Life Sciences Commons^™

Environmental Factors Associated With Triploid Aspen Occurrence In Intermountain West Landscapes, James A. Walton

All Graduate Theses and Dissertations, Fall 2023 to Present

Polyploidy is common among plants and can contribute to physiological and morphological differences, altering how plants respond to environmental changes, promoting genetic diversification and even species radiation. Quaking aspen (Populus tremuloides), a keystone species associated with high plant and animal diversity is frequently found in mixed diploid/triploid populations in the Intermountain West. Triploid aspen carries an extra chromosomal copy, whereas the diploid type contains two chromosomal copies. High mortality rates and widespread population declines in aspen are of increasing concern in the Intermountain West, and often ascribed to changing climates and drought stress events. The goal of this …

Dusky Grouse Population Ecology And Thermal Landscape Ecology In The Great Basin Ecosystem, Stephanie M. Landry

All Graduate Theses and Dissertations, Fall 2023 to Present

Dusky Grouse are a mountainous forest grouse found throughout the western, inland mountain ranges of the United States and Canada. While a few studies have looked at Dusky Grouse in the Rocky Mountain Ecosystem of their range, there have been no prior studies of the Dusky Grouse in the Great Basin Ecosystem aside from a brief survey by Zwickel and Bendell in 2004 in the Duck Creek Range of Nevada. With the available habitats differing in both species diversity and availability on the landscape between the two Ecosystems, I wanted to assess characteristics about the Dusky Grouse populations at the …

Regeneration Of Quaking Aspen And Understory Vegetation Change After Fire Risk Reduction Treatment, Allison M. Trudgeon

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Quaking aspen (Populus tremuloides Michx.) is a keystone species that, when coexisting with conifers (i.e., seral aspen), often undergoes stand-replacing disturbances to sustain long term vigor. Historically, mixed-to-high severity fire reduced fuels and regenerated aspen, but such disturbances have become less common in recent decades. This has often led to high fuel loading, and many seral aspen stands are at now risk of an unpredictable, high-severity fire, posing a threat to development in the wildland-urban-interface. The lack of a commercial market for aspen, and the risk of conducting prescribed fire, means there are few alternate management options. This has …

Quantifying The Indirect Effect Of Wolves On Aspen In Northern Yellowstone National Park: Evidence For A Trophic Cascade?, Elaine M. Brice

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Yellowstone National Park is renowned for its incredible wildlife, and perhaps the most famous of these species is the gray wolf, which was reintroduced to the Park in the mid-1990s. After reintroduction, it was highly publicized by scientists, journalists, and environmentalists that the wolf both decreased elk density and changed elk behavior in a way that reduced elk effects on plants, a process known as a “trophic cascade.” Aspen, which is eaten by elk in winter, is one species at the forefront of Yellowstone trophic cascade research because it has been in decline across the Park for over a century. …

Patterns Of Post-Fire Aspen Seedling Establishment, Growth, And Mortality In The Western United States, Mark Regier Kreider

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Sexual seedling establishment in aspen is increasingly recognized as an important natural regeneration pathway for the species in the western U.S. However, information on seedling abundance as well as factors influencing aspen sexual regeneration is limited and frequently anecdotal, due to historical assumptions of seedling rarity as well as difficulty identifying sexual seedlings from asexual aspen sucker regeneration. This thesis contributes to the field of aspen seedling ecology in three major ways. Chapter 1 utilizes historical aspen seedling occurrences in the western U.S. and a systematic field survey of 2018 fire footprints to explore patterns and test assumptions of aspen …

Effect Of Foliage And Root Carbon Quantity, Quality, And Fluxes On Soil Organic Carbon Stabilization In Montane Aspen And Conifer Stands In Utah, Antra Boča

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Soil organic carbon (SOC) positively affects many soil properties (e.g., fertility and water holding capacity), and the amount of carbon (C) in soil exceeds the amount in the atmosphere by about three times. Forest soils store as much C as is found in trees. Tree species differ in their effect on SOC pools. Quaking aspen forests in the Western US often store more stable SOC in the mineral soil than nearby conifers. During the last decades a decline in aspen cover, often followed by conifer encroachment, has been documented. A shift from aspen to conifer overstories may negatively affect the …

