Plant Science & Landscape Architecture Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/2797

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Activating a 60's Modernist Plaza Using the Principles of Human Scale Design: Re-imagining HUD Plaza
(2021) Velez-Lopez, Sebastian; Sullivan, Jack; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Population growth has increased rapidly across many large American cities in the last 20 years. The growing population generates a need for quality public open space, but it also increases the development of housing making land increase drastically in value, making it harder for municipalities to acquire land for public open space projects. One strategy that cities can use to address this issue, is to leverage existing public spaces that are currently underutilized. This project explores the contemporary principles of public space and human scale design through a review of the existing literature. The principles gathered from the literature, are demonstrated by using them as the basis for re-imagining an underutilized urban public space. The project establishes a link between the research on public space design and practice, providing an example of how it can be used to create innovative ways to better utilize our existing public spaces.
Addressing New Stormwater Policies in the Redesign of the National Grove of State Trees at the United States National Arboretum
(2012) Kreiseder, Kory Anne; Myers, David N; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The National Grove of State Trees at the United States National Arboretum is in need of redesign to meet ecological and social needs. The Grove serves as a scientific and cultural landscape and can be repurposed to serve the public as an ecological demonstration for contemporary environmental issues. In an intensive effort to clean up the local rivers of the District of Columbia and the Chesapeake Bay, the two agencies of the District Department of the Environment and DC Water have enacted stormwater runoff fees, based on impervious surface fees, on all property owners located in the District of Columbia. The redesign of the Grove is compounded by the Arboretum's need to add more parking to the area where the Grove is currently located. The objective of this thesis is to reimagine the design and interpretation of the Grove as well as address the impervious area charge assessments.
After the Flood: Designing Land Reuse in New York's Hudson Valley
(2022) Savio, Hannah L; Ellis, Christopher D; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Flooding is a recurring event in the water cycle that has the potential to devastate what is in its path. Climate change is projected to make flooding worse in the Northeastern United States because of increased intensity of rainfall. An increase in the number of flooded homes where homeowners choose not to rebuild in place can be viewed as a symptom of climate change. These issues take place at the confluence of land and water, the balance of humans and our environment, and what can be learned from the past and from projections and models of the future. How can flooded sites that are not suitable for rebuilding be adaptively reused to leverage their ecological, social, and economic value? This question is assessed through a multi-scalar examination of a series of FEMA buyouts along the Kaaterskill Creek, a rural tributary to the Hudson River in New York.
Agricultural Drainage Ditches: Soils and Implications for Phosphorus Transport and Retention
(2005-12-13) Vaughan, Robert Edward; Needelman, Brian A; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Agricultural drainage ditches act as pathways for nutrients to local surface waters. Knowledge of ditch materials, the spatial variation and distribution of ditch soil phosphorus, is critical to effective ditch nutrient management strategies. Ditch materials from the University of Maryland Eastern Shore Research Farm in Princess Anne, Maryland were described and characterized using a pedological approach. The spatial variation of phosphorus was also investigated. The materials found within these ditches are natural soil bodies. Pedogenic processes operating in these soils include organic matter accumulation, structure formation, Fe oxidation and reduction, sulfuricization, sulfidization, and bioturbation. Soil phosphorus was well autocorrelated, and exhibited a high degree of spatial variation. Ditch soil phosphorus at depth ranged from 4 to 4882 mg kg-1 for total phosphorus, 4 to 4631 mg kg-1 for oxalate-extractable phosphorus, and 2 to 401 mg kg-1 for Mehlich-3 phosphorus. Future ditch management strategies should include a subsurface soils component.
