Matching Items (8)
Filtering by
- All Subjects: Social-Ecological Systems
- All Subjects: Soil Sciences
- Creators: Childers, Daniel L.
- Creators: Abbott, Joshua K
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
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
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
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
Nature-based recreation is a popular way for people to interact with the environment that also confers numerous economic and health benefits. It is important that the social-ecological systems (SES) that host nature-based recreation be managed effectively, both to preserve the benefits of this important human-environment interaction, and to avoid the potential negative outcomes of recreational commons. The SES that host nature-based recreation are characterized by complex and dynamic feedbacks that complicate their management. Managing these systems is made more complex by the suite of external, multi-scalar, and anthropogenic forces (e.g., climate change, trans-boundary pollution) that plague them with increasing frequency. This dissertation investigates the importance of accounting for this full range of system feedbacks when managing for nature-based recreation. I begin with a broad discussion of the types of dilemmas faced by managers of nature-based recreation. I create a systems-thinking typology of management dilemmas that apply across different recreation modes and system contexts, and which are characterized as feedbacks within the broader recreational system. My findings in this chapter have important implications for understanding and anticipating how different exogenous and endogenous shocks (including management interventions, themselves) may work through or change the processes in SES that host nature-based recreation. In the following two chapters, I narrow my focus to examine case studies of specific dilemma archetypes and proposed management interventions. First, I perform an ex ante analysis of a prospective policy response to a regulatory spiral of excess recreational fishing effort and abridged fishing seasons in the U.S. Gulf of Mexico. I estimate behavioral models of fishers’ responses to a prospective incentive-based intervention, and find evidence that such a policy could improve multiple fishery outcomes. Second, I perform an ex post program evaluation of an invasive species bounty program. My results suggest that the program underperformed because it failed to overcome countervailing incentives. Together, my case study analyses reveal the value of modeling for designing policy for these complex SES and show the importance of accounting for the full set of system feedbacks (including the incentives that drive recreator behaviors and the impacts of those behaviors) when managing nature-based recreation.
ContributorsJungers, Brenna (Author) / Abbott, Joshua K (Thesis advisor) / Leonard, Bryan (Committee member) / Anderies, John M (Committee member) / Bair, Lucas S (Committee member) / Arizona State University (Publisher)
Created2023
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
Description
My research is motivated by a rule of thumb that no matter how well a system is designed, some actors fail to fulfill the behavior which is needed to sustain the system. Examples of misbehavior are shirking, rule infraction, and free riding. With a focus on social-ecological systems, this thesis explored the effectiveness of social feedback mechanisms driven by the two available individual options: the exit option is defined as any response to escape from an objectionable state of affairs; and the voice option as any attempt to stay put and improve the state. Using a stylized dynamic model, the first study investigates how the coexistence of participatory and groundwater market institutions affects government-managed irrigation systems. My findings suggest that patterns of bureaucratic reactions to exit (using private tubewells) and voice (putting pressure on irrigation bureaus) are critical to shaping system dynamics. I also found that the silence option – neither exit nor voice – can impede a further improvement in public infrastructure, but in some cases, can improve public infrastructure dramatically. Using a qualitative comparative analysis of 30 self-governing fishing groups in South Korea, the second study examines how resource mobility, group size, and Ostrom’s Design Principles for rule enforcement can co-determine the effectiveness of the voice option in self-controlling rule infractions. Results suggest that the informal mechanism for conflict resolution is a necessary condition for successful self-governance of local fisheries and that even if rules for monitoring and graduated sanctions are not in use, groups can be successful when they harvest only stationary resources. Using an agent-based model of public good provision, the third study explores under what socioeconomic conditions the exit option – neither producing nor consuming collective benefits – can work effectively to enhance levels of cooperation. The model results suggest that the exit option contributes to the spread of cooperators in mid- and large-size groups at the moderate level of exit payoff, given that group interaction occurs to increase the number of cooperators.
ContributorsShin, Hoon Cheol (Author) / Anderies, John M (Thesis advisor) / Abbott, Joshua K (Committee member) / Janssen, Marcus A (Committee member) / Arizona State University (Publisher)
Created2020