Influence of western dwarf mistletoe (Arceuthobium campylopodum Engelm.) on surface fuels and snag abundance in mature ponderosa pine and mixed conifer stands in Central Oregon

Abstract

We examined the influence of western dwarf mistletoe (Arceuthobium campylopodum) infestation on fuel loads in mature mixed-conifer forest in Crater Lake National Park and unmanaged ponderosa pine (Pinus ponderosa) stands in Lave Cast Forest, Oregon. We measured biomass of woody surface fuels (1-, 10-, 100-, and 1000-hr), litter and duff, and snag basal area in 29 stands infested with mistletoe and 21 non-infested stands. Univariate tests revealed no significant differences in total surface fuel loads or snag basal area between infested and non-infested plots in either stand type, but there were more fine fuels and litter in infested stands at Lava Cast Forest. Ordination analyses showed that stand level variables other than mistletoe abundance explained more variance in fuel loads. Ponderosa pine basal area and stand age were stronger predictors of fuel loads in pure ponderosa pine stands at Lava Cast Forest, while basal area of non-host fir was a key explanatory variable in the mixed-conifer stands at Crater Lake. Our results indicate that mistletoe has weak direct and indirect effects on fuel loads in mature forests, resulting primarily in greater accumulations of fine woody fuels.