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- All Subjects: Ecology
- Creators: School of Life Sciences
- Creators: Hall, Sharon J
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
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
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
This paper explores the relationship between wildfire management and the consideration of ecological and environmental concerns in Arizona. To get a proper perspective on the current state of wildfire management in Arizona, information on two wildfire management programs, the Four Forests Restoration Initiative and FireScape, was researched and analyzed, as well as contemporary fire policy, a history of wildfire in Arizona, and two recent fires in Sedona, AZ. The two fires in Sedona, the Brins Fire of 2006 and the Slide Fire of 2014, act as a focal point for this ecological management transition, as even within an 8-year period, we can see the different ways the two fires were managed and the transition to a greater ecological importance in management strategies. These all came together to give a full spectrum for the factors that have led to more ecologically-prominent wildfire management strategies in Arizona.
ContributorsGeorge-Sills, Dylan (Author) / Pyne, Stephen (Thesis director) / Hirt, Paul (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor) / School of Sustainability (Contributor)
Created2015-05
Description
Water is the main driver of net primary productivity (NPP) in arid ecosystems, followed by nitrogen and phosphorous. Precipitation is the primary factor in determining water availability to plants, but other factors such as surface rocks could also have an impact. Surface rocks may positively affect water availability by preventing evaporation from soil, but at higher densities, surface rocks may also have a negative impact on water availability by limiting water infiltration or light availability. However, the direct relationship between rock cover and aboveground net primary productivity (ANPP), a proxy for NPP, is not well understood. In this research we explore the relationship between rock cover, ANPP, and soil nutrient availability. We conducted a rock cover survey on long-term fertilized plots at fifteen sites in the Sonoran Desert and used 4 years of data from annual plant biomass surveys to determine the relationship between peak plant biomass and surface rock cover. We performed factorial ANCOVA to assess the relationship among annual plant biomass, surface rocks, precipitation, and fertilization treatment. Overall we found that precipitation, nutrients, and rock cover influence growth of Sonoran Desert annual plants. Rock cover had an overall negative relationship with annual plant biomass, but did not show a consistent pattern of significance over four years of study and with varying average winter precipitation.
ContributorsShaw, Julea Anne (Author) / Hall, Sharon (Thesis director) / Sala, Osvaldo (Committee member) / Cook, Elizabeth (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor)
Created2015-05
Description
In today's world, critical thinking and using a systems approach to problem solving are skills that are far too rare. In the age of information, the truth has become muddled by "fake news" and a constant barrage of exaggerations or blatant falsehoods. Without critical thinking skills, "many members of our society do not command the scientific literacy necessary to address important societal issues and concerns" (NCES 2012, p.11). Additionally, far too many people are incapable of thinking long term and understanding how their actions affect others. Because of this shortsightedness our world is facing one of its biggest ecological crises \u2014 global warming confounded by overpopulation and overconsumption. Now, more than ever, it is critical "for our young people to have a basic understanding of the relevant scientific ideas, technologies and ethical issues and powers of reasoning, to be prepared to face these issues" (Harlen et al., 2015). I believe that investigating innovative ways to teach ecology could be an important step to accomplishing this. Learning to think like a scientist forces people to rely on facts, follow similar protocols to deduce these facts, and be able to think critically about misleading events. More specifically, ecology education will allow people to develop those skills while also learning about team work, open-mindedness, and their environment. Ecology is defined as "the branch of biology that deals with the relations of organisms to one another and to their physical surroundings" (Dictionary.com, 2018). It is clear that this subcategory of science could act as a powerful introduction to the scientific world and how we relate to it. Its introduction at a young age has the potential to create a generation of conscientious and curious lifelong learners. In an attempt to support effective ways to teach ecology, I developed an educational unit and applied it in different educational contexts. My target audience was elementary aged students and I tested this unit with children in Phoenix Metropolitan Area afterschool programs. I taught core concepts of ecology \u2014 the water cycle, the sun's energy, plants and photosynthesis, and food webs \u2014in a sequence of lesson plans that build upon each other. Finally, I determined the appropriate age group and setting for these lesson plans through research and in-class observations. In this document, I explain the process I went through in developing my lesson plans, why I felt compelled to make them, and my experiences in implementing them.