Alleviation of Soil Compaction by Brassica Cover Crops
(2009) Chen, Guihua; Weil, Ray R; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Soil compaction is a worldwide problem in modern agriculture associated with overuse of heavy machinery and intensification of cropping systems. Though tillage is traditionally used to alleviate compaction effect, increasing concerns about environmental impacts of tillage have led to interest in conservational tillage systems and incorporation of cover crops into crop rotations. Previous study showed soybean (Glycine Max L.) roots grew through a plowpan soil using channels left by canola (Brassica napus) cover crop roots, a process termed "biodrilling" to alleviate compaction effect. However, this study did not provide any quantitative data to support the observational conclusion. We studied "biodrilling" abilities of three cover crops and the effects of "biodrilling" on corn (Zea mays)/soybean growth by conducting three experiments. The first two experiments included three surface horizon compaction treatments (high, medium and no compaction), four cover crops [FR (forage radish: Raphanus sativus var. longipinnatus, cultivar `Daikon') and rape (rapeseed: Brassica napus, cultivar `Essex') (tap-rooted species in the Brassica family), rye (cereal rye: Secale cereale L., cultivar `Wheeler') (fibrous-rooted species) and NC (no cover crop)] in Exp. 1, and three cover crops (FR, rape and NC) in Exp. 2. The third experiment was conducted on field with a legacy plowpan (subsoil compaction) using FR, rye and NC cover crops. Roots of FR were least inhibited by compaction, while rye roots were severely arrested by compaction. The order of "biodrilling" ability was FR > rape > rye. Soil bulk density, strength and least limiting water range were controlled by compaction treatments. Soil air permeability was greatly reduced by compaction. Air permeability was greater in rape/FR treatments than in rye/NC treatments under high/medium compaction. Corn/soybean root penetrations, subsoil water uptake in the compacted soils were enhanced by FR/rape treatments but not by rye/NC treatments. Compaction decreased corn yield only in Exp. 2 where soil sand fraction was greater. The yield of corn was greater in three cover crop treatments than in NC control. In terms of "biodrilling", Brassica cover crops (FR and rape) were more effective than rye cover crop, would alleviate effects of soil compaction on plant growth in no-till farming systems.
Anacostia: Community As Form
(2014) Mendoza, Adriana; Cook, Kelly D; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The essence of this thesis is to explore what form public art takes on in order to visualize Anacostia's community identity during the urban revitalization of the neighborhood. The current small and large-scale revitalization efforts by the City (Washington D.C.) are showing change in both the physical and social fabric of the community and neighborhood. As a predominantly African American community that has faced disinvestment and injustices--socially, economically, and politically--many residents are concerned that these City efforts will physically displace them, as well as the collective memory of the community. This thesis seeks to transform a vacant lot, slated for development, into a temporary, transient, multi-functional public art design for engaging the community in the process of exploration and expression of their community identity. Public art is used as a strategy to provide a platform for residents to effectively become present, visible and audible at a time when many residents feel as though they are not part of Anacostia's future.
ANALYSIS OF ARABIDOPSIS ABCB AUXIN TRANSPORTER MUTANTS REVEALS A PRIMARY ROLE IN MEMBRANE EXCLUSION
(2018) Jenness, Mark Kubo; Murphy, Angus; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Polar transport of the phytohormone auxin regulates multiple of aspects of plant growth and development. A subset of plant ATP-binding cassette subfamily B (ABCB) transporters mediate cellular auxin export. Loss of these transporters results in reduced polar auxin movement and altered plant architecture but no significant defects in embryogenesis or organ formation. Several of lines of evidence suggest that isotropically-localized ABCB transporters mediate auxin exclusion from the plasma membrane and prevention of reuptake after directional PIN-mediated efflux. Examination of the Arabidopsis auxin transporters ABCB1 and ABCB19 indicates a primary role in exclusion from small auxin producing cells in apical regions and prevention of leakage from polar auxin transport streams. Analysis of abcb mutants identifies a contribution from ABCB21 in restricting auxin to within the root vasculature in seedlings. In mature tissues, ABCB6, ABCB21, and ABCB11 make additional contributions to polar auxin transport in inflorescence stems, leaves, and flowers, respectively. The results presented herein reflect an evolutionarily conserved function for ABCB transporters in maintaining polar transport streams and prevention of cellular reuptake via exclusion.
Applying Green Complete Streets on Georgia Avenue NW: Redesigning an Urban Right-of-Way for Sustainable Mobility and Urban Water Quality
(2023) Mejias, Aliya; Ellis, Christopher D.; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The public right-of-way (ROW) makes up nearly one-third of all the public space in cities. With the majority global population expected to reside in cities by 2050, climate change posing a significant threat to urban residents and infrastructure, impervious urban surface impacts on water quality, and knowing traffic fatalities in the US reached a 16-year high, cities must reconsider how this public good can serve people and the environment over to car-centric mobility. Using a segment of Georgia Avenue NW in Washington, DC, this thesis removes automobiles from the ROW to demonstrate how Green Complete Streets, which prioritizes sustainable transportation and urban water quality, can support urban livability on a corridor scale.
