Browsing by Subject "Natural resources science & Management"

Now showing 1 - 4 of 4
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    Factors influencing detection of American woodcock during singing-ground surveys.
    (2011-07) Bergh, Stefanie M.
    Abstract summary not available
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    Hydrologic, nutrient, and sediment responses of restored perennial vegetation/wetland complexes in southern Minnesota.
    (2012-05) Fransen, Greg David
    The Blue Earth River basin, located in the prairie pothole region of northern Iowa and southern Minnesota, is intensively ditched and drained to improve agricultural production. Agricultural drainage systems increase watershed drainage density and can efficiently transport easily leachable agricultural contaminants, such as nitrate, to receiving water bodies. This thesis examines the hydrologic and water quality benefits provided by two restored perennial vegetation-wetland complexes in the Elm Creek subwatershed of the Blue Earth River basin. Flow measurements and water quality samples were collected at the wetland outlets and at drain tiles and surface channels flowing into the wetlands. Four years of flow data showed that the wetlands reduced the magnitude of peak flows to Elm Creek, but that they did not significantly reduce water yield compared to the agricultural watersheds. The restored wetlands decreased nitrate export by 85 percent during the months of April to June, the period when nitrate from agricultural drainage water contributes to formation of the “dead zone” in the Gulf of Mexico. The wetlands did not significantly decrease phosphorus or sediment export to Elm Creek. Water quality benefits attained by trapping phosphorus and sediment from surface runoff were offset by internal phosphorus loading, algal blooms, and sediment resuspension. Empirical modeling of one wetland basin showed that wind speed and wind direction could explain 60 percent of the suspended sediment concentration within the wetland. Active management of water levels and wetland vegetation are presented as strategies to reduce sediment and phosphorus export from restored wetland basins.
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    Impacts of biomass harvesting on biomass, carbon, and nutrient stocks in populus tremuloides forests of Northern Minnesota, U.S.A.
    (2012-02) Klockow, Paul Alan
    Globally, there is widespread interest in using forest-derived biomass as a source of bioenergy. While conventional timber harvesting generally removes only merchantable tree boles, harvesting biomass feedstock can remove all forms of biomass (i.e., trees down through to forest floor material) resulting in a greater loss of biomass, nutrients, and habitat from a site. To investigate the potential impacts of this practice, this study examined the initial impacts (pre- and post-harvest) of various levels of slash and live-tree retention on biomass and nutrient stocks in Populus tremuloides-dominated forests of northern Minnesota. Treatments examined included 0%, 20%, and 100% slash retention with no, dispersed, and aggregate live-tree retention. Slash retention was the primary factor affecting immediate post-harvest biomass and nutrient stocks within total ecosystem and woody debris pools. High levels of biomass and nutrients in harvest slash were observed in all treatments compared to the unharvested control. Typically, 100% slash retained treatments contained significantly greater biomass and nutrient stocks than no slash retained treatments. Stocks of biomass and nutrients within the 20% slash retained treatment, a slash retention level currently recommended by Minnesota’s biomass harvesting guidelines, were generally similar to both no slash retained and 100% slash retained treatments. Given the importance of fine woody debris as a source of nutrients following harvest, nutrient concentrations were measured across an array of woody debris size and decay classes within the Populus tremuloides-dominated forests examined. Results indicate that fine woody debris has significantly greater nutrient concentrations than coarse woody debris. In addition, nutrient concentrations generally increased within both coarse and fine woody debris as decay progressed. Collectively, the results of this study underscore the importance of deliberate retention of fine woody debris as a source of nutrients following harvests of biomass feedstocks.
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    Nest-site selection and nesting ecology of red-headed woodpeckers.
    (2012-05) Waldstein, Ariane Lentz
    Red-headed woodpeckers (Melanerpes erythrocephalus) were once a common and widespread species in the Midwest but have declined sharply in the last 40 years. This species is a Minnesota Species of Greatest Conservation Need and an oak-savanna specialist; its decline is ascribed to severe habitat loss throughout the Upper Midwest. Despite numerous oak savanna restoration efforts throughout Minnesota, populations continue to decline, and most restoration sites have failed to attract red-headed woodpeckers. Most restoration focuses on prescribed fire but few studies have examined red-headed woodpecker habitat use and nest success in a long-term managed landscape. This thesis explores red-headed woodpecker nest-site selection and distribution at Cedar Creek Ecosystem Science Reserve (Chapter 1) and also describes a cavity camera system to measure woodpecker nest success (Chapter 2). Using data collected at 102 nest sites and 104 random, non-used sites, logistic regression models showed that woodpeckers preferred low densities of small snags and high densities of trees with dead limbs < 10 m above ground level. Models also showed a preference for large dead nest trees. These results are consistent with other studies and are likely a function of this species’ diverse foraging ecology. Examination of the distribution of nests revealed that the highest density occurred in areas burned between 20 - 25 times since 1964. Implementation of a high-frequency burn regime may be effective at creating red-headed woodpecker habitat. The cavity camera system utilized in 2011 was cheaper and easier to assemble than published designs (Chapter 2). One season of use revealed an average of 3 nestlings and two instances of nest depredation.