Geography Theses and Dissertations

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30+ YEARS OF LAND COVER AND LAND USE CHANGE IN SOUTH AMERICA
(2020) Zalles Ballivian, Viviana; Hansen, Matthew C.; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The modification of the Earth’s surface constitutes the most impactful way in which humans affect their surrounding environment, with broad and lasting consequences. Changes in land cover accelerate biodiversity loss, contribute to climate change, and affect the provisioning of ecosystem services. Such negative environmental impacts can have important effects on human health and livelihoods. The South American continent, in particular, has undergone significant transformations over the past decade, due in large part to the conversion of natural land to more economically productive land uses, such as crops, pastures, and tree plantations. The agricultural commodities produced in South America are traded and consumed globally, and land will likely continue to be converted if demand for these commodities continues to rise. Despite the environmental and commercial importance of land cover and land use change dynamics in South America, the extent and rates of land change have not yet been thoroughly characterized and quantified. This dissertation aims to advance scientific knowledge on the extent and rates of change of important land covers and land uses, especially as they relate to the production of agricultural commodities, by leveraging the 34-year Landsat archive of Earth observation data. The general approach employed throughout follows a two-step process of mapping and sampling, in order to provide spatially explicit information on the patterns of land cover/land use change, as well as associated unbiased area estimates. This approach is first employed for the use-case of Brazilian cropland expansion from 2000 to 2014, and results show a near doubling of cropland area, the majority of which (80%) came about through the conversion of existing pastures. The methodology is then repeated at broader thematic, temporal, and geographic scales, resulting in area estimates of changes in cropland, pasture, plantation, natural tree regrowth, semi-natural land, tree cover and degraded tree cover from 1985 to 2018. Altogether, these changes amount to a 60% increase in human impact on natural land over the study period. Finally, an analysis and evaluation of the methodology employed for mapping and sampling when there is a multitude of target classes instead of a single one is provided as an assessment of methodological approaches.
ADDRESSING GEOGRAPHICAL CHALLENGES IN THE BIG DATA ERA UTILIZING CLOUD COMPUTING
(2020) Lan, Hai; Stewart, Kathleen; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Processing, mining and analyzing big data adds significant value towards solving previously unverified research questions or improving our ability to understand problems in geographical sciences. This dissertation contributes to developing a solution that supports researchers who may not otherwise have access to traditional high-performance computing resources so they benefit from the “big data” era, and implement big geographical research in ways that have not been previously possible. Using approaches from the fields of geographic information science, remote sensing and computer science, this dissertation addresses three major challenges in big geographical research: 1) how to exploit cloud computing to implement a universal scalable solution to classify multi-sourced remotely sensed imagery datasets with high efficiency; 2) how to overcome the missing data issue in land use land cover studies with a high-performance framework on the cloud through the use of available auxiliary datasets; and 3) the design considerations underlying a universal massive scale voxel geographical simulation model to implement complex geographical systems simulation using a three dimensional spatial perspective. This dissertation implements an in-memory distributed remotely sensed imagery classification framework on the cloud using both unsupervised and supervised classifiers, and classifies remotely sensed imagery datasets of the Suez Canal area, Egypt and Inner Mongolia, China under different cloud environments. This dissertation also implements and tests a cloud-based gap filling model with eleven auxiliary datasets in biophysical and social-economics in Inner Mongolia, China. This research also extends a voxel-based Cellular Automata model using graph theory and develops this model as a massive scale voxel geographical simulation framework to simulate dynamic processes, such as air pollution particles dispersal on cloud.
ADDRESSING THE IMPACT ON SOIL DEGRADATION OF CHANGE FROM GRASSLAND TO CROPLAND: A CASE STUDY IN THE URUGUAYAN GRASSLANDS
(2017) Castano-Sanchez, Jose P; Prince, Stephen D; Izaurralde, Roberto C; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Globally, there has been large-scale conversion of natural grassland to cropland ecosystems which this has led to land degradation that could reduce future food security, other ecosystem services and even climate. Currently, there is a dearth of quantitative information assessing the severity, distribution, and causes of this land degradation. For practical purposes, this information is needed to develop improved methods of land use (LU) conversion. Uruguay, in contrast with many other regions, still has a high proportion of unimproved grasslands but, during the last 15 years, there has been extensive conversion to grow grain crops. The fundamental goal of this dissertation was to quantify soil degradation resulting from this LU change. Two aspects of soil degradation were studied, soil organic carbon (SOC) and erosion by water. The Environmental Policy Integrated Climate biophysical simulation model (EPIC) was used to model the grassland and cropping systems. The study consisted of three steps: (1) calibration and validation of the model for the Uruguayan agroecosystems, and development of a spatial version, (2) identification of the LU change areas, and (3) quantification of soil degradation as a result of the LU changes. The EPIC model adequately reproduced the field-scale SOC dynamics and erosion in field validation sites. Further, the spatial version of the model was found to simulate spatial and temporal performance adequately. LU change areas during 2000-2013 were mapped and found to cover an area of 410,000 ha, about 13% of potential area for commercial agriculture. LU greatly affected soil degradation. It was greatest for continuous Soybean cultivation with no crop rotation, and lowest for grassland (no conversion to cropping). In addition to LU, slope and initial SOC had significant effects on degradation. The main conclusions were that the recent and continuing conversion from grassland to cropland has caused significant soil degradation, but that some modifications of LU can reduce the risk of degradation.
