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An Evaluation Of Landscape, Climate, And Management Impacts On Bumble Bees (Hymenoptera: Apidae: Bombus) In Agroecosystems, Morgan Elizabeth Christman

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Bumble bees play pivotal roles in pollinating wild and cultivated plant communities. Unfortunately, bumble bee populations are declining due to disturbances such as landscape conversion and climate change. Additionally, traps used to monitor pest insect populations often capture bumble bees, leading to a concern that trap captures increase bumble bee mortality. First, I studied bumble bee communities based on land cover and weather variables in agricultural fields in Utah. Bumble bee communities were more diverse in agricultural fields with more agricultural land in the surrounding area, low temperatures, and high humidity during the growing season, and less diverse in fields …

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 …

Impacts Of The Changing Pacific On North American Drought, Atmospheric Rivers, And Explosive Cyclones, Jacob Stuivenvolt-Allen

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The impacts of specific weather events can vary greatly from year to year. Much of these impacts depend heavily on the frequency of impactful weather which is constrained by the state of the climate system each year. This research focuses largely on the impacts that climate oscillations from year-to-year or even from decade-to-decade have on the frequency of impactful weather. There are numerous examples of impactful weather that impact North America, but this work focuses on drought in the western United States, atmospheric rivers in Northern California and rapidly developing winter storms along the east coast. While seemingly disparate events, …

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 …