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  • Thumbnail for A Micrometeorological Study of an Abrupt Treeline on Pike’s Peak
    A Micrometeorological Study of an Abrupt Treeline on Pike’s Peak by Parish, Meredith

    Pike’s Peak Treeline Microclimatology: Our study site in Pike’s Peak is one of the few abrupt treelines that is advancing with recent regional warming. We established that there is most likely an eddy in the lee of timberline during askew flow as evidenced by the increasing size (both length and height) of a slow air bubble from parallel to askew flow. This increased size of the slowed air bubble creates sheltered conditions downwind of the shelterbelt. Shelterbelts are known to ameliorate agricultural health because eddies can create beneficial climatic conditions through decreased wind speeds. However, the eddy created in our study site may not create a better environment for tree growth. Tree establishment above 2H must be inhibited by too high of wind speeds creating high shear and near non-existent snow cover during the winter. The area between timberline and 2H has been slowly filling in with seedlings since the mid/late 1800’s. The trees in this section do not grow into krummholz form. If a seedling can be established it grows into a fully-grown symmetrical tree. It is difficult, but not impossible for seedlings to become established in this zone. Tree establishment is most likely dependent on very specific microsites within this area that have some wind flow, moderate snow cover in the winter, and 40-80% open sky exposure.

  • Thumbnail for Community Interactions between Two Monkeyflowers and their Pollinators in Mt. Rainier National Park: Mimulus guttatus and Mimulus tilingii
    Community Interactions between Two Monkeyflowers and their Pollinators in Mt. Rainier National Park: Mimulus guttatus and Mimulus tilingii by Sebastian, Laurel Taylor

    Community interactions form the foundation of ecosystems, but their complexity makes predicting species responses to new pressures a difficult challenge. For example, if climate change forces the upward range shift of one species in a system, closely interacting species will either suffer or excel under the new community compositions. This study explores the interactions between two closely related monkeyflowers (Mimulus tilingii var. caespitosus and Mimulus guttatus) and their shared pollinators in order to understand potential responses to future climate changes or species loss. We arranged plants in three community composition treatments (heterospecific, conspecific, and no neighbors) to understand how plant fitness and pollinator visitation are affected by neighboring plants. Specifically, does plant fitness decrease due to pollen limitation or heterospecific pollen deposition under any community treatment? Furthermore, how does environmental data illustrate the system’s response to climate variation at different temporal scales? In our experiment, M. tilingii produced fewer seeds under the conspecific community composition and pollinator exclusion treatments (both p<.001), likely due to intraspecific resource competition and pollen-limitation. Rather than impeding plant fitness, it appears heterospecific interactions may actually stabilize M. tilingii populations. Plants and pollinators also responded positively to higher temperatures and lower cloud cover, indicating sensitivity to climate. Thus, changes in plant or pollinator species abundances, or climate could severely impact the dynamics or viability of the system.

  • Thumbnail for Effects of Wildfire on Soil Carbon Bioavailability in Forested Ecosystems of Colorado
    Effects of Wildfire on Soil Carbon Bioavailability in Forested Ecosystems of Colorado by Wolf, Kyra

    Given a trend of increasing wildfire frequency and intensity in the Western U.S., it is important to understand how the recovery and resilience of forest C stocks are impacted by severe fire. The purpose of this study was to look at how fire affected the size and relative bioavailability of soil C stocks, influencing rates of C mineralization. Study sites were in a montane Ponderosa Pine forest of Central Colorado and a subalpine Lodgepole Pine forest of Northern Colorado. I measured terrestrial C stocks and soil C bioavailability in plots burned in the 2002 Hayman and Hinman fires as well as undisturbed reference plots in each forest. Analyses included estimates of charcoal, aboveground biomass C, soil (top 10 cm) and water-extractable C and N. Soil incubation experiments were also conducted to measure the rate of microbial respiration per g soil C (a proxy for relative bioavailability). Total terrestrial C was ~53% lower in the montane ecosystem relative to the subalpine ecosystem, and >50% lower in burned plots relative to reference plots in both ecosystems. Soil C bioavailability did not vary with fire history in the subalpine forest, but was ~44% higher in burned plots in the montane forest. These results suggest that fire resulted in a significant reduction in terrestrial C storage. In addition, soil C bioavailability depended on plant regrowth. In the montane ecosystem, there were no tree seedlings in burned plots; as a result, C inputs to soil came primarily from grass and forb litter, which is more bioavailable than woody material. Comparatively rapid reestablishment of saplings in the subalpine forest meant that the quality of the soil C pool was similar in burned and undisturbed plots. Therefore, ecosystem response to wildfire differed with forest type, and lasting effects of wildfire on the quantity and bioavailability of soil C was determined by regrowth of trees.

  • Thumbnail for Neonicotinoids and Their Effects On Pollinators
    Neonicotinoids and Their Effects On Pollinators by Maurelli, Marissa Nicole

    Abstract Neonicotinoids are a unique class of insecticide used extensively in the agricultural industry. They were first introduced to the agrochemical industry in the early 1990’s. Since then, neonicotinoid use has grown almost exponentially due to their favorable qualities. The insecticide is effective because it acts as a neurotoxin that targets insect neuronal nicotinic acetylcholine receptors, which allows the chemical to be selectively lethal to insects. Scientists, farmers, and beekeepers have recently become concerned about pollinator exposure to neonicotinoids due to dramatic declines bee populations. Pollinators can be exposed to neonicotinoids through a variety of different pathways, including consumption of contaminated pollen and nectar. Scientific research suggests that neonicotinoid exposure can have both lethal and sublethal effects on pollinators. Pollinators provide a very important ecosystem service, yet they are constantly subject to risk through neonicotinoid exposure. This study examines the role of the Environmental Protection Agency in regulating potentially harmful pesticides and concludes with suggestions for amending the Federal Insecticide Rodenticide and Fungicide Act as well as for regulating neonicotinoids.