ADOPTION, IMPACT EVALUATION, AND TECHNICAL EFFICIENCY OF IRON BIOFORTIFIED BEAN PRODUCTION IN RWANDA
(2020) Funes, Jose Elias; Sun, Laixiang; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Micronutrient malnutrition, also known as hidden hunger, is a public health problem in many developing countries. Hidden hunger limits cognitive and physical development of children and increases both children’s and adults’ susceptibility to infectious diseases. The most common outcome of iron deficiency is anemia and in Rwanda, iron micronutrient malnutrition is highly pervasive. Thirty seven percent of children under five years of age and nearly 20 percent of women of childbearing age suffer from anemia in the country. Since 2012, HarvestPlus and its partners have been intensively disseminating iron biofortified common beans (Phaseolus Vulgaris) (IBB) varieties to help alleviate iron deficiency in Rwanda. On one hand, Rwandan farmers may be uncertain about the economic returns of this new technology owing to insufficient knowledge about the types and costs of inputs needed, the yield distribution, expected market prices, and the demand for the produce. On the other hand, policy makers and donors cannot observe the outcomes that bean farmers would experience under all treatments of the IBB program. The counterfactual outcomes that a bean farming household would have experienced under other treatments are not observable. In this context, this dissertation uses a multiprong analytical framework to: 1) analyze how peer interactions, households and farm characteristics, as well as regional factors influence smallholder farming households’ decisions to grow IBB varieties, 2) evaluate the impact of the IBB program on Rwandan farmer’s livelihoods, focusing on the outcomes of yields and incomes for beneficiary households, and 3) estimate the impact of the IBB program on smallholder farming households’ technical efficiency. The spatial econometric results indicate spatial interdependence in smallholder farming households' decisions to adopt IBB. In addition to the directly targeted beneficiaries, the spatial parameters from the econometric analysis suggest that the biofortification program affected non-beneficiaries as well. This finding indicates that (1) a household is more likely to grow IBB if the household is near other early IBB adopters who informed them about the nutritional and yield benefits of IBB technology and (2) the propensity of a household to grow IBB varies with the characteristics of neighboring farmers. The impact evaluation analysis supports the hypothesis that IBB growers had significantly higher yields and incomes, as compared to farmers that grew non-biofortified beans, whether improved or traditional. In addition, the impact assessment shows that farmers who grew iron biofortified varieties were relatively more efficient and obtained greater bean production than the control group.
Advanced Modeling Using Land-use History and Remote Sensing to Improve Projections of Terrestrial Carbon Dynamics
(2021) Ma, Lei; Hurtt, George; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Quantifying, attributing, and projecting terrestrial carbon dynamics can provide valuable information in support of climate mitigation policy to limit global warming to 1.5 °C. Current modeling efforts still involve considerable uncertainties, due in part to knowledge gaps regarding efficient and accurate scaling of individual-scale ecological processes to large-scale dynamics and contemporary ecosystem conditions (e.g., successional states and carbon storage), which present strong spatial heterogeneity. To address these gaps, this research aims to leverage decadal advances in land-use modeling, remote sensing, and ecosystem modeling to improve the projection of terrestrial carbon dynamics at various temporal and spatial scales. Specifically, this research examines the role of land-use modeling and lidar observations in determining contemporary ecosystem conditions, especially in forest, using the latest land-use change dataset, developed as the standard forcing for CMIP6, and observations from both airborne lidar and two state-of-the-art NASA spaceborne lidarmissions, GEDI and ICESat-2. Both land-use change dataset and lidar observations are used to initialize a newly developed global version of the ecosystem demography (ED) model, an individual-based forest model with unique capabilities to characterize fine-scale processes and efficiently scale them to larger dynamics. Evaluations against multiple benchmarking datasets suggest that the incorporation of land-use modeling into the ED model can reproduce the observed spatial pattern of vegetation distribution, carbon dynamics, and forest structure as well as the temporal dynamics in carbon fluxes in response to climate change, increased CO2, and land-use change. Further, the incorporation of lidar observations into ED, largely enhances the model’s ability to characterize carbon dynamics at fine spatial resolutions (e.g., 90 m and 1 km). Combining global ED model, land-use modeling and lidar observation together can has great potential to improve projections of future terrestrial carbon dynamics in response to climate change and land-use change.
