Plant Science & Landscape Architecture Theses and Dissertations

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GENOMICS ENABLED GENE DISCOVERY IN DIPLOID AND POLYPLOID WHEAT
(2024) Yadav, Inderjit Singh; Tiwari, Vijay; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Hexaploid bread wheat (Triticum aestivum) is one of the most important staple food crops for humans. Sustainable genetic improvement in wheat is critical for ensuring global food security and requires the introduction of new genes and alleles into elite wheat cultivars. The progenitor species and wild wheat relatives are a reservoir of genetic diversity for wheat improvement. This doctoral thesis demonstrates the application of genomic resources and bioinformatics pipelines to characterize the wild germplasm and to streamline the gene discovery pipeline using five diverse species involving wheat progenitor, wild, and related species. Genomics-assisted characterization of the genetic diversity present in gene banks is a major step towards the systematic utilization of unexploited germplasm to ensure the sustainable development of new varieties. Toward this end, we used genomics datasets to curate wild and related accessions of tetraploid wheat from two distinct species Triticum turgidum and Triticum timopheevii. Using Genotyping by sequencing (GBS) data and a unique similarity matrix and powercore analysis, a set of 102 accessions were identified as the core set accessions that represent 20 and 35 percent of the total accessions of the WGRC tetraploid wheat collection of T. turgidum and T. timopheevii, respectively. Further, three distinct centers of rich genetic diversity were identified for wild and domesticated emmer and T. timopheevii in the Fertile Crescent. GWAS analysis of the genotypic and phenotypic dataset identified a novel QTL for leaf rust resistance on chromosome 2B in T. timopheevii. Triticale is a man-made cereal derived from a cross between tetraploid and hexaploid wheat with diploid rye. There are large numbers of triticale germplasm available in different gene banks; however, in many cases, the ploidy information is not accurate and affects the quality of work with large triticale germplasm. In this work, using the low-cost GBS datasets, a pipeline was developed to detect contamination in the UMD triticale collection and facilitated the accurate classification of ploidy, ensuring the purity of the triticale germplasm. This approach identified contamination of 11 wheat accessions and enabled the correct classification of 236 hexaploid and 12 octoploid triticale, these results were further confirmed through GISH experiments. Wild and related germplasms are considered as the goldmine of genetic diversity for wheat improvement. The modern wheat cultivars have gone through several rounds of heavy selections for yield related traits and have lost the genetic diversity against several abiotic and biotic stresses. On the other hand, wild relatives of wheat have been growing naturally without any substantial artificial selection pressure and it allowed them to preserve their genetic diversity. This study investigates the genetic diversity of a selected set of genes to visualize the differences in wild wheat relatives and polyploid wheat cultivars. To study these differences, group 5 chromosome of Aegilops geniculata and Aegilops umbellulata, belonging to the tertiary gene pool, were assembled. Comparative analysis revealed a higher rate of pseudogenization in bread wheat compared to these two wild relatives, primarily due to the difference in exon/intron length between the genes, rendering these genes non-functional. Diploid einkorn wheat (Triticum monococcum), with inherent disease resistance, offers a valuable resource for wheat improvement. To facilitate its proper utilization, two of the reference genomes-one wild (T. monococcum ssp. aegilopoides) and one domesticated (T. monococcum ssp. monococcum) were assembled in the study. Kmer-GWAS identified seven novel QTLs associated with powdery mildew resistance, three for leaf rust resistance, and two for stem rust resistance. These QTLs harbor diverse gene classes encoding for resistance gene analogs, cysteine-rich receptor kinases, transcription factors, and G-type lectins. Overall, the knowledge and resources developed in this research would contribute to the characterization of vast germplasm and the development of climate-resilient wheat.
DESIGNING AN ACCESSIBLE AGRICULTURAL GARDEN: CONNECTING SOLIDARITY & AGROECOLOGY
(2024) Boyle, Patrick Robert; Ruggeri, Deni; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
This thesis explores the potential of agroecology as a transformative framework for guiding the transition of Bergamo's agricultural landscape toward sustainability, resilience, and community well-being. Grounded in the evolution of agroecology from farm-scale design to regional planning, the research investigates how this approach can integrate ecological methodologies and participatory action research in design to implement sustainable farming practices, rehabilitate landscapes, and cultivate solidarity-driven producer-consumer relationships. By emphasizing the interconnectedness of ecology, economy, and society, the study addresses whether agroecology can shape a district into a resilient landscape that enhances people's lives and promotes health and well-being.Through an interdisciplinary lens, the thesis also delves into the broader concept of landscape, highlighting its role in social well-being and advocating for the protection and responsible management of landscapes as a fundamental human right. It explores the principles of landscape democracy and solidarity, aiming to empower communities to reconnect with their environments and promote ecological restoration through collective action and ethical practices. Ultimately, the research strives to contribute to the discourse on agroecology and landscape planning, offering proposals and strategies for actionable change in regenerative and organic agricultural systems that prioritize the needs and values of local communities.
