Theses and Dissertations from UMD
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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
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Item The Economics of Spruce Budworm Monitoring and Management in Eastern Canada(2024) Holm Perrault, Alexandre Ismaël Eliot; Olson, Lars J; Agricultural and Resource Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation uses techniques that were developed for renewable natural resource and invasive pest management to describe the two principal challenges of eastern spruce budworm (SBW) monitoring and management in Eastern Canada, with a specific focus on the province of Quebec. The primary empirical components of this dissertation can be found in Chapters 2 and 3. Chapter 1 provides the necessary historic, entomological, ecological and policy context to understand Chapters 2 and 3. Chapter 4 provides a conclusion to this dissertation by proposing extensions that would make the models presented in Chapters 2 and 3 more readily applicable to real-world spruce budworm management. These extensions involve making the models spatially explicit, as the models presented in Chapters 2 and 3 are spatially crude for the sake of tractability. Chapter 2 describes the management of an endemic irruptive forest pest and, using the spruce budworm-balsam fir forest interaction, proposes an optimization model that determines optimal pest treatment and forest harvest levels for a single, dimensionless forest stand that is currently undergoing an active budworm outbreak. Budworms cause both growth reductions and mortality on the forest biomass stock, and increasing forest biomass will provide budworms with more prey, causing their growth rate to increase. Treatment decisions are limited to three discrete possibilities (0, 1 or 2 on the landscape) that impose mortality on budworms, while harvests remove a proportion of the forest biomass. Using a numerical solution algorithm, we find that the optimal policy is generally to apply treatments over budworms and to harvest the forest at a sustainable rate, which confirms that the current management programs used in Eastern Canada are welfare-improving relative to letting an outbreak run its course. The time path for our baseline scenario indicates that budworms can be treated down to endemic levels quickly. Sensitivity analysis describes scenarios where budworm levels will rebound every year as well as scenarios where the optimal policy is to clearcut the forest as quickly as possible. Chapter 3 considers the pre-outbreak monitoring phase for spruce budworm management. This context is informed by the Early Intervention Strategy, a management practice that is currently being successfully employed in New Brunswick and other Maritime provinces. EIS requires extensive monitoring and proactive treatment. As such, we adapt a model known as CESAT to determine the locations for which EIS would yield positive net benefits in eastern Quebec. Under our baseline scenario, we find that EIS is optimal in some zones bordering New Brunswick, which indicates that EIS is unlikely to be welfare-improving over current management practices used in Quebec. Under different assumptions, however, we find that EIS is optimal across a much larger landscape, yielding millions of CAD net benefits over a thirty year horizon.Item Characterizing the Multi-scale Post-fire Forest Structural Change in North American Boreal Forests using Air- and Space-borne Lidar Observations(2024) Feng, Tuo; Duncanson, Laura; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Wildfire is the dominant stand-replacing disturbance regime in boreal North America, shaping the pattern, structure and composition of forested landscapes. Forest losses and gains through wildfires are two linked ecological processes, despite their varied functionalities in terrestrial carbon budgets. Combustion of forest biomass through wildfires results in the release of terrestrial carbon, whereas subsequent forest recovery process would re-sequestrate atmospheric CO2 back to the plants, and therefore at least partially offsets fire-induced carbon emissions. However, the magnitude of forest carbon fluxes and its association with wildfires is highly uncertain, especially under the context of large anomalies in fire regimes during the past few decades due to climate change. To fill the knowledge gaps, this dissertation focuses on integrations of air- and space-borne Light Detection and Ranging (lidar) to assess the magnitudes of forest structure and Aboveground Biomass Density (AGBD) changes with respect to wildfires. This dissertation starts with a systematic evaluation of multi-resolution Ice, Cloud and land Elevation Satellite -2 (ICESat-2) terrain and canopy height estimates over boreal North America. As one of the first ICESat-2 validation studies, this work demonstrates ICESat-2 as a suitable platform for large-scale terrain and canopy height measurements, and further provides a suite of standards for ICESat-2 data filtering over boreal