Advances in Mapping Forest Biomass and Old-Growth Conditions Using Waveform Lidar
(2023) Bruening, Jamis; Dubayah, Ralph; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The Global Ecosystem Dynamics Investigation (GEDI) is a spaceborne waveform lidar sys- tem that has transformed scientific understanding of the world’s forests through billions of pre- cise measurements of ecosystem structure. Relative to forest processes that operate on decadal to millennial timescales, the four year period during which GEDI collected these measurements is short, and GEDI’s ability to analyze how forest structure changes over time is mostly unproven. However, fusion efforts that integrate GEDI data with forest inventory measurements and ecosys- tem models hold immense potential for discovery. In this dissertation, I explore the limitations and capabilities of GEDI data for inference into structural and successional dynamics within east- ern US forests. First, I used a forest gap model to quantify uncertainty in biomass predictions for individual GEDI waveforms, and discovered a relationship between biomass uncertainty and successional stage. Next, I investigated uncertainties and errors in large-scale GEDI biomass estimates relative to unbiased estimates from the US forest inventory. I developed a novel mod- eling framework based on fusion between GEDI and the US forest inventory data that corrected these errors, and I produced unbiased and precise maps of forest biomass for the continental US. Lastly, I assessed GEDI’s ability to identify and map different types of old-growth forests, and discovered that GEDI can detect some old forests more effectively than others. This research identified key limitations associated with using GEDI to study forest dynamics, and I leveraged these discoveries to develop new ways of using GEDI data for ecological and successional in- ference. These discoveries will inform new uses of GEDI data and its integration with inventory data and ecosystem modeling to better characterize changes within forest ecosystems.
Advancing Indonesian Forest Resource Monitoring Using Multi-Source Remotely Sensed Imagery
(2014) Margono, Belinda Arunarwati; Hansen, Matthew C; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Tropical forest clearing threatens the sustainability of critically important global ecosystems services, including climate regulation and biodiversity. Indonesia is home to the world's third largest tropical forest and second highest rate of deforestation; as such, it plays an important role in both increasing greenhouse gas emissions and loss of biodiversity. In this study, a method is implemented for quantifying Indonesian primary forest loss by landform, including wetlands. A hybrid approach is performed for quantifying the extent and change of primary forest as intact and degraded types using a per-pixel supervised classification mapping followed by a GIS-based fragmentation analysis. The method was prototyped in Sumatra, and later employed for the entirety of Indonesia, and can be replicated across the tropics in support of REDD+ (Reducing Emissions from Deforestation and forest Degradation) initiatives. Mapping of Indonesia's wetlands was performed using cloud-free Landsat image mosaics, ALOS-PALSAR imagery and topographic indices derived from the SRTM. Results quantify an increasing rate of primary forest loss over Indonesia from 2000 to 2012. Of the 15.79 Mha of gross forest cover loss for Indonesia reported by Hansen et al. (2013) over this period, 38% or 6.02 Mha occurred within primary intact or degraded forests, and increased on average by 47,600 ha per year. By 2012, primary forest loss in Indonesia was estimated to be higher than Brazil (0.84 Mha to 0.47 Mha). Almost all clearing of primary forests (>90%) occurred within degraded types, meaning logging preceded conversion processes. Proportional loss of primary forests in wetlands increased with more intensive clearing of wetland forests in Sumatra compared to Kalimantan or Papua, reflecting a near-exhaustion of easily accessible lowland forests in Sumatra. Kalimantan had a more balanced ratio of wetland and lowland primary forest loss, indicating a less advanced state of natural forest transition. Papua was found to have a more nascent stage of forest exploitation with much of the clearing related to logging activities, largely road construction. Loss within official forest-land uses that restrict or prohibit clearing totaled 40% of all loss within national forest-land, another indication of a dwindling resource. Methods demonstrated in this study depict national scale primary forest change in Indonesia, a theme that until this study has not been quantified at high spatial (30m) and temporal (annual) resolutions. The increasing loss of Indonesian primary forests found in this study has significant implications for climate change mitigation and biodiversity conservation efforts.
AGRICULTURAL LAND USE, DROUGHT IMPACTS AND VULNERABILITY: A REGIONAL CASE STUDY FOR KARAMOJA, UGANDA
(2017) Nakalembe, Catherine Lilian; Justice, Christopher O; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
The increasing frequency of extreme climate events brings into question the sustainability of agriculture in marginal lands, especially those already experiencing drought such as the Karamoja region in northeastern Uganda. A significant amount of research often qualitative has been conducted documenting drought and its impact on Karamoja. Taking a mixed methods approach, this study combined remotely-sensed satellite data, national agricultural surveys, census, and field data to expand on empirical knowledge on agricultural drought, land use and human perceptions of drought necessary for comprehensive drought forecasting, monitoring, and management. Results from this study showed that Karamoja is at least twice more vulnerable to drought than any other region in Uganda. This is because of its very low adaptive capacity in part due to high poverty rates and a higher dependency on the natural environment for livelihood. Analysis of satellite data quantified a 229 percent increase in cropland area in Karamoja between 2000 and 2011/12, driven largely by agricultural development programs. Underlying forces (e.g., cropland expansion programs and controlled grazing) originating from land use policy and development programs, more than proximate causes (direct local level actions) remain the major drivers of this expansion. Although the cultivated area has dramatically increased, there is no quantifiable overall increase in yield or per-capita production as evidenced by the recurrent poor food security. This status quo, (poor yields and dependence on food aid) is likely to continue as more land is put to crop cultivation by poor households and meager investments are made in livestock-based livelihood opportunities. The cropland area mask developed in this research facilitated the characterization of drought within agricultural areas. The drought information developed by this study is spatially and temporally explicit, showing differences in severity between years and between districts. Overall Abim District showed the least variation and is the least impacted while, Moroto District had the highest inter-annual variability and was often the most severely impacted. This research presents an approach to predict the number of people who would require food aid during the lean season in Karamoja (December to March) within a reasonable margin of error (less than 10\%) at the peak of the growing season (August/September), although the need for more extensive testing is recognized. The method takes advantage of readily available satellite data and can contribute to planning for a timely and appropriate response. A case study of farmer's perceptions of drought in Moroto District found that many farmers feel helpless and have no control of their future. For the majority of farmers in the district, past experiences of drought do not necessarily impact on future expectations of drought and many have no long-term adjustment plans. Quite often the majority of the population depends on emergency food assistance, building a culture of dependency. The analysis indicates that factors such as; conflict (insecurity) and interventions by government and international agencies intermingle with culture to have a profound direct influence on farmers' perception of drought amongst communities in Moroto district. This research shows that satellite data can provide the much-needed information to fill the gaps that inhibit long-term drought monitoring, at a significantly lower cost than traditional climate station-based monitoring in data scarce regions like Karamoja. It also points to a way forward for proactive assessment, planning, and response.
