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Description
Aboveground net primary production (ANPP) is an important ecosystem process that, in drylands, is most frequently limited by water availability. Water availability for plants is in part controlled by the water holding capacity of soils. Available water holding capacity (AWHC) of soils is strongly influenced by soil texture and depth.

Aboveground net primary production (ANPP) is an important ecosystem process that, in drylands, is most frequently limited by water availability. Water availability for plants is in part controlled by the water holding capacity of soils. Available water holding capacity (AWHC) of soils is strongly influenced by soil texture and depth. This study drew upon localized rain gauge data and four data-sets of cover-line and biomass data to estimate ANPP and to determine annual precipitation (PPT). I measured soil depth to caliche and texture by layer of 112 plots across the four landscape units for which estimation of ANPP were available. A pedotransfer function was used to estimate AWHC from soil depth increments to depth of caliche measurements and texture analysis. These data were analyzed using simple and multivariate regression to test the effect of annual precipitation and available water holding capacity on aboveground net primary production. Soil texture remained constant among all plots (sandy loam) and depth to caliche varied from 15.16 cm to 189 cm. AWHC and the interaction term (PPT*AWHC) were insignificant (p=0.142, p=0.838) and annual PPT accounted for 18.4% of the variation in ANPP. The y-intercept was significantly different for ANPP ~ annual PPT when considering AWHC values either above or below 3 cm. Shrub ANPP was insensitive to precipitation regardless of AWHC (R2=-0.012, R2=0.014). Results from this study indicate that a model incorporating annual PPT and AWHC may not serve as a good predictor for ANPP at a site level where there is little variation in soil texture.
ContributorsWagner, Svenja K (Author) / Sala, Osvaldo E. (Thesis advisor) / Cease, Arianne (Committee member) / Hall, Sharon (Committee member) / Peters, Debra (Committee member) / Arizona State University (Publisher)
Created2019
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Description
Plastics are an emerging issue in aquatic ecosystems due to their slow degradation and ability to fragment into smaller more mobile parts. Concluding this process, plastics <5mm are categorized as Microplastics, MPs. Currently, the majority of MP studies bring attention to marine pollution and the impacts that follow. However, it

Plastics are an emerging issue in aquatic ecosystems due to their slow degradation and ability to fragment into smaller more mobile parts. Concluding this process, plastics <5mm are categorized as Microplastics, MPs. Currently, the majority of MP studies bring attention to marine pollution and the impacts that follow. However, it remains a high priority to understand how MPs move through urban aquatic environments, and the impacts this may have for surrounding urban ecosystems. Little is known about how MPs move through tertiary treated wastewater plants, such as constructed wetlands, and how much, if any, remain trapped in abiotic and biotic material such as soil or plant life, respectively. An analysis of MP distribution using Tres Rios, a tertiary wastewater treatment wetland, as the study site may help to shed light on the source-occurrences of MPs. Microplastics extraction was performed on soil, plant, and water samples that were collected along major access points within the system with emphasis on inflow and outflow. The inflow of the wetland receives between 246-398 MPs/L vs the outflow of 90-199 MPs/L. Tres Rios soil concentrations ranged between 1,017-10,100 per kg and 133-700 MPs per kg in sampled vegetation throughout the wetland. The distribution of soil and vegetation samples differed throughout Tres Rios, as soil sampled exhibited higher quantities towards inflow site and vegetation MP occurrences were increased throughout the middle of the system. Additionally, this study aimed to determine if seasonality impacted the concentration of plastics seen throughout the system. There was no evidence that suggested seasonal variations were occurring in any sample type. Atmospheric deposition fluxes of microplastics were considered as a potential additional influx but even at the measured 1510 MP m-2 day-1 they were small compared to the water influx. Overall, the results suggest that the Tres Rios wetland removed 55% of the microplastics it receives and hence performs a substantial ecosystem service.
ContributorsCisco, Jordan (Author) / Green, Douglas (Thesis advisor) / Herckes, Pierre (Thesis advisor) / Childers, Daniel (Committee member) / Arizona State University (Publisher)
Created2023
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Description
Under current climate conditions northern peatlands mostly act as C sinks; however, changes in climate and environmental conditions, can change the soil carbon decomposition cascade, thus altering the sink status. Here I studied one of the most abundant northern peatland types, poor fen, situated along a climate gradient from tundra