forests. Thereafter, I analyze magnitude of forest structure and AGBD changes through wildfire events with multi-temporal airborne lidar and Landsat. This study establishes quantitative linkages between multispectral and structural measurements of fire effects on forest damage, and further reveals burn severity levels, pre-fire forest structure and fire-return intervals as dominant drivers for the magnitude of forest damage through fires. Finally, this dissertation investigates continental-scale forest recovery rate through a full-collection of high-resolution ICESat-2 observations, Landsat-based disturbance history and multi-decadal climatology records. The forest recovery rates under different warming trend are found to be converging over the past few decades, demonstrated as the growth rate of forests across high-latitudinal North gradually approaching their counterparts over Southern boreal zones. This work further reveals a positive effect of growing season warming on forest deciduousness shift, and concludes that regions with warming and associated increase in deciduous compositions would experience greatest growth rate acceleration. This dissertation leverages the potential of multi-sourced remote sensing datasets to assess spatial extents, magnitudes, and underlying drivers of forest carbon feedbacks to climate change and wildfires over North American boreal ecosystem.Item INTEGRATED MONITORING OF DISTURBANCE AND FOREST ATTRIBUTES(2024) Lu, Jiaming; Huang, Chengquan; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Forests provide numerous ecosystem services and are shaped by historical disturbance events. The intensity of disturbance significantly influences the post-disturbance forest structure, species composition, and subsequent forest regrowth. Under the influence of anthropogenic activities and climate change, disturbance regime has undergone unprecedent changes and is subsequently affecting a suite of interrelated forest attributes that are critical in understanding forests dynamics. Historical large-scale disturbance intensity information is needed for understanding the change in disturbance regimes and create linkage to forest dynamics, but such dataset was not available. Forest attributes can be estimated from the spectral information of remote sensing imagery; however, inconsistency exists among the developed product, and the usage of the dataset is limited by accuracy. To fill the research gaps, this dissertation aims to develop a framework that integrates the historical disturbance and the inter-relationship between forest attributes to provide more consistent, and likely more accurate forest attribute estimations. Age, a key attribute that can be the determinant of many ecosystem processes and tree/forest stand develop stage, was selected as the prototype attribute to study. The dissertation started by producing the first set of annual forest disturbance intensity map products quantifying thepercentage of basal area removal (PBAR) at the 30-m resolution for the CONUS from 1986 to 2015, by integrating field plot measurements collected by the Forest Inventory and Analysis program with time series Landsat observations. Compared to other published disturbance products, the maps derived through this study can provide the unique thematic (intensity) information on forest disturbances, precise details critical for understanding forest dynamics across CONUS over multiple decades. The dissertation then proceeded to quantify individual tree age. The tree age was estimated for every tree in the FIA database (over 10 million trees) across the US from our modeling approach that had higher accuracies than existing studies. The developed tree age dataset allows better characterization of tree age distribution, which is important for understanding the disturbance history, functioning, and growth vigor of forest ecosystems. With the disturbance intensity and tree age dataset, the dissertation was able to develop an integrated modeling approach for the forest age mapping. The forest age and complexity maps were produced for 2015 and 2005. The combination of the two metrics should provide a more comprehensive characterization of the forest development condition. The maps provide valuable information for knowing forest conditions, estimating forest growth and carbon sequestration potential, understanding the relationship between age and other forest attributes, evaluating forest health, and planning sustainable forest management practices. This modeling framework developed by the dissertation will enhance the ability to retrieve forest attributes in a broader scale so that with the remote sensing observation, we can not only provide spatially explicit forest structure information, but also review forest status over the decades. Furthermore, when combined with the ecosystem models, these estimations will provide a better prediction for future vegetation and climate dynamics.Item FINE RESOLUTION ASSESSMENT OF THE CARBON FLUXES FROM CONTEMPORARY FOREST