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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Carbon isotopes and the plant fossil record : taphonomic and diagenetic controls

Simpson, Nicola Jane January 2000 (has links)
No description available.
2

Suitable Habitat Modelling for the Yellow-breasted Chat (Icteria virens virens) in Point Pelee National Park, Canada.

Walker, Jessica Rose January 2012 (has links)
In order for conservation managers to preserve species within an area, an in-depth knowledge of the distributional patterns of focal species within a landscape is required. This is especially true when the species of concern is Threatened or Endangered and conservation of habitat is essential for species preservation. The yellow-breasted chat (Icteria virens virens) is one such species that is listed as Special Concern under the Species at Risk Act of Canada; the virens subspecies meets the criteria for Endangered. Populations within Canada are limited due the bird’s natural range, which extends north into the extreme southern part of Ontario. Point Pelee National Park is one of two strongholds for this species. However, populations within the park have been declining greatly over the past few years with a 70% rate of decline between 1982 and 2008 (n =10, n=3). This decline is likely due to the lack of natural disturbance such as fire, as well as land use change to agriculture and urbanization that has resulted in a decrease of suitable habitat, outside the park. To examine these hypotheses, habitat suitability modelling is a useful tool. It offers conservation managers insight into current distributions of species, especially species of concern. The purpose of this research was to examine environmental variables relating to three bird species and use these variables to model suitable habitat within the study site (Anders Field Complex). In my study, ArcMap 10 was used to model and map suitable habitat within the Anders Field Complex of Point Pelee National Park, as this is the last known nesting grounds for the yellow-breasted chat within the park. The willow flycatcher (Empidonax traillii) and the white-eyed vireo (Vireo griseus) were also studied as they fill a similar niche and therefore strengthen the results of the study. Environmental variables were modeled to predict suitable habitat and therefore predict potential species distribution. The model used predictors such as vegetation composition of breeding territories and nest patch vegetation composition to identify potential suitable habitat within the study site. Results of the models show that there is likely no suitable habitat (0.04 ha) available for the yellow-breasted chat within the complex. Some suitable habitat was available for the willow flycatcher but seemed limited within the study site (4.1 ha), while an absence of available data on nest scale vegetation characteristics rendered modelling of the white-eyed vireo’s habitat moot. Conditions within the Anders Field Complex have succumbed to succession resulting in mature conditions in vegetation structure and composition, as low dense shrub with high herbaceous cover is being replaced with tall thicket with very little ground cover. Height of vegetation has succeeded the requirements of the yellow-breasted chat. These results show that habitat succession and therefore the loss of suitable habitat is a likely factor influencing chat populations within the Anders Field Complex. There are also factors outside the park likely affecting chat distribution including habitat loss and fragmentation at the landscape scale. Management practices, such as the re-introduction of lost mechanisms or processes within the park should focus on a broad-scale ecological approach that considers novel thinking to restoring ecological integrity. Human induced influences including land use change and introduction of exotic species have forever changed conditions within and surrounding the park, therefore restoration should be mindful to new ecosystems, as restoring to past conditions is likely unproductive. Implementing a disturbance regime such as prescribed burnings, is recommended in order to restore a lost mechanism for the renewal of early-successional habitat. Concentrating on restoration of ecosystems and the re-establishment of a shifting mosaic will provide habitat for a plethora of species including the chat, which is legally mandated by law. However, restoring habitat for the chat will likely not result in the increase of chat abundance within the park until factors outside of the park, including habitat loss and fragmentation are rectified.
3

The influences of large woody debris on British headwater streams

Linstead, Conor January 1999 (has links)
This thesis examines the influence of large woody debris (LWD) on the physical habitat of British headwater streams. The distribution and density of LWD accumulations throughout catchments is considered using data from the River Habitat Survey (RHS) and more detailed catchment scale surveys. The effect of accumulations of LWD on stream hydraulics and physical habitat at a reach scale is examined using transect based measurements of depth and velocity over a range of discharges before and after LWD removal for two reaches, measurement of reach average hydraulic parameters for 25 reaches with differing levels of LWD and the application of the Aggregated Dead Zone (ADZ) and Physical Habitat Simulation (PHABSIM) models. The RHS and catchment scale surveys showed that LWD accumulations exhibit systematic patterns in abundance within catchments, smaller streams having a higher density of LWD and a greater number of LWD accumulations. The most hydraulically active type of LWD accumulations were found to reduce flow velocity by an average of 55%, increase channel roughness by 149% and increase depth by 165%. This impact was, however, found to vary with discharge. Application of the Aggregated Dead Zone (ADZ) model showed that LWD increases the volume of ADZ, which may indicate greater ecological refuge potential. Using the Physical Habitat Simulation (PHABSIM) model, it was found that LWD improved habitat quality and overall habitat diversity.
4

Suitable Habitat Modelling for the Yellow-breasted Chat (Icteria virens virens) in Point Pelee National Park, Canada.