INTEGRATING FORWARD AND REVERSE GENETIC TOOLS FOR FAST FORWARDING WHEAT IMPROVEMENT
(2024) Schoen, Adam William; Tiwari, Vijay K; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Bread wheat (Triticum aestivum) provides roughly 20% of the human daily caloric intake and is an important crop for global food security. Changing climatic conditions as well as biotic and abiotic stresses are threatening wheat production worldwide. Sustainable and continuous improvement of wheat using novel genes and alleles is critical to tackle wheat’s imminent challenges. Recent advances in wheat genomics have allowed researchers now to fast-track gene discovery pipelines by implementing strategies first developed in less complex model species. This thesis explores the use of forward and reverse genetic approaches to efficiently discover, map, and validate genes controlling important agronomic traits in bread wheat as well as describes a robust protocol to reduce the generation time in winter wheat. Speed breeding is an important tool that utilizes an increased photoperiod and growing temperature to increase vegetative growth and reduce the time from sowing to harvest. Chapter 1 of this thesis outlines a reproducible method to significantly reduce the generation time in winter wheat from over 120 days based on what has been previously reported to 93 days regardless of vernalization requirements or photoperiod sensitivity and provide a useful tool to increase the pace of the genetic gains in the winter wheat breeding programs. Tillering in wheat directly influences the major yield-related trait, spikes per unit area. Using the forward genetics approach, chapter 2 of thesis reports the identification of a novel tiller inhibition gene (tin6) to a small physical region of 2.1 Mb region on chromosome 2DS. This was the first example of using a genome coming from the pan-genome of wheat to perform MutMap. Using reverse genetics also has the potential to improve the end-use properties of wheat by knocking out genes which result in an increase of the nutritional value of the flour. Chapter 3 of this thesis, TILLING was used to identify knockouts in all three homeologous copies of the starch synthase gene SSIIa, which has been shown to increase the amount resistant starch in the endosperm of wheat which is known to have health benefits in humans. The grains coming from triple knockouts of SSIIa contained 118% higher resistant starch, and though they showed a decrease in thousand kernel weight, they did not have a shriveled phenotype which had been seen in other ssiia mutants. Chapter 4 of the thesis demonstrate reference genome enabled positional cloning of a tiller inhibition gene (tin3) in diploid wheat species Triticum monococcum. A MutMap population generated from a cross between tin3 and wildtype T. monococcum resulted in the identification of a single candidate gene, encoding a BLADE-ON-PETIOLE-Like protein, containing a splice-variant mutation. To show the power of using a diploid species for translational research in hexaploid wheat, the reverse genetics approach TILLING (Targeting Induced Local Lesions IN Genomes) was used to identify mutations in all three homeologous copies of tin3 in the Jagger mutant population. The full null mutant for the tin3 locus in wheat showed significantly reduced tillering in comparison to wildtype providing concrete evidence that genetic discoveries that are found in diploid wheat can be effectively translated to hexaploid wheat. There are some genes and QTLs have been identified that increase spike length, spikelets per spike, and grain size, very few studies have focused on increasing the number of grains per floret. Chapter 5 of the thesis was focused on positional cloning of the Mov-1 locus which is the underlying gene responsible for the multiovary (MOV) phenotype. The Mov-1 locus dominantly expresses as three ovaries per wheat floret, each of which develop into a grain. Using high resolution genetic mapping with the MOV-reference genome and gene expression data, we identified a single candidate gene that was localized to a small 144kb region on the Mov-1 physical region. To validate the role of the Mov-1 candidate gene in the MOV phenotype, ethyl methanesulfonate (EMS) and gamma radiation mutagenesis was performed to create deleterious point and deletions mutations, respectively. Using 5 independent TILLING and 5 deletion mutants this study demonstrate that Mov-1 candidate gene is required for the MOV phenotype in wheat. It is an exciting time to work in wheat research as the growing wheat genomic toolbox allows for researchers to efficiently identify and validate genes that have potential to improve wheat performance. The methods and findings in this body of work provide a breadth of knowledge that can be implemented in additional genetic studies in wheat in order to fast-track gene and trait discovery for the benefit of wheat geneticists and breeders alike.
INVESTIGATING THE RELATIONSHIPS BETWEEN BUILT AND NATURAL WINDOW VIEWS, AND STUDENTS PERCEIVED RESTORATION USING VRITUAL REALITY
(2024) Esmaeili, Azadeh; Ellis, Christopher C.E; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
This thesis explores the concept of perceived restorativeness in virtual window views, which have significant contributions to the field of landscape architecture and environmental psychology. It begins with a comprehensive literature review to define perceived restorativeness which lies on Attention Restoration Theory(ART). The main emphasis in literature is on the importance of four restorative factors: fascination, being away, extent, and compatibility. All these four factors contribute to an environment’s restorative quality.This study acknowledges the existing gaps regarding the impact of virtual views both built and natural environments on perceived restoration within design studio , because the studio environments are critical in landscape architecture, architecture, and all the fields related to design. This study wants to fill this gap. In terms of research questions, all the research questions are designed to explore how different virtual window views affect perceived restoration, and whether variation in the natural and built environment affects that restorative quality. In the methodology chapter, the process of collecting data from participants for data analysis is described.45 participants responded to the perceived restorativeness scale (PRS-16), after displaying virtual window views from the School of Architecture Design Studio. All the responses were analyzed by using paired t-test and ANOVA to measure the restorative quality of different window views. Findings from data analysis indicate that not all virtual window views make the same restorative impact on participants. A significant variation was observed within and between categories of built and nature. Although all the nature views have significant restorative quality, the plaza as a virtual built window view perceived restorative benefit as well. This study makes an important contribution to investigating the restorative quality of virtual views in educational settings.