Applying Vegetation Dynamics Theory to the Long-Term Ecological Design and Management of Urban Public Parks: Upper Long Branch Stream Valley, Maryland
(2021) Podietz, Emma; Myers, David N; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Calls for ecological applications in landscape architecture have increased as the world faces compounding crises of climate change, biodiversity loss, and human disconnection with natural systems. Landscape architects are uniquely situated to address these crises as practitioners who engage at multiple scales with ecological systems, placemaking, and land use planning. A sustainability ethic exists within the discipline, but ecological principles and theory are inconsistently applied in built work. Vegetation dynamics theory generalizes the mechanisms of plant community change over time, and presents a useful framework for the planting design, long-term adaptive management, and stewardship of urban parks. The principles of the theory can be interwoven with ecological and aesthetic goals of designed landscapes. This thesis demonstrates how centering vegetation dynamics theory in urban park design can enhance ecological function of urban landscapes, create heightened place attachment through aesthetic and interpretive experience, and guide the long-term management and stewardship of urban ecosystems in the Mid-Atlantic United States.
Assessing evapotranspiration rates of a Mid-Atlantic red maple riparian wetland using sap flow sensors.
(2005-04-13) Renz, Jennifer Theresa; Momen, Bahram; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Riparian forests are unique due to increased exposure of trees to winds and radiation and the subsequent effects on the quality and quantity of water discharge from the system. Since "edge effects" can enhance evapotranspiration (ET) of exposed trees, ET rates of a first-order red maple riparian wetland were assessed with thermal dissipation probes during the 2002 growing season to address: a) if edge trees transpire more water daily than interior trees, b) correlations among sap flow rates and energy balance-derived estimates, c) variations in ecosystem ET estimates based on 6 scaling variables, and d) diurnal correlations between maximum sap flow rates and streamflow losses. Results from this study indicate that: a) edge trees transpire more water daily than interior trees during early summer, b) choice of scaling variable affects estimation of ecosystem ET rates, and c) maximum sap flow rates correlate with streamflow losses diurnally under specific environmental conditions.
Assessment of select isolates of Trichoderma virens as a potential biocontrol against Meloidogyne incognita
(2004-05-03) Mallozzi, Tonya Suzanne; Kratochvil, Robert J.; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Three isolates of the soil-dwelling fungal organism, Trichoderma virens (Miller, Giddens and Foster) von Arx., were studied as potential biocontrols for the management of root-knot nematode (RKN) on bell pepper (Capsicum annuum L.). The study was conducted within the Moisture Replacement System (MRS), which was concurrently evaluated for its ability to serve as a culture system for Meloidogyne incognita (Kofoid and White) Chitwood and as an environment supportive of the growth and maintenance of Trichoderma isolates for biocontrol studies of this nature. Trichoderma isolates selected for study did not suppress populations of RKN on bell pepper under the conditions of this study. A review of the literature provided a multitude of complexities potentially contributing to the final results obtained. Investigation into these various complexities with the incorporation of the MRS will help to fully ascertain Trichoderma's potential as a biocontrol and perhaps reveal viable alternatives in the management of RKN.
Association Analysis in Soybean
(2008-08-29) Hwang, Eun-Young; COSTA, JOSE; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Association analysis is a new approach to identify the location of gene(s)/allele(s) of interest. There are a number of factors determining the feasibility of whole-genome association analysis which include the level of linkage disequilibrium (LD) and the magnitude of population structure in a population. The goal of this study was to evaluate the success of whole-genome association analysis in soybean germplasm accessions using DNA markers across the whole genome. Firstly, the extent of LD and the presence of population structure were estimated. Secondly, whole-genome association analysis was performed to detect the location of the allele/gene controlling flower color, pubescence color, and seed protein quantitative trait loci (QTLs) in 319 soybean [Glycine max (L.) Merr.] germplasm accessions. The soybean germplasm accessions had a relatively low level of LD which declined very rapidly to 0.8 in less than 4 Kbp as indicated by r² as well as highly diverse population structure. Despite the low LD and the presence of high population structure, whole-genome case-control analysis successfully detected the 65 bp insertion in the GmF3'5'H (GenBank acc. AY117551) gene controlling purple vs. white flower color, as well as a single base deletion in the F3'H (GenBank acc. AB191404) gene controlling tawny vs<\em>. gray pubescence color. However, there were 28 gray pubescence lines that did not contain the deletion suggesting that there is a second mutation determining the pubescence color alteration. In the case of seed protein QTL, whole-genome regression analysis detected one of four previously reported seed protein QTLs which reside on linkage group (LG) E and a new seed protein QTL on LG K. The detection of three other previously reported seed protein QTLs on LGs A1, I and M was not successful. It is unclear why association analysis was not successful in the detection of the three previously reported QTLs. However, a number of reasons including incomplete adjustment for population structure, lack of statistical power, an inadequate number of genetic markers in light of the low level of LD, and the power of association analysis to detect alleles with relatively modest genetic effects are suggested as possible reasons.
