Physical Sciences and Mathematics Commons^™

Complex Vegetation Dynamics At The Fire-Grazing-Drought Nexus, Christine H. Bielski

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

The discipline of ecology long ago moved away from viewing systems as static entities where disturbance processes, environmental stochasticity, and spatiotemporal variability play minor roles in determining ecosystem structure and function. Ecological theory continue to develop frameworks and statistical techniques capable of describing the inherent complexity in natural systems. However, in dealing with the complexity in nature, many applied disciplines have yet to adopt such frameworks or statistical techniques. The objective of this study was bridge the gap between ecological theory and application by using complex systems theory to describe grassland vegetation dynamics at the fire-grazing-drought nexus. Chapters 2 and …

Size As A Trait For Understanding The Role Of Zooplankton In The Biological Carbon Pump, Karen Stamieszkin

Electronic Theses and Dissertations

Living organisms impact carbon transport between the atmosphere and the ocean through the biological carbon pump. Some plankton communities augment carbon export from the ocean’s surface, and are thought to have a major role in global climate. These export communities are often characterized by larger organisms that sink to depths where the carbon they contain is sequestered from the atmosphere. Zooplankton can enhance export by aggregating prey into larger sinking fecal pellets; however fecal pellet flux is a highly variable component of the biological carbon pump. Relating plankton trophic dynamics to changes in particulate carbon flux is an important step …

Flood Events Can Reduce Key Fatty Acid Content Of Early-Stage Benthic Algal Assemblages In An Urban Stream, Sarah Whorley, John Wehr

Articles & Book Chapters

Effects of urbanization on stream chemistry and biota have been widely examined. However, few studies quantify the effect of urban stream characteristics on the biochemical properties of basal food resources, such as benthic algae, which can affect aquatic consumers and food webs. A common feature of urban streams is the high frequency of short floods, which may disrupt aquatic communities and their biotic controls. These disturbances can create algal assemblages low in biomass and which remain in early successional stages. This study examined the effects of frequent flood events and macroinvertebrate grazing on biomass, elemental stoichiometry, and essential fatty acid …

Effect Of Grazing Prairie Dog—Colonized Rangeland On Cattle Nutrition And Performance: A Progress Report, Kenneth C. Olson, Christopher Schauer, Chanda Engel, Janna J. Kincheloe, Jameson R. Brennan, Ben L. Hauptman

Natural Resource Management Faculty Publications

On the Ground

• One objective of the ongoing Renewal on Standing Rock Reservation project is to evaluate the response of grazing steers to the level of prairie dog colonization on Northern Mixed Grass Prairie.
• We fenced four pastures to create an increasing gradient of a proportion of the pasture area colonized by prairie dogs. Pastures are stocked with yearling steers during each growing season.
• Comparing steer performance, Global Positioning System (GPS) locations of grazing, diet samples, and ingestive behavior at each proportion of the prairie dog colony per pasture allows prediction of the optimal proportion of colonization, which enables selection …

Sustainable Grassland Management: An Exploratory Study Of Progressive Ranchers In Nebraska, Stephanie M. Kennedy, Mark E. Burbach, Maggi S. Sliwinski

School of Natural Resources: Faculty Publications

Well-managed grasslands provide numerous ecosystem services. Ranchers who employ sustainable grazing practices limit grassland conversion and conserve critical habitats. This phenomenological study explored the grassland management decisions of progressive ranchers in Nebraska. Each individual interviewed for this study is proactive about the state of their grasslands, whether they are motivated by financial or conservation factors. Throughout the evolution of their businesses, these ranchers have taken steps to improve their management techniques and continue to employ new strategies while planning for the long-term productivity of their grasslands. For policy makers and educators seeking to improve grassland management decisions, demonstrating new methods …

Foraging Decisions Underlying Restricted Space Use: Effects Of Fire And Forage Maturation On Large Herbivore Nutrient Uptake, Edward J. Raynor, Anthony Joern, Jesse B. Nippert, John M. Briggs

School of Natural Resources: Faculty Publications

Recent models suggest that herbivores optimize nutrient intake by selecting patches of low to intermediate vegetation biomass. We assessed the application of this hypothesis to plains bison (Bison bison) in an experimental grassland managed with fire by estimating daily rates of nutrient intake in relation to grass biomass and by measuring patch selection in experimental watersheds in which grass biomass was manipulated by prescribed burning. Digestible crude protein content of grass declined linearly with increasing biomass, and the mean digestible protein content relative to grass biomass was greater in burned watersheds than watersheds not burned that spring (intercept; F_{1,251 …}

Size-Dependent Top-Down Control On Phytoplankton Growth By Microzooplankton In Eutrophic Lakes, Wai Hing Wong, Nancy N. Rabalais, R. Eugene Turner

Faculty Publications

We hypothesized that the grazing on phytoplankton by the microzooplankton community is size-dependent and, therefore, the top-down control on phytoplankton by microzooplankton community could be one possible mechanism explaining why small phytoplankton become less abundant than large phytoplankton in eutrophic waters. We tested this hypothesis using the dilution method to measure microzooplankton grazing rates and phytoplankton growth rates in the eutrophic waters of the Barataria estuary, southeastern Louisiana. Microzooplankton grazing rates on the slower growing, small phytoplankton (\5 lm) were higher than on the large phytoplankton ([20 lm) which had relatively faster growth rates. The proportional loss of the small, …

Synergistic Effects Of Climate Change And Grazing On Net Primary Production Of Mongolian Grasslands, Shree R. S. Dangal, Hanqin Tian, Chaoqun Lu, Shufen Pan, Neil Pederson, Amy Hessl

Faculty & Staff Scholarship

In arid and semi-arid regions, grassland degradation has become a major environmental and economic problem, but little information is available on the response of grassland productivity to both climate change and grazing intensity. By developing a grazing module in a process-based ecosystem model, the dynamic land ecosystem model (DLEM), we explore the roles of climate change, elevated CO2, and varying grazing intensities in affecting aboveground net primary productivity (ANPP) across different grassland sites in Mongolia. Our results show that both growing season precipitation totals and average temperature exert important controls on annual ANPP across six sites over a precipitation gradient, …