Co-Creating the Yard: A study in defining dignity in the workplace for landscape labor
(2024) McCormick, Katherine; Ruggeri, Deni; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Landscape architecture and landscape labor share a reciprocal relationship; one does not exist without the other. A landscape designer or architect produces a set of plants and a labor crew installs and maintains the work of the landscape designer or architect. This thesis project explores the definition of dignity as it pertains to landscape labor through participatory research methods: interviews, photovoice, vignettes, and co-design. The crew members of one landscape design/build and maintenance firm participated in the research. The research gathered informed the re-design of the Yard: the workspace where the landscape crew members report to work each morning and afternoon.
INTEGRATED EDIBLE LANDSCAPES: CELEBRATING MULTICULTURALISM AT BROOKSIDE GARDENS
(2024) Dirmeyer, Brandt; Ellis, Christopher; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Cultural diversity is an integral part of twenty-first century societies. The planet is interconnected now more than ever. The effects of climate change are forcing people to leave their homes in search of better living conditions. When people immigrate to a new place, they take with them their experiences, their traditions, and their identities, including their preferred foods, but the raw ingredients that one is accustomed to may be difficult to access. One way in which public spaces can help individuals adapt to their new environment is by making a place feel familiar through integrated edible landscape designs. By growing culturally relevant edible plants in a public space, the feeling of being at home can be cultivated while at the same time increasing the availability of culturally relevant crops to foreign born persons dealing with food insecurity.
Spreading the Seeds of a Solidarity Landscape: Co-creating a Biophilic Landscape and Training Curriculum in Northern Italy
(2024) Christensen, Mary Elizabeth; Ruggeri, Deni; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
A wealth of research explores the link between biophilia, access to nature, health, well-being, and quality of life (Wilson, 1984; Kellert, 1997; Louv, 2008; Kaplan & Kaplan, 1989; Cooper Marcus & Sachs, 2013). Drawing on this body of research, nature-based interventions employed by social work professionals promote positive connections to nature and improve health and well-being for vulnerable populations (Obeng et al., 2023; Overbey et al., 2021). This thesis explores a participatory action research project using the case study of Villaggio Solidale, a charitable co-housing community in Northern Italy. Following the use of participatory methods, including co-creation, listening, observation, and prototyping, researchers are co-designing a Solidarity Landscape and co-creating a training curriculum with community social workers and educators to integrate nature-based interventions, biophilia, and well-being into the larger ecosystem surrounding Villaggio Solidale, ensuring that the landscape will become a central tool to support community solidarity, health, and well-being.
MAKING APPLES BLUSH: UNDERSTANDING HOW THE COMBINED USE OF REFLECTIVE GROUNDCOVERS AND PLANT GROWTH REGULATORS IMPACT RED SKIN COLORATION AND QUALITY OF ‘HONEYCRISP’ APPLES IN THE MID-ATLANTIC US
(2024) Miah, Md Shipon; Farcuh, Macarena; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Apples are among the most valuable fruits globally, with 'Honeycrisp' ranking as the top sales-producing cultivar in the US. However, challenges such as insufficient red skin coloration and increased preharvest fruit drop significantly diminish their market value. Reflective groundcovers have been reported to enhance apple skin coloration, while the application of the plant growth regulator AVG reduces fruit drop but may negatively impact skin coloration. Research on the impacts of these practices in mid-Atlantic US-grown apples remains limited. In this two years study, our aims were 1) to evaluate the effect of reflective groundcovers on solar radiation (PPFD, UV) distribution; 2) to assess the combined effect of reflective groundcovers and ethylene inhibitor (AVG) on preharvest fruit drop, ethylene production, red blush percentage, and overall fruit quality; 3) to investigate the combined effect of reflective groundcovers and ethylene inhibitor (AVG) on expression level of key anthocyanin and ethylene biosynthesis related genes; 4) to determine the combined effect of reflective groundcovers and ethylene inhibitors (AVG) in the accumulation of total anthocyanin. Apples underwent four treatment combinations of reflective groundcover (Extenday) and AVG (130 mg L−1). Our findings revealed that Extenday significantly enhanced skin coloration (>75% blush) through increased reflectance of PPFD and UV radiation, along with increased IEC, while also accelerating fruit maturity, i.e., overripening. In fact, Extenday-only treated fruit exhibited the highest upregulation of ethylene and anthocyanin biosynthetic-related genes, as well as total anthocyanins. Conversely, AVG notably reduced fruit drop and decreased IEC, delaying fruit maturity while significantly diminishing red coloration (30–48% blush). AVG treated fruit significantly suppressed the expression of key ethylene and anthocyanin biosynthetic structural and regulatory genes, as well as total anthocyanins. The combined application of Extenday and AVG synergistically decreased fruit drop while enhancing skin coloration (>50% blush), but without inducing overripening. This combination fine-tuned the transcript accumulation of ethylene and anthocyanin biosynthetic-related genes, as well as total anthocyanins, enabling 'Honeycrisp' fruit to exceed 50% blush, while moderately increasing IEC (compared to Extenday-only and control fruit), thus enhancing fruit economic value. Therefore, combining Extenday and AVG can boost the market value for 'Honeycrisp' apples in the mid-Atlantic US.
