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- Genre: Doctoral Dissertation
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
The explicit role of soil organisms in shaping soil health, rates of pedogenesis, and resistance to erosion has only just recently begun to be explored in the last century. However, much of the research regarding soil biota and soil processes is centered on maintaining soil fertility (e.g., plant nutrient availability) and soil structure in mesic- and agro- ecosystems. Despite the empirical and theoretical strides made in soil ecology over the last few decades, questions regarding ecosystem function and soil processes remain, especially for arid areas. Arid areas have unique ecosystem biogeochemistry, decomposition processes, and soil microbial responses to moisture inputs that deviate from predictions derived using data generated in more mesic systems. For example, current paradigm predicts that soil microbes will respond positively to increasing moisture inputs in a water-limited environment, yet data collected in arid regions are not congruent with this hypothesis. The influence of abiotic factors on litter decomposition rates (e.g., photodegradation), litter quality and availability, soil moisture pulse size, and resulting feedbacks on detrital food web structure must be explicitly considered for advancing our understanding of arid land ecology. However, empirical data coupling arid belowground food webs and ecosystem processes are lacking. My dissertation explores the resource controls (soil organic matter and soil moisture) on food web network structure, size, and presence/absence of expected belowground trophic groups across a variety of sites in Arizona.
ContributorsWyant, Karl Arthur (Author) / Sabo, John L (Thesis advisor) / Elser, James J (Committee member) / Childers, Daniel L. (Committee member) / Hall, Sharon J (Committee member) / Stromberg, Juliet C. (Committee member) / Arizona State University (Publisher)
Created2014
Description
Despite the breadth of studies investigating ecosystem development, an underlying theory guiding this process remains elusive. Several principles have been proposed to explain ecosystem development, though few have garnered broad support in the literature. I used boreal wetland soils as a study system to test a notable goal oriented principle: The Maximum Power Principle (MPP). The MPP posits that ecosystems, and in fact all energy systems, develop to maximize power production or the rate of energy production. I conducted theoretical and empirical investigations to test the MPP in northern wetlands.
Permafrost degradation is leading to rapid wetland formation in northern peatland ecosystems, altering the role of these ecosystems in the global carbon cycle. I reviewed the literature on the history of the MPP theory, including tracing its origins to The Second Law of Thermodynamics. To empirically test the MPP, I collected soils along a gradient of ecosystem development and: 1) quantified the rate of adenosine triphosphate (ATP) production--literally cellular energy--to test the MPP; 2) quantified greenhouse gas production (CO2, CH4, and N2O) and microbial genes that produce enzymes catalyzing greenhouse gas production, and; 3) sequenced the 16s rRNA gene from soil microbes to investigate microbial community composition across the chronosequence of wetland development. My results suggested that the MPP and other related theoretical constructs have strong potential to further inform our understanding of ecosystem development. Soil system power (ATP) decreased temporarily as the ecosystem reorganized after disturbance to rates of power production that approached pre-disturbance levels. Rates of CH4 and N2O production were higher at the newly formed bog and microbial genes involved with greenhouse gas production were strongly related to the amount of greenhouse gas produced. DNA sequencing results showed that across the chronosequence of development, the two relatively mature ecosystems--the peatland forest ecosystem prior to permafrost degradation and the oldest bog--were more similar to one another than to the intermediate, less mature bog. Collectively, my results suggest that ecosystem age, rather than ecosystem state, was a more important driver for ecosystem structure and function.
