Matching Items (34)
Description
In 2010, a monthly sampling regimen was established to examine ecological differences in Saguaro Lake and Lake Pleasant, two Central Arizona reservoirs. Lake Pleasant is relatively deep and clear, while Saguaro Lake is relatively shallow and turbid. Preliminary results indicated that phytoplankton biomass was greater by an order of magnitude in Saguaro Lake, and that community structure differed. The purpose of this investigation was to determine why the reservoirs are different, and focused on physical characteristics of the water column, nutrient concentration, community structure of phytoplankton and zooplankton, and trophic cascades induced by fish populations. I formulated the following hypotheses: 1) Top-down control varies between the two reservoirs. The presence of piscivore fish in Lake Pleasant results in high grazer and low primary producer biomass through trophic cascades. Conversely, Saguaro Lake is controlled from the bottom-up. This hypothesis was tested through monthly analysis of zooplankton and phytoplankton communities in each reservoir. Analyses of the nutritional value of phytoplankton and DNA based molecular prey preference of zooplankton provided insight on trophic interactions between phytoplankton and zooplankton. Data from the Arizona Game and Fish Department (AZGFD) provided information on the fish communities of the two reservoirs. 2) Nutrient loads differ for each reservoir. Greater nutrient concentrations yield greater primary producer biomass; I hypothesize that Saguaro Lake is more eutrophic, while Lake Pleasant is more oligotrophic. Lake Pleasant had a larger zooplankton abundance and biomass, a larger piscivore fish community, and smaller phytoplankton abundance compared to Saguaro Lake. Thus, I conclude that Lake Pleasant was controlled top-down by the large piscivore fish population and Saguaro Lake was controlled from the bottom-up by the nutrient load in the reservoir. Hypothesis 2 stated that Saguaro Lake contains more nutrients than Lake Pleasant. However, Lake Pleasant had higher concentrations of dissolved nitrogen and phosphorus than Saguaro Lake. Additionally, an extended period of low dissolved N:P ratios in Saguaro Lake indicated N limitation, favoring dominance of N-fixing filamentous cyanobacteria in the phytoplankton community in that reservoir.
ContributorsSawyer, Tyler R (Author) / Neuer, Susanne (Thesis advisor) / Childers, Daniel L. (Committee member) / Sommerfeld, Milton (Committee member) / Arizona State University (Publisher)
Created2011
Description
Sinaloa, a coastal state in the northwest of Mexico, is known for irrigated conventional agriculture, and is considered one of the greatest successes of the Green Revolution. With the neoliberal reforms of the 1990s, Sinaloa farmers shifted out of conventional wheat, soy, cotton, and other commodities and into white maize, a major food staple in Mexico that is traditionally produced by millions of small-scale farmers. Sinaloa is now a major contributor to the national food supply, producing 26% of total domestic white maize production. Research on Sinaloa's maize has focused on economic and agronomic components. Little attention, however, has been given to the environmental sustainability of Sinaloa's expansion in maize. With uniquely biodiverse coastal and terrestrial ecosystems that support economic activities such as fishing and tourism, the environmental consequences of agriculture in Sinaloa are important to monitor. Agricultural sustainability assessments have largely focused on alternative agricultural approaches, or espouse alternative philosophies that are biased against conventional production. Conventional agriculture, however, provides a significant portion of the world's calories. In addition, incentives such as federal subsidies and other institutions complicate transitions to alternative modes of production. To meet the agricultural sustainability goals of food production and environmental stewardship, we must put conventional agriculture on a more sustainable path. One step toward achieving this is structuring agricultural sustainability assessments around achievable goals that encourage continual adaptations toward sustainability. I attempted this in my thesis by assessing conventional maize production in Sinaloa at the regional/state scale using network analysis and incorporating stakeholder values through a multicriteria decision analysis approach. The analysis showed that the overall sustainability of Sinaloa maize production is far from an ideal state. I made recommendations on how to improve the sustainability of maize production, and how to better monitor the sustainability of agriculture in Sinaloa.
