Thesis (M.SC.) - Carleton University, 2007. / Includes bibliographical references (p. 124-131). Also available in electronic format on the Internet.

Thesis (M. S. in Earth and Environmental Sciences)--Vanderbilt University, Dec. 2008. / Title from title screen. Includes bibliographical references.

Thesis (Ph.D.) - University of Queensland, 2006. / Includes bibliography.

No description available.

abstract: Understanding agricultural land use requires the integration of natural factors, such as climate and nutrients, as well as human factors, such as agricultural intensification. Employing an agroecological framework, I use the Perry Mesa landscape, located in central Arizona, as a case study to explore the intersection of these factors to investigate prehistoric agriculture from A.D. 1275-1450. Ancient Perry Mesa farmers used a runoff agricultural strategy and constructed extensive alignments, or terraces, on gentle hillslopes to slow and capture nutrient rich surface runoff generated from intense rainfall. I investigate how the construction of agricultural terraces altered key parameters (water and nutrients) necessary for successful agriculture in this arid region. Building upon past work focused on agricultural terraces in general, I gathered empirical data pertaining to nutrient renewal and water retention from one ancient runoff field. I developed a long-term model of maize growth and soil nutrient dynamics parameterized using nutrient analyses of runoff collected from the sample prehistoric field. This model resulted in an estimate of ideal field use and fallow periods for maintaining long-term soil fertility under different climatic regimes. The results of the model were integrated with estimates of prehistoric population distribution and geographical characterizations of the arable lands to evaluate the places and periods when sufficient arable land was available for the type of cropping and fallowing systems suggested by the model (given the known climatic trends and land use requirements). Results indicate that not only do dry climatic periods put stress on crops due to reduced precipitation but that a reduction in expected runoff events results in a reduction in the amount of nutrient renewal due to fewer runoff events. This reduction lengthens estimated fallow cycles, and probably would have increased the amount of land necessary to maintain sustainable agricultural production. While the overall Perry Mesa area was not limited in terms of arable land, this analysis demonstrates the likely presence of arable land pressures in the immediate vicinity of some communities. Anthropological understandings of agricultural land use combined with ecological tools for investigating nutrient dynamics provides a comprehensive understanding of ancient land use in arid regions. / Dissertation/Thesis / Ph.D. Anthropology 2013

The problem that I have identified during my research for this dissertation is the quantifiable depletion and exhaustion of large percentages of the world's soils through human activity in agriculture and other industrial practices. In the course of researching this problem I have looked closely at some of the primary causes, and a range of proposed and applied solutions in the field of ecology. The primary focus of the research has been in looking at how artists have responded to ecological issues and have engaged in environmental activism in their practices. Integral to the research has been direct participation in collaborative art practices that investigate and strive to raise public awareness about issues related to soil ecology. It has proceeded through reading established texts, interviewing expert practitioners, publishing my findings, and presenting at numerous conferences, concurrently with direct participation in ecologically oriented practices, related artistic projects, professional art exhibits, activist events, and working in the field of professional organic farming. During the research phase I attended nine Planetary Collegium Sessions with fellow researchers and received valuable direction from supervising professors. The result is a written, theoretical dissertation that documents the research through text and photography in seven chapters. It has also produced a body of sculptures and documented physical experiments and performances that are motivated by, and speak directly to issues of soil ecology. The efficacy of the artwork that has been made in the course of researching problems in soil ecology comes from its continuation of, and direct participation in, established, contemporary art projects and movements that have had a demonstrable influence of society. The contribution that it makes to new knowledge is by addressing in unique ways the emerging subject of soils, which have tended to be overlooked in many ecological discussions, and in so doing it also brings to bear a unique combination of influences in its practice. These include: Art practice, Situationist performances, Core Shamanic practice (as developed by Michael Harner), soil science, inspiration drawn from a number of continental theorists, participation in sustainable agriculture, and political activism, applied simultaneously in a transdisciplinary body of work described herein specifically on behalf of soils. In this endeavor the dissertation and its body of produced objects and performances has also sought to blur some of the conventional lines between theoretical research, contemplation and practice, as appropriate to a trans-disciplinary project. Numerous discoveries have been made in the course of the research, chief among them that the new transdisciplinary approach to soil studies that my collaborators and I have taken turns out to be of necessity if we are to avert large-scale collapses of agriculture due to soil degradation on a global scale in the course of this century.