Permafrost degradation is leading to rapid wetland formation in northern peatland ecosystems, altering the role of these ecosystems in the global carbon cycle. I reviewed the literature on the history of the MPP theory, including tracing its origins to The Second Law of Thermodynamics. To empirically test the MPP, I collected soils along a gradient of ecosystem development and: 1) quantified the rate of adenosine triphosphate (ATP) production--literally cellular energy--to test the MPP; 2) quantified greenhouse gas production (CO2, CH4, and N2O) and microbial genes that produce enzymes catalyzing greenhouse gas production, and; 3) sequenced the 16s rRNA gene from soil microbes to investigate microbial community composition across the chronosequence of wetland development. My results suggested that the MPP and other related theoretical constructs have strong potential to further inform our understanding of ecosystem development. Soil system power (ATP) decreased temporarily as the ecosystem reorganized after disturbance to rates of power production that approached pre-disturbance levels. Rates of CH4 and N2O production were higher at the newly formed bog and microbial genes involved with greenhouse gas production were strongly related to the amount of greenhouse gas produced. DNA sequencing results showed that across the chronosequence of development, the two relatively mature ecosystems--the peatland forest ecosystem prior to permafrost degradation and the oldest bog--were more similar to one another than to the intermediate, less mature bog. Collectively, my results suggest that ecosystem age, rather than ecosystem state, was a more important driver for ecosystem structure and function.
ContributorsChapman, Eric (Author) / Childers, Daniel L. (Thesis advisor) / Cadillo-Quiroz, Hinsby (Committee member) / Hall, Sharon J (Committee member) / Turetsky, Merritt (Committee member) / Arizona State University (Publisher)
Created2015
Description
Humans have dramatically increased phosphorus (P) availability in terrestrial and aquatic ecosystems. As P is often a limiting nutrient of primary production, changes in its availability can have dramatic effects on ecosystem processes. I examined the effects of calcium carbonate (CaCO3) deposition, which can lower P concentrations via coprecipitation of phosphate, on P availability in two systems: streams in the Huachuca Mountains, Arizona, and a stream, Río Mesquites, in Cuatro Ciénegas, México. Calcium carbonate forms as travertine in the former and within the microbialites of the latter. Despite these differences, CaCO3 deposition led to lowered P availability in both systems. By analyzing a three-year dataset of water chemistry from the Huachuca Mountain streams, I determined that P concentrations were negatively related to CaCO3 deposition rates. I also discovered that CaCO3 was positively correlated with nitrogen concentrations, suggesting that the stoichiometric effect of CaCO3 deposition on nutrient availability is due not only to coprecipitation of phosphate, but also to P-related constraints on biotic nitrogen uptake. Building from these observations, bioassays of nutrient limitation of periphyton growth suggest that P limitation is more prevalent in streams with active CaCO3 deposition than those without. Furthermore, when I experimentally reduced rates of CaCO3 deposition within one of the streams by partial light-exclusion, areal P uptake lengths decreased, periphyton P content and growth increased, and periphyton nutrient limitation by P decreased. In Río Mesquites, CaCO3 deposition was also associated with P limitation of microbial growth. There, I investigated the consequences of reductions in CaCO3 deposition with several methods. Calcium removal led to increased concentrations of P in the microbial biomass while light reductions decreased microbial biomass and chemical inhibition had no effect. These results suggest that CaCO3 deposition in microbialites does limit biological uptake of P, that photoautotrophs play an important role in nutrient acquisition, and, combined with other experimental observations, that sulfate reduction may support CaCO3 deposition in the microbialite communities of Río Mesquites. Overall, my results suggest that the effects of CaCO3 deposition on P availability are general and this process should be considered when managing nutrient flows across aquatic ecosystems.
ContributorsCorman, Jessica R. (Author) / Elser, James J (Thesis advisor) / Anbar, Ariel D (Committee member) / Childers, Daniel L. (Committee member) / Grimm, Nancy (Committee member) / Souza, Valeria (Committee member) / Arizona State University (Publisher)
Created2015
Description
Landscape restoration is a global priority as evidenced by the United Nations’ 2020 goal to restore 150 million hectares of land worldwide. Restoration is particularly needed in estuaries and their watersheds as society depends on these environments for numerous benefits. Estuary restoration is often undermined by social-ecological scale mismatch, the incongruence between governing units and the bio-physical resources they seek to govern. Despite growing recognition of this fact, few empirical studies focus on scale mismatches in environmental restoration work. Using a sub-basin of Puget Sound, Washington, U.S.A., I analyze scale mismatches in estuary restoration. I take a network science approach because governance networks can bridge scale mismatches. I combine quantitative social network analysis (SNA), geographic information systems (GIS), and qualitative interview analysis.
