Spelling suggestions: "subject:"aglobal change biology"" "subject:"galobal change biology""
1 |
Potentially toxic cyanobacteria in Queensland: Impacts of predicted climate change on blooms and toxin productionGarnett, C. M. Unknown Date (has links)
No description available.
|
2 |
EFFECTS OF ALTERED PRECIPITATION REGIMES ON ECOSYSTEM PROCESSES AND PLANT COMMUNITIES IN TERRESTRIAL ECOSYSTEMSLaura W. Ploughe (5930153) 04 January 2019 (has links)
<p>Since 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.</p><p><br></p><p>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.</p>
<p><br></p><p>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.</p>
<p><br></p><p>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. </p><p><br></p><p>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.</p>
|
3 |
Pollinator biodiversity, functional complementarity and dynamic plant-pollinator interaction networks / Bestäuberdiversität, funktionelle Komplemenarität und dynamische Pflanze-Bestäuber-InteraktionsnetzwerkeFründ, Jochen 08 November 2012 (has links)
No description available.
|
4 |
DEPREDATION OF OLIVE RIDLEY AND LOGGERHEAD TURTLE CLUTCHES ON BEACHES WITH AND WITHOUT PREDATOR MANAGEMNTCarlynn Nicole Cornhill (11002167) 23 July 2021 (has links)
<p>Management of predation on sea
turtle nesting beaches is vital to conservation efforts for the vulnerable
loggerhead turtles (<i>Caretta caretta</i>) and olive ridley turtles (<i>Lepidochelys
olivacea</i>). 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.</p>
|
5 |
INTERACTIVE AND INDIVIDUAL EFFECTS OF ANTHROPOGENIC ENVIRONMENTAL STRESS ON FRESHWATER ORGANISMSParadyse Blackwood (18953554) 02 July 2024 (has links)
<p dir="ltr">In this dissertation, I explore how human actions (climate change, road salt, land use change, species invasions) interact with and influence morphology, disease, and population dynamics in freshwater organisms (amphibians and aquatic crustaceans). First, I examined how the incidence and timing of disease epidemics in native species (<i>Daphnia dentifera</i>) caused by a generalist parasite (<i>Metschnikowia bicuspidata</i>) influenced the success and impact of an invasive species (<i>Daphnia lumholtzi</i>) in freshwater zooplankton (Chapter 1). In the following chapter, I explored how host-parasite interactions are affected by the interactive effects of multiple environmental stressors, focusing on American bullfrog tadpoles (<i>Lithobates catesbeianus</i>), two of their common parasites (<i>Batrachochytrium dendrobatidis</i> (<i>Bd</i>) and trematode parasites in the family Echinostomatidae), and two common stressors (fluctuating temperatures and sublethal road salt pollution; Chapter 2). Finally, I investigated how the combination of climate (temperature and precipitation) and land use (developed and/or forested area) change have influenced the body size of a common toad (Fowler’s toad, <i>Anaxyrus fowleri</i>) from 1930 – 2020 utilizing museum specimens (Chapter 3). Together, this research establishes how emerging and persistent anthropogenic environmental stressors will interact to affect morphology, disease, and population dynamics in vulnerable freshwater organisms.</p>
|
6 |
Thousand Cankers Disease of Eastern Black Walnut: Ecological Interactions in the Holobiont of a Bark Beetle-Fungal DiseaseGeoffrey M Williams (11186766) 27 July 2021 (has links)
<p>Eastern black walnut (<i>Juglans
nigra</i> 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
<i>Juglans</i> spp. (Juglandaceae), <i>J. nigra</i> is threatened by thousand
cankers disease (TCD), an insect-vectored disease first described in 2009. TCD
is caused by the bark beetle <i>Pityophthorus
juglandis</i> Blackman (Corthylini) and the phytopathogenic fungus <i>Geosmithia morbida</i> Kol. Free. Ut. &
Tiss. (Bionectriaceae). Together, the <i>P.
juglandis</i>-<i>G. morbida</i> 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 <i>J.
nigra</i> and <i>J. regia</i> planted
outside their native distributions.</p>
<p> 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 <i>J. nigra</i> 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 <i>G. morbida</i> in <i>J. nigra</i>
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 <i>holobiont</i> is defined as the whole
multitrophic community of organisms—including <i>J. nigra</i>, microinvertebrates, fungi and bacteria—that interact with
one another and with the host.</p>
<p>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 <i>G.
morbida</i> 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 <i>G. morbida</i> was
also associated with a distinct community of microbes in stems compared to <i>G. morbida</i>-negative trees. The soil
microbiome from intensively-managed plantations facilitated positive feedback
between <i>G. morbida</i> and a
disease-promomting endophytic <i>Fusarium
solani</i> species complex sp. in roots of <i>J.
nigra</i> seedlings. Finally, the nematode species <i>Bursaphelenchus juglandis</i> associated with <i>P. juglandis</i> synergizes with <i>G.
morbida</i> to cause foliar symptoms in seedlings in a shadehouse; conversely,
experiments and observations indicated that the nematode species <i>Panagrolaimus</i> sp. and cf. <i>Ektaphelenchus</i> sp. could suppress WTB
populations and/or TCD outbreaks.</p>
<p>In conclusion, the composition,
function, and interactions within the <i>P.
juglandis</i> and <i>J. nigra</i> 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>i.e.</i>, <i>J. nigra</i>) growing in environments that are favorable to novel pests
or pest complexes (<i>i.e.</i>, the western
U.S.) may provide connectivity between emergent forest health threats (<i>i.e.</i>, TCD) and native host populations (<i>i.e.</i>, <i>J. nigra</i> in its native range).</p>
|
7 |
Soundscape dynamics in the social-ecological systems of Tierra del FuegoDante P Francomano (9738650) 14 December 2020 (has links)
<p>Human 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.</p><p><br></p><p> </p><p>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.</p><p><br></p><p> </p><p>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 (<i>Spheniscus magellanicus</i>) and southern rockhopper penguins (<i>Eudyptes chrysocome</i>) at different spatial and temporal scales. We conducted <i>in situ</i> 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. </p><p><br></p><p> </p><p>Chapter 4, “Acoustic monitoring shows invasive beavers (<i>Castor canadensis</i>) increase avian diversity in Tierra del Fuego”, is focused on impacts of the invasive North American beaver (<i>Castor canadensis</i>) 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.</p><p><br></p><p> </p>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.
|
Page generated in 0.1917 seconds