Bacterial communities of the specialty crop phyllosphere: response to biological soil amendment use, rainfall, and insect visitation
(2016) Allard, Sarah Michelle; Micallef, Shirley A; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Microorganisms in the plant rhizosphere, the zone under the influence of roots, and phyllosphere, the aboveground plant habitat, exert a strong influence on plant growth, health, and protection. Tomatoes and cucumbers are important players in produce safety, and the microbial life on their surfaces may contribute to their fitness as hosts for foodborne pathogens such as Salmonella enterica and Listeria monocytogenes. External factors such as agricultural inputs and environmental conditions likely also play a major role. However, the relative contributions of the various factors at play concerning the plant surface microbiome remain obscure, although this knowledge could be applied to crop protection from plant and human pathogens. Recent advances in genomic technology have made investigations into the diversity and structure of microbial communities possible in many systems and at multiple scales. Using Illumina sequencing to profile particular regions of the 16S rRNA gene, this study investigates the influences of climate and crop management practices on the field-grown tomato and cucumber microbiome. The first research chapter (Chapter 3) involved application of 4 different soil amendments to a tomato field and profiling of harvest-time phyllosphere and rhizosphere microbial communities. Factors such as water activity, soil texture, and field location influenced microbial community structure more than soil amendment use, indicating that field conditions may exert more influence on the tomato microbiome than certain agricultural inputs. In Chapter 4, the impact of rain on tomato and cucumber-associated microbial community structures was evaluated. Shifts in bacterial community composition and structure were recorded immediately following rain events, an effect which was partially reversed after 4 days and was strongest on cucumber fruit surfaces. Chapter 5 focused on the contribution of insect visitors to the tomato microbiota, finding that insects introduced diverse bacterial taxa to the blossom and green tomato fruit microbiome. This study advances our understanding of the factors that influence the microbiomes of tomato and cucumber. Farms are complex environments, and untangling the interactions between farming practices, the environment, and microbial diversity will help us develop a comprehensive understanding of how microbial life, including foodborne pathogens, may be influenced by agricultural conditions.
Biology of Ophiosphaerella agrostis, epidemiology of dead spot, and a molecular description of the pathogen
(2004-10-21) Kaminski, John; Dernoeden, Peter H.; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Ophiosphaerella agrostis is a newly described pathogen that incites dead spot disease of creeping bentgrass (Agrostis stolonifera) putting greens throughout the eastern United States. The objectives of this research project were to: 1) monitor environmental conditions and develop a predictive model for disease progress and pathogen dispersal under field conditions; 2) determine the effect of various fertilizers on dead spot recovery in bentgrass; and 3) develop molecular methods to diagnoses the disease and determine genetic variation among O. agrostis isolates. Field studies showed that the appearance of dead spot infection centers was influenced predominantly by air (greater than or equal to 18 degrees Centigrade) and soil (greater than or equal to 20 degrees Centigrade) temperature, but other factors including low relative humidity (less than or equal to 80%), shortened periods of leaf wetness (less than or equal to 14 hours), and high levels of solar radiation (greater than or equal to 230 W m to the minus 2) were associated with the development of dead spot epidemics. Patch diameter of O. agrostis infection centers and pseudothecia production generally increased at a linear rate between mid-June and early to mid-August. In a growth chamber study, ascospores were released from pseudothecia following a sharp decrease in relative humidity. Field studies revealed that ascospore release occurred primarily at dawn and dusk or during precipitation events. During precipitation events, ascospores may be forcefully discharged during the entire event, but most ascospores are released within the first 10 hours after precipitation begins. O. agrostis successfully over-wintered in bentgrass leaf sheaths, crowns, roots, and stolons, but little or no reactivation of the disease occurred in the second year. Plots treated with ammonium sulfate and isobutylidene diurea were among the fastest and slowest to recover from dead spot, respectively. In the second year (2003), dead spot recurred in plots treated since 2002 with KNO3, Ca(NO3)2, urea, and a complete fertilizer (20-20-20), but disease symptoms did not recur in plots receiving ammonium sulfate. Species-specific primers capable of detecting O. agrostis at very low concentrations (5 pg DNA) were developed and can be used to assist in diagnosing dead spot. Amplified fragment length polymorphism (AFLP) DNA fingerprinting resulted in placement of isolates (n=77) into three distinct clades that were greater than or equal to 69% similar.