Spatial network analysis reveals several areas with weak scale mismatch bridging networks. These weak social networks are then compared to ecological restoration needs to identify coupled social-ecological restoration concerns. Subsequent study investigates jurisdictional and sectoral network integration because governance siloes contribute to scale mismatch. While the network is fairly well integrated, several sectors do not interact or interact very little. An analysis of collaboration reasons disentangles the idea of generic collaboration. Among three relationship types considered, mandated relationships contribute almost 5.5 times less to perceived collaboration productivity than shared interest relationships, highlighting the benefits of true collaborations in watershed governance. Lastly, the effects of scale mismatch on individual restoration projects and landscape level restoration planning are assessed through qualitative interview analysis. Results illustrate why human-environment processes should be included in landscape restoration planning. Social factors are not considered as constraints to restoration but rather part of the very landscape fabric to be restored. Scale mismatch is conceptualized as a complex social-ecological landscape pattern that affects the flow of financial, human, and natural capital across the landscape. This represents a new way of thinking about scale mismatch and landscape restoration in complex multi-level governance systems. In addition, the maps, network diagnostics, and narratives in this dissertation can help practitioners in Puget Sound and provide proofs of concepts that can be replicated elsewhere for restoration and broader conservation sciences.
Spatial network analysis reveals several areas with weak scale mismatch bridging networks. These weak social networks are then compared to ecological restoration needs to identify coupled social-ecological restoration concerns. Subsequent study investigates jurisdictional and sectoral network integration because governance siloes contribute to scale mismatch. While the network is fairly well integrated, several sectors do not interact or interact very little. An analysis of collaboration reasons disentangles the idea of generic collaboration. Among three relationship types considered, mandated relationships contribute almost 5.5 times less to perceived collaboration productivity than shared interest relationships, highlighting the benefits of true collaborations in watershed governance. Lastly, the effects of scale mismatch on individual restoration projects and landscape level restoration planning are assessed through qualitative interview analysis. Results illustrate why human-environment processes should be included in landscape restoration planning. Social factors are not considered as constraints to restoration but rather part of the very landscape fabric to be restored. Scale mismatch is conceptualized as a complex social-ecological landscape pattern that affects the flow of financial, human, and natural capital across the landscape. This represents a new way of thinking about scale mismatch and landscape restoration in complex multi-level governance systems. In addition, the maps, network diagnostics, and narratives in this dissertation can help practitioners in Puget Sound and provide proofs of concepts that can be replicated elsewhere for restoration and broader conservation sciences.
ContributorsSayles, Jesse Saemann (Author) / Turner II, B L (Thesis advisor) / Childers, Daniel L. (Committee member) / Janssen, Marco A (Committee member) / Arizona State University (Publisher)
Created2015
Description
Often, when thinking of cities we envision designed landscapes, where people regulate everything from water to weeds, ultimately resulting in an ecosystem decoupled from biophysical processes. It is unclear, however, what happens when the people regulating these extensively managed landscapes come under stress, whether from unexpected economic fluctuations or from changing climate norms. The overarching question of my dissertation research was: How does urban vegetation change in response to human behavior? To answer this question, I conducted multiscale research in an arid urban ecosystem as well as in a virtual desert city. I used a combination of long-term data and agent-based modeling to examine changes in vegetation across a range of measures influenced by biophysical, climate, institutional, and socioeconomic drivers. At the regional scale, total plant species diversity increased from 2000 to 2010, while species composition became increasingly homogeneous in urban and agricultural areas. At the residential scale, I investigated the effects of biophysical and socioeconomic drivers – the Great Recession of 2007-2010 in particular – on changing residential yard vegetation in Phoenix, AZ. Socioeconomic drivers affected plant composition and increasing richness, but the housing boom from 2000 through 2005 had a stronger influence on vegetation change than the subsequent recession. Surprisingly, annual plant species remained coupled to winter precipitation despite my expectation that their dynamics might be driven by socioeconomic fluctuations. In a modeling experiment, I examined the relative strength of psychological, social, and governance influences on large-scale urban land cover in a desert city. Model results suggested that social norms may be strong enough to lead to large-scale conversion to low water use residential landscaping, and governance may be unnecessary to catalyze residential landscape conversion under the pressure of extreme drought conditions. Overall, my dissertation research showed that urban vegetation is dynamic, even under the presumably stabilizing influence of human management activities. Increasing climate pressure, unexpected socioeconomic disturbances, growing urban populations, and shifting policies all contribute to urban vegetation dynamics. Incorporating these findings into planning policies will contribute to the sustainable management of urban ecosystems.
