Drying rates of saturated masticated fuelbeds from Rocky Mountain mixed-conifer stands

Abstract

Mastication is becoming a popular wildland fuel treatment in the United States but little is known about how masticated fuels dry over time, especially as these atypical fuelbeds age. This report summarises measured drying rates of different-aged masticated fuelbeds built from material collected from sites that were treated using one of four mastication techniques. We recreated three replicates of masticated fuelbeds in wire mesh cages using material collected from 13 sites sampled throughout the US Rocky Mountains. These caged fuelbeds were saturated and then their moisture contents were measured daily as they dried over 10 days in both a controlled growth chamber and outdoors. Relative moisture content after 24 and 96h of drying and a drying rate were response variables that were analysed across fuel age, drying environment and mastication method. While our sites occurred across different forest types and climates and the mastication equipment used was different, we found that all fuelbeds dried within 3% of the equilibrium moisture contents (3–6%) after ~96h for both growth chamber and outdoors under moderately dry environments. We also found that mastication method influenced fuelbed drying rates whereas age had little effect. Fire managers may use these drying rates to implement effective prescribed burns to reduce adverse impacts when masticated fuelbeds burn during wildfire conditions.