Analyze Municipal Annexations: Case Studies in Frederick and Caroline Counties of Maryland, 1990-2010
(2012) Pomeroy, Jennifer Yongmei; Geores, Martha E; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Municipal annexations play an important role in converting undeveloped land to development, influencing landscape change. However, the existing literature does not explore the links between annexation and development. An additional inadequacy is the failure to consider environment/landscape aspect of annexation. Therefore, this dissertation proposes a new theoretical framework that is drawn upon political ecology and structuration theory to examine annexation phenomenon processes: environmental/landscape sensitivity and its causal social structures. Frederick and Caroline counties in Maryland from 1990 to 2010 were the two case-study areas because both counties experience increased annexation activities and are representative of suburban and exurban settings at rural - urban continuum of the United States. The data used in this qualitative research were collected from multiple data sources, including key-person interviews, a review of Maryland's annexation log, annexation applications and meeting minutes, and observations at public meetings. Triangulating content analysis, discourse analysis, and social network analysis, this research finds that environmental/landscape is not considered more widely in annexation practices. Although environmental mitigation measures are considered at site level if a property has site environmental elements, the overall environmental/landscape sensitivity is low. It is also found that the economic-centered space remains dynamic in the annexation processes determining annexation approvals and low-density zoning. In addition, the triangulated analyses reveal that current social structures are not conducive to environmental-conscious landscape planning because environmentally oriented non-profit organizations and residents are injected at a later stage of annexation process and is not being fully considered in the evaluation process. Power asymmetry in current annexation structures is due to a lack of environmental voice in annexation processes. The voice of such groups needs to be institutionalized to facilitate more tenable annexation practices.
ANALYZING FOREST CHANGE AND POLICY IN WASHINGTON, DC SUBURBAN COUNTIES
(2005-05-27) Jantz, Claire Ann; Geores, Martha E; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Geographical approaches for landscape studies have emphasized the interpretation of landscape change as a cultural phenomenon, but often have neglected modern geographic techniques, such as remote sensing observations and quantitative spatial analysis, to characterize and understand landscape change. This study attempts to bridge these gaps by integrating a socio-cultural analysis of land use policy formation and quantitative assessments of land cover change to demonstrate how policy decisions can influence forest landscape patterns in suburban areas. Historical data from Montgomery County, MD and Fairfax County, VA, two counties adjacent to the Washington, DC urban core that have different governmental structures, were assembled and analyzed. A policy database was developed and analyzed using qualitative techniques, such as grounded theory and content analysis, to address questions related to policy formation and trends. Key findings included the identification of a strong link between land use policies and the broader environmental discourse, demonstrating that dominant cultural values are institutionalized in the development of land use policy. Furthermore, many policies related to forest management and preservation, particularly in recent decades, had a strong focus on protecting riparian forests. Land cover change between the late 1930s and 1998 was studied for local case study areas using time series of aerial photographs, and between 1990 and 2000 across both counties using satellite-derived land cover maps. Using a statistical technique, weights of evidence, the processes of new development, deforestation, and forest persistence were modeled. The results highlighted the role of biophysical variables, such as steep slopes and the presence of poorly drained soils, in constraining new development and enhancing forest persistence. However, the role of land use policies was also evident in enhancing forest persistence through the establishment of protected areas and riparian protection policies. This study demonstrated the impact that land use regulations can have on the evolution of forested landscape patterns within the built environment. The links between socio-cultural values and policy formation highlighted the institutional and cultural barriers that prevent rapid shifts in policy orientation, despite social and environmental problems that arise within a rapidly changing landscape.
