Browsing by Subject "Vegetation"
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Item AirTAP Briefings (Summer 2021, vol. 21, no. 3)(Airport Technical Assistance Program (AirTAP) (Center for Transportation Studies, University of Minnesota), 2021) Airport Technical Assistance Program (AirTAP)Articles include: High season for managing airport vegetation; Custom zoning offers airports new flexibility; An airport’s story: Carlton County–Cloquet Airport; Upcoming training & events; FAA Update; MnDOT UpdateItem The effects of fluid flow and epiphytes on submerged aquatic vegetation(2012-05) Hansen, Amy ThereseThe intent of this research was to investigate the effects of fluid flow characteristics and epiphyte colonization on submerged aquatic vegetation (SAV) photosynthesis and dissolved material uptake. SAV, with its stems and leaves completely submerged in the water column, is strongly affected by both the physical characteristics of the water, such as dissolved material concentrations and fluid motion, and by factors that alter its interaction with the water, such as epiphyte colonization of SAV surfaces. The nature of these interactions was investigated through a series of four separate studies. First, through a laboratory mesocosm experiment, epiphyte uptake and SAV uptake of a dissolved contaminant (nickel) were shown to occur at different rates and due to different mechanisms. Second, a model of photosynthetic rates, based on mass transfer theory, was developed requiring only three parameters that accounted for the effect of water motion on photosynthetic rates. This model was experimentally validated with dissolved oxygen and velocity profiles over blades of giant kelp, Macrocystis pyrifera. Third, using two separate microscale velocity imaging methods, photosynthesis was shown to alter fluid motion near the surface of a Cladophora spp. filament by more than doubling velocity gradients and thus surface shear stress. In this investigation, bacterial epiphytes had no effect on shear stresses but assemblages consisting primarily of diatom epiphytes strongly decreased the surface shear stress from what would have been experienced during photosynthesis without epiphytes present; indicating a harmful interaction with epiphytes. Fourth, in agreement with the microscale results in the third study, epiphyte removal was shown to increase local dissolved oxygen concentrations throughout the water column as well as decrease water column soluble reactive phosphorus concentrations due to higher photosynthetic rates in field research in a constructed wetland. In a related laboratory study, epiphyte detachment rates were functionally related to water velocity. Overall, I have shown through laboratory and field experiments that SAV photosynthesis is closely linked to fluid flow characteristics, SAV and epiphyte uptake are not equally affected by flow conditions, and epiphyte colonization decreases SAV photosynthetic rates.Item Regional Optimization of Roadside Turfgrass Seed Mixtures(Minnesota Department of Transportation, 2019-12) Watkins, Eric; Sessoms, Florence; Hollman, Andrew; Laskowski, Michael; Moncada, KristineCurrent MnDOT specifications for roadside turfgrasses suggest statewide planting of mixtures that are grouped into five broad categories such as low maintenance turf and high maintenance turf. The objective of this research was to identify turfgrasses that possess traits necessary to survive in the harsh roadside environments found throughout Minnesota. We investigated the impacts of possibly the three most limiting environmental conditions (heat, salt and ice cover) on multiple cultivars from up to fifteen individual turfgrass species. Salt stress screening revealed several species with good levels of adaptation including alkaligrass and tall fescue. In the heat stress trial, we found cultivars and selections of Canada bluegrass, tall fescue, Kentucky bluegrass, strong creeping red fescue and slender creeping red fescue were among the top performers. Finally, in our ice cover screening, tall fescue and Chewings fescue did well; however, these results did not correlate well with our typical field observations. For each of these stresses, we identified top-performing cultivars that will be evaluated in field studies with the goal of identifying optimized mixtures for stakeholders in Minnesota.Item Selection of vegetation and flexible vegetal drag coefficients for erosion control in lacustrine wave environments(2014-06) Chapman, JohnThe restoration of plant communities in littoral zones often fails. Because littoral habitats around the world often are subject to changing water regimes and potentially changing future climates, a better understanding of species competitive interactions under such conditions is needed for restoration plant selection. To represent shoreline plant communities, we grew eight freshwater species used in shoreline restoration projects in Minnesota and Wisconsin, USA, in outdoor basins and manipulated water levels to determine the effect on above ground biomass. Biomass production of some species in the competing environment was related to the proximity to water or inundation depth and frequency. Sparganium eurycarpum and Bolboschoenus fluviatilis dominated the total biomass in all water manipulations. These findings allow for better design of plant community composition and better vegetative erosion control under a variety of water conditions. This thesis also investigates the ability of plants to reduce waves and flow, through a comparison of parameters that characterize vegetation flexibility effects on flow resistance and drag. Drag forces measured in a flume for simple cylindrical obstructions of the same shape and size but with different flexibility under several flow conditions. A novel formulation is developed where the drag coefficient is evaluated as a function of the relative velocity and the elastic modulus of the obstruction. Current methods for estimating energy dissipation require plant specific parameters that are difficult to estimate for the large variety of plant morphologies used in shoreline protection, requiring testing on each species of interest. The method developed herein directly measures hydrodynamic forces on individual plant shoots using a torque sensor mounted beneath the bed of a flume. The data collected also suggests that more flexible objects result in less drag force on each element and suggests that frequency response is related to the frequencies existing in the driving wave and the natural frequency of the obstruction element, although harmonic synchronization appears to occur in some cases, doubling the expected drag force magnitude. A case study is also included as an example of how the findings presented here can be applied to a shoreline erosion control evaluation. The case study is an inland lake in northern Minnesota currently having erosion soil losses. Data from this research is used to develop a vegetation scenario that is predicted to limit the erosion.