Life Sciences Commons^™

The Effects Of Recent Climate Change On Spring Phenology, With A Special Focus On Patterns Of Bee Foraging, Michael Stemkovski

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The date on which plants flower and on which bees begin to pollinate varies year-to-year depending on differences in weather. This seasonal timing is known as phenology, and it is already clear that climate change has pushed the spring phenology of many species earlier by increasing temperatures. This is particularly clear in flowering plants, but studying how and why the phenology of pollinators is shifting is more difficult. Most flowering plants rely on pollinators such as bees for their reproduction, and most bees rely on flowers for their sustenance, so bee and flower phenology has to overlap for the crucial …

Local And Regional Landscape Characteristics Driving Habitat Selection By Greater Sage-Grouse Along A Fragmented Range Margin, Aidan T. Beers

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

In response to ongoing landscape change, wildlife species are likely to respond in varied ways. By studying habitat specialists, we are able to better understand the most likely ways in which the denizens of threatened ecosystems will react to those changes. Among the most threatened ecosystem types in North America are sagebrush ecosystems of the Intermountain West, where one of its most well-known residents, greater sage grouse (hereafter, “sage-grouse), have lost more than 50% of their habitat due to fire, invasive species, climate change, encroachment by coniferous forests and avian predators using it, and human-caused landscape conversion. Sage-grouse rely on …

Hidden Mechanisms Of Climate Impacts In Western Forests: Integrating Theory And Observation For Climate Adaptation, Sara J. Germain

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Fire, insects, and disease are necessary components of forest ecosystems. Yet, climate change is intensifying these tree stressors and creating new interactions that threaten forest survival. This dissertation combined field observations with statistical predictions of changing disturbances in western forests to identify 1) how conventional models may underestimate future forest loss, and 2) how positive relationships between trees may be exploited by managers to prevent forest loss.

In Chapter II, I tested whether increasingly extreme weather with climate change increases Pacific yew extinction risk. I found that conventional modeling methods underestimated local extinction risk because trees were adapted to a …

The Impacts Of Increased Precipitation Intensity On Dryland Ecosystems In The Western United States, Martin C. Holdrege

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

As the atmosphere warms, precipitation events become larger, but less frequent. Such increases in precipitation intensity are expected regardless of changes in total annual precipitation. Despite strong evidence for increases in precipitation intensity, disagreement exists regarding how these changes will impact plants, and studies are lacking in many types of ecosystems. This dissertation addresses how increased precipitation intensity affects soil water availability, and how plants respond to any such changes. I address this question in the context of big sagebrush ecosystems and dryland winter wheat agriculture, which are both environments that can be sensitive to changes in water availability. Results …

Susceptibility Of High-Elevation Forests To Mountain Pine Beetle (Dendroctonus Ponderosae Hopkins) Under Climate Change, David N. Soderberg

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Across western North America, pine forests are important for timber, wildlife habitat, and at high elevations are important for water retention and yield from rain and snowmelt. The mountain pine beetle (MPB) is one of the most significant disturbance agents shaping pine forests, and like all insects, temperature is a major driver of its population success and the dynamics of the landscapes that they inhabit. Changing temperature regimes can therefore directly influence MPB population persistence at a particular location, in addition to potential shifts in the range boundaries that they inhabit. MPB is currently expanding its range northward in British …

Harmful Algal Blooms: Dominance In Lakes And Risk For Cyanotoxin Exposure In Food Crops, Austin D. Bartos

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Climate change and human activities are promoting the dominance of a photosynthetic family of aquatic bacteria, cyanobacteria. Blooms of cyanobacteria are not only a visual nuisance but can produce a variety of cyanotoxins than can harm the liver, skin, and nervous system of animals and humans. We analyzed lakes in the contiguous United States and found that between 2007 and 2012, the number of lakes that produced measurable quantities of cyanotoxins increased from 33% to 45%. Nitrogen and phosphorus pollution were the main drivers of cyanobacteria blooms and toxin production between these years. Many of these lakes and reservoirs are …

