Browsing by Subject "black spruce"

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    Effects of Eastern Spruce Dwarf Mistletoe (Arceuthobium Pusillum Peck) Infestation in Lowland Black Spruce (Picea Mariana (Mill.) B. S. P.) at Multiple Scales
    (2022-05) Gray, Ella
    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.
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    Effects of fire and harvesting on tree regeneration and ground-layer vegetation in forested peatland communities in northern Minnesota
    (2016-02) Rowe, Erika
    Large-scale, catastrophic fires have historically been rare in peatland ecosystems in the Great Lakes region with surface fires, windthrow, and insects being the main disturbance agents. With climate change, these disturbances are predicted to become more common due to increases in the frequency and severity of drought. Boreal peatlands at their southern range margin, such as those in northern Minnesota, are expected to be particularly vulnerable to these impacts. In 2012, a wildfire burned over 10,000 ha of a large forested peatland complex in north-central Minnesota providing a rare opportunity to document the early regeneration response of vascular and nonvascular plant species in black spruce (Picea mariana) and tamarack (Larix laricina) dominated communities. Post-fire vegetation data were also used to compare with data collected from clearcuts, the most commonly used management approach for these systems. Selected clearcut sites were harvested the same year as the fire and within the same community types. Distinct differences in tree regeneration and vegetation composition were observed between burned and harvested sites. Community response to disturbance was also varied, largely reflecting the amount of disturbance to the peat layer. Burned areas had a greater abundance of tree seedlings in black spruce-dominated stands relative to harvests, however, the reverse was true for tamarack-dominated communities due to a complete removal of suitable seed beds and seed sources by the fire. In these tamarack communities, fire disturbance shifted plant community composition towards marsh-like conditions with cattails (Typha spp.) now the dominant species creating challenging conditions for future tree regeneration in these areas. In contrast, fire increased the availability of favorable seedbed conditions in black spruce by reducing the depth of peat and the abundance of Labrador tea (Rhododendron groenlandicum (Oeder) Kron & Judd), an ericaceous shrub known to compete with conifer seedling regeneration and growth. These divergent responses indicate that tamarack-dominated systems may be more vulnerable to increases in the frequency and severity of fire due to the potential for phase shifts towards non-forested conditions. The increased levels of black spruce regeneration following fire relative to harvests suggest that application of prescribed fire should be considered for enhancing regeneration efforts in these important communities.
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