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Description
Mycorrhizal fungi form symbiotic relationships with plant roots, increasing nutrient and water availability to plants and improving soil stability. Mechanical disturbance of soil has been found to reduce mycorrhizal inoculum in soils, but findings have been inconsistent. To examine the impact of restoration practices on riparian mycorrhizal inoculum potential, soil

Mycorrhizal fungi form symbiotic relationships with plant roots, increasing nutrient and water availability to plants and improving soil stability. Mechanical disturbance of soil has been found to reduce mycorrhizal inoculum in soils, but findings have been inconsistent. To examine the impact of restoration practices on riparian mycorrhizal inoculum potential, soil samples were collected at the Tres Rios Ecosystem Restoration and Flood Control Project located at the confluence of the Salt, Gila, and Agua Fria rivers in central Arizona. The project involved the mechanical removal of invasive Tamarix spp.( tamarisk, salt cedar) and grading prior to revegetation. Soil samples were collected from three stages of restoration: pre-restoration, soil banks with chipped vegetation, and in areas that had been graded in preparation for revegetation. Bioassay plants were grown in the soil samples and roots analyzed for arbuscular mycorrhizal (AM) and ectomycorrhizal (EM) infection percentages. Vegetations measurements were also taken for woody vegetation at the site. The mean number of AM and EM fungal propagules did not differ between the three treatment area, but inoculum levels did differ between AM and EM fungi with AM fungal propagules detected at moderate levels and EM fungi at very low levels. These differences may have been related to availability of host plants since AM fungi form associations with a variety of desert riparian forbs and grasses and EM fungi only form associations with Populus spp. and Salix spp. which were present at the site but at low density and canopy cover. Prior studies have also found that EM fungi may be more affected by tamarisk invasions than AM fungi. Our results were similar to other restoration projects for AM fungi suggesting that it may not be necessary to add AM fungi to soil prior to planting native vegetation because of the moderate presence of AM fungi even in soils dominated by tamarisk and exposed to soil disturbance during the restoration process. In contrast when planting trees that form EM associations, it may be beneficial to augment soil with EM fungi collected from riparian areas or to pre-inoculate plants prior to planting.
ContributorsArnold, Susanne (Author) / Stutz, Jean (Thesis advisor) / Alford, Eddie (Committee member) / Green, Douglas (Committee member) / Arizona State University (Publisher)
Created2012
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Description
Increasing concentrations of carbon dioxide in the atmosphere will inevitably lead to long-term changes in climate that can have serious consequences. Controlling anthropogenic emission of carbon dioxide into the atmosphere, however, represents a significant technological challenge. Various chemical approaches have been suggested, perhaps the most promising of these is based

Increasing concentrations of carbon dioxide in the atmosphere will inevitably lead to long-term changes in climate that can have serious consequences. Controlling anthropogenic emission of carbon dioxide into the atmosphere, however, represents a significant technological challenge. Various chemical approaches have been suggested, perhaps the most promising of these is based on electrochemical trapping of carbon dioxide using pyridine and derivatives. Optimization of this process requires a detailed understanding of the mechanisms of the reactions of reduced pyridines with carbon dioxide, which are not currently well known. This thesis describes a detailed mechanistic study of the nucleophilic and Bronsted basic properties of the radical anion of bipyridine as a model pyridine derivative, formed by one-electron reduction, with particular emphasis on the reactions with carbon dioxide. A time-resolved spectroscopic method was used to characterize the key intermediates and determine the kinetics of the reactions of the radical anion and its protonated radical form. Using a pulsed nanosecond laser, the bipyridine radical anion could be generated in-situ in less than 100 ns, which allows fast reactions to be monitored in real time. The bipyridine radical anion was found to be a very powerful one-electron donor, Bronsted base and nucleophile. It reacts by addition to the C=O bonds of ketones with a bimolecular rate constant around 1* 107 M-1 s-1. These are among the fastest nucleophilic additions that have been reported in literature. Temperature dependence studies demonstrate very low activation energies and large Arrhenius pre-exponential parameters, consistent with very high reactivity. The kinetics of E2 elimination, where the radical anion acts as a base, and SN2 substitution, where the radical anion acts as a nucleophile, are also characterized by large bimolecular rate constants in the range ca. 106 - 107 M-1 s-1. The pKa of the bipyridine radical anion was measured using a kinetic method and analysis of the data using a Marcus theory model for proton transfer. The bipyridine radical anion is found to have a pKa of 40±5 in DMSO. The reorganization energy for the proton transfer reaction was found to be 70±5 kJ/mol. The bipyridine radical anion was found to react very rapidly with carbon dioxide, with a bimolecular rate constant of 1* 108 M-1 s-1 and a small activation energy, whereas the protonated radical reacted with carbon dioxide with a rate constant that was too small to measure. The kinetic and thermodynamic data obtained in this work can be used to understand the mechanisms of the reactions of pyridines with carbon dioxide under reducing conditions.
ContributorsRanjan, Rajeev (Author) / Gould, Ian R (Thesis advisor) / Buttry, Daniel A (Thesis advisor) / Yarger, Jeff (Committee member) / Seo, Dong-Kyun (Committee member) / Arizona State University (Publisher)
Created2015
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Description
ABSTRACT The February 2008 study of a Snowflake, Arizona site measured changes in soil organic carbon, total nitrogen, extractable phosphorus, and soil moisture, to determine what affect One-seed Juniper (Juniperus monosperma) trees have on surrounding soil, thus affecting native grass growth. Increasing juniper densities in grasslands also decrease populations of

