Dissertations / Theses on the topic '069902 Global Change Biology'
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Cyrus, Caitlin. "Floristic Change Spanning 45 Years of Global Change in the College Woods, Williamsburg, Va." W&M ScholarWorks, 2016. https://scholarworks.wm.edu/etd/1477068006.
Full textPye, Marian C. "Global change impacts on organic matter dynamics in stream ecosystems." Thesis, Cardiff University, 2017. http://orca.cf.ac.uk/98879/.
Full textKharouba, Heather M. "Predicting and mitigating the impacts of global change on species' distributions." Thesis, University of Ottawa (Canada), 2007. http://hdl.handle.net/10393/27867.
Full textDowning, Jason L. "Consequences of Anthropogenic and Global Change on Orchids: An Emphasis on Biotic Interactions." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2448.
Full textKissoon, Ian. "Using tropical forests to combat global climate change without comprimising local livelihoods." Master's thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/4752.
Full textHealy, Megan. "Global climate change, habitat fragmentation, and the lesser long-nosed bat what next? /." Online pdf file accessible through the World Wide Web, 2007. http://archives.evergreen.edu/masterstheses/Accession86-10MES/Healy_MMESThesis%202007.pdf.
Full textStewart, Rebecca. "Global warming in freshwaters : implications for the microbial-meiofaunal loop." Thesis, Queen Mary, University of London, 2012. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8624.
Full textTrisos, Matthew Owen. "Global change drivers and their impact on herbaceous, ant, and grasshopper assemblages in an African semi-arid savanna." Doctoral thesis, University of Cape Town, 2020. http://hdl.handle.net/11427/32517.
Full textSrinivasan, Madhusudan P. "THE ECOLOGY OF DISTURBANCES AND GLOBAL CHANGE IN THE MONTANE GRASSLANDS OF THE NILGIRIS, SOUTH INDIA." UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_diss/213.
Full textMurphy, Meaghan. "Getting to the root of the matter: variations in vascular root biomass and production in peatlands and responses to global change." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66793.
Full textPeu d'études ont été faites sur la biomasse racinaire, sa production et décomposition malgré les évidences montrant qu'autant la biomasse racinaire et sa production serait égale ou plus grande que la contrepartie hors terre des plantes vasculaires. De plus, celles-ci contribueraient de manière significative à la quantité de C (carbone) contenue dans le réservoir de matière organique du sol. Les changements globaux tels la diminution du niveau de la nappe phréatique (via une augmentation des températures), et une augmentation de la quantité d'azote dans les dépôts atmosphériques menacent de changer de manière dramatique l'équilibre de ces systèmes par un changement de végétation. Mesurer la biomasse racinaire, sa production et décomposition est critique pour notre compréhension du cycle du C dans les tourbières. Une meilleure connaissance des processus régissant la variation des réservoirs et flux souterrains par rapport à la composante hors-terre des plantes, en relation avec les facteurs environnementaux (climat, nappe phréatique) et biologique (type de végétation, diversité des espèces) permet de mieux comprendre comment les communautés de plantes de tourbières s'adaptent aux différents environnements. De plus, nous devons considérer l'implication de ces adaptations dans le cycle du C à l'intérieur d'un site et entre différents sites, et ce en réponse au phénomène de changement globaux. Ma recherche débute par l'évaluation de la relation entre la biomasse et la production souterraine et hors-terre à l'aide d'une revue de littérature des communautés de plantes de milieux humides. Cette revue de littérature permet de déterminer l'effet des types de végétation, de l'environnement et des facteurs climatiques sur les différentes relations à l'intérieur d'un même site et entre différents types de milieux humides, incluant les tourbières. Les recherch
Perez, Jaime Abraham. "PATTERNS AND DRIVERS OF ANT BIODIVERSITY ALONG URBANIZATION GRADIENTS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1591823939916649.
Full textHinz, Daria J. "Emiliania huxleyi and climate change : a genetic and biogeographic investigation of bloom dynamics for a key phytoplankton species in the global carbon cycle." Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/191961/.
Full textDunn, Troy S. "Plant and Insect Responses to Experimental Warming in a Temperate Grassland." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1494192401311883.
Full textGarland, Michael A. "Multi-stress proteomics: The global protein response to multiple environmental stressors in the porcelain crab Petrolisthes cinctipes." DigitalCommons@CalPoly, 2015. https://digitalcommons.calpoly.edu/theses/1441.
