Matching Items (35)
Description
Irrigation agriculture has been heralded as the solution to feeding the world's growing population. To this end, irrigation agriculture is both extensifying and intensifying in arid regions across the world in an effort to create highly productive agricultural systems. Over one third of modern irrigated fields, however, show signs of serious soil degradation, including salinization and waterlogging, which threaten the productivity of these fields and the world's food supply. Surprisingly, little ecological data on agricultural soils have been collected to understand and address these problems. How, then, can expanding and intensifying modern irrigation systems remain agriculturally productive for the long-term? Archaeological case studies can provide critical insight into how irrigated agricultural systems may be sustainable for hundreds, if not thousands, of years. Irrigation systems in Mesopotamia, for example, have been cited consistently as a cautionary tale of the relationship between mismanaged irrigation systems and the collapse of civilizations, but little data expressly link how and why irrigation failed in the past. This dissertation presents much needed ecological data from two different regions of the world - the Phoenix Basin in southern Arizona and the Pampa de Chaparrí on the north coast of Peru - to explore how agricultural soils were affected by long-term irrigation in a variety of social and economic contexts, including the longevity and intensification of irrigation agriculture. Data from soils in prehispanic and historic agricultural fields indicate that despite long-lived and intensive irrigation farming, farmers in both regions created strategies to sustain large populations with irrigation agriculture for hundreds of years. In the Phoenix Basin, Hohokam and O'odham farmers relied on sedimentation from irrigation water to add necessary fine sediments and nutrients to otherwise poor desert soils. Similarly, on the Pampa, farmers relied on sedimentation in localized contexts, but also constructed fields with ridges and furrows to draw detrimental salts away from planting surfaces in the furrows on onto the ridges. These case studies are then compared to failing modern and ancient irrigated systems across the world to understand how the centralization of management may affect the long-term sustainability of irrigation agriculture.
ContributorsStrawhacker, Colleen (Author) / Spielmann, Katherine A. (Thesis advisor) / Hall, Sharon J (Committee member) / Nelson, Margaret C. (Committee member) / Sandor, Jonathan A (Committee member) / Arizona State University (Publisher)
Created2013
Description
Human activity has increased loading of reactive nitrogen (N) in the environment, with important and often deleterious impacts on biodiversity, climate, and human health. Since the fate of N in the ecosystem is mainly controlled by microorganisms, understanding the factors that shape microbial communities becomes relevant and urgent. In arid land soils, these microbial communities and factors are not well understood. I aimed to study the role of N cycling microbes, such as the ammonia-oxidizing bacteria (AOB), the recently discovered ammonia-oxidizing archaea (AOA), and various fungal groups, in soils of arid lands. I also tested if niche differentiation among microbial populations is a driver of differential biogeochemical outcomes. I found that N cycling microbial communities in arid lands are structured by environmental factors to a stronger degree than what is generally observed in mesic systems. For example, in biological soil crusts, temperature selected for AOA in warmer deserts and for AOB in colder deserts. Land-use change also affects niche differentiation, with fungi being the major agents of N2O production in natural arid lands, whereas emissions could be attributed to bacteria in mesic urban lawns. By contrast, NO3- production in the native desert and managed soils was mainly controlled by autotrophic microbes (i.e., AOB and AOA) rather than by heterotrophic fungi. I could also determine that AOA surprisingly responded positively to inorganic N availability in both short (one month) and long-term (seven years) experimental manipulations in an arid land soil, while environmental N enrichment in other ecosystem types is known to favor AOB over AOA. This work improves our predictions of ecosystem response to anthropogenic N increase and shows that paradigms derived from mesic systems are not always applicable to arid lands. My dissertation also highlights the unique ecology of ammonia oxidizers and draws attention to the importance of N cycling in desert soils.