Refining the understanding of the crosstalk between auxin and indolic defense compound metabolism in Arabidopsis thaliana to improve transferability of the model system to major crops
(2024) House, Lillyanna; Peer, Wendy A; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The main natural auxin, indole-3-acetic acid (IAA), modulates a diversity of plant growth and developmental responses through the tight regulation of auxin biosynthesis and inactivation, transport, and signaling. Evidence that analogous auxin metabolic pathways contributing to programmed and plastic development exist amongst different plant species, points to the necessity for refinement of the current understanding of auxin metabolism in Arabidopsis thaliana to improve its transferability as a model system to major crops. Evaluation of the current understanding of auxin biology in plants and analytical tools available for the visualization and quantification of auxin reveal several gaps of knowledge. This work seeks to address this by 1.) elucidating the specific roles of DIOXYGENASE FOR AUXIN OXIDATION 1 and 2 (DAO1 and DAO2) in the oxidative catabolism of IAA and IA-conjugates and functionality of oxidized IAA (oxIAA), 2.) clarifying the function of ATP-BINDING CASSETTE subfamily B (ABCB) transporters and the interplay of auxin, brassinolide, and ethylene in apical hook development and 3.) investigating the possibility of an analogous auxin metabolic pathway involving the natural auxin, phenylacetic acid (PAA), in Oryza sativa. Herein, it is shown that DAO2 activity is similar to DAO1 and assists in the regulation of auxin homeostasis under high auxin conditions and DAO1 is both soluble and plasma membrane associated. Additionally, oxIAA functions as a weak “anti-auxin” to modulate processes like apical hook development, where a subset of ABCB transporters is found to function in auxin mobilization downstream of ethylene signaling and brassinolide transport. The detection of PAA was achieved using LC-MS, however further method development is required for accurate quantification of PAA in rice tissue samples. Application of previous and new knowledge pertaining to the crosstalk between auxin and indolic defense metabolism in Arabidopsis revealed a seemingly analogous pathway in rice whereby phenyl acetonitrile (PAN) is converted to PAA, likely via nitrolases. The results presented herein, refine the understanding of auxin metabolism in Arabidopsis and exemplify the use of a model system in elucidating similar pathways in agriculturally significant crops.
THE ECONOMIC EFFECTS OF STORMWATER BEST MANAGEMENT PRACTICES (BMPS) ON HOUSING SALE PRICES IN WASHINGTON, D.C.
(2024) Park, Boyoung; Kweon, Byoung-Suk; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The aim of this dissertation seeks to investigate the economic effects of stormwater best management practices (BMPs) on housing sale prices in Washington, D.C. Stormwater best management practices (BMPs) were designed to address flooding and water quality issues that impact environmental, social, and economic effects. As awareness of the BMPs increased, municipalities and local governments developed regulations to require developers and property owners to implement BMPs. Effective stormwater management was not merely a matter of environmental responsibility but may create significant economic incentives. To study the economic effects of BMPs on housing prices, this study reviewed 32 years of research articles answering following questions: 1) How do BMPs affect housing prices? 2) What kinds of stormwater BMPs have been studied that affect housing prices? This review study used the PRISMA approach to conduct an in-depth systematic review. The search parameters included articles written in English and published between January 1990 and September 2022 using Google Scholar, ProQuest, and EBSCO host search engines. Initially, more than 20,000 studies were identified. Ultimately, 23 Studies were selected for inclusion with specific search terms. The results of this study show that many BMPs (trees, detention basins, retention basins, parks, etc.) use various measurements (e.g., percent coverages, proximity) to estimate the economic impacts on housing prices. Our robust findings address that BMPs have more substantially positive (82.6%) than negative effects (52.2%) on housing prices. Trees and parks had an impact that is more positive on housing prices than detention and retention basins. While studies on the economic value of BMPs were limited, literature found that the capitalization of real estate can be affected by nearby stormwater BMPs using the hedonic pricing method. To extend the economic effects of BMPs on housing sale prices in Washington, D.C., this study addresses research questions: Do stormwater BMPs positively impact housing sale prices? How do proximity and number or structural BMPs affect the housing sale prices? This study used the hedonic pricing method by applying hierarchical regression models to determine whether a set of independent variables significantly improved the models. The primary findings indicate that BMPs have positive, negative, or no effects on housing sale prices. Proximity to BMPs inside of parks increased housing sale prices in all buffers. In contrast, proximity to BMPs outside of parks and impervious roads decreased housing sale prices in all buffers. Percent tree canopy coverage negatively linked to a 50 m buffer and no relationship with other buffers on housing sale prices. This study implies that BMPs impact housing prices and can be improved by landscape architects, policy makers, and stakeholders. To compare the economic effects of BMPs on housing sale prices in high-income and low-income wards in Washington, D.C., this study addresses how environmental, structural, neighborhood and locational variables hierarchically affect housing sale prices in high-income and low-income wards. The robust findings of this study conclude that environmental variables (e.g., proximity of houses to parks with BMPs, house to BMPs inside of parks, and house to BMPs outside of parks, impervious surfaces, and impervious roads) can be attractive factors for purchasing homes, according to model 1 and model 3 in high-income ward. In contrast, there was no evidence of the economic effects of environmental variables on housing sale prices in low-income ward. All structural variables in the high-income ward were statistically significant on housing sale prices. In contrast, limited structural variables in low-income ward were statistically significant on housing sale prices. Several locational and neighborhood variables (e.g., population density, unemployment rate, and poverty rate) in the high-income ward were statistically significant on housing sale prices. These results contribute to property owners considering how environmental, structural and neighborhood and locational variables could be beneficial between high-income and low-income communities. However, such disproportionate economic effects of factors concern remain. The intervention of green gentrification should be considered between local government and disparate community groups by supporting financial incentives for homeownership or having an equity project for existing residents to improve their communities. This could change the neighborhood composition which is associated with the availability of stormwater BMPs as well as the involvement of these efforts from landscape architects, urban planners, stakeholders, and government is essential to accelerate the strategies to fair distribution and effects of stormwater BMPs on housing sale prices.