Full textFagua, José Camilo. "Geospatial Modeling of Land Cover Change in the Chocó-Darien Global Ecoregion of South America: Assessing Proximate Causes and Underlying Drivers of Deforestation and Reforestation." DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/7362.
Full textMacWilliams, Graham. "Potential for Climate Induced Methane Hydrate Dissociation." Scholarship @ Claremont, 2018. http://scholarship.claremont.edu/pomona_theses/179.
Full textRegos, Sanz Adrián. "Global change and the uncertain future of biodiversity in Mediterranean-type ecosystems: insights from a strategic foresight process." Doctoral thesis, Universitat Autònoma de Barcelona, 2015. http://hdl.handle.net/10803/323074.
Full textConservation needs strategic foresight leading to effectively address the ongoing challenges posed by global change. Mediterranean Basin has been identified as priority area for conservation, particularly vulnerable to the combined effects of climate change, land-use change and fire disturbance regime. The interacting effects of these drivers, and the large uncertainties associated to their forecasting, might also bring conservation opportunities to intervene through better policies. Strategic foresight exercises may offer decision-makers with tools to creatively think about the future and make decisions that create a more desirable future. In this thesis, we illustrate the role for horizon scanning, scenario planning and simulation-based scenario analysis in underpinning the strategic foresight approach — using storylines as conceptual scenarios, and simulations as numerical estimates of future environmental changes. In particular, this strategic foresight exercise contributes to opening up two promising fire management policy options (‘letting unplanned fires burn’ and ‘forest biomass extraction for bioenergy uses’) alternatives to the current fire suppression paradigm of “stopping all fires’’. Both fire management policies could be strategically combined in order to achieve the fuel reduction objectives required to mitigate the increasing impact of large fires caused by global change. Conservation planning may be considerably improved through the implementation of such fire management strategies. Two main emerging conservation opportunities have been identified and should be prioritized in order to effectively protect community-interest bird species in the near future: 1) promoting early-succession stages of vegetation for open-habitat dwelling species through ‘letting unplanned fires burn’ policies; and 2) increasing the resilience of key forest habitats to climate change for forest-dwelling species. This thesis emphasizes the need for an integrative conservation perspective wherein agricultural, forest and fire management policies should be explicitly considered to effectively preserve key habitats for threatened birds in fire-prone, highly-dynamic systems. Our findings also shed light about the importance of considering landscape dynamics and the synergies between different driving forces when assessing the long-term effectiveness of fire management at reducing fire risk and safeguarding biodiversity in Mediterranean-type ecosystems.
Helmle, Kevin P. "Coral Schlerochronology and the Relationship Between Coral Growth Records and Climate Change." NSUWorks, 2009. http://nsuworks.nova.edu/occ_stuetd/60.
Full textWu, Jin. "How do Amazonian Tropical Forest Systems Photosynthesize under Seasonal Climatic Variability: Insights from Tropical Phenology." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/594653.
Full textAdams, Henry. "Temperature Sensitivity, Physiological Mechanism, and Implications of Drought-Induced Tree Mortality." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/228494.
Full textLange, Priscila Kienteca. "Putting marine microbes on the map : determining the global distribution of marine picophytoplankton using a combination of satellite and field data." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:ae64c955-336e-46b2-bee1-db41fb4be1c9.
Full textHotaling, Scott. "GENETIC PERSPECTIVES ON BIODIVERSITY IN ROCKY MOUNTAIN ALPINE STREAMS." UKnowledge, 2017. http://uknowledge.uky.edu/biology_etds/44.
Full textLättman, Håkan. "Description of spatial and temporal distributions of epiphytic lichens." Licentiate thesis, Linköping University, Linköping University, Department of Physics, Chemistry and Biology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-11561.
Full textLichens are, in most cases, sensitive to anthropogenic factors such as air pollution, global warming, forestry and fragmentation. Two studies are included in this thesis. The first is an evaluation of the importance of old oak for the rare epiphytic lichen Cliostomum corrugatum (Ach.) Fr. This study analysed whether C. corrugatum was limited by dispersal or restricted to tree stands with an unbroken continuity or the substrate old oaks. The results provide evidence that the investigated five populations in Östergötland, Sweden, of C. corrugatum exhibit substantial gene flow, an effective dispersal and a small genetic variation between the sites. Most of the genetic variation was within the populations. Thus, C. corrugatum is more dependent of the substrate old oaks, rather than limited by dispersal. The second study investigated possible range shift of some common macrolichens, due to global warming, from 64 sites in southern Sweden comparing the two years 1986 and 2003. The centroid of three lichen species had moved a significant distance, all in a north east direction: Hypogymnia physodes (L.) Nyl. and Vulpicida pinastri (Scop.) J.-E. Mattsson and M. J. Lai on the tree species Juniperus communis L. (50 and 151 km, respectively) and H. physodes on Pinus sylvestris L. (41 km). Considering also the non-significant cases, there is strong evidence for a prevailing NE direction of centroid movement.