ContributorsMarusenko, Yevgeniy (Author) / Hall, Sharon J (Thesis advisor) / Garcia-Pichel, Ferran (Thesis advisor) / Mclain, Jean E (Committee member) / Schwartz, Egbert (Committee member) / Arizona State University (Publisher)
Created2013
Description
An understanding of diet habits is crucial in implementing proper management strategies for wildlife. Diet analysis, however, remains a challenge for ruminant species. Microhistological analysis, the method most often employed in herbivore diet studies, is tedious and time consuming. In addition, it requires considerable training and an extensive reference plant collection. The development of DNA barcoding (species identification using a standardized DNA sequence) and the availability of recent DNA sequencing techniques offer new possibilities in diet analysis for ungulates. Using fecal material collected from controlled feeding trials on pygmy goats, (Capra hicus), novel DNA barcoding technology using the P6-loop of the chloroplast trnL (UAA) intron was compared with the traditional microhistological technique. At its current stage of technological development, this study demonstrated that DNA barcoding did not enhance the ability to detect plant species in herbivore diets. A higher mean species composition was reported with microhistological analysis (79%) as compared to DNA barcoding (50%). Microhistological analysis consistently reported a higher species presence by forage class. For affect positive species identification, microhistology estimated an average of 89% correct detection in control diets, while DNA barcoding estimated 50% correct detection of species. It was hypothesized that a number of factors, including variation in chloroplast content in feed species and the effect of rumen bacteria on degradation of DNA, influenced the ability to detect plant species in herbivore diets and concluded that while DNA barcoding opens up new possibilities in the study of plant-herbivore interactions, further studies are needed to standardize techniques and for DNA bar-coding in this context.
ContributorsMurphree, Julie Joan (Author) / Miller, William H. (Thesis advisor) / Steele, Kelly (Committee member) / Salywon, Andrew (Committee member) / Arizona State University (Publisher)
Created2012
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
A mule deer herd exists on the northern rim of the Grand Canyon, located on the North Kaibab Plateau. Historical references to this indigenous mule deer herd presented reports of periodic population irruption and collapse. Partially funded by the Arizona Game and Fish Department and the Arizona Deer Association, examination of herd nutritional and metabolic status from the Fall 2005 - Spring 2008 was completed at the request of AzGFD and ADA. Habitat analysis included forage micro-histological, protein, and caloric content plus whole blood and plasma assays gauging herd metabolic response. Modelling was completed using best management practices wildlife energy demand calculations and principal component analysis. Forage quality analysis and modelling suggest a sufficient amount of nitrogen (N) available (DPI) to the deer for protein synthesis. Energy analysis (MEI) of forage suggest caloric deficiencies are widely prevalent on the north Kaibab plateau. Principal component analysis integrates forage and metabolic results providing a linear regression model describing the dynamics of forage utilization, energy availability, and forage nitrogen supply with metabolic demand and response of the mule deer herd. Most of the plasma and blood metabolic indicators suggest baseline values for the North Kaibab mule deer. Albumin values are in agreement with albumin values for mule deer in the Southwest. I suggest that the agreed values become a standard for mule deer in the Southwestern U.S. As excess dietary N is converted to a caloric resource, a continual state of under-nutrition exists for the deer upon entering the N. Kaibab winter range. The population is exceeding the nutritional resource plane that the winter habitat provides. Management recommendations include implementation of multiple small-scale habitat rehabilitation efforts over time, including invasive juniper (Juniperous osteosperma) and piñon (Pinus edulis) management, prescribed burning to control big sage (Artemesia tridentata) populations, and reseeding treated areas with a seed mix of native shrubs, grasses and forbs. I recommended that the population size of the North Kaibab deer herd is maintained at the current size with natural selection controlling growth, or the population be artificially reduced through increased hunting opportunities.
ContributorsActon, Matthew W (Author) / Miller, William H. (Thesis advisor) / Brady, Ward W. (Committee member) / Huffman, Holly (Committee member) / Arizona State University (Publisher)
Created2014
Description
Though cities occupy only a small percentage of Earth's terrestrial surface, humans concentrated in urban areas impact ecosystems at local, regional and global scales. I examined the direct and indirect ecological outcomes of human activities on both managed landscapes and protected native ecosystems in and around cities. First, I used highly managed residential yards, which compose nearly half of the heterogeneous urban land area, as a model system to examine the ecological effects of people's management choices and the social drivers of those decisions. I found that a complex set of individual and institutional social characteristics drives people's decisions, which in turn affect ecological structure and function across scales from yards to cities. This work demonstrates the link between individuals' decision-making and ecosystem service provisioning in highly managed urban ecosystems.