Walker, Jessica Rose January 2012 (has links)
In order for conservation managers to preserve species within an area, an in-depth knowledge of the distributional patterns of focal species within a landscape is required. This is especially true when the species of concern is Threatened or Endangered and conservation of habitat is essential for species preservation. The yellow-breasted chat (Icteria virens virens) is one such species that is listed as Special Concern under the Species at Risk Act of Canada; the virens subspecies meets the criteria for Endangered. Populations within Canada are limited due the bird’s natural range, which extends north into the extreme southern part of Ontario. Point Pelee National Park is one of two strongholds for this species. However, populations within the park have been declining greatly over the past few years with a 70% rate of decline between 1982 and 2008 (n =10, n=3). This decline is likely due to the lack of natural disturbance such as fire, as well as land use change to agriculture and urbanization that has resulted in a decrease of suitable habitat, outside the park. To examine these hypotheses, habitat suitability modelling is a useful tool. It offers conservation managers insight into current distributions of species, especially species of concern. The purpose of this research was to examine environmental variables relating to three bird species and use these variables to model suitable habitat within the study site (Anders Field Complex). In my study, ArcMap 10 was used to model and map suitable habitat within the Anders Field Complex of Point Pelee National Park, as this is the last known nesting grounds for the yellow-breasted chat within the park. The willow flycatcher (Empidonax traillii) and the white-eyed vireo (Vireo griseus) were also studied as they fill a similar niche and therefore strengthen the results of the study. Environmental variables were modeled to predict suitable habitat and therefore predict potential species distribution. The model used predictors such as vegetation composition of breeding territories and nest patch vegetation composition to identify potential suitable habitat within the study site. Results of the models show that there is likely no suitable habitat (0.04 ha) available for the yellow-breasted chat within the complex. Some suitable habitat was available for the willow flycatcher but seemed limited within the study site (4.1 ha), while an absence of available data on nest scale vegetation characteristics rendered modelling of the white-eyed vireo’s habitat moot. Conditions within the Anders Field Complex have succumbed to succession resulting in mature conditions in vegetation structure and composition, as low dense shrub with high herbaceous cover is being replaced with tall thicket with very little ground cover. Height of vegetation has succeeded the requirements of the yellow-breasted chat. These results show that habitat succession and therefore the loss of suitable habitat is a likely factor influencing chat populations within the Anders Field Complex. There are also factors outside the park likely affecting chat distribution including habitat loss and fragmentation at the landscape scale. Management practices, such as the re-introduction of lost mechanisms or processes within the park should focus on a broad-scale ecological approach that considers novel thinking to restoring ecological integrity. Human induced influences including land use change and introduction of exotic species have forever changed conditions within and surrounding the park, therefore restoration should be mindful to new ecosystems, as restoring to past conditions is likely unproductive. Implementing a disturbance regime such as prescribed burnings, is recommended in order to restore a lost mechanism for the renewal of early-successional habitat. Concentrating on restoration of ecosystems and the re-establishment of a shifting mosaic will provide habitat for a plethora of species including the chat, which is legally mandated by law. However, restoring habitat for the chat will likely not result in the increase of chat abundance within the park until factors outside of the park, including habitat loss and fragmentation are rectified.
5

The application of ocean front metrics for understanding habitat selection by marine predators