Calder-Potts, Ruth Naomi. "The biological and ecological impacts of hypoxia on coastal benthic communities." Thesis, University of Plymouth, 2017. http://hdl.handle.net/10026.1/9352.
Full textBellantuono, Anthony John. "Acclimatization of the Tropical Reef Coral Acropora millepora to Hyperthermal Stress." FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/1005.
Full textKersting, Diego K. "Ecology and conservation of the Mediterranean endemic coral Cladocora caespitosa = Ecología y conservación del coral endémico del Mediterráneo Cladocora caespitosa." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/132996.
Full textLos ecosistemas marinos están siendo amenazados por un número cada vez mayor de impactos. Entre ellos, los impactos derivados del cambio global han puesto en relieve la necesidad de nuevas medidas de conservación que puedan complementar a las ya existentes. Sin embargo, su desarrollo requiere un amplio conocimiento de las especies, procesos e impactos implicados. Esta tesis se centra en la adquisición de nuevos conocimientos sobre la biología y ecología del coral Cladocora caespitosa con el objetivo de aportar información útil para su conservación. Los resultados obtenidos pueden servir como guía para la conservación de aquellas especies de características parecidas sobre las que no se tiene información. Esta especie es el único coral escleractinio, colonial y zooxantelado, endémico del Mediterráneo. Se trata de uno de los pocos ejemplos de especie longeva y estructural que se encuentra en las comunidades mediterráneas de aguas someras. La Bahía de L'Illa Grossa (Reserva Marina de las Islas Columbretes) alberga una de las poblaciones más importantes de este coral, con campos de colonias y arrecifes que muestran una superficie acumulada de 2900 m2. Los resultados obtenidos muestran que se trata de una especie de lento crecimiento, con bajas tasas de reclutamiento y mortalidad natural y que muestra importantes divergencias en sus características reproductoras entre el Mediterráneo Occidental y el Adriático. La población de C. caespitosa de Columbretes ha sufrido mortalidades recurrentes asociadas al calentamiento del agua, que han afectado a más de la mitad del área ocupada por este coral en la bahía. Por otra parte, las algas invasoras Lophocladia lallemandii y Caulerpa racemosa han invadido exitosamente la Bahía de L'Illa Grossa, solapando su distribución con la de C. caespitosa. De momento, no se han observado efectos letales de estas algas sobre el coral; sin embargo, se ha podido detectar la actividad tóxica de esta especie, que podría explicar el bajo recubrimiento de sus partes vivas por C. racemosa. El potencial de recuperación de esta población es limitado dado el bajo reclutamiento y la frecuencia e intensidad de las mortalidades. Además, no se pueden descartar efectos subletales del calentamiento y las algas invasoras sobre la reproducción, reclutamiento y la supervivencia de los juveniles. A partir de esta información esta especie podría cumplir los criterios de la UICN para ser catalogada como especie en peligro.
Salinas, Zapata Cristian C. "Seagrass soils as paleoenvironmental tools and biogeochemical sinks for management." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2022. https://ro.ecu.edu.au/theses/2542.
Full textSelhorst, Adam Louis. "Carbon Sequestration By Home Lawn Turfgrass Development and Maintenance in Diverse Climatic Regions of the United States." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306499049.
Full textLightle, Nicole E. "Effects of Air vs. Air+Soil Heating During a Simulated Heat Wave on White Oak (Quercus alba) and Black Oak (Quercus velutina)." University of Toledo / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1365159241.
Full textUrli, Morgane. "Réponse des rabres forestiers aux changements globaux : approches biogéographique et écophysiologique." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2013. http://tel.archives-ouvertes.fr/tel-00821979.
