Desert Ecology Commons^™

Watershed Amendments: Assembling New Pervious Ground From Landscape Waste, Sophie Kaplan-Bucciarelli

Masters Theses

In Providence, Rhode Island, much of the downtown area is built over a vast historic tidal estuary. Though we no longer see the salt marshes, wooded bluffs, or meadows that once characterized this landscape, we recognize their absence in contemporary crises of urban heat, flooding, polluted soils and stormwater runoff, and habitat loss. These conditions are particularly acute along the city’s industrialized river corridors, where vacant lots and parking areas sit idle, their history paved over and potential constrained by limited imagination and resources.

These lots - already experiments in fill and land building after centuries of disturbance - can …

The Concept 'Pollination' And Bee Pan-Trap Color And Uv Reflectance Determine The Taxonomic Compositions Of Bee Taxa Captures Across An Elevation Gradient And Seasons In The Jemez Mountains Of New Mexico, Esther A. Burton, Kelly B. Miller, Paul J. Watson, David C. Witherington, Steven Poe, David Lightfoot

Biology ETDs

This thesis examines the pollinator concept and tests how sampling methods shape bee communities. Chapter 1 provides a conceptual and philosophical analysis, arguing that pollination is a process and that pollinators are context-dependent functional roles rather than fixed taxonomic categories. It traces the concept’s development from natural history to ecological theory, introduces a dual-goal model separating plant reproduction from visitor foraging, and proposes a classification framework based on evidentiary certainty and pollination potential to resolve ambiguity in pollination research.

Chapter 2 applies these ideas empirically by evaluating how pan-trap color and ultraviolet (UV) reflectance influence bee assemblages across elevation and …

Machine Learning-Based Spatio-Temporal Modeling Of Climate Dynamics And Desertification In The Sahara–Sahel Region, Stephen M. Tivenan

Theses and Dissertations

Arid climate classifications are threshold-dependent and easily interpretable mappings that are widely used in ecological, agricultural, and climate-related studies. These classifications inform scientific understanding, support policy and land management decisions, and provide an intuitive summary of environmental conditions. Despite their usefulness, traditional arid climate classifications often fail to quantify uncertainty, incorporate spatial context, or account for complex relationships among relevant environmental variables. Existing approaches to uncertainty assessment have largely relied on comparing classifications across multiple datasets or alternative formulas, but these methods generally overlook important spatial dependence and latent structure in the data.

This dissertation develops three machine learning-based statistical …

Efficacy Of Oil And Gas Production Site Remediation In U.S. Arid/Semi-Arid Regions, Skye Ontiveros

Architecture and Planning ETDs

Oil and gas production (OGP) is expanding, paralleled by its polluting leaks and spills (LS), and outpaced by its waste. This raises the question: Does remediation of LS occur effectively when needed to protect the environment and public, particularly in major producing regions like arid/semi-arid regions (ASAR), which account for approximately 72% of US oil and 42% of gas production? To answer, a review of the eight largest national remedial laws, sourced from the Code of Federal Regulations (CFR), identified 14 OGP exemptions for remedial determinants (RDs): factors affecting remedial frequency and efficacy (e.g. LS monitoring and chemical disclosure). An …

Using Triple Oxygen Isotopes To Investigate Water Usage In Desert Ecosystems, Cloe V. Knutson

Earth and Planetary Sciences ETDs

In arid environments, maintaining water balance can be more critical for survival than obtaining food. As droughts intensify, understanding how animals manage body water is essential. Triple oxygen isotope analysis provides a novel way to trace water sources in animals, distinguishing contributions from free water, food-derived oxygen, and atmospheric O₂. We developed an equilibration method using CO₂–H₂O oxygen exchange and measured δ^’18O and Δ^’17O values via tunable infrared laser direct spectroscopy (TILDAS). Validated against traditional fluorination methods, this technique enables streamlined analysis of whole blood and plant samples. Applied to …

Nitrogen Addition Additively Boosts Climate-Driven Salsola Tragus (Russian Thistle) Invasion Into Southwestern Usa Grasslands, Melissa A. Bacigalupa