The Brain Does Not Lie: A Case Study of Psychophysiology and Landscape in South Clifton Park
(2023) Seiz, Audrey; Kweon, Byoung-Suk; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Researchers have long explored how humans respond psychologically and physiologically to distinct landscapes and natural features. Walking in nature and viewing photographs of natural landscapes have been shown to reduce stress measured through physiological responses of blood pressure, salivary cortisol concentration, and pulse rate. Exposure to natural landscapes has also been shown to improve feelings of relaxation and positive emotion. The increased popularity of virtual reality (VR) in landscape architecture provides an additional visualization tool to immerse a participant in a landscape at human scale. Little research has focused on the potential impact of visualization through VR, studied the impact of urban nature, or compared the impact of landscape design using the same site. This study explores how employment of psychophysiological measures provides objective assessment of humans' landscape perception in response to the restorativeness of a virtual place. Twenty students were recruited to view an actual site in South Clifton Park, Baltimore City. Utilizing VR, participants observed the site as it exists currently and reimagined using the tenets of Attention Restoration Theory (ART), Stress Reduction Theory (SRT), and community vision. Psychological response was analyzed using the Perceived Restorativeness Scale (PRS-16), a survey designed to evaluate a place’s restorativeness through principles of ART, and physiological response was analyzed using electroencephalogram (EEG), the non-invasive measurements of the electrical brain activity. Findings indicated that perceived restorativeness increased in the designed site for the factors Being Away/Fascination and Compatibility; however, no significant difference was identified for the factor Extent. Regarding EEG data, alpha brain frequencies (broadband alpha, low alpha, and high alpha) were not significantly different when viewing the vacant versus designed site within the frontal or parietal lobes; however, beta brain frequencies (broadband beta, low beta, and high beta) demonstrated a marginally significant effect of sex in the frontal and parietal lobes with male beta brain frequencies decreasing when viewing the designed site and female beta brain frequencies increasing. Finally, frontal alpha asymmetry, a measure of approach-withdrawal motivation, demonstrated a marginally significant decrease when viewing the designed site, indicating increased withdrawal motivation in the designed site. The present research seeks to fill a gap in understanding objective indicators of restorativeness of a place and explore the power of VR as a tool for visualizing place.
Brassica Cover Crops for Nitrogen Retention in the Maryland Coastal Plain
(2006-07-27) Dean, Jill Elise; Weil, Ray R; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The Brassica cover crops, forage radish (Raphanus sativus L. cv 'Daichon'), oilseed radish (Raphanus sativus L. cv 'Adagio'), rape (Brassica napus L. cv 'Dwarf Essex'), and cereal rye (Secale cereale L. cv 'Wheeler') were examined for ability to decrease mineral N losses and influence organic N cycling at two Maryland Coastal Plain agricultural sites. Brassicas were similar or superior to rye regarding N uptake and soil profile NOsub3-N depletions (105-180 cm depth). Rape and rye maintained soil porewater NOsub3-N below 3 mg L to the minus 1 throughout spring while radish performed similarly on fine-textured soil, but caused porewater NOsub3-N > 10 mg L to the minus 1 on coarse-textured soil. Dissolved organic N averaged 51% of total N in porewater, but was unaffected by cover crops. Brassicas were as effective as rye in minimizing mineral N losses, but the role of cover crops in managing organic N was unclear.
Breeding Considerations for Improving Cadmium and Zinc Hyperaccumulation in Two Thlaspi caerulescens Populations
(2004-05-05) Synkowski, Eva Claire Creighton; McIntosh, Marla S; Plant Science and Landscape Architecture (PSLA)
Cadmium is the second most widespread soil metal contaminant in the world and it has been suggested that phytoremediation using hyperaccumulator plants could be used to effectively remove harmful levels of soil metals. This research was conducted to provide basic information necessary for developing a breeding program to improve the phytoremediation potential of Thlaspi caerulescens, a promising hyperaccumulator plant. By determining the genetic structure of the source populations and estimating the heritability of traits of interest, gain from selection was predicted. Bulk segregrant analysis of DNA polymorphisms was used to identify markers linked to cadmium hyperaccumulation. DNA markers would reduce time and expense of selecting superior genotypes. However, confounding effects from marker technology, experimental design, and sample size reduced the potential for implementing the detected markers in a breeding program. Future experiments may still detect markers for hyperaccumulation and the T. caerulescens populations studied are valuable for phytoremediation application.