DYNAMICS(2021) Gong, Weishu; Huang, Chengquan; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Current estimation of the Earth’s carbon budget contains large uncertainties, with the largest ones in its terrestrial components. With an overarching goal to improve the understanding of carbon budget at regional to global scales, this study aimed to: 1. Develop a grid-based carbon accounting (GCA) model for estimating carbon fluxes from forest disturbance, tested over North Carolina; 2. Develop a consistent timber product output (TPO) record for a globally important timber production region, including seven states in the southeast U.S.; and 3. Further improve the GCA model based on results from objectives 1 and 2, and use it to derive carbon source/sink estimates for all forest land in North Carolina.The results show that several inputs/parameters such as pre-disturbance carbon density, disturbance intensity, allocation of removed carbon among slash and different wood product pools, and forest growth rates could have large impact on carbon estimates. The total emission between 1986 and 2010 from logging over North Carolina was reduced by one third and two thirds, respectively, when remote sensing-based disturbance intensity and biomass data were used to replace parameter values inherited from the original bookkeeping carbon accounting (BCA) model, and was reduced by over 70% when both were used. Use of the TPO data derived in Chapter 3 to partition the removed carbon among slash and different wood product pools resulted in noticeably higher emission estimates than those derived using the partitioning ratios provided by the original BCA model. In addition, without considering legacy effect from wood products harvested before 1986, the emission value derived using the prompt release method was 50% higher than that derived using the delayed release method. This study addresses multiple sources of uncertainties related to the terrestrial carbon budget. The TPO study demonstrated an approach for deriving consistent TPO records for large timber production regions. The GCA model produced state level carbon estimates comparable to those reported by the U.S. Forest Service while providing critical spatial details needed to support carbon management and advance forest-driven climate change mitigation initiatives.Item SOIL MICROBIAL COMMUNITIES IN URBAN STREAM RESTORATIONS AND FORESTED SITES IN FAIRFAX COUNTY, VA(2022) Wood, Lindsay; Yarwood, Stephanie; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Urbanization is rapidly occurring worldwide and can increase hydrological flows into urban streams and alter forest structure and soil properties. Stream restoration projects are ongoing in Fairfax County, Virginia in order to reconnect the channel to the floodplain and increase nutrient removal via microbially mediated processes. Ecological assessment of urban forests is also ongoing to understand the ecosystem services that urban forests provide. Using Illumina sequencing and qPCR, the bacterial and fungal communities were analyzed between stream riparian zones and reference sites, and between different forest qualities. Fungal communities differed significantly after stream restoration and between forest quality types. qPCR was also used to quantify denitrifying genes between restoration types. Post restoration sites had higher abundances of nirS, while reference sites were higher in nirK. The high quality forest sites were most colonized by arbuscular mycorrhizal fungi and were highest in ectomycorrhizal fungal sequences.Item YOUNG FOREST MANAGEMENT FOR SENSITIVE BIRD SPECIES IN WESTERN MARYLAND(2020) Taillie, Dylan Maher; Elmore, Andrew J; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Golden-winged warbler, cerulean warbler, and wood thrush populations are in decline in the eastern United States. Golden-winged warblers rely on young forests – such as those created using silviculture – for nesting and early life stages; however, the loss of late-successional forest through timber harvest likely degrades habitat for cerulean warblers and wood thrush. To quantify these complexities, I mapped current habitat quality for these three species in Western Maryland using models based on forest metrics. The creation of young forest through silviculture and field succession scenarios was then simulated to project how modeled changes affect predicted habitat quality. Field succession scenarios and silviculture scenarios both improved predicted habitat quality for golden-winged warblers and wood thrush; however, for cerulean warblers, field succession scenarios improved habitat quality while silviculture scenarios degraded habitat quality. This modeling approach will assist managers in using funds to simultaneously improve habitat quality for multiple sensitive species.Item Characterizing tree species diversity in the tropics using full-waveform lidar data(2019) Marselis, Suzanne; Dubayah, Ralph; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Tree species diversity is of paramount value to maintain forest health and to