Biology ETDs

Effective management of invasive, non-native plants requires understanding key drivers of invasion, including nitrogen enrichment from atmospheric deposition and agriculture. Long-term studies are essential for capturing complex invasion dynamics yet remain uncommon. We used 22 years of observations and 14 years of nitrogen experiments to examine invasion by Salsola tragus (Russian thistle) into three semi-arid grasslands of central New Mexico. Invasion patterns varied, with rapid expansion in Chihuahuan Desert grassland and the Desert-Plains ecotone but stability in Plains grassland. Under ambient nitrogen, precipitation most strongly correlated with Russian thistle biomass and high native grass biomass was associated with Russian thistle …

The Ecophysiology Of The Enigmatic Namib Succulent, Lithops Ruschiorum, Garrett Macleod Althausen

Environmental Studies Senior Theses

Water availability is the primary constraint for plant survival and reproduction in hyper-arid ecosystems. In such environments, plant fitness depends on an alignment between physiological traits and limited water resources. The Namib Desert of Namibia exemplifies this extreme selection pressure. Within the Namib Desert, Lithops ruschiorum, a succulent endemic to the gravel plains, exhibits habitat specificity and numerous physiological adaptations to cope with the hyper-aridity.

This research explores the intersection of two fitness strategies for L. ruschiorum: habitat selection and exploitation of alternative moisture sources. The first chapter explores the population dynamics and micro-site habitat conditions preferred by …

Gone With The Flow: Flow Reduction Coincides With Reduced Metabolism And Standing Stock Of Benthic Algae And Macroinvertebrates In Desert Rivers, Chloe E. Lyles

All Graduate Theses and Dissertations, Fall 2023 to Present

River metabolism, the measure of energy flow in a river, is driven by hydrological and physicochemical regimes (e.g., temperature, turbidity, and nutrients). However, these regimes are increasingly altered by human water demand and climate change-driven drought. These stressors alter the magnitude, timing, and duration of critical spring-snowmelt floods with poorly understood consequences on ecosystem function, particularly in desert rivers. To investigate the linkages between flow reduction, river metabolism, and basal food resource productivity (i.e., algae and aquatic invertebrates), we measured metabolism and basal resource availability in seven desert tributaries with varying degrees of flow reduction during low-flow conditions in 2023 …

Patterns Of Stand Structure And Species Composition Through Time And Space In A Piñon- Juniper Woodland In The Southwestern Us, Kyle H. Gonterman

Biology ETDs

Piñon- juniper (PJ) woodlands in the Southwest United States are expected to see mortality and structural change in response to climate change. The extent to which this habitat structures itself as well as its response to these changes over time are not well known yet and have not been examined to this extent for the location of this study within the Sevilleta National Wildlife Refuge. Within a small range, we discovered these woodlands consist of persistent woodland, shrubby woodland, and juniper savanna in which structural, spatial, and regeneration patterns differ. In this study, we discovered the specific differences between these …

Resolving The Paradox Of Polyploidy: Underexplored Facets Of Polyploid Plants, Benjamin P. Gerstner

Biology ETDs

Polyploidy, or whole genome duplication, is a common phenomenon in plants, but the establishment and persistence of mixed-ploidy populations remains a paradox. This dissertation explores factors that contribute to the persistence and establishment of mixed-ploidy populations in nature. The first chapter investigates the role of unreduced gametes in neopolyploid establishment and finds that variability in their formation rate can have a significant impact on polyploid establishment and persistence. The second chapter searches for evidence of soil microbes exhibiting ploidy-specificity, a pre-condition for microbe-mediated niche differentiation, a possible stabilizing mechanism contributing to ploidy coexistence. Finally, the third chapter tests for microbe-mediated …

National Development And The Sustainability Of Mining In The Atacama Desert, Chile, Dakota Soleil Osgood

Capstone Collection

As climate change continues to intensify on a global scale, efforts have been made to implement renewable energies and progressive technologies. These tools are critical in the shift towards a more sustainable practice, and yet analysis of localized impacts from the development of these mechanisms is inadequate. Chile has been and continues to be a leading country in mineral extraction, with an economic history founded in the mining industry. The establishment of mining in Chile as a progressive tool has aided the social and economic development of the nation. Consequences of mining extraction, however, include intensive environmental degradation, human rights …

Restoring An Iconic Joshua Tree Forest: Natural Recovery, Restoration Success, And Soil Microhabitats On A Desert Burn Area, Riley Scaff