PRODUCTION RECOMMENDATIONS FOR INDUSTRIAL HEMP (CANNABIS SATIVA) FOR FIBER PRODUCTION IN MARYLAND: OPTIMIZING PLANTING DATE FOR FIBER YIELD, QUALITY, AND WEED MANAGEMENT
(2024) Myers, Erin; Fiorellino, Nicole; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Management recommendations, namely timing of planting and harvest, are well established for a wide range of agronomic crops, but this data is lacking for industrial fiber hemp (Cannabis sativa L.), especially in the Mid-Atlantic region. With the re-introduction of legal hemp production in the US in 2014, farmers faced many challenges to growing this crop, both policy and production challenges alike. As hemp production was illegal since World War II, there was virtually no applied agronomic research performed on hemp in that time. Moreover, there are no pre-emergence herbicides approved for weed management in industrial hemp production, and research is needed to determine which cultural practices can be utilized to manage weeds in this crop. This void of applied research performed on fiber hemp has left many Land-Grant universities and Extension personnel unable to provide basic production recommendations to farmers interested in growing this novel crop. To begin providing such recommendations to Maryland farmers interested in incorporating fiber hemp into their crop rotation, the objectives of this research were to 1) determine the effect of planting and harvest date on fiber hemp yield, plant characteristics, and fiber quality and 2) observe weed populations under a competition or germination prevention scenario in fiber hemp across the planting date spectrum. Based on this research, we believe fiber hemp can be successfully incorporated into Maryland crop rotations, as early planting and harvest of fiber hemp will result in quality fiber hemp, management of weeds through available cultural practices, and minimal disruption to other agronomic crops.
THE USE OF ORGANIC WASTE PRODUCTS AS SOIL AMENDMENTS FOR TURFGRASS ESTABLISHMENT: EFFECTS AND REGULATORY INFLUENCES
(2024) Morash, Jennifer Dawn; Lea-Cox, John; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The use of organic waste products as soil amendments in highly disturbed urban soil is poised to grow due to rising fertilizer costs, waste-management issues, and greater emphasis on creating sustainable circular economies. Despite the advantages of using waste products as organic amendments to enhance fertility, their incorrect use may result in short-term unintended consequences such as nutrient losses or the immobilization of plant-essential nutrients, which could diminish efforts to establish vegetation on disturbed soil. To avoid these consequences, transportation authorities – cited as the largest users of compost in some states – have implemented measures to improve product specifications. This research details the efforts of one such organization, the Maryland Department of Transportation State Highway Administration (MDOT SHA), and the results of an initiative to increase the quality of manufactured topsoil and compost use through agency topsoil specifications. After determining which products were most likely to be incorporated into manufactured topsoil (finely shredded wood mulch and composted leaf yard waste), two greenhouse microcosm experiments were conducted to evaluate plant growth responses and the efficiency of nutrient uptake compared to leachate losses when those amendments were used in accordance with MDOT SHA specifications. Composted yard waste provided excellent results while wood mulch suppressed growth in the short-term studies. A biosolids treatment was included in the experiments due to widespread availability and growing interest. Biosolids improved soil fertility and plant growth. However, the difference between nitrogen (N) uptake and leachate mass losses required a second set of experiments, to quantify the effects of four biosolids amendments on plant growth, nutrient uptake, and leachate losses. Treatments were applied at the rate recommended by UMD for turfgrass establishment (2.54 cm, incorporated) and included fresh biosolids, biosolids that were stockpiled for two years, two blended products made from either the fresh or aged biosolids and fine wood mulch, an inorganic fertilizer, and a control. Aging and wood fines reduced N leaching losses but at the expense of N inputs to soil. The cumulative N leachate mass loss from the new biosolids treatment was 63 times greater than the cumulative fertilizer total. Aging did not reduce phosphorus (P) leaching losses but wood fines did by diluting the concentration of P in blends. However, biosolids mostly retained P in the soil and cumulative fertilizer losses were 2 times higher. Overall, growth measurements showed that biosolids enhanced growth during the first and second growing seasons. However, based on the results of this research, 2.54 cm of pure biosolids is not required to enhance turfgrass establishment. An application of 1.27 cm of pure biosolids or 2.54 cm of a biosolid/wood fine blend should provide comparable enhanced turfgrass growth results while reducing overall nutrient leachate losses.