ContributorsBausch, Julia Christine (Author) / Eakin, Hallie (Thesis advisor) / Bojórquez-Tapia, Luis (Committee member) / Childers, Daniel L. (Committee member) / Arizona State University (Publisher)
Created2011
Description
Sustainability visioning (i.e. the construction of sustainable future states) is considered an important component of sustainability research, for instance, in transformational sustainability science or in planning for urban sustainability. Visioning frees sustainability research from the dominant focus on analyzing problem constellations and opens it towards positive contributions to social innovation and transformation. Calls are repeatedly made for visions that can guide us towards sustainable futures. Scattered across a broad range of fields (i.e. business, non-government organization, land-use management, natural resource management, sustainability science, urban and regional planning) are an abundance of visioning studies. However, among the few evaluative studies in the literature there are apparent deficits in both the research and practice of visioning that curtails our expectations and prospects of realizing process-based and product-derived outcomes. These deficits suggests that calls instead should focus on the development of applied and theoretical understanding of crafting sustainability visions, enhancing the rigor and robustness of visioning methodology, and on integrating practice, research, and education for collaborative sustainability visioning. From an analysis of prominent visioning and sustainability visioning studies in the literature, this dissertation articulates what is sustainability visioning and synthesizes a conceptual framework for criteria-based design and evaluation of sustainability visioning studies. While current visioning methodologies comply with some of these guidelines, none adhere to all of them. From this research, a novel sustainability visioning methodology is designed to address this gap to craft visions that are shared, systemic, principles-based, action-oriented, relevant, and creative (i.e. SPARC visioning methodology) and evaluated across all quality criteria. Empirical studies were conducted to test and apply the conceptual and methodological frameworks -- with an emphasis on enhancing the rigor and robustness in real world visioning processes for urban planning and teaching sustainability competencies. In-depth descriptions of the collaborative visioning studies demonstrate tangible outcomes for: (a) implementing the above sustainability visioning methodology, including evaluative procedures; (b) adopting meaningful interactive engagement procedures; (c) integrating advanced analytical modeling, sustainability appraisal, and creativity enhancing procedures; and (d) developing perspective and methodological capacity for long-range sustainability planning.
ContributorsIwaniec, David (Author) / Wiek, Arnim (Thesis advisor) / Childers, Daniel L. (Committee member) / Lant, Timothy (Committee member) / Arizona State University (Publisher)
Created2013
Description
Human activity has increased loading of reactive nitrogen (N) in the environment, with important and often deleterious impacts on biodiversity, climate, and human health. Since the fate of N in the ecosystem is mainly controlled by microorganisms, understanding the factors that shape microbial communities becomes relevant and urgent. In arid land soils, these microbial communities and factors are not well understood. I aimed to study the role of N cycling microbes, such as the ammonia-oxidizing bacteria (AOB), the recently discovered ammonia-oxidizing archaea (AOA), and various fungal groups, in soils of arid lands. I also tested if niche differentiation among microbial populations is a driver of differential biogeochemical outcomes. I found that N cycling microbial communities in arid lands are structured by environmental factors to a stronger degree than what is generally observed in mesic systems. For example, in biological soil crusts, temperature selected for AOA in warmer deserts and for AOB in colder deserts. Land-use change also affects niche differentiation, with fungi being the major agents of N2O production in natural arid lands, whereas emissions could be attributed to bacteria in mesic urban lawns. By contrast, NO3- production in the native desert and managed soils was mainly controlled by autotrophic microbes (i.e., AOB and AOA) rather than by heterotrophic fungi. I could also determine that AOA surprisingly responded positively to inorganic N availability in both short (one month) and long-term (seven years) experimental manipulations in an arid land soil, while environmental N enrichment in other ecosystem types is known to favor AOB over AOA. This work improves our predictions of ecosystem response to anthropogenic N increase and shows that paradigms derived from mesic systems are not always applicable to arid lands. My dissertation also highlights the unique ecology of ammonia oxidizers and draws attention to the importance of N cycling in desert soils.
ContributorsMarusenko, Yevgeniy (Author) / Hall, Sharon J (Thesis advisor) / Garcia-Pichel, Ferran (Thesis advisor) / Mclain, Jean E (Committee member) / Schwartz, Egbert (Committee member) / Arizona State University (Publisher)
Created2013
Description
Irrigation agriculture has been heralded as the solution to feeding the world's growing population. To this end, irrigation agriculture is both extensifying and intensifying in arid regions across the world in an effort to create highly productive agricultural systems. Over one third of modern irrigated fields, however, show signs of serious soil degradation, including salinization and waterlogging, which threaten the productivity of these fields and the world's food supply. Surprisingly, little ecological data on agricultural soils have been collected to understand and address these problems. How, then, can expanding and intensifying modern irrigation systems remain agriculturally productive for the long-term? Archaeological case studies can provide critical insight into how irrigated agricultural systems may be sustainable for hundreds, if not thousands, of years. Irrigation systems in Mesopotamia, for example, have been cited consistently as a cautionary tale of the relationship between mismanaged irrigation systems and the collapse of civilizations, but little data expressly link how and why irrigation failed in the past. This dissertation presents much needed ecological data from two different regions of the world - the Phoenix Basin in southern Arizona and the Pampa de Chaparrí on the north coast of Peru - to explore how agricultural soils were affected by long-term irrigation in a variety of social and economic contexts, including the longevity and intensification of irrigation agriculture. Data from soils in prehispanic and historic agricultural fields indicate that despite long-lived and intensive irrigation farming, farmers in both regions created strategies to sustain large populations with irrigation agriculture for hundreds of years. In the Phoenix Basin, Hohokam and O'odham farmers relied on sedimentation from irrigation water to add necessary fine sediments and nutrients to otherwise poor desert soils. Similarly, on the Pampa, farmers relied on sedimentation in localized contexts, but also constructed fields with ridges and furrows to draw detrimental salts away from planting surfaces in the furrows on onto the ridges. These case studies are then compared to failing modern and ancient irrigated systems across the world to understand how the centralization of management may affect the long-term sustainability of irrigation agriculture.
