Effects of Eastern Spruce Dwarf Mistletoe (Arceuthobium Pusillum Peck) Infestation in Lowland Black Spruce (Picea Mariana (Mill.) B. S. P.) at Multiple Scales

Abstract

Forests are shaped by stand dynamics and disturbances. Knowledge of the effects and interactions of these dynamics is important for understanding the processes that determine forest structure and composition and inform management decision making. Our understanding of the role of disturbances in stand dynamics has shifted over time, with the view that they are important components of forest development, rather than an external influence. This view has influenced management actions, with an increase in disturbance-based silvicultural prescriptions. For these prescriptions to be effective in mimicking post-disturbances conditions, the effects of the disturbance of interest should be well understood across multiple scales. Here, I investigated the effects of a native, morality-causing disturbance agent, eastern spruce dwarf mistletoe (Arceuthobium pusillum Peck; hereafter ESDM), on lowland black spruce (Picea mariana (Mill.) B. S. P.) forests of Minnesota. Using a combination of observational field studies and statistical modeling of publicly available large-scale datasets, effects of ESDM infestations across multiple scales were quantified and their influence on stand dynamics and management were assessed. Results show ESDM to be a complex disturbance agent, with effects manifesting differently at the tree, stand, and landscape scales. ESDM infestations result in increased species diversity and structural heterogeneity at sub-stand scales, with implications for landscape-scale diversity. As forestry continues to implement disturbance-based forest management, the management of black spruce in the presence of ESDM should reflect these complex effects, by assessing the trade-offs of infestation to different ecosystem services.