Pitzer Senior Theses

Wildfires are a novel disturbance type in the Mojave Desert, but have been increasing in size and frequency since the 1970s due to the proliferation of invasive grasses. Burned areas are more susceptible to invasion, which can lead to the establishment of a grass-fire cycle. For this reason, restoration is often necessary to facilitate natural plant community recovery, but the extreme desert climate makes returning native vegetation to burn areas challenging. Planting in nutrient-rich soil microhabitats could be a helpful tool to improve revegetation success, but has yet to be tested. This study surveyed natural postfire recruitment across two seasons …

Demography And Habitat Associations Of The Basalt Cactus: Pediocactus Nigrispinus, Zarha Dillon-Zuppelli

All Master's Theses

Cacti are iconic, conspicuous, and important contributors to arid ecosystems. They stabilize soil and provide essential food and habitat to wildlife. Pediocactus nigrispinus is a species of cactus endemic to the Pacific Northwest and has been listed as a sensitive species due to its vulnerability to habitat loss. Pediocactus nigrispinus is being threatened by habitat fragmentation, poaching, and a changing climate. Best conservation methods for this species are poorly understood, due in part to a limited understanding of its demography and associations that may help define its occurrence.

A demographic study in Washington State was implemented in 2016 to give …

Effects Of Solar Arrays On Southwestern Desert Thermal Landscapes: Consequences For Terrestrial Ectotherms, Adrian Slade

All Master's Theses

Solar energy development in the Southwestern United States coincides with habitat for many sensitive and endemic species, including reptiles such as Mojave Fringe-toed Lizards and Mojave Desert Tortoises who are threatened by a warming and drying climate. While utility-scale solar energy reduces carbon emissions and should ultimately benefit climate-sensitive species, it locally destroys fragile desert habitat, displaces wildlife, and has been shown to incur local air and surface temperature changes. Mitigation-based translocation of wildlife species in the face of solar development yields mixed results, and the unprecedented pace of solar expansion in the desert highlights the need for alternative practices …

Ectotherm Thermoregulation At Fine Scales: Novel Methods Reveal A Link Between The Spatial Distribution Of Temperature And Habitat Quality, Ian Axsom

Master's Theses

Investigating ecological questions at the scale of individual organisms is necessary to understand and predict the biological consequences of environmental conditions. For small organisms this can be challenging because we need tools with the appropriate accuracy and resolution to record and quantify their ecological interactions. Unfortunately, many of our existing tools are only appropriate for medium to large organisms or those that are wide ranging, inhibiting our ability to investigate the ecology of small organisms at fine scales.

In Chapter 1, I tested a novel workflow for recording animal movements at very fine spatial and temporal scales. The workflow combined …

Extreme, Positive Geomorphic Change In A Historically Degraded Desert River: Implications For Imperiled Fishes, Tansy T. Remiszewski

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Rivers comprise some of the most unique and biodiverse ecosystems on the planet with their waters supporting both human societies as well as the organisms that make these rivers their home. Large rivers like the Colorado are often highly regulated and diverted in order to support human residence in arid regions like the desert Southwest, and these water diversions often have dramatic, negative impacts on the natural flow regime of the river. These impacts leave large reaches of the river dry, reduce the river’s capacity to transport sediment, cause channel and habitat homogenization, and significantly reduce the amount of suitable …

Above- And Belowground Responses To Environmental Change In The Northern Chihuahuan Desert, Renée Françoise Brown

Biology ETDs

Drylands cover 45% of the terrestrial surface and are expanding rapidly due to anthropogenic drivers. Altered precipitation regimes, atmospheric nitrogen deposition, and wildfire will likely have significant consequences in these regions where ecological processes are limited by water and nitrogen. In this dissertation, I explored temporal dynamics of net primary production (NPP) and related above- and belowground processes under several environmental change drivers in the Sevilleta National Wildlife Refuge, central New Mexico, USA. Located in the northern Chihuahuan Desert, this region experiences strong seasonal precipitation patterns driven by the North American Monsoon, historically characterized by frequent small rain events hypothesized …

Biodiversity And Global Change In Terrestrial Ecosystems, Timothy John Ohlert

Biology ETDs

Terrestrial ecosystems are critical to human and ecological processes but many gaps in our knowledge remain regarding how terrestrial plant communities assemble and respond to global change. I used field experiments distributed around the world, including long-term experiments from the Sevilleta National Wildlife Refuge (SNWR) in New Mexico and deserts of the southwestern U.S., to evaluate the consequences of drought and other abiotic stressors on plant communities. Dominant grasses were particularly important for the productivity and structure of grasslands at SNWR. In general, the structure of desert plant communities had high resistance to extreme drought, though grasses and other perennial …