Antibiotic resistance is ubiquitous due to high usage of antibiotics and the capability of bacteria to transfer genes both horizontally and vertically. While this has dire implications for human health, the potential to disturb microbial communities and ecosystem functions they regulate is under appreciated. Antibiotics are commonly used in the livestock sector, accounting for 80% of antibiotic use domestically. This dissertation addresses three facets of this problem. Chapter 2 is a nation-wide survey of antibiotic resistance at dairy operations, aimed at understanding how ecosystem function is affected in situ. Chapter 3 describes a field-experiment, seeking to determine whether antibiotics have effects beyond soil through impacts on plant-microbe-soil feedbacks, thus potentially altering terrestrial ecosystem function. Chapter 4 investigates how rising global temperature interacts with antibiotic exposure through a microcosm-incubation experiment. These multiple stressors (i.e. temperature and antibiotics) could alter microbial community composition or physiology with repercussions on function. Additionally, chapter 4 seeks to determine whether microbes acclimate to continued antibiotic exposure. In chapter 2 I present evidence that increased antibiotic resistant gene (ARG) abundance with exposure to antibiotics and manure, and a correlation between ARGs and microbial stress. This increase in microbial stress results in elevated soil carbon loss. Chapter 3 shows that antibiotic exposure can change plant function – presumably through impacts on rhizospheric microbial community composition. Plants assimilate more nitrogen, but more carbon is lost from the system overall seemingly due to plant-soil-microbe tradeoffs. Chapter 4 shows a temporally dependent temperature–antibiotic interactive effect. Initially, pirlimycin increased microbial respiration at high temperatures, however this diminishes with time. Additional studies of microbial respiration at a range of temperatures show that microbial acclimation to antibiotic exposure may be taking place. However, interactive effects of high temperature and antibiotics appear to inhibit active microbial biomass production. Possible explanations to both of these patterns are the underlying differences in microbial community composition, specifically the fungal:bacterial. My results show that antibiotics not only lead to increased ARG abundance, but also have wide ranging effects on communities and ecosystem processes that are likely to be compounded in the face of global change. / Ph. D. / Antibiotic resistance is becoming ubiquitous. While implications for human health are dire, underappreciated are the potential effects on environmental microbes, given that microbes are drivers of ecosystem function. Antibiotics are commonly used in livestock production, accounting for 80% of antibiotic use domestically, with a substantial proportion of the administered antibiotics passing through livestock while still functional. Therefore understanding how antibiotics may be impacting livestock-associated soils is critical. This dissertation is divided into three data-driven chapters, each addressing a facet of this question. In chapter 2 I show that antibiotic exposure can increase microbial stress and decrease microbial efficiency. This reduction in microbial efficiency results in increased soil carbon loss. In chapter 3 I show that antibiotic exposure can change carbon and nitrogen cycling in plants, presumably through impacts on root-associated microbial composition. Plants assimilated more nitrogen, but more carbon was lost from the system overall, when soil was exposed to manure from cattle administered the antibiotic pirlimycin. Chapter 4 describes an interactive effect between temperature and antibiotic exposure, however, this effect appears to diminish with time. The pirlimycin treatment increased microbial respiration at high temperatures, however this effect was not observed in the second year of v the field portion of this study. Additional experimentation showed some evidence of microbial acclimation to multiple stressors. However other evidence described within this chapter paints a different picture, as interactive effects of high temperature and antibiotics appeared to inhibit active microbial biomass production. Possible explanations to both of these patterns are the underlying differences in microbial community composition, specifically broad differences in the ratio of fungi to bacteria. Therefore antibiotics not only lead to reduced microbial efficiency, but also have wide ranging effects on communities and ecosystem processes that are likely to be compounded in the face of global change.

Kwan Sai Ho. / Thesis (M.Ph.)--Chinese University of Hong Kong. / Bibliography: leaves 316-339.

Thesis (Ph.D.)--University of Western Australia, 2005.

It was found that Azotobacter vinelandii grown in a dialyzed soil medium did not fix nitrogen and had a much lower rate of respiration than when grown in Burk's nitrogen-free medium. When para-hydroxybenzoic acid served as the added oxidizable organic carbon source in dialyzed soil medium, the azotobacter grown in it were found to be unable to fix nitrogen. On the other hand, A. vinelandii fixed nitrogen when grown in soil supplemented with glucose. It was concluded that natural conditions in the soil are not conducive to nitrogen fixation by A. vinelandii.