Influence Of Stand Composition On Soil Organic Carbon Stabilization And Biochemistry In Aspen And Conifer Forests Of Utah, Mercedes Román Dobarco

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Social concern about climate change and the elevated level of atmospheric CO2 demands understanding carbon (C) storage and dynamics in forest soils, especially since soils are the largest C reservoir in terrestrial ecosystems, storing two thirds of total C. Quacking aspen (Populus tremuloides Michx.) is an iconic species in western United States that offers multiple ecosystem services, such as habitat and forage for wildlife and cattle, biodiversity, water yield, and C storage. A decline in quaking aspen cover has been documented during the last decades, possibly due to fire suppression and ungulate browsing. A shift from aspen- to conifer-dominated …

Factors Influencing The Successful Regeneration Of Aspen In Southern Utah, Usa, Justin M. Britton

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This study addresses critical issues and concerns relating to aspen forest management across the Intermountain West. These concerns have been raised due to the declining condition of aspen forests. As a result, aspen decline has been a topic of interest among academics and popular media outlets alike in recent years due to the economical and ecological value of aspen. Some land managers and management agencies have used forest management techniques as a means to deal with this issue. These management techniques are designed to stimulate the reproduction of aspen in order to provide a bank of seedlings and saplings for …

Developing A Field Indicator For Suckering Ability Of Quaking Aspen, Abbey M. Hudler Oksness

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Quaking aspen is an ecologically valuable deciduous tree species in the high elevation environment typical across many parts of western North America. It is a clonal tree species which primarily depends on vegetative regeneration by root suckering after an aboveground disturbance, e.g., wildfire, removes the stems. A flush of suckers will be stimulated after a disturbance and the resulting regeneration relies on available resources from the undamaged root system for resprouting. Due to wildfire suppression efforts of the last century, many aspen stands are considered mature, overmature, or decadent and lack regeneration to replace the overstory mortality. In the absence …

Habitat Characteristics And Occupancy Rates Of Lewis's Woodpecker In Aspen, Amy M. Vande Voort

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Lewis‘ woodpeckers (Melanerpes lewis) are generally associated with open ponderosa pine (Pinus ponderosa), open riparian, and burned pine habitats in the West; however, this species has recently been found to nest in aspen (Populus tremuloides) stands in Utah. This study describes the habitat characteristics of Lewis‘ woodpecker nest sites in aspen and investigates how well aspen stand characteristics predict Lewis‘ woodpecker occupancy. I surveyed for Lewis‘ woodpeckers at previously occupied nesting locations in aspen and took habitat measurements at nest sites. In addition, nest-centered Forest Inventory and Analysis (FIA)-type plots provided stand-level habitat characteristics. I used logistic regression to …

Assessing Quaking Aspen (Populus Tremuloides) Decline On Cedar Mountain In Southern Utah Using Remote Sensing And Geographic Information Systems, Chad M. Oukrop

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Quaking aspen (Populus tremuloides Michx.) is the most widespread deciduous tree species in North America and aspen ecosystems are highly valued for multiple use, being noted for forage production, understory diversity, wildlife habitat, timber, hydrological assets, and aesthetics. However, aspen communities in the Intermountain Region of the western United States are in evident decline, with certain areas experiencing rapid mortality over the past decade. One location of special interest is the quaking aspen on Cedar Mountain in Southern Utah, USA, an isolated population in the southwestern portion of aspen's geographic range.

Lacking critical information on the location, extent, and …

Ecological Effects Of Genotypic Diversity On Community And Ecosystem Function, Megan K. Kanaga

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Genotypic diversity within populations can have important evolutionary consequences, but the ecological effects of intraspecific genetic variation on community and ecosystem function have only been studied in a few systems. I present the results of a three-year study designed to address the ecological impacts of genotypic diversity in quaking aspen (Populus tremuloides Michx.), using aspen genotypes planted across genotypic diversity levels (monoculture and mixture) and watering treatment levels (well-watered and water-limited). First, I demonstrated that significant variation exists among genotypes for a wide range of growth, morphological and physiological traits, and quantified high heritability and coefficient of genetic variation …

Comparison Of Water Dynamics In Aspen And Conifer: Implications For Ecology Water Yield Augmentation, Eric Martin Lamalfa

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Differences in water dynamics between deciduous aspen (Populus tremuloides) and co-occurring evergreen conifer species in the Northern Rocky Mountains result from complex physical and biological interactions. A comprehensive evaluation of individual water transfer mechanisms was used to elucidate the relative importance of several components of the hydro logic cycles of aspen and conifer, and determine which water transfer mechanisms have potential to cause differences in net water yield.