IMPROVING TREE CANOPY COVER WITHIN SINGLE FAMILY RESIDENTIAL FRONT YARDS AND THE CASE FOR NEIGHBORHOOD TREES CASE STUDY: GALWAY ELEMENTARY SCHOOL DISTRICT
(2023) Bentley, Daniel; Myers, David DM; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Trees contribute to many social and health benefits for citizens when trees areplanted appropriately and maintained into maturity. A healthy tree canopy cover layer should be enjoyed by all residents no matter their location or income level. While many communities and organizations have developed robust tree program and provide free trees, homeowners have difficulty imagining what mature trees might look like and what the benefits of the trees would be to them. This thesis strives to develop design methods to support homeowner decision-making for tree planting . A case study focused on the selected front yards of residential homes in the Galway Elementary School walk zone will be used to document these methods. The research is focused on how to demonstrate tree placement to homeowners, tree benefits and but also bring to their attention the opportunities offered to make the process simple and rewarding for the future of their children and the neighborhood.
Dual water quality responses after more than 30 years of agricultural management practices in the rural headwaters of the Choptank River basin in the Chesapeake Bay watershed
(2023) Silaphone, Keota; Fisher, Thomas R; Natural Resource Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Eutrophication is the water quality response to over-enrichment by nitrogen (N) and phosphorus (P) in fresh, estuarine, and coastal waters globally. Agricultural best management practices (BMPs) are the primary tool for controlling eutrophication in rural areas, particularly in the Chesapeake Bay watershed, where BMPs are vital to achieving TMDL goals. However, despite the application of BMPs, local water quality in the headwaters of the Choptank River, a major tributary of the Chesapeake Bay on the Delmarva Peninsula, has not improved. Thus, further investigation of agricultural BMP impacts on water quality in the Greensboro watershed is needed. My overarching research question is, “Why have N and P concentrations increased at the USGS Greensboro gauge if agricultural Best Management Practices (BMPs) have been implemented?” I applied statistical approaches to three linked, testable hypotheses to systematically evaluate agricultural BMPs and their impacts on nutrient (N and P) export from the Greensboro watershed. My first hypothesis was that agricultural BMPs have increased significantly in the Greensboro watershed. To test this hypothesis, I obtained publicly available modeling data via the Chesapeake Assessment Scenario Tool (CAST) and estimated the subsequent edge-of-stream N and P export. My findings indicated that the number of BMPs in the agricultural sector increased significantly between 1985 and 2021, supporting the hypothesis. Overall, modeled agricultural N and P export significantly decreased between 2010 and 2021 (p < 0.001). However, the modeled edge-of-stream agricultural nutrient export resulted in no significant change in N export and an increase of 3% in agricultural P export resulting from BMP implementation levels in 2021 compared to 2010. This study demonstrated the use of CAST to acquire reported BMP implementation levels and increased nutrient inputs into the Greensboro watershed between 1985 and 2021. The watershed nutrient inputs mirror the upward trends in N and P export captured by the USGS long-term monitoring station at Greensboro. With this improved access to BMP implementation and nutrient data, decision-makers can consider adaptive management measures to decrease nutrient export downstream. My second hypothesis was that agricultural BMPs have an adequate basis for estimating their capacity to reduce N export. To test this hypothesis, I conducted a meta-analysis on 689 cover crop N efficiencies reported in 18 empirical and modeling studies. The cover crop N efficiency was calculated as the ratio of an N interception by cover crop biomass or a reduction in soil or groundwater N divided by an N input, e.g., previous spring fertilizer or a previous soil or groundwater N concentration or flux. These variable approaches resulted in wide ranges in mean cover crop N efficiency (10-80%) due to empirical and modeling experimental approaches, varying methods, and parameters used to calculate efficiency. The modeling approach generally resulted in N efficiency values significantly higher than the empirical approach, as did the parallel control-treatment experiments compared to the sequential before-and-after implementation method. Because of these variables, there appears to be no standard methodology to report the effects of cover crops or standardized metadata describing the variables used in the N efficiency calculations. I suggest a standard methodology and metadata that should accompany future reports of cover crop N efficiencies to improve the modeled effects of BMPs on nutrient export. My third hypothesis was that three methods of estimating N and P concentrations and yields are in agreement and show a relationship to BMP implementation in the Greensboro watershed. To test this hypothesis, I compiled annual nutrient (N and P) datasets based on (1) USGS field measurements of concentrations and discharge, (2) USGS flow-normalized weighted regression based on time, discharge, and season (WRTDS) of concentrations and yields, and (3) CAST-modeled nutrient yields. Statistical analyses revealed time, discharge, agricultural BMPs, and animal waste management practice trends of the three methods. Results indicated that the USGS field measurements and WRTDS flow-normalization methods consistently showed an increase in N and P concentrations and yields. In contrast, all CAST-modeled regressions showed significantly decreasing nutrient concentrations and yields (p ≤ 0.05), which did not support the hypothesis that all three methods are in agreement. Despite CAST-modeled results decreasing with increasing BMPs, which supports the hypothesis that N and P concentrations and yields show a relationship with BMP implementation, USGS methods resulted in increasing nutrient concentrations and trends. These results indicated significant underestimates of modeled N and P export by