Bt GENETICS EFFECT ON CORN HYBRID PERFORMANCE: A COMPARISON OF TWO NEAR ISOLINE CORN HYBRIDS
(2018) Thorne, Louis; Kratochvil, Robert J; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Most corn (Zea mays L.) hybrids planted in the U.S. are the result of genetic modification that gives them a Bt gene or genes obtained from the bacterium, Bacillus thuringiensis (Berliner) (Bt), that express insecticidal proteins and enables these hybrids to be resistant to several insects. European corn borer (ECB) (Ostrinia nubilalis, Hübner) is the main Lepidopteran pest targeted by the Bt corn technology. All Bt events used in current corn hybrids provide 100% control of ECB. This has led to widespread use of Bt hybrids and has resulted in a drastic decrease in the ECB population. This raises the question whether it is still economically feasible to plant Bt hybrids that have higher seed costs in environments where the ECB pest level is low. The objectives of this study were: 1) compare the yield and agronomic performance of a pair of corn near-isoline hybrids with and without the ¬Bt traits; and 2) evaluate the agronomic and economic optimums for yield and nitrogen (N) rate for each near-isoline hybrids. A two-year study at three University of Maryland research farms in 2013-2014 examined each hybrid type for stalk damage due to ECB, yield performance, the optimum N rate for maximizing yield, and the economic returns the two hybrids provided. This study found minimal ECB stalk damage and no consistent agronomic or economic yield difference between the Bt and non-Bt hybrids. Neither hybrid type was determined to have a consistent nitrogen use efficiency (NUE) advantage. The results of this study indicate that producers should not have concerns over hybrid type choice, now that there is significant regional suppression of ECB below economic levels.
CALIBRATING CAPACITANCE SENSORS TO ESTIMATE WATER CONTENT, MATRIC POTENTIAL, AND ELECTRICAL CONDUCTIVITY IN SOILLESS SUBSTRATES
(2009) Arguedas Rodriguez, Felix Ruben; Lea-Cox, John D; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The nursery and greenhouse industry requires precise methods to schedule irrigations, since current practices are subjective and contribute to water and nutrient runoff. Capacitance sensors were calibrated to precisely estimate substrate water content, matric potential, and pore water electrical conductivity (EC) in five soilless substrates. Regression coefficients (R2) ranged from 0.29 - 0.88 and 0.16 - 0.79 for water content in 5-cm and 20-cm column heights; matric potential R2 ranged from 0.10 - 0.98 and 0.79 - 0.98, respectively. Pore water EC calibrations were investigated, contrasting two sensor types and two prediction models. Results were applied to an empirical greenhouse dataset. Better precision and accuracy were achieved with ECH₂O-TE sensor and Rhoades model. Capacitance sensors provide precise estimates of plant-available water in most soilless substrates, while pore water EC accuracy and precision depends on the sensor-model combination. These results will enable growers to precisely schedule irrigations based on water content and pore water EC.
Changes in the community structure of urban and rural forest patches in Baltimore from 1998 to 2015
(2016) Templeton, Laura Kristine; Sullivan, Joseph; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Urban forests are often highly fragmented with many exotic species. Altered disturbance regimes and environmental pollutants influence urban forest vegetation. One of the best ways to understand the impacts of land-use on forest composition is through long-term research. In 1998, the Baltimore Ecosystem Study established eight forest plots to investigate the impacts of urbanization on natural ecosystems. Four plots were located in urban forest patches and four were located in rural forests. In 2015, I revisited these plots to measure abundances and quantify change in forest composition, diversity, and structure. Sapling, shrub, and seedling abundance were reduced in the rural plots. Alpha diversity and turnover was lower in the rural plots. Beta diversity was reduced in the rural plots. The structure of the urban plots was mostly unchanged, except for a highly reduced sapling layer. Beta diversity in the urban plots was consistent across surveys due to high species turnover.