Theses and Dissertations from UMD
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Item ASSESSING THE IMPACTS OF ORGANIC AMENDMENTS ON DISTURBED SOIL PROPERTIES, WATER QUALITY AND VEGETATION GROWTH(2024) Pamuru, Sai Thejaswini; Davis, Allen P; Aydilek, Ahmet H; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Deficiencies in essential organic matter (OM) are exhibited in disturbed roadside soils rendering them less favorable for plant growth. Vegetation plays a crucial role in maintaining the health of ecosystems, providing a myriad of benefits in protecting against soil erosion and effectively managing stormwater. National and state transportation departments are therefore prioritizing roadside vegetation using sustainable practices, leading to increased use of organic amendments (OAs) such as compost or related materials. OAs are commonly recycled and repurposed materials that serve as valuable soil conditioners, and their characteristics vary depending on their parent materials. Many OAs are cost-effective, readily available, and offer significant benefits to urban soils, which often are bereft of plant-essential nutrients and stability. This necessitates a better understanding of their impact on soil health and the environment, when applied at “acceptable” rates. This research aims to explore soil-water-plant interactions in urban soils (with and without OAs) focusing on vegetation establishment, soil fertility, and nutrient transport via leaching/runoff. Greenhouse and laboratory experiments were conducted to assess the potential use of these OAs for roadside projects.One set of experiments (greenhouse tub studies) focused on three OAs (leaf compost, shredded aged wood mulch, biosolids) which are widely available across Maryland. The amended soils were mixed to meet the topsoil OM requirements (4 – 8 %) of the state. Water quality results highlighted that the biosolids, while effective in retaining influent rainwater (tap water) phosphorus, caused significant nitrogen losses, exceeding typical stormwater concentrations by 40-200 times. Leaf compost also contributed to nitrogen leaching but only during the initial stages. Mulch reduced nutrient loss but caused limited vegetative cover. The study found that soil properties, such as the carbon-to-nitrogen (C:N) ratio and nitrogen content, play a vital role in the magnitude and patterns of nitrogen leaching. Additionally, it was speculated that the presence of soil minerals, such as iron and calcium, successfully retained phosphorus in the amended soils. The shear and hydraulic properties of the soils improved with the incorporation of amendments. Based on the results of the tub studies, leaf compost identified as a suitable OA for plants and water quality. However, the tub studies had limitations in their evaluation of compost amendments derived from different feedstock sources and their impacts on native vegetation growth. Therefore, a pot study was conducted to determine the optimum mixing ratios of soils and OAs to facilitate rapid vegetation growth. Three types of composts (turkey litter, food waste and yard waste) with varying nutrient properties were tested. A wood-based biochar was the fourth chosen OA because of its valuable use in agriculture and environmental remediation. The findings showed that turkey litter compost severely inhibited growth at higher application rates due to excess salts content. However, this compost showed improved plant nitrogen and leaf area whenever vegetation was established. Alternatively, biochar, while not inhibiting growth, resulted in visibly weak plant morphology, and led to nitrogen deficiencies. Yard waste and food waste composts showed positive impacts in terms of coverage, leaf area index and plant N contents. Between the tub studies and the pot study, yard waste compost has consistently emerged as the favorable soil amendment. Given biochar’s well documented advantages for water quality and soil structural properties, a scaled-up mesocosm experiment that simulated sloped road shoulders was conducted to test the effectiveness of combining compost and biochar in urban soils, aiming to meet vegetation and water quality goals. The runoff phosphorus and nitrogen mass transports were highest (261 mg-P/m2 and 8645 mg-N/m2, respectively) when compost was the sole amendment mixed into the control soil. However, adding biochar to the soil reduced these losses by up to 5.6x for phosphorus and 8.8x for nitrogen compared to compost. Strong correlation between soil C:N and effluent N was noted, higher ratios (>20:1) reduced nitrogen losses. Biochar, due to its high carbon content and pH, also helped retain phosphorus in the soils. Conversely, compost, being more readily decomposable than biochar, caused nutrients to run off. Compost-biochar mixtures also showed greater plant growth compared to the control soil. Together, this research shows that not all high-nutrient OAs provide favorable outcomes when incorporated into soils to enhance the OM content. Leaf or yard waste-based composts are preferred for roadside vegetation due to their reduced issues related to nutrient losses compared to other nutrient-rich materials tested in this study. However, the yard waste compost incorporation rate should be limited to achieve a soil OM increase of 1-2% to prevent high nutrient levels in the runoff. Furthermore, combining biochar and yard waste compost offers a promising approach for construction projects particularly