The Vulnerability Of Littoral Structures Under Multiyear Drought Conditions, Jenna M. Keeton

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Climate change is associated with altered environmental conditions and shifting mosaics of suitable habitats for organisms. Climate change in the form of drought can shift important lake shoreline habitats downslope, altering the lakes chemistry and habitat availability. Additionally, negative biological consequences can occur after a loss of submerged habitat along shorelines, hereafter littoral habitat. The objective of this study is to evaluate whether littoral habitat is lost (cobble, coarse woody habitat (fallen trees; CWH), and aquatic vegetation) under drought conditions across the United States. I used the National Lakes Assessment physical habitat data collected in summer 2012, when 75% of …

Landscape Planning For Climate Change Resilience In The Southern Rockies, Jeffrey D. Haight

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The unique species, ecosystems and landscapes of the Western United States are experiencing unprecedented pressures from climate change, creating new challenges for conservation. As temperatures rise and patterns of precipitation shift, plant and wildlife species have been shifting their ranges to new areas in search of more suitable climates, building groupings of species that are historically unfamiliar. These climate -driven migrations place an additional burden on species that are already threatened from habitat loss and other human-related activities. The impacts of climate change are of particular concern in landscapes that have long been conserved and managed based on the ecological …

Plant Evolutionary Response To Climate Change: Detecting Adaptation Across Experimental And Natural Precipitation Gradients, Jacqueline J. Peña

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Global climate change is a real-time problem that presents threats to many species. Climate change can alter ecosystems and may lead to species extinction. Species can respond to climate change by moving to a better environment or adapting. Therefore, it is necessary to rely on several approaches and perspectives to anticipate ecological impacts of climate change. A common strategy uses models to understand how populations respond to different climate scenarios. Ecological models have helped us understand population persistence, but they often ignore how populations adapt to environmental stress. Adaptive evolution has been ignored because it was assumed that evolution was …

Direct And Indirect Effects Of Climate Change On Plant Populations And Communities In Sagebrush Steppe, Andrew R. Kleinhesselink

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Rapid climate change presents humanity with a number of big problems. Foremost among these is the sad fact that the climate we will pass on to our children will likely be nothing like the climate that we inherited from our parents. Ecologists have collected solid evidence that climate change has already begun to affect the living things around us and the ecosystems humans depend on. Unfortunately, predicting the future effects of climate change on life on earth is not easy. We focused on three research goals as part of an effort to improve our ability to predict how plants and …

A Spatiotemporal Mountain Pine Beetle Outbreak Model Predicting Severity, Cycle Period, And Invasion Speed, Jacob P. Duncan

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The mountain pine beetle (MPB, Dendroctonus ponderosae), a tree-killing bark beetle, has historically been part of the normal disturbance regime in lodgepole pine (Pinus contorta) forests. In recent years, warm winters and summers have allowed MPB populations to achieve synchronous emergence and successful attacks, resulting in widespread population outbreaks and resultant tree mortality across western North America. We develop an age-structured forest demographic model that incorporates temperature-dependent MPB infestations: the Susceptible-Infested-Juvenile (SIJ) model. Stability of equilibria is analyzed as a function of population growth rates, and indicates the existence of periodic outbreaks that intensify as growth rates …

Rapid Savanna Response To Changing Precipitation Intensity, Ryan S. Berry

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Climate change has the potential to cause large-scale changes in plant growth, biodiversity, and biosphere-climate feedbacks. A pervasive aspect of climate change is that as the atmosphere warms, precipitation events are likely to become less frequent but more intense, because warmer air can hold more water. Larger precipitation events can be expected to change plant productivity and community composition, particularly in semiarid ecosystems such as savannas. Savannas are of particular interest because they are spatially expansive at the global scale, they are important to humans for food production, and they are known to be sensitive to changes in soil water …