Second, I examined the distribution of urban-generated air pollutants and their complex ecological outcomes in protected native ecosystems. Atmospheric carbon dioxide (CO2), reactive nitrogen (N), and ozone (O3) are elevated near human activities and act as both resources and stressors to primary producers, but little is known about their co-occurring distribution or combined impacts on ecosystems. I investigated the urban "ecological airshed," including the spatial and temporal extent of N deposition, as well as CO2 and O3 concentrations in native preserves in Phoenix, Arizona and the outlying Sonoran Desert. I found elevated concentrations of ecologically relevant pollutants co-occur in both urban and remote native lands at levels that are likely to affect ecosystem structure and function. Finally, I tested the combined effects of CO2, N, and O3 on the dominant native and non-native herbaceous desert species in a multi-factor dose-response greenhouse experiment. Under current and predicted future air quality conditions, the non-native species (Schismus arabicus) had net positive growth despite physiological stress under high O3 concentrations. In contrast, the native species (Pectocarya recurvata) was more sensitive to O3 and, unlike the non-native species, did not benefit from the protective role of CO2. These results highlight the vulnerability of native ecosystems to current and future air pollution over the long term. Together, my research provides empirical evidence for future policies addressing multiple stressors in urban managed and native landscapes.
ContributorsMiessner Cook, Elizabeth (Author) / Hall, Sharon J (Thesis advisor) / Boone, Christopher G (Committee member) / Collins, Scott L. (Committee member) / Grimm, Nancy (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
In riparian ecosystems, reptiles and amphibians are good indicators of environmental conditions. Herpetofauna have been linked to specific microhabitat characteristics, microclimates, and water resources in riparian forests. My objective was to relate herpetofauna abundance to changes in riparian habitat along the Virgin River caused by the Tamarix biological control agent, Diorhabda carinulata, and riparian restoration.
During 2013 and 2014, vegetation and herpetofauna were monitored at 21 riparian locations along the Virgin River via trapping and visual encounter surveys. Study sites were divided into four stand types based on density and percent cover of dominant trees (Tamarix, Prosopis, Populus, and Salix) and presence of restoration activities: Tam, Tam-Pros, Tam-Pop/Sal, and Restored Tam-Pop/Sal. Restoration activities consisted of mechanical removal of non-native trees, transplanting native trees, and introduction of water flow. All sites were affected by biological control. I predicted that herpetofauna abundance would vary between stand types and that herpetofauna abundance would be greatest in Restored Tam-Pop/Sal sites due to increased habitat openness and variation following restoration efforts.
Results from trapping indicated that Restored Tam-Pop/Sal sites had three times more total lizard and eight times more Sceloporus uniformis captures than other stand types. Anaxyrus woodhousii abundance was greatest in Tam-Pop/Sal and Restored Tam-Pop/Sal sites. Visual encounter surveys indicated that herpetofauna abundance was greatest in the Restored Tam-Pop/Sal site compared to the adjacent Unrestored Tam-Pop/Sal site. Habitat variables were reduced to six components using a principle component analysis and significant differences were detected among stand types. Restored Tam-Pop/Sal sites were most similar to Tam-Pop/Sal sites. S. uniformis were positively associated with large woody debris and high densities of Populus, Salix, and large diameter Prosopis.
Restored Tam-Pop/Sal sites likely supported higher abundances of herpetofauna, as these areas exhibited greater habitat heterogeneity. Restoration activities created a mosaic habitat by reducing canopy cover and increasing native tree density and surface water. Natural resource managers should consider implementing additional restoration efforts following biological control when attempting to restore riparian areas dominated by Tamarix and other non-native trees.
During 2013 and 2014, vegetation and herpetofauna were monitored at 21 riparian locations along the Virgin River via trapping and visual encounter surveys. Study sites were divided into four stand types based on density and percent cover of dominant trees (Tamarix, Prosopis, Populus, and Salix) and presence of restoration activities: Tam, Tam-Pros, Tam-Pop/Sal, and Restored Tam-Pop/Sal. Restoration activities consisted of mechanical removal of non-native trees, transplanting native trees, and introduction of water flow. All sites were affected by biological control. I predicted that herpetofauna abundance would vary between stand types and that herpetofauna abundance would be greatest in Restored Tam-Pop/Sal sites due to increased habitat openness and variation following restoration efforts.
Results from trapping indicated that Restored Tam-Pop/Sal sites had three times more total lizard and eight times more Sceloporus uniformis captures than other stand types. Anaxyrus woodhousii abundance was greatest in Tam-Pop/Sal and Restored Tam-Pop/Sal sites. Visual encounter surveys indicated that herpetofauna abundance was greatest in the Restored Tam-Pop/Sal site compared to the adjacent Unrestored Tam-Pop/Sal site. Habitat variables were reduced to six components using a principle component analysis and significant differences were detected among stand types. Restored Tam-Pop/Sal sites were most similar to Tam-Pop/Sal sites. S. uniformis were positively associated with large woody debris and high densities of Populus, Salix, and large diameter Prosopis.