on steep terrains to achieve and preserve a balanced soil-water-plant ecosystem.Item Characterizing a Multi-Sensor System for Terrestrial Freshwater Remote Sensing via an Observing System Simulation Experiment (OSSE)(2022) Wang, Lizhao; Forman, Barton A; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Terrestrial freshwater storage (TWS) is the vertically-integrated sum of snow, ice, soilmoisture, vegetation water content, surface water impoundments, and groundwater. Among these components, snow, soil moisture, and vegetation are the most dynamic (i.e., shortest residence time) as well as the most variable across space. However, accurately retrieving estimates of snow, soil moisture, or vegetation using space-borne sensors often requires simultaneous knowledge of one or more of the other components. In other words, reasonably characterizing terrestrial freshwater requires careful consideration of the coupled snow-soil moisture-vegetation response that is implicit in both TWS and the hydrologic cycle. One challenge is to optimally determine the multi-variate, multi-sensor remote sensing observations needed to best characterize the coupled snow-soil moisture-vegetation system. Different types of sensors each have their own unique strengths and limitations. Meanwhile, remote sensing data is inherently discontinuous across time and space, and that the revisit cycle of remote sensing observations will dictate much of the efficacy in capturing the dynamics of the coupled snow-soil moisture-vegetation response. This study investigates different snow sensors and simulates the sensor coverage as a function of different orbital configurations and sensor properties in order to quantify the discontinuous nature of remotely-sensed observations across space and time. The information gleaned from this analysis, coupled with a time-varying snow binary map, is used to evaluate the efficacy of a single sensor (or constellation of sensors) to estimate terrestrial snow on a global scale. A suite of different combinations, and permutations, of different sensors, including different orbital characteristics, is explored with respect to 1-day, 3-day, and 30-day repeat intervals. The results show what can, and what cannot, be observed by different sensors. The results suggest that no single sensor can accurately measure all types of snow, but that a constellation composed of different types of sensors could better compensate for the limitations of a single type of sensor. Even though only snow is studied here, a similar procedure could be conducted for soil moisture or vegetation. To better investigate the coupled snow-soil moisture-vegetation system, an observing system simulation experiment (OSSE) is designed in order to explore the value of coordinated observations of these three separate, yet mutually dependent, state variables. In the experiment, a “synthetic truth” of snow water equivalent, surface soil moisture, and/or vegetation biomass is generated using the NoahMP-4.0.1 land surface model within the NASA Land Information System (LIS). Afterwards, a series of hypothetical sensors with different orbital configurations is prescribed in order to retrieve snow, soil moisture, and vegetation. The ground track and footprint of each sensor is approximated using the Trade-space Analysis Tool for Constellations (TAT-C) simulator. A space-time subsampler predicated on the output from TAT-C is then applied to the synthetic truth. Furthermore, a hypothesized amount of observation error is injected into the synthetic truth in order to yield a realistic synthetic retrieval for each of the hypothetical sensor configurations considered as part of this dissertation. The synthetic retrievals are then assimilated into the NoahMP-4.0.1 land surface model using different boundary conditions from those used to generate the synthetic truth such that the differences between the two sets of boundary conditions serve as a realistic proxy for real-world boundary condition errors. A baseline Open Loop simulation where no retrievals are assimilated is conducted in order to evaluate the added utility associated with assimilation of one (or more) of the synthetic retrievals. The impact of the assimilation of a given suite of one or more retrievals on land surface model estimates of snow, soil moisture, vegetation, and runoff serve as a numeric laboratory in order to assess which sensor(s), either separate or in a coordinated fashion, yield the most utility in terms of improved model performance. The results from this OSSE show that the assimilation of a single type of retrieval (i.e., snow or soil moisture or vegetation) may only improve the estimation of a small part of the snow-soil moisture-vegetation system, but may also degrade of other parts of that same system. Alternatively, the assimilation of more than one type of retrieval may yield greater benefits to all the components of the snow-soil moisture-vegetation system, because it yields a more complete, holistic view of the coupled system. This OSSE framework could potentially serve as an aid to mission planners in determining how to get the most observational “bang for the buck” based on the myriad of different sensor types, orbital configurations, and error characteristics available in the selection of a future terrestrial freshwater mission.Item HUMAN-INDUCED VEGETATION DEGRADATION IN A SEMI-ARID RANGELAND(2017) Jackson, Hasan; Prince, Stephen D; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Current