by fuel type, stand and tree species composition. This variability may be advantageous for managers seeking to foster structural diversity and resilience in forest stands.