Adjacent aspen and conifer stands were monitored to determine snow accumulation and ablation (snow survey), soil moisture recharge (capacitance probes), snowpack sublimation (sublimation pan), transpiration period (thermal dissipation probes), and …

Restoration Of Aspen In Different Stages Of Mortality In Southern Utah, Seth Ray Ohms

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Aspen clones of an aspen-dominated community in Southwestern Utah are declining, some having experienced high mortality coupled with in sufficient regeneration. The objectives of this study were to (I) determine if decadent, non-regenerating mature aspen stands could be regenerated through disturbance of the 111 auxin/cytokinin hormone relationship by clearcutting; (2) determine the extent of ungulate use of regenerating aspen ramets. Clearcuts were made in late summer of 2001 in 10 different clones that exhibited various levels of decline on a continuum from relatively healthy to extremely deteriorated. Nested wildlife/livestock exclosures were constructed in each clearcut plot, as well as in …

Forage Quality Comparison Of Burned And Nonburned Aspen Communities, Deborah L. Blank

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The objectives of this study were to assess the effects of prescribed burning on herbaceous and browse forage quality in the aspen forest type for elk and domestic sheep.

Plant samples of selected forage species were taken from burned and nonburned plots within three different prescribed burns in southeastern Idaho. These samples were analyzed for in vitro dry matter digestibility, crude protein, calcium and phosphorus. Data were analyzed using the analysis of variance.

There was little improvement in forage quality as a result of prescribed burning, with some reduction in quality in 1983 exhibited by pinegrass (Calamagrostis rubescens). …

Density And Diversity Responses Of Summer Bird Populations To The Structure Of Aspen And Spruce-Fir Communities On The Wasatch Plateau, Utah, Janet Lee Young

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Sixteen stands representing a range of structural variation in aspen, mixed aspen-conifer, and spruce-fir communities of the Wasatch Plateau, Utah, were censused by the sample count method. The stands were classified as eleven community types based on the understory dominants or indicator species and the cover types. Fifty bird species were recorded during the two seasons; thirty-two occurred in aspen cover, forty-four in mixed aspen-conifer cover, and twenty-two in spruce-fir.

Comparisons of the composition and density of bird populations were made between uniform stands of a single life form and more structurally complex stands of either single or mixed life …

A Comparison Of Dewpoint And Psychrometric Mode In Leaf Water Potential Measurements, Gladys Durand-Campero

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Leaf water potential of two maize plants (Zea mays L.) two chlorophytum plants (Chlorophytwn capense, Kuntze), a schefflera (Brassaia actinophylla) and one aspen (Populus tremuloides Michx.), were measured under laboratory conditions with aluminum block in situ leaf hygrometers and with stainless steel single junction chamber hygrometer using excised entire leaves. Plants were subjected to a drying cycle. The hygrometers were controlled with a dewpoint microvoltmeter and all readouts were recorded on a chart recorder. A typical reading and control schedule included 20 second cooling before a first psychrometric reading allowing the output to …

The Effect Of Cattle, Sheep, And Other Factors On Aspen (Populus Tremuloides) Reproduction After Clear-Cut Logging In Southern Utah, Paul A. Lucas

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Aspen is the most widespread deciduous tree of the western United States and the aspen type is important for water, forage, and wood products. Aspen reproduction on cutover areas was thought to be hindered by browsing and other factors, therefore a study was conducted to determine the effects of livestock, pocket gophers, disease, and snowpack damage on aspen reproduction during the first three years after clear-cutting. An enclosure was constructed and divided into nine paddocks. Controlled grazing by cattle and sheep was applied to six different paddocks during three summer periods. Three paddocks were protected from grazing. Results show that …