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Soil Health Assessment For The Agroecosystems Of West Tennessee, Surendra Singh

Doctoral Dissertations

Soil health assessment is important for making informed sustainable management decisions in production systems. An established standardized method to quantify soil health is lacking and the validity of the existing methods across agroecoregions and cropping systems is not yet proven. Therefore, this study aims to evaluate the feasibility of widely discussed three soil health tests - Haney’s Soil Health Test (HSHT), Comprehensive Assessment of Soil Health (CASH), and Alabama Soil Health Index (ASHI) to assess soil health in diverse cropping systems of Tennessee. Since these approaches were originally developed for specific agroecoregions, we hypothesized that these tests are not sensitive …

A Review Of Horticultural Therapy And Horticultural Therapy Education In The United States: Addressing Challenges And Opportunities, Derrick R. Stowell

Doctoral Dissertations

The Horticultural Therapy (HT) profession has been formally organized in the United States since 1973. Despite the long history of horticulture being used as therapy, the profession of HT in the United States has not advanced as quickly as other allied healthcare professions. This study will review the current challenges and opportunities for HT and HT education in the United States.

A qualitative study of the status of the profession was conducted to determine what challenges and opportunities the profession of HT currently has and how the profession can meet those challenges and opportunities. The study sample was recruited from …

Soil Moisture Sensitivity Of Microbial Processing Of Soil Organic Carbon, Shikha Singh

Doctoral Dissertations

Soil organic carbon (SOC) is the largest terrestrial C pool and understanding SOC decomposition in response to environmental factors is critical for accurate predictions of climatic change. Soil moisture is one of the most important, yet less explored, environmental factors controlling soil microbial respiration. The relationship between soil moisture and respiration also varies with soil texture. Currently, it is difficult to predict feedbacks to climatic changes from changes in soil moisture, as most earth system models lack site-specific, experimentally-derived parameters to represent soil moisture-texture-respiration relationships. The overarching goals of this dissertation are to gain a fundamental understanding of the interactive …

Root Stage Distributions And Their Importance In Plant-Soil Feedback Models, Tyler Poppenwimer

Doctoral Dissertations

Roots are fundamental to PSFs, being a key mediator of these feedbacks by interacting with and affecting the soil environment and soil microbial communities. However, most PSF models aggregate roots into a homogeneous component or only implicitly simulate roots via functions. Roots are not homogeneous and root traits (nutrient and water uptake, turnover rate, respiration rate, mycorrhizal colonization, etc.) vary with age, branch order, and diameter. Trait differences among a plant’s roots lead to variation in root function and roots can be disaggregated according to their function. The impact on plant growth and resource cycling of changes in the distribution …

Root Phosphomonoesterase As A Vital Component Of Increasing Phosphorus Availability In Tropical Forests, Kristine Grace Manno Cabugao

Doctoral Dissertations

Tropical forests, relative to other terrestrial ecosystems, exchange the largest amount of carbon with the atmosphere and also constitute a significant carbon sink. However, nutrient limitation, particularly of phosphorus (P), could limit growth of tropical forests and their function with the global carbon cycle. Thus, understanding root mechanisms to acquire P is necessary to representing the P cycle and corresponding interactions with plant growth. A large portion of total soil P in tropical forests occurs in organic forms, only accessible through root and microbial production of phosphatase enzymes. These phosphatase enzymes mineralize organic P into orthophosphate, the form of P …

Genetic And Epigenetic Control Of Soybean Agronomic Traits, Daniel Niyikiza

Doctoral Dissertations

Greater soybean productivity depends on the genetic improvement of yield components, epigenetic effects and the interactions with surrounding environment. We explored the possibility of soybean improvement by conventional biparental crossing of soybean lines, differing by seed quality, yield, and resistance to a range of pathogens, including soybean cyst nematode (SCN). We investigated the role of Resistance to Heterodera glycines (Rhg) 1 and 4 loci in soybean resistance to SCN, race 2 and 3. Further, we evaluated the adaptability of temperate-origin soybean lines in tropical environments of Rwanda. Lastly, we examined gene expression, RNA splicing, DNA methylation and their interactions in …

Needles In A Haystack Of Protein Diversity: Interrogation Of Complex Biological Samples Through Specialized Strategies In Bottom-Up Proteomics Uncover Peptides Of Interest For Diverse Applications, Manuel I. Villalobos Solis

Doctoral Dissertations

Peptide identification is at the core of bottom-up proteomics measurements. However, even with state-of the-art mass spectrometric instrumentation, peptide level information is still lost or missing in these types of experiments. Reasons behind missing peptide identifications in bottom-up proteomics include variable peptide ionization efficiencies, ion suppression effects, as well as the occurrence of chimeric spectra that can lower the efficacy of database search strategies. Peptides derived from naturally abundant proteins in a biological system also have better chances of being identified in comparison to the ones produced from less abundant proteins, at least in regular discovery-based proteomics experiments. This dissertation …