assessments of anthropogenic land degradation and its impact on vegetation at regional scales are prone to large uncertainties due to the lack of an objective, transferable, spatially and temporally explicit measure of land degradation. These uncertainties have resulted in contradictory estimates of degradation extent and severity and the role of human activities. The uncertainties limit the ability to assess the effects on the biophysical environment and effectiveness of past, current, and future policies of land use. The overall objective of the dissertation is to assess degradation in a semi-arid region at a regional scale where the process of anthropogenic land degradation is evident. Net primary productivity (NPP) is used as the primary indicator to measure degradation. It is hypothesized that land degradation resulting from human factors on the landscape irreversibly reduces NPP below the potential set by environmental conditions. It is also hypothesized that resulting reductions in NPP are distinguishable from natural, spatial and temporal, variability in NPP. The specific goals of the dissertation are to (1) identify the extent and severity of degradation using productivity as the primary surrogate, (2) compare the degradation of productivity to other known mechanisms of degradation, and (3) relate the expression of degradation to components of vegetation and varying environmental conditions. This dissertation employed the Local NPP Scaling (LNS) approach to identify patterns of anthropogenic degradation of NPP in the Burdekin Dry Tropics (BDT) region of Queensland (14 million hectares), Australia from 2000 to 2013. The method started with land classification based on the environmental factors presumed to control NPP to group pixels having similar potential NPP. Then, satellite remotely sensing data were used to compare actual NPP with its potential. The difference, in units of mass of carbon fixed in NPP per unit area per monitoring interval and per year, also its percentage of the potential, were the measures of degradation. Degradation was then compared to non-green components of vegetation (e.g. wood, stems, leaf litter, dead biomass) to determine their relationship in space and time. Finally, the symptoms of degradation were compared to land management patterns and the environmental variability (e.g. drought, non-drought conditions). Nearly 20% of the region was identified as degraded and another 7% had significant negative trends. The average annual reduction in NPP due to anthropogenic degradation was -17% of the non-degraded potential, although the severity of degradation varied substantially throughout the region. Non-green vegetation cover was strongly correlated with the inter-annual and intra-annual temporal trends of degradation. The dynamics of degradation in drought and non-drought years provided evidence of multiple stables states of degradation.Item MULTI-CRITERIA VEGETATION SELECTION FOR MARYLAND BIORETENTION, WITH NITROGEN FOCUS(2015) Muerdter, Claire; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Stormwater is a leading source of nutrient pollution in natural waters. Bioretention cells can mitigate stormwater pollution. This study examines the role of vegetation in bioretention. In a bioretention field study; of Eutrochium dubium, Solidago rugosa, and Erigeron sp.; E. dubium had the thickest root and tallest aboveground biomass. The root length of the three species averaged 29.1 cm. A greenhouse bioretention mesocosm study examined three plant species: Eutrochium dubium, Iris versicolor, and Juncus effusus. Only J. effusus created significant nitrate (NO3-) removal from synthetic stormwater influent, 0.21 mg to 0.066 mg NO3--N L-1, only in low-density plantings. However, all planted treatments prevented nitrogen export vis-à-vis the unplanted treatment in two storms. J. effusus had the greatest average biomass growth of the three species, 29-fold vis-à-vis 1.3- and 2.7-fold. J. effusus is the most highly recommended plant for Maryland bioretention in this study. E. dubium is cautiously recommended.Item VEGETATION PATTERNS IN DEPRESSIONAL RESTORED, NATURAL REFERENCE, AND PRIOR-CONVERTED WETLANDS IN THE USA MID-ATLANTIC COASTAL PLAIN.(2012) Yepsen, Metthea; Baldwin, Andrew; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Vegetation responds quickly to environmental changes, making it a useful tool for assessing the success of wetland restorations. Plant community composition was compared in 47 sites across the coastal plain of Maryland, Delaware, Virginia, and North Carolina, USA. Fifteen of the sites were isolated depressional wetlands (natural reference), 16 were farmed "prior-converted cropland" sites (ditched and drained former wetlands), and 17 were restored wetlands. Prior-converted sites were highly disturbed and dominated by non-wetland conventional row crops. Natural reference sites were dominated by native woody species and restored sites were dominated by herbaceous wetland species. Natural reference sites had lower Anthropogenic Activity Index scores, higher average coefficients of conservatism, and higher Floristic Quality Assessment Index scores than restored and prior-converted sites. Wetland restorations have succeeded in developing wetland plant communities, but have not developed plant communities that match natural reference wetlands. This is likely due to continued human disturbance, age, and a lack of proper propagules.