Keeping Your Cool: Thermoregulatory Performance And Plasticity In Desert Cricetid Rodents, Richard W. Ramirez, Eric A. Riddell, Steven R. Beissinger, Blair O. Wolf

Biology ETDs

Small mammals in hot deserts often avoid heat via nocturnality and fossoriality and are thought to have a limited capacity to dissipate heat using evaporative cooling. Research to date has focused on thermoregulatory responses to air temperatures (T_a) below body temperature (T_b). Consequently, the thermoregulatory performance of small mammals exposed to high air temperatures is poorly understood, particularly responses across geographic and seasonal scales. We quantified the seasonal thermoregulatory performance of four cricetid rodents (Neotoma albigula, N. lepida, Peromyscus eremicus, P. crinitus) exposed to high T_a, at four sites …

Global Population Divergence Of A Cosmopolian Desert Plant, Victor Ryan Alfaro

Biology ETDs

Genetic and phenotypic variation can have different patterns within a species if it has populations with contrasting histories. Populations can have discrete differences that are shaped by different evolutionary scenarios, but within each population, range, or region, traits and association with fitness can also be affected by both edaphic and landscape variation. For my dissertation, I surveyed and experimentally analyzed variation and adaptive potential in Sahara mustard (Brassica tournefortii), a desert annual that has endemic, invasive, and agricultural populations in Africa, Asia, and the Americas. Although my multi-trait analysis generated complex results, my findings can be applied to …

Dietary Shifts Related To Water Availability And The Demographic Response To Changing Prey Abundance Of Carnivores In The West Desert, Utah, Ashley E. Hodge

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The decrease in number and range of North American large carnivores, has often all owed smaller carnivores ( < 15 kg) to fill the role of the top predator. This has favored some carnivores such as coyotes (Canis latrans), who have expanded their distribution. Other small carnivores such as kit foxes (Vulpes macrotis) have experienced a range shrinkage and their population status throughout the United States is a concern. Historically, western U.S. natural resource management agencies installed artificial water sources to assist desert wildlife, but some researchers believe the access to water allowed more coyotes to live in Utah’s West Desert. In the late-1980s, research proposed that without free drinking water, coyotes would have to triple …

Effects Of Wetland Management And Associated Abiotic Factors On Rare Plant Communities Of Spring-Fed Arid Wetlands, Antonio Cantu De Leija

LSU Master's Theses

Spring-fed arid wetlands support high biological productivity and are hotspots for endemism and distribution of rare plants, making them areas of high conservation value. These systems are driven by complex interactions among groundwater discharge and the geomorphic and climatic features of the setting, which provide gradients of edaphic conditions, particularly soil moisture and salinity that influence the presence and abundance of rare plant communities. However, spring-fed arid wetlands are at particular risk of increases in salinity and drier hydrological regimes due to anthropogenic activities. Such alterations to abiotic conditions may jeopardize the distribution and abundance of rare plants by exceeding …

Habitat Heterogeneity Affects The Thermal Ecology Of The Federally Endangered Blunt-Nosed Leopard Lizard, Nicole Gaudenti

Master's Theses

Global climate change is already contributing to the extirpation of numerous species worldwide, and sensitive species will continue to face challenges associated with rising temperatures throughout this century and beyond. It is especially important to evaluate the thermal ecology of endangered ectotherm species now so that mitigation measures can be taken as early as possible. A recent study of the thermal ecology of the federally endangered Blunt-Nosed Leopard Lizard (Gambelia sila) suggested that they face major activity restrictions due to thermal constraints in their desert habitat, but that large shade-providing shrubs act as thermal buffers to allow them …

Effects Of Environmental Change On Ancestral Pueblo Fishing In The Middle Rio Grande, Jonathan William Dombrosky

Anthropology ETDs

It has long been assumed that fishes were unimportant in the diet of past Pueblo people in the U.S. Southwest. Yet, small numbers of fish remains are consistently recovered from Late pre-Hispanic/Early Historic archaeological sites in the Middle Rio Grande of New Mexico. The end of drought conditions may have impacted food choice and fishing decisions during this time. I use behavioral ecology to understand how fishing could have been an optimal food-getting strategy for Ancestral Pueblo farmers. Stable isotope analysis offers a way to account for environmental change. I provide a refined ¹³C Suess correction model to support …

Some (Im)Material Girls, Living In (Im)Material Worlds, With Seeds, Stars, And Shit, Matthew Weiderspon

Theses and Dissertations

This writing situates material and gestural vocabularies cultivated in my artwork in relation to my lived experience; primarily my rural upbringing in Colorado. Scattered floor dispersals, calling sounds, and bodily movements desire reconsiderations of hope in precarity through a disorientation of place, association, scale, and language.

