Mountain Scholar

Mountain Scholar is an open access repository service that collects, preserves, and provides access to digitized library collections and other scholarly and creative works from Colorado State University and the University Press of Colorado. It also serves as a dark archive for the Open Textbook Library.

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Colorado State University, Fort Collins 29052
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Open Textbook Library Archive 1866
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University Press of Colorado 1106
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Recent Submissions

Access status: Open Access ,
Spatial and temporal variation of disturbance: effects on riparian and aquatic communities along two headwater streams in Puerto Rico
(2000) Henry, Julie Kay, author; Covich, Alan P., advisor; Kondratieff, Boris C., committee member; Laituri, Melinda J., committee member
The structure and composition of tropical ecosystems are often shaped by disturbance events, especially in areas that experience hurricanes and other severe storms. The structure of riparian forests along headwater streams in the Luquillo Long Term Ecological Research Site of Puerto Rico reflects the patchiness of periodic hurricane disturbance as well as the spatial pattern of past human land use. The result of these disturbance patterns is a clumped distribution of the dominant riparian tree species (the Sierra palm, Prestoea montana) within and between riparian forests along two headwater streams, Quebrada Prieta and Quebrada Toronja. Fruit-fall and frond input from the Sierra palm is an important source of food and refuge for stream consumers. Patchiness of palm fruit and frond availability may have important effects on the distribution patterns and relative abundance of consumers in headwater stream communities. I studied the effects of disturbance from Hurricane Georges on a dominant riparian tree species in the Luquillo Forest Dynamics Plot of the Luquillo Long Term Ecological Research Site in northeastern Puerto Rico. I established 300 m by 10 m riparian transects along the Prieta and Toronja, which were both dominated by the Sierra palm (Prestoea montana). Following Hurricane Georges, I periodically surveyed Sierra palm individuals for damage and subsequent recovery (measured by initial loss and subsequent regrowth of palm fronds), palm height, and reproductive status. I used Geographic Information System (GIS) data to determine variation in riparian topography (elevation, slope, and aspect) and tree densities within riparian transects. I analyzed logistic regression models to determine the influence of riparian topography, tree density, and palm height on spatial patterns of palm damage and recovery due to Hurricane Georges. Palm height was the factor most related to initial hurricane damage to palms, with tall canopy palms receiving the most damage. Post-hurricane palm recovery was also related to wind exposure, measured by higher elevation of riparian transects and lower surrounding tree densities. A larger proportion of palms were damaged along the Toronja (33%) than the Prieta (25%), which may be a result of historical human disturbance in the Toronja basin which led to a shift in forest species composition. Large canopy palms constitute a greater proportion of the riparian forest along the Toronja than the Prieta, and so had a greater proportion of palms that were exposed to stronger hurricane winds. These spatial patterns of hurricane damage to riparian forests often affect detrital input to stream pools, which can influence distribution patterns and relative abundance of stream consumers. Stream communities in the Luquillo Mountains of Puerto Rico support several species of omnivorous freshwater decapods. One of the most abundant predatory decapods is the freshwater crab, Epilobocera sinuatifrons. I studied habitat selection of freshwater crabs in stream pools within the same 300 m riparian transects along the Prieta and the Toronja. Nine study pools were established along each stream transect, and were periodically sampled for juvenile crabs, mayfly nymphs, and physical and substrate characteristics. Juvenile crabs and mayfly nymphs were abundant in all pools, but both showed higher numbers along the Prieta. Because the land use history in the Toronja drainage has resulted in a less stable channel and increased abundance of fine sediment in Toronja pools, the more stable pools along the Prieta may retain more leaf litter and provide better pool habitats for juvenile crabs. Temporal variation and within-pool habitat variables (substrate composition, pool depth, flow velocity, and heterogeneity of pool width) were best at explaining variations in juvenile crab distributions. To determine food web relationships of juvenile crabs within the stream community, I studied predation rates of juvenile crabs on mayfly nymphs, larval shrimp, and conditioned leaf disks collected from leaf packs within stream pools. Pools were apparently dominated by one mayfly species, Farrodes taino (Ephemeroptera: Leptophlebiidae). Feeding experiments demonstrated mayfly nymphs to be the preferred food source for juvenile crabs (8 mm to 18 mm carapace width), with feeding rates increasing with crab size. The observed predation rates were relatively high, ranging from 2 to 72 mayfly nymphs per crab per night. These feeding experiments suggest that aquatic insects may be an important source of protein for juvenile crab growth, and high aquatic insect predation rates by juvenile crabs may influence the low relative abundance of aquatic insects found in these two insular tropical streams. In summary, detrital inputs are an important source of food, cover, and substrate for aquatic communities in tropical headwater streams. Spatial patterns of riparian palm damage influence the spatial distribution of detrital inputs across a watershed, in tum affecting distributions and relative abundance of stream consumers. The magnitude and frequency of disturbance, such as hurricanes or high rainfall events, influence the standing stock of detritus in stream pools, the availability of refuge, and the stability of the stream environment.