Scales, Kylie Lisa January 2015 (has links)
Marine predators such as seabirds, cetaceans, turtles, pinnipeds, sharks and large teleost fish are essential components of healthy, biologically diverse marine ecosystems. However, intense anthropogenic pressure on the global ocean is causing rapid and widespread change, and many predator populations are in decline. Conservation solutions are urgently required, yet only recently have we begun to comprehend how these animals interact with the vast and dynamic oceans that they inhabit. A better understanding of the mechanisms that underlie habitat selection at sea is critical to our knowledge of marine ecosystem functioning, and to ecologically-sensitive marine spatial planning. The collection of studies presented in this thesis aims to elucidate the influence of biophysical coupling at oceanographic fronts – physical interfaces at the transitions between water masses – on habitat selection by marine predators. High-resolution composite front mapping via Earth Observation remote sensing is used to provide oceanographic context to several biologging datasets describing the movements and behaviours of animals at sea. A series of species-habitat models reveal the influence of mesoscale (10s to 100s of kilometres) thermal and chlorophyll-a fronts on habitat selection by taxonomically diverse species inhabiting contrasting ocean regions; northern gannets (Morus bassanus; Celtic Sea), basking sharks (Cetorhinus maximus; north-east Atlantic), loggerhead turtles (Caretta caretta; Canary Current), and grey-headed albatrosses (Thalassarche chrysostoma; Southern Ocean). Original aspects of this work include an exploration of quantitative approaches to understanding habitat selection using remotely-sensed front metrics; and explicit investigation of how the biophysical properties of fronts and species-specific foraging ecology interact to influence associations. Main findings indicate that front metrics, particularly seasonal indices, are useful predictors of habitat preference across taxa. Moreover, frontal persistence and spatiotemporal predictability appear to mediate the use of front-associated foraging habitats, both in shelf seas and in the open oceans. These findings have implications for marine spatial planning and the design of protected area networks, and may prove useful in the development of tools supporting spatially dynamic ocean management.
6

Population ecology of bottlenose dolphins (Tursiops truncatus) off the east coast of Scotland

Arso Civil, Mònica January 2015 (has links)
The population of bottlenose dolphins off the east coast of Scotland has been studied since the late 1980s, initially focused on the inner Moray Firth, where a Special Area of Conservation (SAC) was designated under the EU Habitats Directive. The population has since expanded its distributional range and currently ranges from the Moray Firth to the Firth of Forth. The main aims of this thesis were: (1) to estimate population parameters for this population using a 25 year individual recognition dataset, and (2) to increase knowledge of the distribution and abundance of dolphins in areas outside the SAC, especially to investigate areas of high use in St Andrews Bay. Apparent survival rate for adults and sub–adult dolphins was estimated at 0.946 (SE=0.005) accounting for temporary emigration caused by the population's range expansion. Sex-specific survival was estimated for males (0.951, SE=0.013) and females (0.956, SE=0.011) using multistate models to minimize bias caused by individuals of unknown sex. Using a newly developed approach, fecundity rate was estimated at 0.222 (95% CI=0.218-0.253) from an expected mean inter-birth interval of 4.49 yrs (95% CI=3.94-4.93). Total population size was estimated as ~200 individuals, after accounting for temporary emigration and for heterogeneity in capture probabilities. In St Andrews Bay, an area used regularly in summer by approximately half the estimated population, habitat use modelling identified the entrance to the Firth of Tay and waters around Montrose as high use areas for dolphins, whose presence was influenced by tidal current speed and direction. The results suggest that the conservation and management plan for this small and isolated population of bottlenose dolphins should be reviewed to adapt it to current knowledge, especially regarding the uncertainty around the potential impacts of offshore renewable energy developments off the east coast of Scotland.
7

Drivers of variation in the migration and foraging strategies of pelagic seabirds

Clay, Thomas Anthony January 2017 (has links)
The ability to move and forage efficiently plays a major role in determining the fate of individuals, and has important implications for population dynamics and ecosystem functioning. Migration is a particular type of movement strategy, whereby animals may travel remarkable distances in order to take advantage of seasonality in resource availability or to avoid arduous winter conditions; however, this can be at a cost in terms of increased mortality. Indeed, anthropogenic threats in non-breeding areas are a major cause of population declines and a better understanding of non-breeding spatial ecology is required in order to advance both ecological theory and conservation management. The recent development of animal tracking technologies, in particular light-based geolocation, has made it possible to track large-scale and long-term movements; however, there are still gaps in our knowledge, such as the links between migratory and reproductive performance, connectivity among populations and the ontogeny of migration strategies. In this thesis, I utilise multi-species and longitudinal datasets from albatrosses and petrels, some of the most mobile species on Earth, to explore the drivers of variation in movements, habitat use and foraging behaviour, and the implications for life history and conservation. In Chapter 1, I provide an overview of the key topics of this thesis. In Chapter 2, I provide quantitative recommendations of minimum sample sizes needed to track pelagic seabird migrations, using data from 10 species. In Chapter 3, I examine between- and within-population differences in the habitat preferences and distributions of albatrosses, including the relative roles of habitat specialization and intra-specific competition. In Chapter 4, I investigate the year-round movement and foraging strategies of petrels living in nutrient-poor environments. In Chapter 5, I examine potential links between foraging behaviour during the non-breeding season and reproductive senescence. In Chapter 6, I explore the ontogeny of foraging behaviour and foraging site fidelity in young albatrosses, shedding light on their “lost years” at sea. Finally, I conclude with a general discussion summarizing main findings and suggesting future work. Overall, my results highlight the complex relationships among individual traits, the environment, movements and foraging behaviour, and population dynamics across the lifespan of individuals, with implications for the conservation of this highly threatened group of species.
8