Analyzing the Impact of Participatory-Planned Conservation Policies in the Negril Environmental Protection Area, western Jamaica
(2007-05-06) Miller Anderson, Lovette; Defries, Ruth S.; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
ABSTRACT Title of Dissertation: ANALYZING THE IMPACT OF PARTICIPATORY PLANNED CONSERVATION POLICIES IN THE NEGRIL ENVIRONMENTAL PROTECTION AREA, WESTERN JAMAICA Lovette Miller Anderson, Doctor of Philosophy, 2007 Dissertation directed by: Professor Ruth Defries Department of Geography This dissertation research sought to determine the ways in which the participatory-planned conservation policies influence changes in local populations' natural resource use. The research took place in the Negril Environmental Protection Area, western Jamaica and covered the period 1990 to 2005. The two major questions asked were 1) In what ways do participatory-planned conservation policies influence changes in the protected area's natural resource use? 2) How does group membership and demography influence the perception of the conservation policies and of changes in natural resource use? The research employed trend analyses, content analyses, a population survey, discriminant analyses and semi-structured interviews to answer the research questions. In general, the research finds that national socioeconomic development interests were given priority over the participatory-planned conservation policies. The changes in local populations' natural resource use were primarily due to the national socioeconomic policies that were in place prior to the protected area designation as well as those that were implemented during the study period. Second, the research finds that, in general, groups that have shared histories were homogeneous in their views of conservation and/or development. In contrast, newer entrants to the protected area were generally heterogeneous in their views of conservation and/or development. Further, the research finds that changes in the demographic characteristics of local populations significantly influence the perception of conservation and development. For example, respondents who were relatively new to the protected area generally had a positive perception of conservation and of the decline in fishing jobs. In contrast, respondents who have lived there relatively longer had a negative perception of conservation and of the decline in fishing jobs. By examining the complexity of implementing the participatory-planned conservation policies in Negril's postcolonial and non-colonial socioeconomic and political landscape, this research extends the discourse on protected areas from large, relatively low populated areas to the complex geographic landscapes that currently describe some newer protected areas.
AN APPROACH TO ESTIMATE GLOBAL BIOMASS BURNING EMISSIONS OF ORGANIC AND BLACK CARBON FROM MODIS FIRE RADIATIVE POWER
(2009) Ellicott, Evan Andrew; Justice, Christopher O; Vermote, Eric; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Biomass burning is an important global phenomenon affecting atmospheric composition with significant implications for climatic forcing. Wildland fire is the main global source of fine primary carbonaceous aerosols in the form of organic carbon (OC) and black carbon (BC), but uncertainty in aerosol emission estimates from biomass burning is still rather large. Application of satellite based measures of fire radiative power (FRP) has been demonstrated to offer an alternative approach to estimate biomass consumed with the potential to estimate the associated emissions from fires. To date, though, no study has derived integrated FRP (referred to as fire radiative energy or FRE) at a global scale, in part due to limitations in temporal or spatial resolution of satellite sensors. The main objective of this research was to quantify global biomass burning emissions of organic and black carbon aerosols and the corresponding effect on planetary radiative forcing. The approach is based on the geophysical relationship between the flux of FRE emitted, biomass consumed, and aerosol emissions. Aqua and Terra MODIS observations were used to estimate FRE using a simple model to parameterize the fire diurnal cycle based on the long term ratio between Terra and Aqua MODIS FRP and cases of diurnal satellite measurements of FRP made by the geostationary sensor SEVIRI, precessing sensor VIRS, and high latitude (and thus high overpass frequency) observations by MODIS. Investigation of the atmospheric attenuation of MODIS channels using a parametric model based on the MODTRAN radiative transfer model indicates a small bias in FRE estimates which was accounted for. Accuracy assessment shows that the FRE estimates are precise (R2 = 0.85), but may be underestimated. Global estimates of FRE show that Africa and South America dominate biomass burning, accounting for nearly 70% of the annual FRE generated. The relationship between FRE and OCBC estimates made with a new MODIS-derived inversion product of daily integrated biomass burning aerosol emissions was explored. The slope of the relationship within each of several biomes yielded a FRE-based emission factor. The biome specific emission factors and FRE monthly data were used to estimate OCBC emissions from fires on a global basis for 2001 to 2007. The annual average was 17.23 Tg which was comparable to previously published values, but slightly lower. The result in terms of global radiative forcing suggests a cooling effect at both the top-of-atmosphere (TOA) and surface approaching almost -0.5 K which implies that biomass burning aerosols could dampen the warming effect of green house gas emissions. An error budget was developed to explore the sources and total uncertainty in the OCBC estimation. The results yielded an uncertainty value of 58% with specific components of the process warranting future consideration and improvement. The uncertainty estimate does not demonstrate a significant improvement over current methods to estimate biomass burning aerosols, but given the simplicity of the approach should allow for refinements to be made with relative ease.
