Impacts of lodgepole pine dwarf mistletoe (Arceuthobium americanum) infestation on stand structure and fuel load in lodgepole pine dominated forests in central Colorado

Parasitic plants are capable of causing substantial alterations to plant communities through impacts on individual host plants. Lodgepole pine dwarf mistletoe is an important parasite in forests of the western USA that causes reductions to productivity and is thought to alter wildland fuel complexes. These impacts are hypothesized to vary with infestation severity. To test this, we used a linear mixed modeling approach to evaluate the relationship between dwarf mistletoe infestation severity and parameters representing stand structure and surface and canopy fuels in infested lodgepole pine stands in central Colorado. Infestation severity was negatively related to live basal area, average tree size, canopy base height, canopy fuel load, and canopy bulk density, and was positively related to the loading of woody surfaces fuels greater than 0.64 cm in diameter. No relationship was detected between infestation severity and live tree density, or live crown ratio. These results confirm the long-held assumption that dwarf mistletoe increases surface fuel loading in lodgepole pine communities, but also suggest that infested stands have reduced amounts of available canopy fuel. These findings have implications for potential fire behavior and highlight the importance of dwarf mistletoe in predicting the spatial and temporal dynamics of wildland fuels.