ContributorsRipplinger, Julie (Author) / Franklin, Janet (Thesis advisor) / Collins, Scott L. (Thesis advisor) / Anderies, John M (Committee member) / Childers, Daniel L. (Committee member) / York, Abigail (Committee member) / Arizona State University (Publisher)
Created2015
Description
The Basin and Range province of southwestern USA are composed of different grassland and shrubland ecosystems. Particularly understudied ecosystems in this region are playas, which are ephemerally-flooded wetlands located in topographic low areas of hydrologically-closed dryland catchments. There is not much known about the ecological functioning of playas and the role of playas within desert basins. Even less is known about how global change drivers may affect playas in the future. The main objective of this thesis was to better understand the ecological functioning and the impact of climate change on desert playa wetlands. I collected new data, used existing long-term data, and used simulation modelling techniques to address this objective. I compared playa soils to upland soils and found that playas were hotspots of soil organic carbon and nutrient storage within a desert basin. I also used existing data to analyze the response of above-ground net primary productivity (ANPP) to annual precipitation in playas and upland ecosystems. I found that playa ANPP responded in a non-linear concave-down relationship with annual precipitation amount. Playa ANPP peaked in moderately wet years and declined in very wet years, which was most likely due to flooding; whereas, upland ANPP increased linearly with precipitation. I measured soil organic carbon and nitrogen concentrations in a representative subset of playas and measured the biophysical characteristics of the upland catchments associated with each playa. I found that both catchment geomorphology and vegetation cover were correlated to differences in soil organic carbon and nitrogen among playas. These results showed the importance external soil-inputs delivered via surface runon to playas. Finally, I empirically measured groundwater recharge beneath playas and combined these empirical data with modelling data to forecast how playa groundwater recharge may change in the future. I concluded that playas contribute to groundwater recharge in desert aquifers, playa runon is a strong predictor of playa groundwater recharge, and climate change will have a net-positive impact on groundwater recharge beneath playas. Overall, my thesis research increased the understanding of the role of desert playas on the functioning of dryland ecosystems.
ContributorsMcKenna, Philip (Author) / Sala, Osvaldo E. (Thesis advisor) / Monger, H. Curtis (Committee member) / Hall, Sharon J (Committee member) / Childers, Daniel L. (Committee member) / Arizona State University (Publisher)
Created2016
Description
Cities can be sources of nitrate to downstream ecosystems resulting in eutrophication, harmful algal blooms, and hypoxia that can have negative impacts on economies and human health. One potential solution to this problem is to increase nitrate removal in cities by providing locations where denitrification¬— a microbial process in which nitrate is reduced to N2 gas permanently removing nitrate from systems— can occur. Accidental urban wetlands– wetlands that results from human activities, but are not designed or managed for any specific outcome¬– are one such feature in the urban landscape that could help mitigate nitrate pollution through denitrification.