Habitatové preference jelena lesního v Krkonošském národním parku / Habitat preferences of red deer in the Giant Mountains NP

Hazdrová, Kristýna January 2019 (has links)
The thesis deals with the evaluation of habitat preferences of the red deer in the Krkonoše National Park. In the context of Central Europe, the Krkonoše Mountains are an important locality in which many rare and protected ecosystems are located. The current management is trying to restore the species composition of the forest, which was abundant in the past and replaced by atypical spruce species. Red deer (Cervus elaphus), which lives in these forests, has no natural enemy in the Giant Mountains, so it is necessary to control the local population and perform selective management for the purpose of forest protection. For proper management planning it is important to know the life strategies of the red deer: the deer's preffered habitat, physical-geographical characteristics that affect its movement and spatio- temporal use of the area. This information can be obtained through GPS-telemetry collar monitoring. The monitoring campaign in the Giant Mountains was carried out between 2014 and 2018 and the resulting data are used in this work. Information on 71 individuals of red deer are processed and subjected to spatio-temporal analysis, which shows that deer behavior is influenced by both daily and annual cycles. Another aspect influencing its movement is the density and intensity of the use of...
9

Survey protocols for the stream-breeding frogs of Far East Gippsland : the application of habitat modelling and an assessment of techniques

Holloway, Simon, n/a January 1997 (has links)
This study developed a heirarchical approach to improve the efficiency and reliability of surveys for stream-breeding frogs in the montane forests of south-eastern Australia. Areas with suitable climate for some of these species were first determined by bioclimatic modelling. Landscape and habitat preferences were then determined for the four species commonly found in far East Gippsland, along with an assessment of survey techniques from which effective survey protocols were developed. The climate of localities at which five stream-breeding species had been previously found was modelled using BIOCLIM, and maps of the predicted potential distributions having similar climate were developed. Litoria phyllochroa was found to occur in coastal to alpine areas from Melbourne to Nowra, and potentially further inland, in areas with relatively low temperatures and low summer rainfall. Litoria lesueuri had a slightly larger known and predicted distribution, covering a wide range of values for the temperature and precipitation parameters. Both species had predicted areas inland from Melbourne and the Blue Mountains where they had never been recorded, probably largely due to land clearing. The rare Heleioporus australiacus had a slightly more northerly distribution, closer to the coast and adjacent ranges from Central Gippsland to just north of Sydney, with a generally warmer climate and large range of average annual precipitation values. Litoria citropa occupies an even narrower area along the coast, extending slightly further north again, with a climatic profile of few extremes but with relatively high rainfall particularly in summer. The rare Mixophyes balbus had a more northerly known and predicted narrow range along the NSW coast, just extending into Victoria and Queensland, characterised by the subtropical influence of higher summer rainfall. The southern extension into far East Gippsland appears to have an extreme sub-climate, and is hence considered highly susceptible to climate change. Future monitoring sites for these species can now be systematically chosen to include their full climatic range, so that any negative effects of climate change on amphibian populations may have a greater chance of detection. Four species were found commonly enough in the far East Gippsland study area for more detailed study - the three stream-breeding specialist species, L. phyllochroa, L citropa, and L. lesueuri, along with Crinia signifera which was not restricted to streams but commonly found along them. Three species, L. phyllochroa, L citropa and L. lesueuri, were not found at the few higher altitudes sites on the Errinundra Plateau, however they may have been restricted by habitat requirements other than altitude. Litoria phyllochroa was otherwise widespread, but preferred larger in-stream pools and backwaters for breeding with overhanging vegetation for perch and call sites. The other three species preferred stream reaches characterised by wide bedrock outcrops and associated wide break in the tree canopy, which may allow their preferred perch sites on rocky substrates to retain heat after sunset. Litoria lesueuri tadpoles were found in both unconnected and connected pools, and the common association of this species with bedrock outcrops may explain its range being largely restricted to granitic substratum where these outcrops