Assessing Cellulosic Biofuel Feedstock Production Across a Gradient of Agricultural Management Systems in the U.S. Midwest
(2014) Sahajpal, Ritvik; Hurtt, George C; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
While biofuels are widely considered to be a part of the solution to high oil prices, a comprehensive assessment of the environmental sustainability of existing and future biofuel systems is needed to assess their utility in meeting U.S. energy and food needs without exacerbating environmental harm. The following questions guide this research: 1. What is the spatial extent and composition of agricultural management systems that exist in the U.S. Midwest? 2. How does sub-grid scale edaphic variation impact our estimation of poplar biomass productivity across a gradient of spatial scales in the U.S. Midwest? 3. How do location and management interactions impact yield gap analysis of cellulosic ethanol production in U.S. Midwest? In the first chapter, I developed an algorithm to identify representative crop rotations in the U.S. Midwest, using remotely sensed data; and used this information to detect pronounced shifts from grassland to monoculture cultivation in the U.S. Midwest. In the second chapter, a new algorithm is developed to reduce the computational burden of high resolution ecosystem modeling of poplar plantations in U.S. Midwest, with the results from the high resolution modeling being used to estimate the impact of averaging and discretization of soil properties on poplar yield estimates. In the third chapter, a novel yield gap analysis of cellulosic feedstocks on marginal lands in the U.S. Midwest is conducted to determine the management inputs needed to reach their yield potential in a sustainable manner. The significance of this research lies in providing a spatially explicit regional scale analysis of the tradeoffs between food and fuel production and providing an understanding of which biofuel crops should be grown where to maximize production while mitigating environmental damage.
ASSESSING FOREST BIOMASS AND MONITORING CHANGES FROM DISTURBANCE AND RECOVERY WITH LIDAR AND SAR
(2015) Huang, Wenli; Dubayah, Ralph; Sun, Guoqing; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
This dissertation research investigated LiDAR and SAR remote sensing for assessing aboveground biomass and monitoring changes from anthropogenic forest disturbance and post-disturbance recovery. First, waveform LiDAR data were applied to map forest biomass and its changes at different key map scales for the two study sites: Howland Forest and Penobscot Experimental Forest. Results indicated that the prediction model at the scale of individual LVIS footprints is reliable when the geolocation errors are minimized. The evaluation showed that the predictions were improved markedly (20% R2 and 10% RMSE) with the increase of plot sizes from 0.25 ha to 1.0 ha. The effect of disturbance on the prediction model was strong at the footprint level but weak at the 1.0 ha plot-level. Errors reached minimum when footprint coverage approached about 50% of the area of 1.0 ha plots (16 footprints) with no improvement beyond that. Then, a sensitivity analysis was conducted for multi-source L-band SAR signatures, to change in forest biomass and related factors such as incidence angle, soil moisture, and disturbance type. The effect of incidence angle on SAR backscatter was reduced by an empirical model. A cross-image normalization was used to reduce the radiometric distortions due to changes in acquisition conditions such as soil moisture. Results demonstrated that the normalization ensured that the derived biomass of regrowth forests was cross-calibrated, and thus made the detection of biomass change possible. Further, the forest biomass was mapped for 1989, 1994 and 2009 using multi-source SAR data, and changes in biomass were derived for a 15- and a 20-year period. Results improved our understanding of issues concerning the mapping of biomass dynamic using L-ban SAR data. With the increase of plot sizes, the speckle noise and geolocations errors were reduced. Multivariable models were found to outperform the single-term models developed for biomass estimation. The main contribution of this research was an improved knowledge concerning waveform LiDAR and L-band SAR’s ability in monitoring the changes in biomass in a temperate forest. Results from this study provide calibration and validation methods as a foundation for improving the performance of current and future spaceborne systems.
ASSESSING THE RELATIONSHIPS BETWEEN VERTICAL STRUCTURE, BIODIVERSITY, AND SUCCESSION IN A FOREST ECOSYSTEM USING LIDAR REMOTE SENSING
(2014) Whitehurst, Amanda Sharon; Dubayah, Ralph O; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
This thesis used lidar remote sensing to explore the role of vertical structure in forest ecosystem dynamics. In particular, relationship between the vertical distribution, biodiversity, and succession was examined in Hubbard Brook Experimental Forest, NH (HBEF). The first objective was to develop metrics characterizing vertical foliage distribution or canopy layering. Two novel metrics (canopy layer structure categories and number of foliage profile layers) were created, allowing canopy layering to be mapped HBEF. The canopy layer structure metric categorizes areas by comparing the amount of vegetation in under, mid, and overstories. The number of foliage profile layers is related to peaks in the foliage area profile, representing area of dense of "clumped" foliage. Both these metrics varied with canopy height and elevation, areas with taller trees and lower elevations tended to have more foliage profile layers and were classified as categories with a dominant overstory. The second objective was to examine the relationship between vertical canopy structure and avian species diversity. Multiple vertical structure metrics were derived for 370 bird plots in HBEF. Foliage height diversity (FHD) varied greatly in relation to bird species diversity. Of the foliage distribution metrics, vegetation ratio and number of foliage profile layers explained the most variability in bird species diversity. The lidar metric of height at median return (HOME) had the strongest correlation with bird species diversity (r = - 0.56). This study showed a moderate correlation between bird species diversity and foliage distribution metrics. It further supports previous studies which question the applicability of FHD. Finally, change in vertical structure in HBEF was examined using lidar data from 1999 and 2009. Due to significant change in canopy height, canopy cover, vegetation ratio and understory cover during the time period, it was determined that HBEF had not reached steady-state. Recently disturbed areas had significantly higher canopy height growth than undisturbed areas, despite being at higher elevations. This research presents standardized metrics for the characterization and mapping of canopy foliage distribution. It also provides ecological links between lidar metrics and ecological concepts to enabling these measurements of forest structure to be applied in other areas.