ABSTRACT The February 2008 study of a Snowflake, Arizona site measured changes in soil organic carbon, total nitrogen, extractable phosphorus, and soil moisture, to determine what affect One-seed Juniper (Juniperus monosperma) trees have on surrounding soil, thus affecting native grass growth. Increasing juniper densities in grasslands also decrease populations of some grassland bird species. Measurements were taken each meter along a twelve meter line transect, moving from juniper trees, through a bare soil area and into a grassland. Non-linear relationships were examined, in regard to distance from the tree and juniper root mass. Relationships were examined to determine any affect of the juniper tree on soil characteristics along the transect. Organic carbon decreased as distance increased from the trees (F=4.25, df=46, p=0.020). Soil moisture increased with distance from the trees (F=5.42, df=46, p=0.008), and juniper root mass, of roots less than 1 mm diameter, significantly decreased with distance away from the trees (F=11.29, df=46, p=0.0001). Total nitrogen and extractable phosphorus did not significantly change with distance from the tree, or presence of juniper roots. This data is important as grassland restoration projects rely on the availability of soil nutrients and water for reestablishment of native grass species.
ContributorsWeller, Christopher (Author) / Green, Douglas (Thesis advisor) / Miller, William H. (Committee member) / Alford, Edward (Committee member) / Arizona State University (Publisher)
Created2010
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Description
Despite public demand for climate change mitigation and natural open space conservancy, existing political and design efforts are only beginning to address the declining efficacy of the biotic carbon pool (C-pool) to sequester carbon. Advances in understanding of biogeochemical processes have provided methods for estimating carbon embodied in natural open

Despite public demand for climate change mitigation and natural open space conservancy, existing political and design efforts are only beginning to address the declining efficacy of the biotic carbon pool (C-pool) to sequester carbon. Advances in understanding of biogeochemical processes have provided methods for estimating carbon embodied in natural open spaces and enhancing carbon sequestration efficacy. In this study, the benefits of carbon embodied in dryland open spaces are determined by estimating carbon flux and analyzing ecological, social, and economic benefits provided by sequestered carbon. Understanding the ecological processes and derived benefits of carbon exchange in dryland open spaces will provide insight into enhancing carbon sequestration efficacy. Open space carbon is estimated by calculating the amount of carbon sequestration (estimated in Mg C / ha / y) in dryland open space C-pools. Carbon sequestration in dryland open spaces can be summarized in five open space typologies: hydric, mesic, aridic, biomass for energy agriculture, and traditional agriculture. Hydric (wetland) systems receive a significant amount of moisture; mesic (riparian) systems receive a moderate amount of moisture; and aridic (dry) systems receive low amounts of moisture. Biomass for energy production (perennial biomass) and traditional agriculture (annual / traditional biomass) can be more effective carbon sinks if managed appropriately. Impacts of design interventions to the carbon capacity of dryland open space systems are calculated by estimating carbon exchange in existing open space (base case) compared to projections of carbon sequestered in a modified system (prototype design). A demonstration project at the Lower San Pedro River Watershed highlights the potential for enhancing carbon sequestration. The site-scale demonstration project takes into account a number of limiting factors and opportunities including: availability of water and ability to manipulate its course, existing and potential vegetation, soil types and use of carbon additives, and land-use (particularly agriculture). Specific design challenges to overcome included: restoring perennial water to the Lower San Pedro River, reestablishing hydric and mesic systems, linking fragmented vegetation, and establishing agricultural systems that provide economic opportunities and act as carbon sinks. The prototype design showed enhancing carbon sequestration efficacy by 128-133% is possible with conservative design interventions.
ContributorsHuck, Erick (Author) / Cook, Edward (Thesis advisor) / Green, Douglas (Committee member) / Brooks, Kenneth (Committee member) / Montemayor, Gabriel (Committee member) / Arizona State University (Publisher)
Created2012