Life Sciences Commons^™

The Effects Of Enhanced Flows On Community Structure And Ecosystem Functioning In A Montane Utah River System, Joshua A. Epperly

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Due to growing human demands for freshwater within the last century, manmade flow alterations are now a common characteristic of rivers worldwide. Alterations to the volume and timing of flows in rivers are known to negatively impact aquatic biodiversity, biological productivity and ecosystem functions such as nutrient cycling. While previous research has focused on the effects of flow reductions and spates, there is a lack of knowledge on how high flows across longer timespans (i.e. ‘enhanced flows’) impact the structure of river communities and the integrity of ecosystem functions.

The Utah Reclamation, Mitigation and Conservation Commission has expressed interest in …

Plastic And Genetic Determination Of Population, Community, And Ecosystem Properties In Freshwater Environments, Leigh C. Latta Iv

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The hierarchy of biological organization, from molecules to ecosystems, describes the relationships among various biological systems. Of particular interest is assessing how the factors that primarily determine the nature of one hierarchical level also have transcendent qualities that affect the ecology and evolution of higher hierarchical levels. The goal of this dissertation was to use a bottom-up approach to examine the transcendent effects of two factors that strongly determine the nature of their associated level of biological organization. The first, phenotypic plasticity, is a primary factor that determines the phenotype of an individual. The second factor, genetic diversity, largely determines …

Utilization Of Spatially Distributed Soil Resources By Several Species Common To The Great Basin, Sarah Duke

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Heterogeneous spatial and temporal distributions of soil resources important to plant growth have been documented in the sagebrush steppe ecosystem. There can exist as much variability in soil resources within the root zone of individual plants as exists across an entire field. The objective of this dissertation research was to evaluate how plants respond to, utilize and influence the spatial heterogeneity of soil resources. The three specific sets of questions addressed are outlined in the three main chapters of this dissertation.

My first study addressed how the number and concentration of phosphorus (P) patches in the root zone of an …

Impact Of Root Competition On Survival And Growth Of Seedlings Of Important Great Basin Species, Günther Reichenberger

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Belowground competition is pronounced in the arid Great Basin sagebrush ecosystem. Plant demographic and root exclusion approaches were used to examine the influence of roots of adult Artemisia tridentata, Agropyron desertorum, and Agropyron spicatum individuals on seedling survival of Ar. tridentata, Ag. desertorum, Ag. spicatum, and Bromus tectorum. Furthermore, growth rates of Ar. tridentata seedlings and seed production of B. tectorum were assessed.

The probability of a seedling being alive versus dead significantly depended on the seedling species, the neighboring adult species, and on the depth to which root competition was excluded. As seedlings, …

Carnivore Competition And Resource Use In The Serengeti Ecosystem Of Tanzania, George Walter Frame

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Coexisting ungulate-eating carnivores--lion, spotted hyena, cheetah, leopard, African wild dog, black-backed jackal, common jackal, and six species of vulture--are examined in East Africa's Serengeti ecosystem. Niche similarities year-round, by season, and by location are described using food, habitat, time of hunting, and other variables. Intraspecific niches of cheetah sex, age, and social groups show that male coalitions differ most from the others in hunting behavior and habitat use. Tests using the carnivore data failed to support hypotheses about niche breadth variation, niche overlap variation, range of food items, and niche inclusion. Densities of the five largest Carnivora in the 35,500 …

Rhizosphere N2 Fixation In A Forest Ecosystem In Situ Assays And Evaluation Of The Acetylene Reduction Technique, Inger Börjesson

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

In situ assays of N₂ fixation activity, using the acetylene reduction technique, were performed in four successional stages of a Northern Wasatch Mountain subalpine forest ecosystem, elevation 2,800 m. Emphasis was made on rhizosphere fixation in association with Antennaria microphylla and Achillea millefolium. The vegetation period was approximately 100 days.

Assays were performed in Saran bags. A defined amount of propane was injected at initiation of the assay and acetylene was generated from CaC₂. Samples were analyzed for ethylene and propane. Data were evaluated assuming that the ethylene production was directly proportional to the increase in …

Some Effects Of A Grazer, Hyalella Azteca On Ecosystem Level Properties In Aquatic Microcosms, Martin D. Werner

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A study to determine some ecosystem level effects of an aquatic invertebrate grazer, Hyalella azteca, was performed in aquatic ix microcosms. Impact of the grazer was assessed in three general areas: 1) inorganic nutrient levels of the microcosm water column, 2) productivity and respiration of the biotic community, and 3) plant community composition in the microcosms.

The grazing amphipod caused inorganic phosphorus and nitrogen (except ammonia) levels to be elevated in the microcosms. The increase was due, at least partially, to excretion of nutrients into the water by the amphipod. The presence of H. azteca did not significantly …