Autochthonous and Introduced Stores of Biomass Value: Measuring Resilience Outcomes of Enset and Eucalyptus as Green Assets in Three Representative Smallholder Farm Systems of Ethiopia
(2020) Morrow, Nathan; Hansen, Matthew C; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Fundamental shifts in the ability to observe our world with synoptic satellite remote sensing and the profusion of trend tracking longitudinal data sources not only better inform us of the mounting trouble our planet is in but also provide completely new perspectives on basic shared understandings, such as how many trees grow on Earth and where they take root. Observing the dispersed pattern of increasing tree cover across a multidecadal satellite mosaic, developed by Matt Hansen and colleagues at University of Maryland at College Park, sparked an interest in the ramifications of this unanticipated change, marked clearly upon the landscape in Ethiopia. The following chapters explore the relation of changing amounts of autochthonous treelike perrenial enset and introduced eucylyptus trees, commonly found on Ethiopian farms, to smallholder resilience, food security, and well-being. Spatially informed longitudinal models for three representative subnational data sets are used to investigate the central thesis of this dissertation—trees and treelike perennials on farms in rural Ethiopia indicate a fundamental store of value in living biomass, building a household’s assets over time through improved biomass management, for resilient small farm livelihoods that ensure food security and related well-being. Green assets acting as biomass stores indicate natural “value,” representing transformed and stored energy of the sun, that Blaikie and Brookfield (1987) considered inadequately captured as a no-cost contribution to the “use value” concept in development economics, economic geography production, and income-focused research, as well as in Marx’s (1887/2013) labor-focused value constructs that only briefly acknowledge workers are helped by the transformative “natural forces” at work on the land. Model results presented in Chapters 3, 4, and 5 reveal a lack of on-farm trees and treelike perennials often indicates biomass poverty and energy insecurity. Chronic biomass poverty, measured with spatially aware hierarchal models, is related to an inability to maintain a sufficient level of essential green assets, thereby contributing to poor resilience and well-being outcomes on small farms. On the other hand, medium and longer term asset accumulation supports improved well-being when livelihood strategies make use of farm forests, other on-farm trees, and treelike perennials.
Canopy Fuels Inventory and Mapping Using Large-Footprint Lidar
(2005-12-05) Peterson, Birgit; Dubayah, Ralph; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
This dissertation explores the efficacy of large-footprint, waveform-digitizing lidar for the inventory and mapping of canopy fuels for utilization in fire behavior simulation models. Because of its ability to measure the vertical structure of forest canopies lidar is uniquely suited among remote sensing instruments to observe the canopy structure characteristics relevant to fuels characterization and may help address the lack of high-quality fuels data for many regions, especially in more remote areas. Lidar data were collected by the Laser Vegetation Imaging Sensor (LVIS) over the Sierra National Forest in California. Various waveform metrics were calculated from the waveforms. Field data were collected at 135 plots co-located with a subset of the lidar footprints. The field data were used to calculate ground-based observations of canopy bulk density (CBD) and canopy base height (CBH). These observed values of CBD and CBH were used as dependent variables in a series of regression analyses using the derived lidar metrics as independent variables. Comparisons of observed and predicted resulted in an r2 of 0.71 for CBD and an r2 of 0.59 for CBH. These regression models were then used to generate grids of CBD and CBH from all of the lidar waveform data in the study area. These grids, along with lidar-derived grids of canopy height, were then used as inputs to the FARSITE (Fire Area Simulator-Model) fire behavior model in a series of simulations. Comparisons between conventionally derived and lidar-based model inputs showed differences between the two sets of data. Specifically, the lidar-derived inputs contained much more spatial heterogeneity. Outputs from FARSITE using the lidar-derived inputs were also compared to outputs using input maps of CBD and CBH generated from field observations. There were significant differences between the two sets of outputs, especially in the frequency and spatial distribution of crown fire. Experiments in manipulating the effective resolution of the lidar-based inputs confirmed that FARSITE outputs are affected by the spatial variability of the input data. Furthermore, a sensitivity analysis demonstrated that FARSITE is sensitive to potential errors in the canopy structure input grids. The results of this dissertation show that lidar can be used effectively to predict CBD and CBH for the purpose of fire behavior modeling and that investment in these lidar-based canopy structure data is worthwhile, especially for forests characterized by significant heterogeneity. This work affirms that lidar is a useful tool for future canopy fuels inventory and mapping.