The overarching question of this dissertation is: how do hydrology, soil conditions, and plant patches affect patterns of denitrification in accidental urban wetlands? To answer this question, I took a three-pronged approach using a combination of field and greenhouse studies. First, I examined drivers of broad patterns of denitrification in accidental urban wetlands. Second, I used a field study to test if plant traits influence denitrification indirectly by modifying soil resources. Finally, I examined how species richness and interactions between species influence nitrate retention and patterns of denitrification using both a field study and greenhouse experiment.
Hydroperiod of accidental urban wetlands mediated patterns of denitrification in response to monsoon floods and plant patches. Specifically, ephemeral wetlands had patterns of denitrification that were largely unexplained by monsoon floods or plant patches, which are common drivers of patterns of denitrification in non-urban wetlands. Several plant traits including belowground biomass, above- and belowground tissue chemistry and rooting depth influenced denitrification indirectly by changing soil organic matter or soil nitrate. However, several other plant traits also had significant direct relationships with denitrification, (i.e. not through the hypothesized indirect relationships through soil organic matter or soil nitrate). This means these plant traits were affecting another aspect of soil conditions not included in the analysis, highlighting the need to improve our understanding of how plant traits influence denitrification. Finally, increasing species richness did not increase nitrate retention or denitrification, but rather individual species had the greatest effects on nitrate retention and denitrification.
The overarching question of this dissertation is: how do hydrology, soil conditions, and plant patches affect patterns of denitrification in accidental urban wetlands? To answer this question, I took a three-pronged approach using a combination of field and greenhouse studies. First, I examined drivers of broad patterns of denitrification in accidental urban wetlands. Second, I used a field study to test if plant traits influence denitrification indirectly by modifying soil resources. Finally, I examined how species richness and interactions between species influence nitrate retention and patterns of denitrification using both a field study and greenhouse experiment.
Hydroperiod of accidental urban wetlands mediated patterns of denitrification in response to monsoon floods and plant patches. Specifically, ephemeral wetlands had patterns of denitrification that were largely unexplained by monsoon floods or plant patches, which are common drivers of patterns of denitrification in non-urban wetlands. Several plant traits including belowground biomass, above- and belowground tissue chemistry and rooting depth influenced denitrification indirectly by changing soil organic matter or soil nitrate. However, several other plant traits also had significant direct relationships with denitrification, (i.e. not through the hypothesized indirect relationships through soil organic matter or soil nitrate). This means these plant traits were affecting another aspect of soil conditions not included in the analysis, highlighting the need to improve our understanding of how plant traits influence denitrification. Finally, increasing species richness did not increase nitrate retention or denitrification, but rather individual species had the greatest effects on nitrate retention and denitrification.
ContributorsSuchy, Amanda Klara (Author) / Childers, Daniel L. (Thesis advisor) / Stromberg, Juliet C. (Thesis advisor) / Grimm, Nancy (Committee member) / Hall, Sharon (Committee member) / Sabo, John (Committee member) / Arizona State University (Publisher)
Created2016
Description
Constructed treatment wetlands (CTW) have been a cost-efficient technological solution to treat different types of wastewater but may also be sources of emitters of methane (CH4) and nitrous oxide (N2O). Thus, my objective for this dissertation was to investigate CH4 and N2O fluxes via multiple pathways from the Tres Rios CTW located in Phoenix, AZ, USA. I measured gas fluxes from the CTW along a whole-system gradient (from inflow to outflow) and a within-marsh gradient (shoreline, middle, and open water sites). I found higher diffusive CH4 release in the summer compared to spring and winter seasons. Along the whole-system gradient, I found greater CH4 and N2O emission fluxes near the inflow compared to near the outflow. Within the vegetated marsh, I found greater CH4 emission fluxes at the vegetated marsh subsites compared to the open water. In contrast, N2O emissions were greater at the marsh-open water locations compared to interior marsh. To study the plant-mediated pathway, I constructed small gas chambers fitted to Typha spp. leaves. I found plant-mediated CH4 fluxes were greater near the outflow than near the inflow and that CH4 fluxes were higher from lower sections of plants compared to higher sections. Overall, Typha spp. emitted a mean annual daily flux rate of 358.23 mg CH4 m-2 d-1. Third, using a 30-day mesocosm experiment I studied the effects of three different drydown treatments (2, 7, 14 days) on the fluxes of CH4 and N2O from flooded CTW soils. I found that CH4 fluxes were not significantly affected by soil drydown events. Soils that were dry for 7 days shifted from being N2O sources to sinks upon inundation. As a result, the 7-day drydown soils were sinks while the 14-day drydown soils showed significant N2O release. My results emphasize the importance of studying ecological processes in CTWs to improve their design and management strategies so we can better mitigate their greenhouse gas emissions.