  • Thumbnail for Salmon in the Status Quo: Natural Resource Management Decisions &amp; Promoting System Resilience in the Columbia River Basin
    Salmon in the Status Quo: Natural Resource Management Decisions &amp; Promoting System Resilience in the Columbia River Basin by Criswell, Benjamin U

    If society accepts the status quo of salmon recovery and Federal Columbia River Power System operation in the Pacific Northwest, many populations of salmon will not survive into the 22nd century in sustainable, harvestable levels. Status quo management of the Columbia River–similar to past decades–gives priority to hydropower, irrigation, and navigation interests. It oversees earnest and well-funded salmon recovery efforts that amount to meager success. Its management structure is disjointed, juxtaposed with the interconnectedness of the Columbia River Basin’s ecology. Looking decades into the future, a timely combination of increased human population in the Pacific Northwest, a warmer climate, unfavorable ocean conditions, and an unaltered hydropower system will push salmon populations to minimal abundance, perhaps even to extinction. Yet it is entirely possible to design policies that would increase system resilience in the Columbia, and therefore decrease the likelihood of the grim fate mentioned above. These policies and management decisions must consider human resilience and ecological resilience alike, and should have a shared definition of success, with legal, regulatory, ecological, social, cultural, and economic dimensions.

  • Thumbnail for Size-Resolved Aerosol Composition near Rocky Mountain National Park
    Size-Resolved Aerosol Composition near Rocky Mountain National Park by Sussman, Rachel

    Increasing our understanding of aerosol properties is important because of their potential impacts on visibility, human health, and sensitive ecosystems. The Rocky Mountain Airborne Nitrogen and Sulfur (RoMANS) study was conducted in 2006 to identify the sources, transport, and speciation of atmospheric gases and aerosols throughout Colorado that influence Rocky Mountain National Park (RMNP). As one component of this study, Micro-Orifice Uniform Deposition Impactor (MOUDI) samples were collected at two sites in the vicinity of RMNP. Samples were taken over a time span of 48 hours each during a period of 36 days in the spring (March-April) and summer (July-August). The samples were analyzed by ion chromatography to determine the concentrations of NH4+, Na+, Ca2+, K+, Mg2+, Cl-, NO2-, NO3-, SO42-, and C2O42- in either ten or twelve different size bins from >18 μm to <0.18 μm. The diameter of nitrate has important implications for nitrogen deposition in RMNP as larger particles have a higher deposition velocity. In the spring, nitrate was observed to be mainly in the accumulation mode while in the summer it was primarily in the coarse mode. Ammonium and sulfate were the dominant species in the accumulation mode and on several days the sulfate was sufficient to completely neutralize ammonium. However, there were a substantial number of days where the addition of nitrate and oxalate to the ammonium neutralization was not enough to account for complete neutralization. The excess ammonium suggests that other organic acids may be an important component of the aerosol in the region. There is a dearth of research on the size distribution and secondary formation pathways of organic acids, such as aerosol oxalate, which might be contributing to haze and acting as cloud condensation nuclei. The size distribution of oxalate was found to peak in the accumulation mode, specifically between 0.32 and 0.56 μm. We examined three potential contributors to oxalate concentrations: biomass burning, in-cloud processes, and gas-phase photo-oxidation. All three were found to be likely emission and formation mechanisms, but it is unclear which pathway is dominant.

  • Thumbnail for The Cow in the Room: Regulating the Environmental Harms of Industrial Animal Agriculture
    The Cow in the Room: Regulating the Environmental Harms of Industrial Animal Agriculture by Palko, Gabriella

    Despite being the largest US methane emitter, the main source of water pollution, the driving force behind species extinction and habitat loss, and an intensive natural resource user, animal agriculture is scantily regulated and almost never considered as an option for combating climate change. This thesis seeks to provide a comprehensive analysis of the widespread environmental harms of the meat industry to demonstrate why it must be controlled. The historic 2015 Paris Agreement provides a framework for policy makers to address several ecological and climate threats, and regulating animal agriculture falls directly in line with the provisions put forth in the agreement. In order for the US to uphold their emissions reductions commitment and duties under the Paris agreement, industrial animal agriculture must be addressed. Current policies are examined as either hindrances or tools for controlling the detrimental impacts of the industry, followed by recommendations for policy vehicles and outlets to regulate the widespread degradation from industrial animal agriculture. If the earth is to avoid catastrophic climate change and ecological collapse, the cow in the room must be addressed.

  • Thumbnail for Unlocking an Abrupt Tree Line: A Synthesis of Micrometeorology and Vegetative Response
    Unlocking an Abrupt Tree Line: A Synthesis of Micrometeorology and Vegetative Response by Neumeyer, Eric Robert

    The advancement of global tree lines in response to climate change has raised questions among researchers about tree recruitment at elevations beyond tree line. This study aims to help understand this process by examining the progression of an abrupt tree line of engelmann spruce on the western slope of Pikes Peak, in Colorado Springs, Colorado. Methodology for this study includes drone photography, GIS mapping, dendrochronology, tree growth measurements, and soil moisture measurements. The results of our examination suggest that the three main mechanisms controlling advancement at our tree line include a leeward eddy when upslope winds interact with the tree line like a shelterbelt, a spiral eddy when winds are parallel to tree line, and cold air damming of katabatic winds against the tree line at night. Our examination of the vegetative response of trees at our tree line suggests that the most healthy recruitment is occurring on the southern edge of our transect and at the upper extent of the area expected to be protected by the tree line. We have found that trees and limbs that exist within the cold air dam at tree line have experienced decreased growth compared to trees outside of this layer of cold air.