Restored Tam-Pop/Sal sites likely supported higher abundances of herpetofauna, as these areas exhibited greater habitat heterogeneity. Restoration activities created a mosaic habitat by reducing canopy cover and increasing native tree density and surface water. Natural resource managers should consider implementing additional restoration efforts following biological control when attempting to restore riparian areas dominated by Tamarix and other non-native trees.
ContributorsMosher, Kent (Author) / Bateman, Heather L (Thesis advisor) / Stromberg, Juliet C. (Committee member) / Miller, William H. (Committee member) / Arizona State University (Publisher)
Created2014
Description
Over the past century in the southwestern United States human actions have altered hydrological processes that shape riparian ecosystems. One change, release of treated wastewater into waterways, has created perennial base flows and increased nutrient availability in ephemeral or intermittent channels. While there are benefits to utilizing treated wastewater for environmental flows, there are numerous unresolved ecohydrological issues regarding the efficacy of effluent to sustain groundwater-dependent riparian ecosystems. This research examined how nutrient-rich effluent, released into waterways with varying depths to groundwater, influences riparian plant community development. Statewide analysis of spatial and temporal patterns of effluent generation and release revealed that hydrogeomorphic setting significantly influences downstream riparian response. Approximately 70% of effluent released is into deep groundwater systems, which produced the lowest riparian development. A greenhouse study assessed how varying concentrations of nitrogen and phosphorus, emulating levels in effluent, influenced plant community response. With increasing nitrogen concentrations, vegetation emerging from riparian seed banks had greater biomass, reduced species richness, and greater abundance of nitrophilic species. The effluent-dominated Santa Cruz River in southern Arizona, with a shallow groundwater upper reach and deep groundwater lower reach, served as a study river while the San Pedro River provided a control. Analysis revealed that woody species richness and composition were similar between the two systems. Hydric pioneers (Populus fremontii, Salix gooddingii) were dominant at perennial sites on both rivers. Nitrophilic species (Conium maculatum, Polygonum lapathifolium) dominated herbaceous plant communities and plant heights were greatest in effluent-dominated reaches. Riparian vegetation declined with increasing downstream distance in the upper Santa Cruz, while patterns in the lower Santa Cruz were confounded by additional downstream agricultural input and a channelized floodplain. There were distinct longitudinal and lateral shifts toward more xeric species with increasing downstream distance and increasing lateral distance from the low-flow channel. Patterns in the upper and lower Santa Cruz reaches indicate that water availability drives riparian vegetation outcomes below treatment facilities. Ultimately, this research informs decision processes and increases adaptive capacity for water resources policy and management through the integration of ecological data in decision frameworks regarding the release of effluent for environmental flows.
ContributorsWhite, Margaret Susan (Author) / Stromberg, Juliet C. (Thesis advisor) / Fisher, Stuart G. (Committee member) / White, Dave (Committee member) / Holway, James (Committee member) / Wu, Jianguo (Committee member) / Arizona State University (Publisher)
Created2011
Description
Non-native saltcedar (Tamarix spp.) has invaded many riparian communities and is the third most abundant tree in Southwestern riparian areas. I evaluated lizard populations and microhabitat selection during 2009 and 2010 along the Virgin River in Nevada and Arizona to determine the impact of saltcedar. Along the riparian corridor, I observed common side-blotched lizards (Uta stansburiana) within two vegetation types: monotypic non-native saltcedar stands or mixed stands of cottonwood (Populus fremontii), willow (Salix spp.), mesquite (Prosopis spp.) and saltcedar. I predicted that population parameters such as body condition, adult to hatchling ratio, abundance, and persistence would vary among vegetation types. Also, I predicted the presence of saltcedar influences how lizards utilize available habitat. Lizard population parameters were obtained from a mark-recapture study in which I captured 233 individual lizards. I examined habitat selection and habitat availability using visual encounter surveys (VES) for lizards and recorded 11 microhabitat variables where 16 lizards were found. I found no significant difference in population parameters between mixed and non-native saltcedar communities. However, population parameters were negatively correlated with canopy cover. I found that lizards selected habitat with low understory and canopy cover regardless of vegetation type. My results indicate that lizards utilize similar structural characteristics in both mixed and non-native vegetation. Understanding impacts of saltcedar on native fauna is important for managers who are tasked with control and management of this non-native species.
ContributorsNielsen, Danny (Author) / Bateman, Heather L. (Thesis advisor) / Miller, William H. (Committee member) / Sullivan, Brian K. (Committee member) / Arizona State University (Publisher)
Created2011