CAST. I recommend using adjusted BMP efficiencies during cultural and structural BMP lifespans to improve model outputs. I also suggest two approaches to reflect the role of annual poultry manure applications: (1) model nutrient transport via artificial drainage ditches that interfere with natural nutrient flow pathways and exacerbate N and P transport, and (2) model the accumulation of soil-P and saturated soil-P, resulting in increases in dissolved P and particulate P in downstream surface waters. Agronomic recommendations include developing efficient manure recycling approaches within the local agricultural systems via nutrient management practices and concurrent research and development to support alternative uses of animal waste, including composting, bioenergy generation, granulating/pelletizing, and establishing a marketplace to support the sale of these products and to offset the costs of transporting manure from areas of manure surplus to manure deficit areas. This dissertation revealed that modeling studies overestimate cover crop N efficiencies in the United States Coastal Plain province and that CAST modeling is not in agreement with the USGS field measurements. CAST-modeled nutrient concentrations and yields decrease over time, indicating improvements in water quality. In contrast, USGS methods consistently show that nutrient concentrations and yields increase, indicating that BMPs are insufficient, inadequate, overwhelmed by nutrient inputs, or efficiencies are overestimated. Indeed, nutrient-reducing BMPs have increased between 1985 and 2021. With over 35 years of BMP implementation, measurable water quality response is expected. However, BMPs that relocate and apply higher amounts of manure annually have also increased with nutrient-reducing BMPs. Rising manure application rates combined with higher fertilizer application rates due to economic pressures on farmers to increase crop yields appeared to have overwhelmed implemented BMPs. Continued manure applications onto croplands in the Greensboro watershed suggest nutrient export will continue to rise; thus, reaching water quality goals is unlikely.
A Place in Public Space: Designing an Autism-Friendly Experience for Adults in Palmer Park
(2023) Ada, Micaela; Sachs, Naomi A; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
In 2023, the CDC reported that approximately 1 in 36 children in the U.S. is diagnosed with autism spectrum disorder (ASD). Prevalence rates have nearly doubled every decade since the CDC began tracking this data in 2000. When these children come of age and enter adulthood, they face new milestones and challenges such as working, living away from the family home, and navigating the world with more autonomy. Design professions —including architecture, interior design, and landscape architecture— have progressively incorporated considerations for ASD into their spaces. Adult-specific, autism-friendly design guidelines existing today have honed in on improving workplace, home, and therapeutic environments. There is a noticeable gap in addressing landscapes made for the social and leisure aspects of life. To address this gap, this research design thesis focuses on implementing design interventions in Landover, MD’s Palmer Park Community Center outdoors space to create an autism-friendly space for adults seeking comfortable recreation opportunities.
Understanding organic and conventional management programs and rhizosphere microbiome for sports turf in Maryland
(2023) Peddigari, Shravya; Carroll, Mark; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
In response to public concerns about exposure to pesticides, some state and local municipalities have placed restrictions on the use of pesticides on athletic fields. When such restrictions are implemented athletic field management often transitions to the use of natural or organic turf care with little understanding of how the transition away from conventional management practices may affect surface conditions and soil microbial properties.This thesis examined the use of organic and conventional management programs on the turf quality, surface hardness, and shear strength of engineered soil cap, hybrid bermudagrass (Cynodon dactylon x Cynodon transvaalensis) athletic fields, as well as the impact of the two programs on the rhizosphere microbiome. Turf quality was assessed by visual means and by obtaining normalized difference vegetative index (NDVI) readings of the turf canopy. Surface hardness was determined using a Clegg impact surface tester. The rotational shear strength of the surface was measured using a shear vane. The study was conducted for 3 years at two different locations; research plots at the University of Maryland Research Facility and on athletic fields at Laytonia Recreational Park, in Gaithersburg, MD. Surface property data was collected monthly. Turf visual quality and NDVI data revealed use of the organic management program led to higher visual quality during spring, which was primarily the result of the spring retention of fall overseeded intermediate ryegrass (Lolium x hybridum Hausskn) and early season use of natural based fertilizers. In the summer months, crabgrass (Digitaria ischaemum Schreb.) encroachment was limited to the organically managed turfgrass. At both locations, clover (Trifolium repens) encroachment developed by the third year of the study, but the presence of this weed had limited impact on turfgrass quality. There were few significant differences in surface hardness and shear strength between the two management practices over the entire study period. The rhizosphere microbiome data, which was collected 12, 20, and 24 months after the initiation of two programs, did not show any significant difference between the organic and conventional management athletic fields in microbial abundance and/or diversity. The results of this study emphasize that the adoption of organic management programs on bermudagrass athletic fields should, in most instances, center on the establishment of acceptable weed tolerance levels for these fields. The use of organic management programs in the transition zone offers a viable alternative to the conventional chemical management of athletic fields, however over time, growing weed seed banks may necessitate the need for the occasional use of conventional herbicide materials.