Full textCharbonnel, Anaïs. "Influence multi-échelle des facteurs environnementaux dans la répartition du Desman des Pyrénées (Galemys pyrenaicus) en France." Phd thesis, Toulouse, INPT, 2015. http://oatao.univ-toulouse.fr/14261/1/Charbonnel.pdf.
Full textFitzpatrick, Matthew C. "Biological Invasions, Global Climate Change and Species Distribution Models: An Investigation of Species-Climate Relationships Across Space and Time." 2008. http://etd.utk.edu/2008/FitzpatrickMatthew.pdf.
Full textMoura, Catarina. "Carbon and Water Relations in Pinus Taeda: Bridging the Gap across Plant Physiology, Genomics, and Global Climate Change." Diss., 2008. http://hdl.handle.net/10161/690.
Full textPlants respond to changes in their local environment and, at the same time, influence the environment at a global scale. The molecular and physiological mechanisms regulating this interaction are not completely understood and this limits our capacity to predict the response of vegetation to future environmental changes. This dissertation combined tools from genomics, physiology, and ecology to examine the response of plants to environmental change. Specifically, it focused on processes affecting carbon and water exchange in forest trees because (1) trees are long-lived species that might face repeated environmental challenges; (2) relatively little information exists about the genes and the molecular mechanisms regulating structural and physiological traits in adult, long-lived woody plants; and (3) forest trees exchange a significant amount of carbon and water with the atmosphere and are therefore major players in the global carbon and water cycles.
Water flux through forests depends both on environmental conditions (e.g., soil moisture) and on the hydraulic architecture of individual trees. Resistance to xylem cavitation is an important hydraulic trait that is often associated with drought tolerance but potentially at the cost of reduced carbon uptake. The second chapter of this dissertation evaluated the variation in resistance to xylem cavitation, hydraulic conductivity, wood anatomy traits, and leaf gas exchange across 14 co-occurring temperate tree species including both angiosperms and gymnosperms. The relationship between vulnerability to cavitation (ψ50) and hydraulic conductivity within specific organs (i.e. stems and roots) was not significant when considering the phylogenetic association between species. However, even after phylogenetic correction, photosynthetic carbon uptake (A) was positively correlated with both stem and root ψ50, and stomatal conductance (gs ) was strongly correlated with root ψ50 . These results suggest that there is a trade-off between vulnerability to cavitation and water transport capacity at the whole-plant level, and that this functional relationship reflects an adaptive response to the environment.
Forests are an important component of the global carbon cycle that can be directly impacted by a rise in atmospheric CO2 concentration.. The third chapter of this dissertation investigated the effects of long-term exposure to elevated CO2 on the gene expression of mature, field-grown loblolly pine trees. Using cDNA microarrays, I compared the expression of 1784 pine transcripts in trees growing under ambient and those under elevated CO2 at monthly intervals throughout a growing season. Overall, more genes were upregulated than downregulated by elevated CO2, although the total number of genes differentially expressed varied throughout the season. The pattern of increasing number of differentially expressed genes until the peak of the growing season (July and August) followed by a decrease in that number, matched the seasonal trend of tree growth and photosynthetic response to elevated CO2 in this species. The seasonal trend also reflected the interaction among multiple abiotic factors intrinsic to field conditions and emphasized the relevance of evaluating the role of genes in their natural environment. Genes consistently upregulated by elevated CO2 were functionally associated with environmental sensing, cellular signaling, and carbon metabolism, in particular the degradation of carbohydrates through respiration. An increase in carbohydrates degradation is particularly relevant in the context of carbon balance of forest trees because of the potential for enhanced leaf and tree respiration leading to a reduced sink capacity for CO2.
Loblolly pine produces several flushes of needles throughout the year each with an average lifespan of 19 months. Each year, two age classes of needles contribute to the annual carbon sequestration of the loblolly pine forest. To address the impact of leaf age on the effects of elevated CO2 in carbon metabolism regulation, I compared the gene expression profiles from trees under ambient and elevated CO2 conditions in two needle cohorts: one-year-old and current-year. Differential expression under elevated CO2 was seven times more frequent in current-year than in one-year-old needles. Despite differences in magnitude, many of the patterns within specific groups of genes were similar across age classes. For instance, there was a trend for downregulation of genes involved in the light-reactions of photosynthesis and those in photorespiration in both age classes, while genes associated with dark respiration were largely upregulated by elevated CO2 in both cases. The difference between the two cohorts was particularly evident in the group of genes related to energy production (ATP synthesis) and the group associated with carbon partitioning (sucrose and starch metabolism). Because sucrose and starch metabolism categories included many genes known to be important regulators of gene expression and plant physiological processes, this suggests that this stage of carbon metabolism might be an important control point in age-dependent foliar responses to elevated CO2.