ContributorsVotaw, Alexandra Lindsay (Author) / Larson, Kelli (Thesis director) / Herrmann, Lisa (Committee member) / York, Abigail (Committee member) / School of Art (Contributor) / The Design School (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
Peatlands are a type of wetlands where the rate of accumulation of organic matter exceed the rate of decomposition and have accumulated more than 30 cm of peat (Joosten and Clark, 2002). Peatlands store approximately 30% of all terrestrial carbon as recalcitrant peat, partially decomposed plant and microbial biomass, while simultaneously producing almost 40% of the globally emitted methane (Schmidt et al., 2016), making peatlands an important component of the carbon budgets. Published research indicates that the efficiency of carbon usage among microbial communities can determine the soil-carbon response to rising temperatures (Allison et al. 2010). By determining carbon consumption in peatland soils, total community respiration response, and community structure change with additions, models of carbon use efficiency in permafrost peatlands will be well-informed and have a better understanding of how the peatlands will respond to, and utilize, increased availability of carbon compounds due to the melting permafrost. To do this, we will sequence Lutose deep core samples to observe baseline microbial community structure at different depths and different age-gradients, construct substrate incubations of glucose and propionate and observe community respiration response via a gas chromatography flame ionization detector, track the glucose and propionate additions with high-performance liquid chromatography (HPLC), and sequence the samples once more to determine if there was a deviation from the initial community structure obtained prior to the incubations. We found that our initial sequencing data was supported by previous work (Lin et al., 2014), however we were unable to sequence samples post-incubation due to time constraints. In this sequencing analysis we found that the strongest variable that made samples biologically similar was the age-gradient site in which they were extracted. We found that the group with glucose additions produced the most carbon dioxide compared with the other treatments, but was not the treatment that dominated the production of methane. Finally, in the HPLC samples that were analyzed, we found that glucose is likely forming the most by-product accumulation from mass balance calculations, while propionate is likely forming the least. Future experimentation should focus on the shortcomings of this experiment. Further analysis of 16S rRNA sequencing data from after the incubations should be analyzed to determine the change in microbial community structure throughout the experiment. Furthermore, HPLC analysis for the several samples need to be done and followed up with mass balance to determine where the added glucose and propionate are being allocated within the soil. Once these pieces of the puzzle are put into place, our original question of how the microbial community structure changes at different depths and age-gradients within permafrost peatlands will be conclusively answered.
ContributorsFrese, Alexander Nicholas (Author) / Cadillo-Quiroz, Hinsby (Thesis director) / van Paassen, Leon (Committee member) / Sarno, Analissa (Committee member) / School of Life Sciences (Contributor) / School of Mathematical and Statistical Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
Ephemeral and intermittent streams are valuable sources of surface water support in the arid ecosystems of the Southwestern United States. These streams account for over 80% of the streams in the American Southwest and their importance has been indicated in many studies. Ephemeral and intermittent streams support a wide range of plant and animal species in both continuous and episodic fashions. This study aimed to gain a better understanding of the relationship between streamflow permanence and patterns of biomass and secondary production of the riparian fauna these ecosystems support. This was accomplished through a yearlong survey in the Huachuca Mountains of Southeastern, Arizona where macroinvertebrates were collected at various sites along a gradient of streamflow permanence before, during, and after the three month monsoon season that supplies most of the annual rainfall in this region. The results of my surveys indicate that 1) Sites characterized by low streamflow permanence were more responsive to changes in precipitation than sites characterized by relatively high streamflow permanence 2) In ephemeral streams, there is a significant peak in terrestrial macroinvertebrate production and biomass both during and after the monsoon season 3) streamflow permanence may convey consistent but not exceptional secondary production whereas seasonality in rainfall may convey exceptional but episodic secondary production—more so in sites where streamflow is not consistent.
ContributorsMcCartin, Michael Patrick (Author) / Sabo, John (Thesis director) / Stromberg, Juliet (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor)
Created2014-05
Description
It is well known that deficiencies in key chemical elements (such as phosphorus, P) can reduce animal growth; however, recent empirical data have shown that high levels of dietary nutrients can also reduce animal growth. In ecological stoichiometry, this phenomenon is known as the "stoichiometric knife edge," but its underlying mechanisms are not well-known. Previous work has suggested that the crustacean zooplankter Daphnia reduces its feeding rates on phosphorus-rich food, causing low growth due to insufficient C (energy) intake. To test for this mechanism, feeding rates of Daphnia magna on algae (Scenedesmus acutus) differing in C:P ratio (P content) were determined. Overall, there was a significant difference among all treatments for feeding rate (p < 0.05) with generally higher feeding rates on P-rich algae. These data indicate that both high and low food C:P ratio do affect Daphnia feeding rate but are in contradiction with previous work that showed that P-rich food led to strong reductions in feeding rate. Additional experiments are needed to gain further insights.
ContributorsSchimpp, Sarah Ann (Author) / Elser, James (Thesis director) / Neuer, Susanne (Committee member) / Peace, Angela (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor) / School of Sustainability (Contributor)
Created2014-05