Browsing by Subject "Great Plains"

Now showing 1 - 3 of 3
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    Ecology And Chemistry Of Small Mammals And The Implications For Understanding Their Paleoecology And Environments
    (2015-07) Haveles, Andrew
    Fundamental goals of paleoecologists and modern ecologists is to understand the evolutionary and ecological patterns in modern and ancient biodiversity. Diet is one ecological trait species may evolve or vary to exploit food resources and increase their fitness. Stable isotope analysis is one method used to infer diet and is transferable between modern and fossil populations. Stable isotope analysis has not been commonly applied to small mammals, mostly because of sampling limitations. Here, three studies focus on furthering our understanding of small mammal ecology and serve as a baseline comparison for interpreting similar data from the fossil record. Chapter 1 illustrates that small mammals varied their diets independently and indicate granivores focused on C4 derived resources, generalists consumed resources readily available, and an invertivore focused on invertebrates. Results indicate that intermediate ?13C values between C3 and C4 resources are likely from integrating multiple resources through direct consumption and invertivory. Therefore, interpreting ?13C values from consumers in the fossil record must be interpreted with caution. Chapters 2 and 3 include a ?13C dataset that expands to the regional scale and assess how rodent partition C3 and C4 resources as C4 biomass on the landscape varies. Small mammals mostly rely on C3 derived resources, but there are some spatial and ecological tendencies with granivores incorporating the most C4 derived resources and varied with C4 biomass. Climate variables explained some variance in C4 consumption for some species, while other species' diets were not explained by climate. Seasonality metrics were the best predictors of C4 consumption and ?13C values in rodent hairs were more positive during peak C4 growing seasons. Chapter 4 estimates temperature and precipitation using the area extant species' geographic ranges overlap today and then applied to ancient faunas where the same species co-occur. Temperature and precipitation estimates for Pleistocene-Holocene localities reflect the general warming during this transition and interpolated temperature and precipitation for climate intervals illustrate deviating spatial gradients through time. The culmination of work presented here greatly improves our understanding of small mammal ecology and sets s baseline for testing modes of evolution and ecology in the fossil record.
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    Effects of Multiple Stressors on Aquatic Communities in the Prairie Pothole Region
    (University of Minnesota Duluth, 2007) Schoff, Patrick K; Johnson, Lucinda B; Guntenspergen, Glenn R; Johnson, W. Carter
    The prairie potholes wetlands of the Great Plains comprise some of the most ecologically valuable freshwater resources of the nation, but they are also exceptionally vulnerable to anthropogenic stressors, particularly those associated with agricultural land use practices. They are also considered likely to be severely impacted by climate change. In this study we have quantified relationships among stressors associated with climate, agricultural land use and amphibian communities throughout much of the prairie pothole region.
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    Modeling the impact of iIrrigation on precipitation over the Great Plains.
    (2011-08) Harding, Keith John Iliff
    Since World War II, the rapid expansion of irrigation throughout the Great Plains has threatened the sustainability of the Ogallala Aquifer. Irrigation has been shown to modify the surface energy and water budgets over the Great Plains by altering the partitioning of latent and sensible heating. An increase in latent heating from irrigation contributes to a cooler and more humid surface, which has competing impacts on convection. In this study, the Weather Research and Forecasting model was modified to simulate the effects of irrigation at sub-grid scales. Nine April-October simulations were completed for different hydrologic conditions over the Great Plains. Data from these simulations was assimilated into a back-trajectory analysis to identify where evapotranspired moisture from irrigated fields predominantly falls out as precipitation. May through September precipitation increased on average over the Great Plains by 4.97 mm (0.91%), with the largest increases during wet years (6.14 mm; 0.98%) and the smallest increases during drought years (2.85 mm; 0.63%). Large precipitation increases occurred over irrigated areas during normal and wet years, with decreases during drought years. On average, only 15.8% of evapotranspired moisture from irrigated fields fell out as precipitation over the Great Plains, resulting in 5.11 mm of May-September irrigation-induced precipitation. The heaviest irrigation-induced precipitation occurred over north-central Nebraska, coincident with simulated and observed precipitation increases. While irrigation resulted in localized and region-wide increases in precipitation, large evapotranspiration increases suggest that irrigation contributes to a net loss of water in the Great Plains.