Under current climate conditions northern peatlands mostly act as C sinks; however, changes in climate and environmental conditions, can change the soil carbon decomposition cascade, thus altering the sink status. Here I studied one of the most abundant northern peatland types, poor fen, situated along a climate gradient from tundra (Daring Lake, Canada) to boreal forest (Lutose, Canada) to temperate broadleaf and mixed forest (Bog Lake, MN and Chicago Bog, NY) biomes to assess patterns of microbial abundance across the climate gradient. Principal component regression analysis of the microbial community and environmental variables determined that mean annual temperature (MAT) (r2=0.85), mean annual precipitation (MAP) (r2=0.88), and soil temperature (r2=0.77), were the top significant drivers of microbial community composition (p < 0.001). Niche breadth analysis revealed the relative abundance of Intrasporangiaceae, Methanobacteriaceae and Candidatus Methanoflorentaceae fam. nov. to increase when MAT and MAP decrease. The same analysis showed Spirochaetaceae, Methanosaetaceae and Methanoregulaceae to increase in relative abundance when MAP, soil temperature and MAT increased, respectively. These findings indicated that climate variables were the strongest predictors of microbial community composition and that certain taxa, especially methanogenic families demonstrate distinct patterns across the climate gradient. To evaluate microbial production of methanogenic substrates, I carried out High Resolution-DNA-Stable Isotope Probing (HR-DNA-SIP) to evaluate the active portion of the community’s intermediary ecosystem metabolic processes. HR-DNA-SIP revealed several challenges in efficiency of labelling and statistical identification of responders, however families like Veillonellaceae, Magnetospirillaceae, Acidobacteriaceae 1, were found ubiquitously active in glucose amended incubations. Differences in metabolic byproducts from glucose amendments show distinct patterns in acetate and propionate accumulation across sites. Families like Spirochaetaceae and Sphingomonadaceae were only found to be active in select sites of propionate amended incubations. By-product analysis from propionate incubations indicate that the northernmost sites were acetate-accumulating communities. These results indicate that microbial communities found in poor fen northern peatlands are strongly influenced by climate variables predicted to change under current climate scenarios. I have identified patterns of relative abundance and activity of select microbial taxa, indicating the potential for climate variables to influence the metabolic pathway in which carbon moves through peatland systems.
ContributorsSarno, Analissa Flores (Author) / Cadillo-Quiroz, Hinsby (Thesis advisor) / Garcia-Pichel, Ferran (Committee member) / Krajmalnik-Brown, Rosa (Committee member) / Childers, Daniel (Committee member) / Arizona State University (Publisher)
Created2022
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Description
There are two main sections of this thesis: Codebook development and case coding. Over the course of my two years of involvement with the collaborative governance lab with Drs. Schoon and Carr Kelman, I worked on helping to complete the coding manual built by the lab to test variables from

There are two main sections of this thesis: Codebook development and case coding. Over the course of my two years of involvement with the collaborative governance lab with Drs. Schoon and Carr Kelman, I worked on helping to complete the coding manual built by the lab to test variables from the literature using case studies. My main deliverable was building a Qualtrics survey to collect case studies. Using this Qualtrics survey, the lab will be able to collect coded cases by distributing the survey link through research networks. My thesis project included building the interface for the survey, participating in testing the intercoder reliability of the codebook, and coding one case, the Four Forest Restoration Initiative (4FRI), to provide insight on the collaborative governance strategies of this collaboration. Coding 4FRI also acted as a preliminary test of the survey, helping to provide further information on how users of the codebook might interact with the survey, and allowing the lab to generate a test report of survey results.
ContributorsGoddard, Kevin W (Author) / Carr Kelman, Candice (Thesis director) / Childers, Daniel (Committee member) / School of Sustainability (Contributor, Contributor) / School of Geographical Sciences and Urban Planning (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
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Description
Constructed treatment wetlands (CTW) are being increasingly utilized in urbanized areas as a cost-effective and environmentally-friendly method for treating wastewater. CTWs can be especially useful for urban areas in aridland environments because they facilitate the reuse of water during water shortages. In my study, I determined the rates