Access status: Open Access ,
Fetal liver-derived CD34+, KDR+ hematopoietic stem cells: gene transduction with an HIV-based lentiviral vector
(2001) Nasuti, Jacki M., author; Pearson, Leonard D., advisor; Akkina, Ramesh, advisor; Chang, Jeffery, committee member
Gene therapy is a potentially attractive option for treatment of HIV infection as well as for many hematopoietic disorders. To realize this goal, it is critical that hematopoietic stem cells with the highest self-renewal capacity and long-term engraftment capabilities be utilized as cell targets for therapeutic gene transfer. Previous studies have sought to identify the most primitive hematopoietic cells from sources such as umbilical cord blood (UCB), bone marrow (BM), peripheral blood (PB), and mobilized peripheral blood (MPB). As the fetal liver is the major site of hematopoiesis during embryogenesis, it is likely that a significant number of primitive hematopoietic cells exist in this site. Present studies have sought to identify primitive KOR-expressing CD34 stem cells in human fetal liver using direct mAb staining and to isolate these cells by FACS. Results have shown that approximately 1% of CD34+ cells isolated from 16-23 gestational-week old human fetal livers were positive for the KDR marker. This represents a significantly higher proportion compared to the level of 0.1-0.5% CD34, KDR double positive cells that has been found in other sources (UCB, PB, MPB, BM). It was previously shown that stem cells retain long-term hematopoiesis when cultured in the presence of mesenchymal stem cell (MSC) stromal cell layers. Accordingly, the fetal liver derived CD34+/KDR+ stem cells were cultured in the presence of MSC. This has allowed maintenance of a very small numbers ofCD34+/KDR+ cells (1000 cells) in culture and subsequently expand them to 100-fold. These findings provide a means of maintaining low numbers ofCD34+/KDR+ cells and expanding them to a working population for future experimentation. In vitro maintained CD34+/KDR+ cells were subjected to gene transduction with an HIV-1 based lentiviral vector. Although MSC did not serve to significantly increase transduction efficiencies of CD34+/KDR- progenitors, the progenitors cultured in the presence of MSC were relatively more refractory to the apparent toxicity effects of high-titer lentiviral vector exposure. In comparative studies, it was found that the transducibility of CD34+/KDR+ primitive hematopoietic cells is equivalent to that of CD34+/KDR- progenitors (approximately 86% EGFP expression as analyzed by FACS). Results presented here demonstrate the existence of CD34+, KDR+ cells in fetal liver at significantly higher levels than other sources. These cells could possibly serve as key cell targets for achieving sustained gene transduction with lentiviral vectors for current AIDS gene therapy strategies.
Access status: Open Access ,
Amazonian conservation across archipelagos of Indigenous territories
(2024-10-22) Esbach, Michael S., author; Correia, Joel E., author; Valdivia, Gabriela, author; Lu, Flora, author; Wiley Periodicals LLC, publisher
Indigenous stewardship is essential to the conservation of biocultural diversity, yet conventional conservation models often treat Indigenous territories (ITs) as homogeneous or isolated units. We propose that archipelagos of Indigenous territories (AITs), clusters of ITs that span geographies but are connected through shared cultural or political ties maintained by Indigenous nations, are crucial for understanding and enhancing conservation strategies that recognize the complexity of Indigenous stewardship. We classified 3572 ITs in the Amazon into 4 categories—single or multiple nations with either singular IT or AIT—to assess their spatial heterogeneity, governance, and conservation potential. We then assessed species richness, carbon stocks, and pressures across these different categories. To examine how AITs can enhance biocultural conservation efforts, we conducted a case study of the Cofán Nation in Ecuador. AITs covered 45% of the Amazonian land area and had higher species richness and carbon stocks than single IT configurations. However, AITs faced greater pressures from development and extractive activities. In the case study, the Cofán AIT was shaped by colonization and land titling challenges, but their community-driven governance, cross-territorial collaboration, and adaptive responses—such as comanagement agreements and resisting extractive activities—enhanced their ecological and cultural resilience amid growing development pressures. Our findings suggest that AITs facilitate the exchange of resources, knowledge, and cultural practices, which strengthens social connectivity, reinforces governance structures, and enables adaptive management across ITs, thereby enhancing biocultural resilience across discontinuous spaces. This work advocates for a paradigm shift in conservation planning and practice that recognizes the vital role of AITs in sustaining Amazonian ecosystems and Indigenous lifeways, particularly in the face of increasing pressures.