Carbon Sequestration and Agents of Woody Encroachment in Southeastern Arizona Semi-arid Grasslands
(2014) O'Neal, Kelley; Justice, Christopher; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Woody encroachment and proliferation within dryland ecosystems is potentially the second largest portion of the North American carbon sink and one of the largest areas of uncertainty. This dissertation examines a semi-arid grassland located in southeastern Arizona to better understand woody encroachment, agents of change, and the resultant carbon storage from 1984-2008. The objectives were to quantify changes in woody cover, rank agent importance, estimate carbon density, and calculate voluntary market value. The first objective of mapping changes in woody cover was addressed using a Landsat time-series to measure woody cover and calculate the change, rate of change, and change relative to initial cover over the 25-year time period. Results show the change in woody cover varies spatially and ranges from approximately -2 to 11% with most areas experiencing a 5% increase and 92% relative increase over initial cover, indicating woody cover nearly doubled in the region. The second objective of ranking the importance of agents was achieved using an ensemble classifier. Agents examined included grazing, number of times burned, soil texture, soil productivity, elevation, slope, aspect, and initial woody cover. Initial woody cover, number of times burned, elevation, and grazing were ranked as the most important agents of woody encroachment, indicating the importance of historical land management and disturbance, frequent fire, topography and correlated precipitation, and land use. The third objective of producing carbon estimates and calculating economic opportunity in the voluntary carbon markets was accomplished by applying cover to biomass, root:shoot, and carbon equations to the final woody plant cover maps to calculate carbon stocks, carbon density, and voluntary market value. Results show very low carbon density in the study area relative to similar ecosystems and other ecosystems in general. Given the insignificant annual accumulation of carbon on the small ownership parcels, current low carbon trading prices, and high beef prices, management for storage is not economically viable in the study area at this time.
A Case Study of Anacostia: The Role of Housing Vouchers on the Local Housing Market
(2012) Scott, Derrick A; Geores, Martha; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
From the time of the New Deal legislation in the 1930s, the Federal government has provided some form of housing relief for people with low income. Today, the primary demand side subsidy program is the Housing Choice Voucher Program (HCVP), which subsidizes rents for low-income people and households to live in places where market-rate rents are beyond their economic means. During the last two decades many Americans cities have been transitioning and affordable housing is becoming scarce even in formerly low-income neighborhoods. In these transitioning neighborhoods current rents are prohibitive for low-income residents. However, with a subsidy through HCVP, this population can remain in its original neighborhood. Landlords are assured full market value rents, while renting to low-income tenants. The residents of the Anacostia neighborhood in Washington, D.C. are predominately low-income and African-American. Using Anacostia as a case study, this paper shows how HCVP has increased in volume and, in the face of diminishing affordable housing, recipients of this subsidy are concentrating in this low rent neighborhood rather than dispersing throughout Washington DC. This is a mixed methods study using data gathered from the Washington D.C. Housing Authority, home sales, home rental prices, census, and interviews with participants in HCVP. The findings of this study reveal that HCVP has been successful in improving the lives and residences of low-income people but that vouchers are geographically concentrated to the lowest income neighborhoods of Washington D.C.
Changes in Amazon Forest Structure from Land-Use Fires: Integrating Satellite Remote Sensing and Ecosystem Modeling
(2008-11-17) Morton, Douglas; DeFries, Ruth S; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Fire is the dominant method of deforestation and agricultural maintenance in Amazonia, and these land-use fires frequently escape their intended boundaries and burn into adjacent forests. Initial understory fires may increase forest flammability, thereby creating a positive fire feedback and the potential for long-term changes in Amazon forest structure. The four studies in this dissertation describe the development and integration of satellite remote sensing and ecosystem modeling approaches to characterize land-use fires and their consequences in southern Amazon forests. The dissertation contributes three new methods: use of the local frequency of satellite-based active fire detections to distinguish between deforestation and maintenance fires, use of satellite data time series to identify canopy damage from understory fires, and development of a height-structured fire sub-model in Ecosystem Demography, an advanced ecosystem model, to evaluate the impacts of a positive fire feedback on forest structure and composition. Conclusions from the dissertation demonstrate that the expansion of mechanized agricultural production in southern Amazonia increased the frequency and duration of fire use compared to less intensive methods of deforestation for pasture. Based on this increase in the frequency of land-use fires, fire emissions from current deforestation may be higher than estimated for previous decades. Canopy damage from understory fires was widespread in both dry and wet years, suggesting that drought conditions may not be necessary to burn extensive areas of southern Amazon forests. Understory fires were five times more common in previously-burned than unburned forest, providing satellite-based evidence for a positive fire feedback in southern Amazonia. The impact of this positive fire feedback on forest structure and composition was assessed using the Ecosystem Demography model. Scenarios of continued understory fires under current climate conditions show the potential to trap forests in a fire-prone structure dominated by early-successional trees, similar to secondary forests, reducing net carbon storage by 20-46% within 100 years. In summary, satellite and model-based results from the dissertation demonstrate that fire-damaged forests are an extensive and long-term component of the frontier landscape in southern Amazonia and suggest that a positive fire feedback could maintain long-term changes in forest structure and composition in the region.