This dissertation examined both structural and physiological components of plant water and carbon relations (Chapter 2) across different biological scales of organization (whole-plant level in Chapter 2; gene-level response to ecosystem-level changes in Chapters 3 and 4) and reflecting adjustments at distinct temporal scales (life-span of the organism vs. evolutionary selection of traits). An integrative approach was used to advance our understanding of how plants acclimate and adapt to their environment, and to provide a mechanistic framework for predictive models of plant response to environmental change.
Dissertation
(5930153), Laura W. Ploughe. "EFFECTS OF ALTERED PRECIPITATION REGIMES ON ECOSYSTEM PROCESSES AND PLANT COMMUNITIES IN TERRESTRIAL ECOSYSTEMS." Thesis, 2019.
Find full textSince the pre-industrial age, the Earth has been warming at unparalleled rates, and this warming is changing climate and weather, creating a more extreme global hydrological cycle. In this dissertation, I explore how these changes to the hydrological cycle may act ecosystem and community level responses of terrestrial plants in the Midwestern United States. In this region, it is projected that mean annual precipitation (MAP) will increase, but precipitation will become more variable across and within seasons. Ecosystem structure and function are vulnerable to changes in hydrologic patterns, including changes in biogeochemical cycles, plant productivity, and plant community structure and function. In this dissertation, I explore how changes in precipitation will alter these processes using two field experiments, and I suggest potential hypotheses that could explain drought-induced community change.
In chapter 1, I explore how alterations to seasonal precipitation in the winter and summer act ecosystem and community processes in a temperate deciduous forest. Biogeochemical processes and plant communities are sensitive to changes in abiotic conditions, and these conditions will alter forest succession, particularly juvenile woody plant species. Using a fully factorial experiment, I manipulated winter snowfall and summer precipitation to create wet, dry, and control (ambient conditions) treatments and investigated how changes in seasonal precipitation would act mineralization rates, woody plant recruitment, and understory composition. I found that the effects of winter and summer precipitation on these processes acted independently of one another in this system, and the system was resistant to changes in mineralization rates and understory composition. Woody plant recruitment may be more sensitive to altered precipitation, as recruitment of at least one of the four species planted, Lindera benzoin, was impacted by changes in seasonal precipitation. Snow removal treatments reduced germination and increased summer precipitation decreased the relative growth rate of this species. In the short term, slight changes to woody plant recruitment may have little impact on long-term forest succession, but as these changes persist over longer periods of time, they could alter the direction of succession, which could lead to changes in the understory community composition and nutrient cycling.
The second and third chapters explore the effects that drought intensification will have on terrestrial plant communities. Numerous studies have investigated the effects of individual droughts on ecosystem and community responses, but the effects that both the timing and duration of drought have on these responses remain largely unknown. To explore this gap in the literature, I conducted a eld experiment using rainout shelters to reduce growing season precipitation, creating dry periods that varied in length and timing. Drought can impact productivity and diversity in this system, and the timing in which the drought occurs influences these effects. Surprisingly, I found that the length of drought did not affect productivity or community composition.
The final chapter introduces the Community Response to Extreme Drought framework CRED), which addresses the potential temporal progression of mechanisms and plant-plant interactions that may lead to community changes during and after a drought. The mechanisms for the temporal evolution of community-level drought responses are not fully understood, but plant-plant interactions, both competitive (-) and facilitative (+), are increasingly being recognized as important drivers of community compositional changes. The CRED framework provides hypotheses for the roles that plant-plant interactions have on drought-induced community change. CRED addresses how system-specific variables and the intensity of drought may influence the strength of plant-plant interactions over time, and ultimately the systems resistance and resilience to drought.
The results from this dissertation work have revealed that more research needs to be done to fully understand how changes in precipitation regimes and patterns will affect terrestrial ecosystems and plant communities. A better understanding of how ecosystems and communities respond to drought timing and length can help improve climate models and restoration strategies.
Ward, Eric Jason. "Improving Models of Forest Carbon and Water Cycling: Revisiting Assumptions and Incorporating Variability." Diss., 2012. http://hdl.handle.net/10161/5398.