POSITIONAL CLONING OF BROAD-SPECTRUM LEAF RUST RESISTANCE GENE, LR57, FROM AEGILOPS GENICULATA, A TERTIARY GENE POOL MEMBER OF WHEAT
(2023) Schulden, Taylor Francis; Rawat, Nidhi; Erwin, John; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The tertiary gene pool of wheat includes wild relatives like Aegilops geniculata (UUMM, 2n=4x=28) that are valuable genetic reservoirs for novel abiotic and biotic resistance genes. However, modern wheat varieties share limited genomic commonality with these gene pool members presenting barriers to recombination and genetic mapping of desirable genes. We mapped a broad-spectrum leaf rust resistance gene Lr57 located on chromosome 5Mg of Ae. geniculata using a simple but powerful methodology for high-resolution genetic mapping in tertiary gene pool members of wheat. Five gene candidates were revealed all with possible defense related functions. Strategic application of differential expression analysis, Virus-Induced Gene Silencing, and mutagenesis analysis reduced the candidate gene of interest to a singular and novel ID-NLR resistance gene containg a protein kinase, NB-Arc, and LRR domain. Using multiple strategies, validation of Lr57 candidate was completed. Gene complementation by transformation of Lr57 candidate is currently being conducted.
REVIVING CONNECTIONS: A PROPOSAL TO IMPROVE WATER QUALITY OF THE ANACOSTIA RIVER AND CONNECT THE CITY TO ITS RIVER THROUGH SUSTAINABLE URBANISM
(2023) Shah, Jainee Priyesh; Ellis, Christopher D; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
A very significant element of the city of Washington D.C. are its rivers. These rivers have been supporting the civilization around them for years. The Anacostia river has been subject to industrialization for centuries and it has been exposed to pollution mainly due to urban waste and storm water runoff. This pollution not only affects the water quality of the river but also impacts the nearby population, aquatic life and other species in many harmful ways. It is essential that development should take place considering the needs of people as well as the environment. Here, application of various green infrastructure techniques plays an important role in creating a balance. This thesis is an effort towards improving the water quality of the Anacostia River, reconnecting the city to its river and ensuring a healthy environment for humans and other dependent species.
The kinetics and quantum yield of photophosphorylation in Anacystis nidulans (Richt.) Drouet
(1972) Owens, Olga v. H.; Krauss, Robert W.; Plant Physiology; Digital Repository at the University of Maryland; University of Maryland (College Park, MD)
The active metabolite, ATP, serves not only as a high energy intermediate but also as a controller of some enzymatic reactions. In plant cells, the larger part of the ATP is formed by photophosphorylation. In this paper the rates, the quantum yields, and the wavelength dependencies of photophosphorylation in the blue-green alga Anacystis nidulans are reported. A fluorometric method for determination of enzymatically produced NADPH from ATP was adapted for use on cell extracts. In the light, the ATP level was 0.15 to 0.25 µmoles/mg chl. In the dark, the ATP level was 70% of that in light. In both darkness and anaerobosis, the level was 20%. A return to the light restored the ATP level from both conditions. Dark, anaerobic cells were exposed to measured irradiancies of 710 nm and 620 nm. The rate of ATP formation was measured within the first few seconds and found to be directly proportional to absorbed intensity. Saturation of the rates occurred at an intensity one-tenth the optimum for oxygen production. Quantum requirements of 6-8 were similar for each of the two wavelengths. The system II inhibitor DCMU, had a greater effect at 620 nm that at 710 nm indicating an involvement of system II in photophosphorylation only at 620 nm. At low intensities and over long time periods white light failed to produce a saturating steady-state level of ATP indicating a simultaneous consumption of ATP. Measurements in short dark periods following marginal illumination showed consumption of ATP to be 2 to 4 times greater that production in weak light. Thus, the quantum requirement can be calculated to be 2. ATP formation, therefore, is not the limit ing factor in co2 fixation. The evidence is the high quantum yield of photophosphorylation and the unsaturation of co2 fixation at intensities at which ATP synthesis is saturated.
CREATING SPACE FOR NATURE RX AT HISTORICALLY BLACK COLLEGES AND UNIVERSITIES
(2023) Smith, Marci-Ann; Sachs, Naomi A; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
With the rising trend of mental health issues among young adults, many colleges are trying to establish an approach to combat those issues for the well-being of their students. One such approach is Nature Rx. Nature Rx is a program that encourages people, sometimes with an actual prescription, to spend time in nature in order to relieve stress and improve overall health. Nature Rx is a holistic way of addressing mental issues such as stress, anxiety, and depression that are prevalent among college students. The evidence is strong that time spent in and engaging with nature can improve mental and physical health. Colleges like Cornell University and University of Maryland College Park are taking advantage of their existing beautiful landscape as part of their Nature Rx program to help their students. Other schools are implementing this program and providing spaces for their students to find reprieve from the stresses of studies. However, there is a gap in the presence of Nature Rx programs at Historically Black Colleges and Universities (HBCUs). To date, no HBCU has a nature Rx program. This project seeks to fill that gap by using the University of Maryland Eastern Shore, an HBCU, as a case study to answer the following thesis question: “How could a Nature Rx design at the University of Maryland Eastern Shore, a Historically Black College and University, benefit the health and well-being of its students?”

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