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- All Subjects: Biogeochemistry
- All Subjects: carbon cycling
- All Subjects: Nutrition
- Genre: Masters Thesis
- Member of: Theses and Dissertations
Description
Childhood obesity has been on the rise for the past decade, and it has been hypothesized that students' food choices may be influenced by easy access to food outlets near their schools that provide unhealthful options. But the results of recent studies on the relationship between the food environment around schools and student weight status are mixed and often contradictory. Most studies have used measures of weight and height that were self-reported by students, or have relied on data from a relatively small sample of students. I examine the association between weight status among school students and the food environment surrounding their schools using professionally-measured, student-level data across the full school-age spectrum. De-identified data were obtained for over 30,000 K-12 students in 79 public schools located in four New Jersey cities. Locations of alternative food-outlets (specifically, supermarkets, convenience stores, small grocery stores, and limited-service restaurants) were obtained from commercial sources and geocoded to develop proximity measures. A simplified social-ecological framework was used to conceptualize the multi-level the association between students' BMI and school proximity to food outlets and multivariate analyses were used to estimate this relationship controlling for student- and school-level factors. Over twenty percent of the students were obese, compared to the national average at 17% (Ogden, Carroll, Kit, & Flegal, 2012). On average, students had 2.6 convenience stores, 2.9 limited-service restaurants, and 0.1 supermarkets within a quarter mile of their school. This study suggests that easy access to small grocery stores (which this study uniquely examines as a separate food outlet category) that offer healthy choices including five types of fresh vegetable, five types of fresh fruits, low-fat dairy, and lean meats is associated with lower BMI z score and lower probability of being obese for middle and high school students. This suggests that improving access to such small food outlets may be a promising area for future investigation in obesity mitigation research. Also, this study separates students of pre-schools, kindergartens and elementary schools (neighborhood schools) from that of the middle and high schools (non-neighborhood) schools because the two groups of schools have different neighborhood characteristics, as well as open-school and bussing policies that result in different levels of exposure that students have to the food outlets around the schools. The result of this study suggests that the relationship between students' weight outcomes and food environment around schools is different in the two groups of schools.
ContributorsTang, Xuyang (Author) / Abbott, Joshua K (Thesis advisor) / Ohri-Vachaspati, Punam (Thesis advisor) / Aggarwal, Rimjhim (Committee member) / Arizona State University (Publisher)
Created2013
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 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
Description
Soil organic carbon (SOC) is a critical component of the global carbon (C) cycle, accounting for more C than the biotic and atmospheric pools combined. Microbes play an important role in soil C cycling, with abiotic conditions such as soil moisture and temperature governing microbial activity and subsequent soil C processes. Predictions for future climate include warmer temperatures and altered precipitation regimes, suggesting impacts on future soil C cycling. However, it is uncertain how soil microbial communities and subsequent soil organic carbon pools will respond to these changes, particularly in dryland ecosystems. A knowledge gap exists in soil microbial community responses to short- versus long-term precipitation alteration in dryland systems. Assessing soil C cycle processes and microbial community responses under current and altered precipitation patterns will aid in understanding how C pools and cycling might be altered by climate change. This study investigates how soil microbial communities are influenced by established climate regimes and extreme changes in short-term precipitation patterns across a 1000 m elevation gradient in northern Arizona, where precipitation increases with elevation. Precipitation was manipulated (50% addition and 50% exclusion of ambient rainfall) for two summer rainy seasons at five sites across the elevation gradient. In situ and ex situ soil CO2 flux, microbial biomass C, extracellular enzyme activity, and SOC were measured in precipitation treatments in all sites. Soil CO2 flux, microbial biomass C, extracellular enzyme activity, and SOC were highest at the three highest elevation sites compared to the two lowest elevation sites. Within sites, precipitation treatments did not change microbial biomass C, extracellular enzyme activity, and SOC. Soil CO2 flux was greater under precipitation addition treatments than exclusion treatments at both the highest elevation site and second lowest elevation site. Ex situ respiration differed among the precipitation treatments only at the lowest elevation site, where respiration was enhanced in the precipitation addition plots. These results suggest soil C cycling will respond to long-term changes in precipitation, but pools and fluxes of carbon will likely show site-specific sensitivities to short-term precipitation patterns that are also expected with climate change.
ContributorsMonus, Brittney (Author) / Throop, Heather L (Thesis advisor) / Ball, Becky A (Committee member) / Hultine, Kevin R (Committee member) / Munson, Seth M (Committee member) / Arizona State University (Publisher)
Created2019