mostly occurred. Litoria citropa preferred reaches with bedrock and boulder outcrops, although frogs used both rocky and vegetative substrates as perch sites, with tadpoles caught in both unconnected pools and backwaters. Crinia signifera tadpoles were mostly restricted to unconnected pools, with frogs generally only detected within or very close beside these. Habitat models varied in their predictive ability, from 67.5% for L. phyllochroa frogs to 92.7% for L. lesueuri tadpoles. Models developed from normally-distributed habitat variables by discriminant function analysis were generally more predictive than those from logistic regression analysis. The occurrence of frogs and tadpoles of L. phyllochroa, L. citropa and L. lesueuri can be predicted by the measurement of five habitat variables along a 50m reach: average width between the banks, average channel width, an average of the maximum depth of channel cross-sections along the reach, channel slope, and proportion of the stream length as pools. The occurrence of C. signifera along reaches can be predicted with the additional measurement of the proportion of the banks covered in ferns, the maximum cross-sectional channel depth along the reach, and the number of unconnected pools. Several different techniques for surveying frogs were compared for the four species commonly found along the streams. Probability of detection models were derived for each species for each technique, which allowed calculation of the statistical confidence of detecting a species that actually occurred at a site for any given number of surveys. For transect-based techniques, models were also developed which allowed determination of the minimum number of surveys required without detecting a species to be 95 percent statistically confident that the species did not occur there, for various transect lengths. This level of confidence can be obtained for the four common species by four surveys using the reliable night encounter technique along 500m stream transects, during the period from Ocotber to March, with air temperatures above 10°C. The application of habitat models to select favourable 50m reaches for survey also generally improved the detectability of each species. Timer-activated tape recorders, which automatically recorded the calls of frogs for many consecutive nights at a site, were very efficient at detecting all species except the quietcalling L. lesueuri. Night encounter surveys along stream transects detected all species from a reasonable effort, and dip-netting for tadpoles was also effective for most species. Active visual encounter surveys were less reliable, and day encounter surveys detected few frogs but provided some additional data when other activities were being performed along the streams. The findings of this study have important implications for future amphibian surveys and monitoring undertaken in East Gippsland and the south coast of New South Wales. If the standardised survey techniques recommended by this study are used in Environmental Impact Assessments, their results can be objectively assessed and defended. The use of habitat modelling and improvement in survey reliability can also be used more efficiently to find sites with populations suitable for monitoring. The likely amount of effort required by a long-term monitoring program can also be determined so as to largely overcome daily variations in the detection of each species.
10

Změna habitatových preferencí jelena evropského (Cervus elaphus) v Národním parku Šumava / Red deer (Cervus elaphus) habitat preferences change in the Šumava National Park

Lachová, Barbora January 2021 (has links)
6 Abstract The red deer (Cervus elaphus) is a widespread species of so-called grazers in Central Europe, which significantly affects the functioning of forest ecosystems. While in most areas of red deer distribution, its stocks are regulated within hunting and forestry management, within the Šumava National Park there is the largest non-intervention area with hunting restrictions in Central Europe outside the Alpine region. The Šumava NP is also dynamic environment. There is a change in habitat conditions started mainly by windstorm Kyrill and subsequent bark beetle gradation. There has also been a change in terms of habitat management (new zoning, different forest management practices). The thesis contains an extensive dataset of a total of 34 doe monitored by GPS telemetry collars, from two time horizons. A spatiotemporal analysis of the preferences of land cover, altitude, slope and orientation of slopes and distance to anthropogenic structures is performed. The results of this analysis reaffirm that the behaviour of deer in the daily and annual cycle is controlled mainly by food requirements and also showed the effect of anthropogenic disturbance, which significantly modifies the pattern of land use due to the distance from the source of disturbance. The current occurrence is still controlled by...

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