Full textThis dissertation examines issues concerning sap flux scaled estimates of the canopy-averaged transpiration rate of trees per unit leaf area (EL) and stomatal conductance (GS), as well as their implications in the water and carbon balance of individuals and stands, with the final goal of an integrated assessment of 11 years of such data from two species (
Dissertation
Mesquita, Patricia S. "Effects of retrogressive permafrost thaw slumping on benthic macrophyte and invertebrate communities of upland tundra lakes." Thesis, 2008. http://hdl.handle.net/1828/1041.
Full text(11002167), Carlynn Nicole Cornhill. "DEPREDATION OF OLIVE RIDLEY AND LOGGERHEAD TURTLE CLUTCHES ON BEACHES WITH AND WITHOUT PREDATOR MANAGEMNT." Thesis, 2021.
Find full textManagement of predation on sea turtle nesting beaches is vital to conservation efforts for the vulnerable loggerhead turtles (Caretta caretta) and olive ridley turtles (Lepidochelys olivacea). Sea turtles increasingly face threats from invasive and human-tolerant mammalian predators as human disturbances on nesting beaches rises. The intensity of mammalian predation has increased in Las Baulas National Park in Costa Rica which is an important nesting site for several species of threatened and endangered sea turtles. I analyzed loggerhead and olive ridley nest predation on four beaches in the United States and Costa Rica that were chosen for variations in degree of human disturbance and management strategies. My objectives were to 1) determine if egg predation rates differ at the four sites, 2) determine the most destructive predators at each location, and 3) suggest management options to alleviate mammalian threats to turtle clutches on Playa Grande and Playa Cabuyal in Costa Rica. My results show that the beaches without a nest protection or predator control program had very high rates of predation. Invasive mammalian predators and mammalian predators associated with human disturbance were the most destructive at the four sites. I recommend that regulations regarding dogs and the take of eggs from the beach are enforced at Playa Cabuyal and that physical nest protection is rapidly implemented at Playa Grande. I also recommend that the National Park consider managing raccoon predation by removing problem individuals, but caution that they do so in a way that maintains the animals’ role in the ecosystem.
Fründ, Jochen. "Pollinator biodiversity, functional complementarity and dynamic plant-pollinator interaction networks." Doctoral thesis, 2012. http://hdl.handle.net/11858/00-1735-0000-000D-EF81-C.
Full text(11186766), Geoffrey M. Williams. "Thousand Cankers Disease of Eastern Black Walnut: Ecological Interactions in the Holobiont of a Bark Beetle-Fungal Disease." Thesis, 2021.
Find full textEastern black walnut (Juglans nigra L.) ranks among the most highly valued timber species in the central hardwood forest and across the world. This valuable tree fills a critical role in native ecosystems as a mast bearing pioneer on mesic sites. Along with other Juglans spp. (Juglandaceae), J. nigra is threatened by thousand cankers disease (TCD), an insect-vectored disease first described in 2009. TCD is caused by the bark beetle Pityophthorus juglandis Blackman (Corthylini) and the phytopathogenic fungus Geosmithia morbida Kol. Free. Ut. & Tiss. (Bionectriaceae). Together, the P. juglandis-G. morbida complex has expanded from its historical range in southwest North America throughout the western United States (U.S.) and Europe. This range expansion has led to widespread mortality among naïve hosts J. nigra and J. regia planted outside their native distributions.
The severity of TCD was previously observed to be highest in urban and plantation environments and outside of the host native range. Therefore, the objective of this work was to provide information on biotic and abiotic environmental factors that influence the severity and impact of TCD across the native and non-native range of J. nigra and across different climatic and management regimes. This knowledge would enable a better assessment of the risk posed by TCD and a basis for developing management activities that impart resilience to natural systems. Through a series of greenhouse-, laboratory- and field-based experiments, environmental factors that affect the pathogenicity and/or survival of G. morbida in J. nigra were identified, with a focus on the microbiome, climate, and opportunistic pathogens. A number of potentially important interactions among host, vector, pathogen and the rest of the holobiont of TCD were characterized. The holobiont is defined as the whole multitrophic community of organisms—including J. nigra, microinvertebrates, fungi and bacteria—that interact with one another and with the host.