Constructed treatment wetlands (CTW) are being increasingly utilized in urbanized areas as a cost-effective and environmentally-friendly method for treating wastewater. CTWs can be especially useful for urban areas in aridland environments because they facilitate the reuse of water during water shortages. In my study, I determined the rates at which the aboveground and belowground emergent macrophytes sequestered nitrogen in a 42 ha aridland CTW in Phoenix, Arizona, USA. To do so, I measured foliar nitrogen content in aboveground and belowground biomass of three plant species groups (Typha latifolia + Typha domingensis, Schoenoplectus acutus + Schoenoplectus tabernaemontani, and Schoenoplectus californicus). Using these data, I calculated aboveground and belowground nitrogen budgets for the three species groups annually from 2011 to 2018.

Aboveground nitrogen content showed a maximum in 2011, decreasing until 2015, increasing again until 2017, and dropping in 2018; belowground nitrogen content showed the opposite temporal trend. Because foliar nitrogen content was assumed to be relatively constant over time, my data suggested that belowground nitrogen content increased between 2011 and 2015 and decreased between 2015 and 2017. Aboveground nitrogen content underwent fluctuations due to fluctuations in aboveground biomass. This occurred due to ‘thatching’, or events of widespread toppling of large macrophyte stands. The ratio of aboveground to belowground biomass can vary widely in the same CTW. My findings suggested that managing senesced aboveground plant material in CTWs may optimize the CTW’s ability to sequester nitrogen. Further research is needed to determine the best management strategies, as well as its possible implications.
ContributorsCrane, Austin Matthew (Author) / Childers, Daniel (Thesis director) / Sanchez, Christopher (Committee member) / School of Life Sciences (Contributor) / School of Sustainability (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
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Description
Freshwater ecosystems are increasingly threatened by anthropogenic eutrophication (Kolzau et al., 2014) and require mitigation efforts to prevent oxygen depletion and subsequent biodiversity loss. Tres Rios Constructed Treatment Wetland (CTW) relies on wetland ecosystem functioning to reduce nutrient concentrations in order to meet regulatory guidelines. I investigated the impact of

Freshwater ecosystems are increasingly threatened by anthropogenic eutrophication (Kolzau et al., 2014) and require mitigation efforts to prevent oxygen depletion and subsequent biodiversity loss. Tres Rios Constructed Treatment Wetland (CTW) relies on wetland ecosystem functioning to reduce nutrient concentrations in order to meet regulatory guidelines. I investigated the impact of solar irradiance, temperature, and nutrient availability on aquatic net primary productivity, ecosystem respiration, and nutrient cycling using statistical analysis and quantitative modeling informed by field data generated by ASU’s Wetland Ecosystem Ecology Lab (WEEL) in partnership with the City of Phoenix Water Services Department. I found that the extent of daily solar insolation controls Aquatic Net Primary Productivity (ANPP) rates and the seasonal aquatic nutrient processing capacity of Tres Rios, resulting in the following approximate relationship: ANPP = 0.001344(W/m²) - 0.32634 (r² = 0.259; p = 0.005).

This formula was used to estimate the nutrient uptake performance of aquatic primary producers from sampling observations; ANPP accounted for 16.26 metric tons of system wide N uptake, while aquatic ER contributed 6.07 metric tons N of nighttime remineralization and 5.7 metric tons of N throughout the water column during the day. The estimated yearly net aquatic N flux is 4.49 metric tons uptake, compared to about 12 metric tons yearly N uptake by the vegetated marsh (Treese, 2019). However, not accounting for animal respiration results in an underestimation of system-wide N remineralization, and not accounting for soil processes results in an underestimation of N uptake.
ContributorsEvans, Joseph Barrett (Author) / Childers, Daniel (Thesis director) / Hartnett, Hilairy (Committee member) / Watts College of Public Service & Community Solut (Contributor) / School of Sustainability (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
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Description
Animal psychology is the study of how animals interact with one another, their environment, and with humans. This can be done in two different settings, the wild and captivity, and through two different approaches, academic research and practice. Academic research relies primarily on behavioral observation for data collection. Practice uses