ContributorsRamos, Jorge, 1984- (Author) / Childers, Daniel L. (Thesis advisor) / Grimm, Nancy (Committee member) / Sala, Osvaldo E. (Committee member) / Vivoni, Enrique R (Committee member) / Arizona State University (Publisher)
Created2017
Description
Sustainability research and action in communities should be holistic, integrating sociocultural, biogeophysical, and spiritual components and their temporal and spatial dynamics toward the aim of co-creating thriving living systems. Yet scientists and practitioners still struggle with such integration. Regenerative development (RD) offers a way forward. RD focuses on shifting the consciousness and thinking underlying (un)sustainability as well as their manifestation in the physical world, creating increasingly higher levels of health and vitality for all life across scales. However, tools are nascent and relatively insular. Until recently, no empirical scientific research studies had been published on RD processes and outcomes.
My dissertation fills this gap in three complementary studies. The first is an integrative review that contextualizes regenerative development within the fields of sustainability, sustainable design and development, and ecology by identifying its conceptual elements and introducing a regenerative landscape development paradigm. The second study integrates complex adaptive systems science, ecology, sustainability, and regenerative development to construct and pilot the first iteration of a holistic sustainable development evaluation tool—the Regenerative Development Evaluation Tool—in two river restoration projects. The third study builds upon the first two, integrating scientific knowledge with existing RD and sustainable community design and development practices and theory to construct and pilot a Regenerative Community Development (RCD) Framework. Results indicate that the RCD Framework and Tools, when used within a regenerative landscape development paradigm, can facilitate: (1) shifts in thinking and development and design outcomes to holistic and regenerative ones; (2) identification of areas where development and design projects can become more regenerative and ways to do so; and (3) identification of factors that potentially facilitate and impede RCD processes. Overall, this research provides a direction and tools for holistic sustainable development as well as foundational studies for further research.
My dissertation fills this gap in three complementary studies. The first is an integrative review that contextualizes regenerative development within the fields of sustainability, sustainable design and development, and ecology by identifying its conceptual elements and introducing a regenerative landscape development paradigm. The second study integrates complex adaptive systems science, ecology, sustainability, and regenerative development to construct and pilot the first iteration of a holistic sustainable development evaluation tool—the Regenerative Development Evaluation Tool—in two river restoration projects. The third study builds upon the first two, integrating scientific knowledge with existing RD and sustainable community design and development practices and theory to construct and pilot a Regenerative Community Development (RCD) Framework. Results indicate that the RCD Framework and Tools, when used within a regenerative landscape development paradigm, can facilitate: (1) shifts in thinking and development and design outcomes to holistic and regenerative ones; (2) identification of areas where development and design projects can become more regenerative and ways to do so; and (3) identification of factors that potentially facilitate and impede RCD processes. Overall, this research provides a direction and tools for holistic sustainable development as well as foundational studies for further research.
ContributorsGibbons, Leah Veronica (Author) / Cloutier, Scott A (Thesis advisor) / Coseo, Paul J (Committee member) / Childers, Daniel L. (Committee member) / Arizona State University (Publisher)
Created2019