Our findings indicate that interactions among host, vector, pathogen, secondary pathogens, novel microbial communities, and novel abiotic environments modulate the severity of TCD in native, non-native, and managed and unmanaged contexts. Prevailing climatic conditions favor reproduction and spread of G. morbida in the western United States due to the effect of wood moisture content on fungal competition. The microbiome of soils, roots, and stems of trees and seedlings grown outside the host native range harbor distinct, lower-diversity communities of bacteria and fungi compared to the native range, including different communities of beneficial or pathogenic functional groups of fungi. The pathogen G. morbida was also associated with a distinct community of microbes in stems compared to G. morbida-negative trees. The soil microbiome from intensively-managed plantations facilitated positive feedback between G. morbida and a disease-promomting endophytic Fusarium solani species complex sp. in roots of J. nigra seedlings. Finally, the nematode species Bursaphelenchus juglandis associated with P. juglandis synergizes with G. morbida to cause foliar symptoms in seedlings in a shadehouse; conversely, experiments and observations indicated that the nematode species Panagrolaimus sp. and cf. Ektaphelenchus sp. could suppress WTB populations and/or TCD outbreaks.
In conclusion, the composition, function, and interactions within the P. juglandis and J. nigra holobiont play important roles in the TCD pathosystem. Managers and conservationists should be aware that novel associations outside the host native range, or in monocultures, intensive nursery production, and urban and low-humidity environments may favor progression of the disease through the effects of associated phytobiomes, nematodes, and climatic conditions on disease etiology. Trees in higher diversity, less intensively managed growing environments within their native range may be more resilient to disease. Moreover, expatriated, susceptible host species (i.e., J. nigra) growing in environments that are favorable to novel pests or pest complexes (i.e., the western U.S.) may provide connectivity between emergent forest health threats (i.e., TCD) and native host populations (i.e., J. nigra in its native range).
(9738650), Dante P. Francomano. "Soundscape dynamics in the social-ecological systems of Tierra del Fuego." Thesis, 2020.
Find full textHuman society is presently beset by an array of anthropogenic social-ecological crises that threaten the sustainability of the social-ecological systems that sustain our livelihoods. While research alone will not rectify these issues, it can help to answer key questions that must be addressed to develop effective solutions. To address such questions in a cohesive, compelling manner, social-ecological research can be bounded, structured, and distilled through innumerable organizing principles or theoretical frameworks. For this dissertation, I focused on the geographic region of Tierra del Fuego and sought to draw from the array of disciplines and methods that use sound as a lens for biological, ecological, and/or social inquiry. I also endeavored to consider various temporal, spatial, and organizational scales while investigating a selection of topics with a) specific importance in the social-ecological systems of Tierra del Fuego and b) general relevance to global social-ecological challenges. Chapter 1 provides an introduction to the dissertation, and Chapter 6 serves as a conclusion.
The objective of Chapter 2, “Biogeographical and analytical implications of temporal variability in geographically diverse soundscapes”, was to provide some guidance to passive acoustic monitoring (PAM) practitioners on how to design appropriate temporal sampling schemes based on the temporal variability of the sounds one wishes to measure and the power and storage limitations of acoustic recorders. We first quantified the temporal variability of several soundscape measurements and compared that variability across sites and times of day. We also simulated a wide range of temporal sampling schemes in order to model their representativeness relative to continuous sampling.
For Chapter 3, “Sentinels for sentinels: passive acoustic and camera trap monitoring of sensitive penguin populations”, we tested the utility of PAM to monitor behavior and abundance of Magellanic (Spheniscus magellanicus) and southern rockhopper penguins (Eudyptes chrysocome) at different spatial and temporal scales. We conducted in situ observations of the acoustic behavior of each species, and we compared acoustic metrics with penguin counts from narrowly focused camera traps and larger-extent observations of colony density.
Chapter 4, “Acoustic monitoring shows invasive beavers (Castor canadensis) increase avian diversity in Tierra del Fuego”, is focused on impacts of the invasive North American beaver (Castor canadensis) on Fuegian bird communities. We sought to determine how bird communities might differ between intact riparian forests, beaver ponds, and beaver meadows created by pond drainage. We conducted PAM and classic avian point counts under each of these conditions across seasons to test for differences between impact conditions and to compare the two methodologies.
For Chapter 5, “Human-nature connection and soundscape perception: insights from Tierra del Fuego, Argentina”, we evaluated the relationship between soundscape perception and nature relatedness by conducting surveys and soliciting responses to soundscape audio prompts. We also examined the potential for any demographic influences on nature relatedness or soundscape perception in the context of local social tensions.