Animal psychology is the study of how animals interact with one another, their environment, and with humans. This can be done in two different settings, the wild and captivity, and through two different approaches, academic research and practice. Academic research relies primarily on behavioral observation for data collection. Practice uses behavioral observation as well, but allows for a more hands on experience and lets the practitioner make improvements in the quality of life. I interviewed two people, one who practices in captivity, and one who does research in the wild. Dr. David Bunn has done research on wild animals in Kruger National Park in South Africa for over twenty years, studying human-animal interactions. Hilda Tresz has worked in zoos nearly forty years and specializes in chimps. Working within the same field, but utilizing a different setting and approach makes a big difference in the feel of the job. Though I found many differences between the two by doing my own research and from conducting interviews, there are many similarities to note as well. The general field of animal psychology is very rewarding, requires a lot of patience, and leads to a better understanding of animal behavior and how to care for specific species of animals. Working with captive animals allows for the opportunity to make a big difference in animal's lives through behavioral enrichment and general care. Working in the wild allows us to understand the innate animal behaviors displayed. Through practice, people get more hands on experience; while through research, you get to observe animals in their native habitats. Each setting and approach has it's own benefits depending on what each person's goals are for their job.
ContributorsDaniel, Mckenna Lynne (Author) / Childers, Daniel (Thesis director) / Hall, Sharon (Committee member) / School of Social and Behavioral Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
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Description
Elevated nitrate (NO3-) concentration in streams and rivers has contributed to environmental problems such as downstream eutrophication and loss of biodiversity. Sycamore Creek in Arizona is nitrogen limited, but previous studies have demonstrated high potential for denitrification, a microbial process in which biologically active NO3- is reduced to relatively inert

Elevated nitrate (NO3-) concentration in streams and rivers has contributed to environmental problems such as downstream eutrophication and loss of biodiversity. Sycamore Creek in Arizona is nitrogen limited, but previous studies have demonstrated high potential for denitrification, a microbial process in which biologically active NO3- is reduced to relatively inert dinitrogen (N2) gas. Oak Creek is similarly nitrogen limited, but NO3- concentration in reaches surrounded by agriculture can be double that of other reaches. We employed a denitrification enzyme assay (DEA) to compare potential denitrification rate between differing land uses in Oak Creek and measured whole system N2 flux using a membrane inlet mass spectrometer to compare differences in actual denitrification rates at Sycamore and Oak Creek. We anticipated that NO3- would be an important limiting factor for denitrifiers; consequentially, agricultural land use reaches within Oak Creek would have the highest potential denitrification rate. We expected in situ denitrification rate to be higher in Oak Creek than Sycamore Creek due to elevated NO3- concentration, higher discharge, and larger streambed surface area. DEA results are forthcoming, but analysis of potassium chloride (KCl) extraction data showed that there were no significant differences between sites in sediment extractable NO3- on either a dry mass or organic mass basis. Whole-reach denitrification rate was inconclusive in Oak Creek, and though a significant positive flux in N2 from upstream to downstream was measured in Sycamore Creek, the denitrification rate was not significantly different from 0 after accounting for reaeration, suggesting that denitrification does not account for a significant portion of the NO3- uptake in Sycamore Creek. Future work is needed to address the specific factors limiting denitrification in this system.
ContributorsCaulkins, Corey Robert (Author) / Grimm, Nancy (Thesis director) / Childers, Daniel (Committee member) / School of Sustainability (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
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Description
Phosphorus (P), an essential element for life, is becoming increasingly scarce, and its global management presents a serious challenge. As urban environments dominate the landscape, we need to elucidate how P cycles in urban ecosystems to better understand how cities contribute to — and provide opportunities to solve — problems