ensure that forests are able to provide all vital functions, such as creating oxygen, that are needed for mankind to survive. Most of the world’s tree species grow in the tropical region, but many of them are threatened with extinction due to increasing natural and human-induced pressures on the environment. Mapping tree species diversity in the tropics is of high importance to enable effective conservation management of these highly diverse forests. This dissertation explores a new approach to mapping tree species diversity by using information on the vertical canopy structure derived from full-waveform lidar data. This approach is of particular interest in light of the recently launched Global Ecosystem Dynamics Investigation (GEDI), a full-waveform spaceborne lidar. First, successful derivation of vertical canopy structure metrics is ensured by comparing canopy profiles from airborne lidar data to those from terrestrial lidar. Then, the airborne canopy profiles were used to map five successional vegetation types in Lopé National Park in Gabon, Africa. Second, the relationship between vertical canopy structure and tree species richness was evaluated across four study sites in Gabon, which enabled mapping of tree species richness using canopy structure information from full-waveform lidar. Third, the relationship between canopy structure and tree species richness across the tropics was established using field and lidar data collected in 16 study sites across the tropics. Finally, it was evaluated how the methods and applications developed here could be adapted and used for mapping pan-tropical tree species diversity using future GEDI lidar data products.Item Integrated use of Landsat and Corona data for long-term monitoring of forest cover change and improved representation of its patch size distribution(2016) Song, Danxia; Townshend, John R; Huang, Chengquan; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Forest cover change has profound impact on global carbon cycle, hydrological processes, energy balance, and biodiversity. The primary goal of this dissertation is to improve forest cover change characterization by filling a number of knowledge gaps in forest change studies. These include use of Corona data to extend satellite based forest cover change mapping back to pre-Landsat years in the 1960s, quantification of forest cover change over four decades (1960s – 2005) for a major forested province in China using Corona and Landsat data, and development of more accurate patch size-frequency modeling methods for improved representation of forest disturbances in ecosystem and other spatially explicit models. With comprehensive data coverages in the 1960s, Corona data can be used to extend Landsat-based forest change analysis by up to a decade. The usefulness of such data, however, is hindered by poor geolocation accuracy and lack of multi-spectral bands. In this study, it was demonstrated that combined use of texture features and the advanced support vector machines allowed forest mapping with accuracies of up to 95% using Corona data. Further, a semi-automated method was developed for rapid registration of Corona images with residual errors as low as 100 m. These methods were used to assess the forest cover in the 1960s in Sichuan, a major forest province in China. Together with global forest cover change products derived using Landsat data, these results revealed that the forest cover in Sichuan Province was reduced from 45.19% in the 1960s to 38.98% by 1975 and further down to 28.91% by 1990. It then stayed relatively stable between 1990 and 2005, which contradicted trends reported by inventory data. The turning point between sharp decreases before 1990 and the stable period after 1990 likely reflected transitions in forest policies from focuses on timber production to forest conservation. Representation of forest disturbances in spatially explicit ecosystem models typically relies on patch size-frequency models to allocate an appropriate amount of disturbances to each patch size level. Existing patch size-frequency models, however, do not provide accurate representation of the total disturbance area nor the patch sizes at each frequency level. In this study, a hierarchical method was developed for modeling patch size-frequency distribution. Evaluation of this method over China revealed that it greatly improved the accuracy in representing the patch size at different frequency levels and reduced error in total disturbance area estimation over existing methods from around 40% to less than 10%. The significance of this dissertation is the contribution to improve the characterization of forest cover change by extending the satellite-based forest cover change monitoring back to the 1960s and developing a more accurate patch size distribution model to represent the forest disturbance in ecosystem models. The work in the dissertation has a broader impact beyond developing methods and models, as they provide essential basis to understand the relationship between the long-term change