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Altered fuel conditions coupled with changing climate have disrupted fire regimes of forests historically characterisedbyhigh-frequencyandlow-to-moderate-severityfire.Managersusefueltreatmentstoabateundesirablefire behaviour and effects. Short-term effectiveness of fuel treatments to alter fire behaviour and effects is well documented; however, long-term effectiveness is not well known. We evaluated surface fuel load, vegetation cover and forest structure beforeandaftermechanicalandfire-onlytreatmentsover8yearsacross11NationalForestsinCalifornia.Eightyearspost treatment, total surface fuel load returned to 67 to 79% and 55 to 103% of pretreatment levels following fire-only and mechanical treatments respectively. Herbaceous or shrub cover exceeded pretreatment levels two-thirds of the time 8yearsaftertreatment.Fire-onlytreatmentswarrantedre-entryat8yearsposttreatmentowingtotheaccumulationoflive and dead fuels and minimal impact on canopy bulk density. In general, mechanical treatments were more effective at reducing canopy bulk density and initially increasing canopy base height than prescribed fire. However, elevated surface fuel loads, canopy base height reductions in later years and lack of restoration of fire as an ecological process suggest that including prescribed fire would be beneficial. Additional keywords: dry mixed conifer, mechanical treatments, moist mixed conifer, prescribed fire, yellow pine. |