Interactive Effects Of Soil And Browsing On Big Sagebrush: Implications For Restoration Success, Kyle Nehring

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023

Heterogeneity in landscape conditions (e.g., soil types) precludes a “one size fits all” management strategy across large landscapes. New management approaches that explicitly account for heterogeneous landscapes (and the variable conditions therein) will be required to maintain habitat quality. In particular, we require an improved mechanistic understanding of how the outcomes of conservation and restoration actions are contingent upon a) contextual abiotic factors (e.g., moisture availability mediated by soils and precipitation) and b) their interactions with biotic factors (e.g., browsing wildlife).

We propose to answer fundamental questions about how big sagebrush (Artemisia tridentata), the foundational species for sagebrush …

Seed Bank Composition Within Two Sagebrush Communities: A Comparison Of Drought, Microsite, And Aboveground Community Effects, Allison Marie Nunes

Cal Poly Humboldt theses and projects

Soil seed banks are critical biodiversity repositories for many dryland plant communities. Understanding how environmental factors alter seed bank composition can provide valuable information on ecological processes within a community and be useful for creating land management strategies. Using the seedling emergence method, I characterized the seed bank of two adjacent dryland plant communities that vary in dominant sagebrush species, structure, and function. Specifically, within an Artemisia arbuscula dominated community and Artemisia cana dominated community, I assessed the influence of three environmental factors on each seed bank: experimentally imposed drought, shrub microsites (compared to interspaces), and aboveground vegetation. Within the …

A Historical Ecology Of Aridland Springs In Desert National Wildlife Refuge, Nuwu/Nuwuvi (Southern Paiute/Chemehuevi) Ancestral Territory, Nevada, Yarrow Sarah Valentine Geggus

Dissertations and Theses

Aridland springs are among the most threatened ecosystems in the world. Vital to desert ecologies and Indigenous cultures, these complex and individualistic ecosystems have layered histories. To inform management in the changing landscape of Desert National Wildlife Refuge, a 1.6 million acre protected area in Southern Nevada, I conducted a historical ecology study of a sample of ten upland springs. Through a six-part interdisciplinary methodology including interviews, archaeological survey, botanical survey, and archival research, I summarize findings into three broad eras: the Nuwu/Nuwuvi pre-Contact Era, the Settler Era, and the U.S. Fish and Wildlife Service Era.

For millennia, Nuwu/Nuwuvi drank …

Species Distribution Modeling For Arid Adapted Habitat Specialists In Zion National Park, Sam Driver, Chris M. Schalk, Daniel Unger, David Kulhavy

Electronic Theses and Dissertations

The Arizona toad (Anaxyrus microscaphus) and Jones’ waxy dogbane (Cycladenia humilis var. jonesii) are habitat specialists with historical ranges in the desert southwest and specifically, Zion National Park (ZION). The machine learning method, MaxEnt, constructed species distribution models (SDMs) in ZION for the two study species at 30 m and 900 m spatial resolutions using climate, topographic, and remotely sensed data. Additionally, 900 m forecasting models were constructed to observe the shifts in suitable habitat for the years 2050 and 2070, based off two representative concentration pathway scenarios. Results indicate promising predictive power for both high …

Population Structure Of A Federally Endangered Plant (Astragalus Jaegerianus Munz, Fabaceae) With Limited Range Using Microsatellites, Sueann Neal

Electronic Theses, Projects, and Dissertations

Studies on population genetics examine the relationship and effects of population structure, migration, gene flow and demographic history, and are therefore important in the conservation of endangered species. Astragalus jaegerianus, a critically federally endangered species found in a geographically restricted range is investigated to determine population structure and genetic variation. Previous research on A. jaegerianus focused on DNA sequence data for cpDNA and nrDNA showed no variation. Further research on A. jaegerianus utilizing AFLP’s on the whole genome indicated substantial gene diversity and population structure consistent with geographically widespread species. AFLP research is a cost-effective process to identify levels …