of forest and the socioeconomic transitions. They also improve the capacities of ecosystem and other spatially explicit models to simulate the vegetation dynamics and the resultant biodiversity and carbon dynamics.Item A Forest of Complexity: An Ethnographic Assessment of REDD+ Implementation in Indonesia(2016) Enrici, Ashley; Hubacek, Klaus; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Reducing Emissions from Deforestation and forest Degradation (REDD+) is a global initiative aimed at curbing carbon emissions from forest cover change. Indonesia, one of the most biodiverse places on the planet with the third largest extent of tropical forest, has been extensively involved in REDD+. Despite commitments from the government of Indonesia and the international community, the deforestation rate has not stabilized or decreased in the years since REDD+'s introduction in 2007. As of 2012, it was arguably the highest in the world. While there is an extensive body of literature on REDD+, the need for grounded observations from the field could clarify existing challenges and inform future pursuits. This dissertation presents the results of over two years of ethnographic research in Indonesia on REDD+. Qualitative data collection techniques such as participant observation, site visits and interviews provide a rich tapestry of data that was analyzed in combination with scholarly literature and policy. The research finds that despite a number of changes to laws and regulations resulting from REDD+ implementation in Indonesia, weak institutional capacity and corruption have negated gains. The results of a case study of three REDD+ project sites identify important criteria at the root of success or failure: finance, community, boundary enforcement, monitoring, and outcomes of attempted carbon sequestration and biodiversity preservation. Challenges identified for each criteria include a lack of sufficient funding opportunities; inability to enforce boundaries due to corruption; and lack of a solid plan for involving communities. Carbon sequestration and biodiversity preservation results were mixed due to lack of monitoring and problems with encroachment. Finally the results of the qualitative data collection with stakeholders indicates a crisis of confidence among REDD+ stakeholders; cultural barriers to communication; a disconnect between international rhetoric and local reality; corruption and governance issues resulting in a lack of pathways for project implementation. I argue that changes must be made to Indonesian policy, monitoring technologies must be utilized, and stakeholders need to address some of the problems discussed here in order to save REDD+ from crisis.Item Impact of recent forest management and disturbances on carbon dynamics in the Greater Yellowstone Ecosystem(2015) Zhao, Feng; Huang, Chengquan; Dubayah, Ralph; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Protected areas are recognized worldwide as being important components of climate change mitigation and adaptation strategies. With increasing interests in quantifying greenhouse gas emissions and potentially managing forests to increase the rate of carbon sequestration, there are urgent needs to quantify impact of forest management and disturbances on carbon dynamics. The overall goal of this study is to quantify the impact of recent forest management and disturbances on forest carbon dynamics in GYE, by integrating forest inventory, remote sensing data and carbon modeling approach. Four specific goals for this study include: (1) Develop a method to compare historical and current fire regimes using time series remote sensing data and a landscape succession model; (2) Assess post-fire and post-harvest forest recovery in GYE using time series remote sensing data; (3) Characterize recent forest management and disturbance history (1984-2011) in GYE using local management record and time series remote sensing data; (4) Quantify the impact of recent forest management and disturbances on carbon dynamics in GYE by linking forest inventory, time series remote sensing and carbon modeling. This dissertation is a synthesized analysis of the impact of recent forest management and disturbance on carbon dynamics in GYE, by integrating forest inventory, remote sensing and C modeling approach. The results of this study could contribute to a better understanding of management-disturbance-carbon interactions over ecosystems with complex management regimes and environmental gradients, such as GYE. This study provides a comprehensive and consistent annualized record of forest disturbances, post-disturbance forest recovery, carbon stocks, and relative impact of forest management and disturbance on carbon dynamics in GYE. Such a record would be useful for informed forest management and policy making, ecosystem conservation and restoration, biodiversity protection and carbon assessment in this region. With the availability of input data nationwide, this approach can be applied to the rest of U.S. for many research and management purposes.