Browsing by Subject "disturbance"

Now showing 1 - 5 of 5
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    Data for fire regime shapes butterfly communities through changes in nectar resources in an Australian tropical savanna, 2019-2020
    (2023-08-03) Leone, Julia B; Larson, Diane L; Richards, Anna E; Schatz, Jon; Andersen, Alan N; jleone@fmr.org; Leone, Julia B
    We studied responses of butterflies, vegetation structure, and floral resources to fire regime at a long-term fire experiment near Darwin in the Australian tropical savanna. This dataset consists of data collected during the 2019/2020 wet season at 18 1-ha plots in three blocks, where each block contains six randomly assigned fire treatments. We measured butterfly, vegetation structure, and floral resources data, and collected fire regime data. These data are associated with Leone et al. (2023). Fire regime shapes butterfly communities through changes in nectar resources in an Australian tropical savanna. Ecosphere. Along with its associated paper, we hope these data will provide helpful information for those working in fire management, butterfly conservation, and biodiversity conservation more broadly.
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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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    Evaluating regeneration and stand dynamics in tamarack stands impacted by eastern larch beetle in northern Minnesota, USA
    (2022-06) Shaunette, Amy
    Tamarack (Larix laricina DuRoi K. Koch) forests in Minnesota are currently threatened by a landscape-level outbreak of eastern larch beetle (ELB) (Dendroctonus simplex LeConte), a native bark beetle. Since 2001, ELB has impacted 816,833 acres of tamarack forest over 20 consecutive years. This has resulted in many management questions related to stand development, especially in terms of regeneration. To explore how ELB has influenced stand structure and composition, 33 sites across a gradient of ELB damage severity and outbreak timing in north-central Minnesota were sampled. Older mortality sites had the highest overstory tree density, driven largely by a high volume of standing dead tamarack. On average, regeneration exceeded a commonly used standard of 600 trees per acre in older high mortality stands only and was below the suggested stocking level in recent high mortality and low mortality stands. Tree ring analysis of 150 tamarack tree cookies revealed understory tamarack saplings aged 9 to 82 years old, suggesting tamarack may have more robust shade tolerance than previously believed. Tamarack established consistently throughout a period of 64 years, suggesting advance regeneration is a part of tamarack stand dynamics. Finally, we identified temporal differences in establishment periods in stands with varying levels of ELB impacts. The combined results of this work highlight complex and understudied dynamics related to tamarack regeneration. Regeneration may take 10 to 15 years to establish after an ELB outbreak. However, it is not only new germinants present in the seedling, sapling, and small tree layer but also advance regeneration.
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    Impacts of multiple fires and wind disturbance on forest community composition, succession and diversity in the Boundary Waters Canoe Area Wilderness.
    (2018-01) Anoszko, Elias
    Under a warming climate, the Boundary Waters Canoe Area Wilderness (BWCAW) of Northern MN is expected to see an increase in the frequency of disturbances including wildfires and severe windstorms. While boreal forests such as those of the BWCAW are generally considered disturbance adapted, it is uncertain how changing disturbance regimes will impact these forests. We used a series of recent disturbances in the BWCAW ranging from areas affected by wind or fire only, to areas affected by wind followed by fire, or multiple fires, to examine how predicted changes in boreal disturbance regimes are likely to impact these forests. We found that multiple disturbances typically had greater cumulative disturbance severity than single disturbance events and in the case of wind+fire combinations also tended to burn with greater intensity, and fire severity relative to areas affected by a single fire only. While diversity-severity relationships varied in shape, we found that diversity was generally lower at high disturbance severity relative to moderate severities. Multiple disturbances had modestly reduced diversity relative to single disturbances, but this relationship varied depending on the spatial scale of inquiry. Despite only modest impacts on diversity, multiple disturbances did have a pronounced impact on succession and composition. Regardless of pre-disturbance composition, multiple disturbances resulted in succession to aspen and paper birch, with birch being more dominant in areas burned in late season fires and aspen more dominant in areas burned by early season fires. Stands subjected to single disturbance events exhibited multiple successional pathways and mix of forest types. Our results suggest that predicted changes in boreal disturbance regimes are likely to have minor impacts on woody plant diversity, but could adversely affect disturbance adverse species, and alter the age structure and composition of forests by reducing long-lived boreal conifers and increasing the dominance of aspen and paper birch.
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    South Fork Caspar Creek Understory Evapotranspiration Data - 2019
    (2020-12-04) Hammerschmidt, Shelby R; Dymond, Salli F; sdymond@d.umn.edu; Dymond, Salli F
    This dataset consists of evapotranspiration rates measured from different understory trees, shrubs, and ferns at the Caspar Creek Experimental Watersheds in northern California. Evapotranspiration rates were collected from 5 species at two times (June and July 2019) across five topgraphic positions ranging from streamside up to the ridgetop. Measurement species were located across a range of disturbance severities to test the hypothesis that changing light and water dynamics from different levels of disturbance will affect understory plant water use. Evapotranspiration rates were collected using a hand-made portable rapid ET chamber.