Phosphorus (P), an essential element for life, is becoming increasingly scarce, and its global management presents a serious challenge. As urban environments dominate the landscape, we need to elucidate how P cycles in urban ecosystems to better understand how cities contribute to — and provide opportunities to solve — problems of P management. The goal of my research was to increase our understanding of urban P cycling in the context of urban resource management through analysis of existing ecological and socio-economic data supplemented with expert interviews in order to facilitate a transition to sustainable P management. Study objectives were to: I) Quantify and map P stocks and flows in the Phoenix metropolitan area and analyze the drivers of spatial distribution and dynamics of P flows; II) examine changes in P-flow dynamics at the urban agricultural interface (UAI), and the drivers of those changes, between 1978 and 2008; III) compare the UAI's average annual P budget to the global agricultural P budget; and IV) explore opportunities for more sustainable P management in Phoenix. Results showed that Phoenix is a sink for P, and that agriculture played a primary role in the dynamics of P cycling. Internal P dynamics at the UAI shifted over the 30-year study period, with alfalfa replacing cotton as the main locus of agricultural P cycling. Results also suggest that the extent of P recycling in Phoenix is proportionally larger than comparable estimates available at the global scale due to the biophysical characteristics of the region and the proximity of various land uses. Uncertainty remains about the effectiveness of current recycling strategies and about best management strategies for the future because we do not have sufficient data to use as basis for evaluation and decision-making. By working in collaboration with practitioners, researchers can overcome some of these data limitations to develop a deeper understanding of the complexities of P dynamics and the range of options available to sustainably manage P. There is also a need to better connect P management with that of other resources, notably water and other nutrients, in order to sustainably manage cities.
ContributorsMetson, Genevieve (Author) / Childers, Daniel (Thesis advisor) / Aggarwal, Rimjhim (Thesis advisor) / Redman, Charles (Committee member) / Arizona State University (Publisher)
Created2011
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Description

Hydrology and biogeochemistry are coupled in all systems. However, human decision-making regarding hydrology and biogeochemistry are often separate, even though decisions about hydrologic systems may have substantial impacts on biogeochemical patterns and processes. The overarching question of this dissertation was: How does hydrologic engineering interact with the effects of nutrient

Hydrology and biogeochemistry are coupled in all systems. However, human decision-making regarding hydrology and biogeochemistry are often separate, even though decisions about hydrologic systems may have substantial impacts on biogeochemical patterns and processes. The overarching question of this dissertation was: How does hydrologic engineering interact with the effects of nutrient loading and climate to drive watershed nutrient yields? I conducted research in two study systems with contrasting spatial and temporal scales. Using a combination of data-mining and modeling approaches, I reconstructed nitrogen and phosphorus budgets for the northeastern US over the 20th century, including anthropogenic nutrient inputs and riverine fluxes, for ~200 watersheds at 5 year time intervals. Infrastructure systems, such as sewers, wastewater treatment plants, and reservoirs, strongly affected the spatial and temporal patterns of nutrient fluxes from northeastern watersheds. At a smaller scale, I investigated the effects of urban stormwater drainage infrastructure on water and nutrient delivery from urban watersheds in Phoenix, AZ. Using a combination of field monitoring and statistical modeling, I tested hypotheses about the importance of hydrologic and biogeochemical control of nutrient delivery. My research suggests that hydrology is the major driver of differences in nutrient fluxes from urban watersheds at the event scale, and that consideration of altered hydrologic networks is critical for understanding anthropogenic impacts on biogeochemical cycles. Overall, I found that human activities affect nutrient transport via multiple pathways. Anthropogenic nutrient additions increase the supply of nutrients available for transport, whereas hydrologic infrastructure controls the delivery of nutrients from watersheds. Incorporating the effects of hydrologic infrastructure is critical for understanding anthropogenic effects on biogeochemical fluxes across spatial and temporal scales.

ContributorsHale, Rebecca Leslie (Author) / Grimm, Nancy (Thesis advisor) / Childers, Daniel (Committee member) / Vivoni, Enrique (Committee member) / York, Abigail (Committee member) / Wu, Jianguo (Committee member) / Arizona State University (Publisher)
Created2013