Browsing by Subject "forest ecology"
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Item ACRONYM : a hierarchical tree and forest growth model framework.(University of Minnesota, 1998-03) Robinson, Andrew P.; Ek, Alan R.ACRONYM is an extensible tree-level forest growth and dynamics model framework for the synthesis and assessment of models and submodels of forest ecosystem processes. The framework is designed for research in forest ecology and silviculture, development and testing of silvicultural guidelines, forest inventory updates, and long-term projections of forest and landscape dynamics. The framework accepts modules (submodels) of forest regeneration, tree growth, mortality, silviculture, harvesting and natural disturbance, each of which may operate at different spatial or temporal scales and levels of resolution. Component modules can range from empirical to process based, as understanding and data permit. Modules can be interchanged with a minimum of reprogramming to allow for comparison of assumptions about processes, different data input protocols, and project-specific reporting requirements.Item 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, EllaForests 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.Item Physiological evidence for climate limitations of oak distributions at local and regional scales(2017-11) Fallon, BethUnderstanding the extent to which physiological tolerances of climate may limit plant distributions is critical to predicting the effects of a changing climate. This dissertation research focuses on how responses to drought and cooling influence species ranges among oaks (Quercus L.), a globally-distributed woody genus that is highly diverse within the Americas. I used functional and physiological traits to investigate correlations between cold and drought resistances and climate at two scales: 1) local species elevation limits in a semi-arid montane system and 2) regional range limits among North and Central American oaks. In Chapter 1, I found that a trade-off between the leaf-level drought resistance traits of avoidance (leaf abscission) and desiccation recovery (leaf capacitance), and not stem freezing tolerance, influenced species sorting by elevation in a semi-arid mountain system in the southwestern US. In Chapter 2, I found that stem drought tolerance (xylem vulnerability) is correlated with aridity of climate of origin among oaks from across the Americas, but that the seasonality of precipitation best predicted leaf level drought avoidance (leaf habit and stomatal closure). Finally, in Chapter 3, I found that oak species in the Americas have different leaf level cooling responses (chlorophyll fluorescence measurements of photosynthetic stress and yield) that were correlated with minimum temperatures in their climate of origin, but that ability to acclimate to cold temperatures was best predicted by leaf phenology, not climate of origin. I also found that we could predict chlorophyll fluorescence measurements with models created from hyperspectral reflectance data measured on the same leaves. These models included regions of important biological significance, including wavelengths corresponding with reflectance of photosynthetic and protective pigments. Overall, there I found significant evidence that species distributions are strongly influenced by climate. Oak species have suites of traits as mechanisms of drought resistance, and these strategies are correlated with not only overall aridity in their current habitats, but with the seasonality of precipitation. Oak species may also be able to acclimate to cooler temperatures outside of those commonly experienced in their current range. Oak species within the Americas and the mountainous, arid southwest US, may be vulnerable to range shifts as global temperatures continue to rise and precipitation regimes change.