ContributorsStrawhacker, Colleen (Author) / Spielmann, Katherine A. (Thesis advisor) / Hall, Sharon J (Committee member) / Nelson, Margaret C. (Committee member) / Sandor, Jonathan A (Committee member) / Arizona State University (Publisher)
Created2013
Description
The study of son preference in India has been the focus of research for a few decades. The desire for sons leads to unfavorable consequences for daughters such as unequal access to resources, abortion, and female infanticide. Work on men's education and son preference is relatively scarce and this dissertation contributes to existing literature by exploring this relationship from a life course perspective. I have argued that education changes men's attitudes towards son preference by encouraging them to re-evaluate traditional gender roles and that this relationship is mediated by wealth. I use the National Family and Health Survey-III to examine fertility intentions and behaviors as measures of son preference. I have found support for some of my hypotheses. The findings from three studies walk through the different phases of reproduction for the Indian man. They show that son preference manifests itself at the beginning when there are no children, is strongly present after the birth of children, and then shows itself again at the end when the man wishes to stop childbearing. Being educated leads to the preference of sons being weaker and this is perhaps due to traditional gender roles being challenged. Wealth may mediate the relationship between men's education and son preference at the beginning, but does not act as a mediator once children are born.
ContributorsSabharwal, Rebha (Author) / Hayford, Sarah R. (Thesis advisor) / Agadjanian, Victor (Committee member) / Yabiku, Scott T (Committee member) / Arizona State University (Publisher)
Created2013
Description
Health-seeking behaviors are influenced by multiple factors including an assessment of the symptoms, what degree of personal commitment is involved in treatment, and what, if any, alternative methods of treatment are available. In the case of infertility, seeking treatment is likely to occur after the inability to get pregnant or carry a pregnancy to term persists for longer then a year or more. This is after prolonged exposure to the risk of pregnancy fails to provide a successful pregnancy, and the desire for children remains. Most research on health-seeking behaviors for infertility focus on the nulliparous woman who is at risk of primary infertility. This research furthers this examination by comparing the rates of health-seeking behaviors for women at risk of primary infertility to women at risk of secondary infertility. A woman at risk of primary infertility is identified as nulliparous in that she has never been pregnant, or has never had a pregnancy end in live birth. A woman at risk of secondary infertility is identified as parous and has already had one pregnancy end in live birth. Using three pathways that include social factors, biological mechanisms, and contextual effects, I hypothesize that the rates of health-seeking behaviors will vary by infertility risk and that women at risk of primary infertility will have higher rates of health-seeking behaviors for infertility. These hypotheses are based on the Behavioral Model of Health Services Utilization and the Health Belief Model that states health-seeking behaviors are influenced by the presence of enabling and predisposing factors, combined with internal and external cues. Findings from this dissertation suggest that the rates of health-seeking behaviors do indeed vary by infertility risk.