Access status: Open Access ,
Haze, heat, and human bonds: a mixed methods study of attachment's influence on risk information behavior among outdoor workers facing air quality and extreme heat hazards
(2026) Bice, Channing, author; Long, Marilee, advisor; Abrams, Katie, committee member; Anderson, Ashley, committee member; MacPhee, David, committee member; Most, David, committee member
Outdoor workers face disproportionate exposure to compound environmental hazards on the job, yet little is known about the factors that shape how they seek and process relevant risk information. This dissertation investigates these factors by integrating attachment theory into the risk information seeking and processing (RISP) model to examine how attachment anxiety and attachment avoidance influence outdoor workers' risk information seeking behaviors related to extreme heat and poor air quality. Using an explanatory sequential mixed-methods design, the study first employed a national online survey (N = 220) of outdoor workers across the United States, followed by focus groups (N = 29) with municipal outdoor workers in Fort Collins, Colorado. Quantitative results from a series of hierarchical regressions and mediation analyses indicated that attachment orientations shaped key RISP model variables, though the strength and significance of these relationships varied by hazard. Specifically, attachment avoidance predicted reduced risk perception, negative affective response, and informational subjective norms in the extreme heat context, while attachment anxiety predicted increased negative affective response and informational subjective norms for extreme heat. Neither attachment anxiety nor attachment avoidance predicted information insufficiency, attitudes toward information seeking, or perceived information seeking control across either hazard. Core RISP model pathways were broadly supported across both hazard contexts. Qualitative findings yielded five key themes that expanded on and contextualized the quantitative results. First, workers perceived extreme heat as a more urgent and physically threatening hazard than air quality, which they often normalized or noticed only when symptoms became intolerable. Second, information seeking was shaped by peer behavior, supervisor guidance, and workplace norms; workers higher in attachment anxiety exhibited heightened sensitivity to social cues, while those higher in attachment avoidance tended to minimize risk and emphasize self-sufficiency. Third, workers expressed uncertainty about translating hazard indices, particularly the air quality index, into task-relevant decisions. Fourth, workers preferred task-specific information well in advance of hazard events to better plan protective actions into work schedules. Finally, workers expressed strong support for integrating air quality and heat information into a unified communication system to streamline workplace decision-making. Integration of the two phases confirmed that extreme heat functions as a more powerful motivational driver than poor air quality across emotional, social, and behavioral pathways, and expands our understanding of how differences in workers' motivational responses to each hazard can be put to work through integrated communication systems that use heat engagement as an entry point for air quality awareness. Overall, these findings make theoretical contributions by demonstrating that attachment orientation functions as a meaningful individual difference variable within the RISP model by influencing risk perception, affective response, and informational subjective norms, particularly for risks perceived as immediate and salient. These findings also challenge traditional distinctions between active and passive information seeking. Practically, the findings call for risk communication strategies that are emotionally and socially attuned, task-relevant, and reconsider vulnerable population message framing. Future research should continue to examine attachment effects on risk information seeking and avoidance across additional hazard contexts and among more diverse populations.
Access status: Open Access ,
Timing is everything: investigating users' feedback timing and content preferences to enhance computer-based training
(2026) Pharmer, Rebecca L., author; Rhodes, Matthew G., advisor; Wickens, Christopher D., committee member; Nelson, Niccole A., committee member; Ortega, Francisco R., committee member
Feedback is a central instructional component of computerized training systems. Research has shown that the timing and content of feedback impacts learning but less is currently known about how user preferences for the way feedback is received during training impacts its overall effectiveness. Across three experiments, this work examined whether users demonstrate a preference for the timing of feedback they receive (Experiment 1), whether honoring that preference improves their learning outcomes (Experiment 2), and whether honoring learner preferences for the content within their feedback (i.e., whether it is outcome based or explanatory) likewise impacts learning outcomes (Experiment 3). Across experiments, learners consistently preferred immediate over delayed feedback and explanatory over outcome feedback. However, aligning feedback with these preferences did not reliably improve learning outcomes and, in some cases, non-preferred conditions produced equal or better learning performance. Preference alignment more consistently influenced subjective experience, with differences in perceived mental workload, frustration, and performance despite similar objective outcomes. Overall, the results suggest that stable learner preferences do not reliably predict which feedback conditions best support learning. Instead, learning depends more on feedback design than preference matching.