ContributorsWeller, Nicole Maki (Author) / Yabiku, Scott T (Thesis advisor) / Hayford, Sarah (Committee member) / Kronenfeld, Jennie (Committee member) / Arizona State University (Publisher)
Created2012
Description
Urban sustainability is a critical component of sustainable human societies. Urban riparian parks are used here as a case study seeking to understand the social-ecological relationships between the subjective evaluation of ecosystem services and the vision and management of one kind of green infrastructure. This study explored attitudes towards ecosystem services, asking whether 1) the tripartite model is an effective framing to measure attitudes towards ecosystem services; 2) what the attitudes towards ecosystem services are and whether they differ between two types of park space; and 3) what the relationship is between management and the attitudinal assessment of ecosystem services by park users. A questionnaire was administered to 104 urban riparian park users in Phoenix, AZ evaluating their attitudes towards refugia, aesthetics, microclimate and stormwater regulation, and recreational and educational opportunities. The operationalization of the tripartite model was validated and found reliable, but may not be the whole story in determining attitudes towards ecosystem services. All components of attitude were positive, but attitudes were stronger in a habitat rehabilitation area with densely planted native species and low flows, than in a more classic park with mowed lawns and scattered vegetation, a mix of native and non-native species, and open water. Park users were more positive towards refugia, stormwater regulation, recreation, and educational opportunities in the habitat rehabilitation area. On the other hand, microclimate regulation and aesthetic qualities were valued similarly between the two parks. Most attitudes supported management goals, however park users valued stormwater regulation less than managers. Qualitative answers suggest that the quality of human interactions differ between the parks and park users consider both elements of society and the physical environment in their subjective evaluations. These findings reveal that park users highly value ecosystem services and that park design and management mediates social-ecological relationships, which should at least underlie the context of economic discussions of service value. This study supports the provision of ecosystem services through green infrastructure and suggests that an integration of park designs throughout urban areas could provide both necessary services as well as expand the platform for social-ecological interactions.
ContributorsWilson, Lea Ione (Author) / Childers, Daniel L. (Thesis advisor) / Larson, Kelli L. (Committee member) / Stromberg, Juliet (Committee member) / Arizona State University (Publisher)
Created2012
Description
The global transport and deposition of anthropogenic nitrogen (N) to downwind ecosystems are significant and continue to increase. Indeed, atmospheric deposition can be a significant source of N to many watersheds, including those in remote, unpopulated areas. Bacterial denitrification in lake sediments may ameliorate the effects of N loading by converting nitrate (NO3-) to N2 gas. Denitrification also produces nitrous oxide (N2O), a potent greenhouse gas. The ecological effects of atmospheric N inputs in terrestrial ecosystems and the pelagic zone of lakes have been well documented; however, similar research in lake sediments is lacking. This project investigates the effects N of deposition on denitrification and N2O production in lakes. Atmospheric N inputs might alter the availability of NO3- and other key resources to denitrifiers. Such altered resources could influence denitrification, N2O production, and the abundance of denitrifying bacteria in sediments. The research contrasts these responses in lakes at the ends of gradients of N deposition in Colorado and Norway. Rates of denitrification and N2O production were elevated in the sediments of lakes subject to anthropogenic N inputs. There was no evidence, however, that N deposition has altered sediment resources or the abundance of denitrifiers. Further investigation into the dynamics of nitric oxide, N2O, and N2 during denitrification found no difference between deposition regions. Regardless of atmospheric N inputs, sediments from lakes in both Norway and Colorado possess considerable capacity to remove NO3- by denitrification. Catchment-specific properties may influence the denitrifying community more strongly than the rate of atmospheric N loading. In this regard, sediments appear to be insulated from the effects of N deposition compared to the water column. Lastly, surface water N2O concentrations were greater in high-deposition lakes compared to low-deposition lakes. To understand the potential magnitude of deposition-induced N2O production, the greenhouse gas inventory methodology of Intergovernmental Panel on Climate Change was applied to available datasets. Estimated emissions from lakes are 7-371 Gg N y-1, suggesting that lakes could be an important source of N2O.
ContributorsMcCrackin, Michelle Lynn (Author) / Elser, James J (Thesis advisor) / Grimm, Nancy (Committee member) / Hall, Sharon J (Committee member) / Hartnett, Hilairy E (Committee member) / Souza, Valeria (Committee member) / Arizona State University (Publisher)
Created2010
Description
This thesis explores the independent effects of the manipulation of rocks into alignments, prehistoric farming, and season on soil properties in two areas with a history of prehistoric agriculture in central Arizona, Pueblo la Plata within the Agua Fria National Monument (AFNM), and an archaeological site north of the Phoenix basin along Cave Creek (CC). Soil properties, annual herbaceous biomass and the physical properties of alignments and surface soils were measured and compared across the landscape, specifically on: 1) agricultural rock alignments that were near the archaeological site 2) geologically formed rock alignments that were located 0.5-1 km away from settlements; and 3) areas both near and far from settlements where rock alignments were absent. At AFNM, relatively well-built rock alignments have altered soil properties and processes while less-intact alignments at CC have left few legacies.
ContributorsTrujillo, Jolene Eve (Author) / Hall, Sharon J (Thesis advisor) / Collins, Scott L. (Committee member) / Spielmann, Katherine A. (Committee member) / Arizona State University (Publisher)
Created2011