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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.
41

Toolkit to manage key habitat for amphibians in Ontario forests / Toolkit for amphibian habitat monitoring in Ontario

Luymes, Nicholas January 2021 (has links)
Forest-dwelling amphibians contribute to diverse ecosystem services in Ontario but are threatened by habitat degradation and fragmentation. My thesis investigated key amphibian habitats in Ontario forests with the goal of providing resource managers with tools and techniques to protect and restore amphibian populations. I primarily focussed on amphibians that breed in temporary forested wetlands known as vernal pools, as these wetlands are overlooked in provincial legislature and particularly sensitive to changes in land-use and climate. First, I investigated the distribution and community structure of vernal pools in forests of eastern Georgian Bay, Lake Huron. I developed an accurate remote sensing technique to map vernal pool habitat using readily available spatial data and found that undocumented vernal pools accounted for over half of the wetlands in the region. I documented the importance of the length of pool inundation (hydroperiod) and canopy openness in determining the composition of vernal pool amphibian assemblages. In particular, pools with short hydroperiods and closed canopies tended to support only early breeders and canopy generalists. Next, I used two case studies to demonstrate the usefulness of existing amphibian occurrence datasets, specifically for the improvement of habitat mapping and monitoring. For the first case study, I created habitat suitability models using known locations of the endangered Jefferson salamander (Ambystoma jeffersonianum). Models yielded good discriminatory ability between presence and pseudo-absence data and confirmed the importance of deciduous/mixed forests as key habitats. Habitat suitability maps revealed potential undocumented habitat in the Greenbelt region of Ontario. For the second case study, I developed optimizations of time and effort for a salamander monitoring program. I verified the need for at least ten years’ worth of monitoring data for reliable trend detection and demonstrated that the precision and accuracy of occupancy estimates are dependent on the allocation of effort across monitoring sites and repetitions. / Thesis / Doctor of Philosophy (PhD) / Amphibian declines represent one of the hallmarks of the current biodiversity crisis. While there are many factors responsible for amphibian declines, the most significant threats are habitat loss and degradation. This Ph.D. thesis describes amphibian habitat use in Ontario forests and provides resource managers with tools and techniques to protect habitat. Using satellite imagery, I developed a strategy to map small amphibian breeding wetlands (vernal pools) in forests of eastern Georgian Bay. I also identified the importance of pool drying times and forest canopy cover to the amphibians that breed in these wetlands. In the fragmented forest patches of southern Ontario, I mapped suitable habitat for the endangered Jefferson salamander and identified the importance of large deciduous/mixed forests. Lastly, I assessed the effectiveness of a long-term salamander monitoring program in southern Ontario and demonstrated the use of techniques to optimize the allocation of effort and maximize the accuracy of monitoring results.
42

A study of landscape ecology of feng shui woodlands in Hong Kong, using high resolution IKONOS imagery and GIS.

January 2004 (has links)
Ho Ka Yip. / Thesis submitted in: December 2003. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 144-152). / Abstracts in English and Chinese. / Abstract --- p.i / 論文摘要 --- p.iii / Acknowledgements --- p.v / Table of Contents --- p.vi / List of Tables --- p.ix / List of Figures --- p.xi / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Background to the Study --- p.1 / Chapter 1.1.1 --- Feng Shui Woodlands --- p.1 / Chapter 1.1.2 --- Landscape Ecology --- p.4 / Chapter 1.2 --- Objectives of the Study --- p.6 / Chapter 1.3 --- Significance of the study --- p.7 / Chapter 1.4 --- Definitions --- p.9 / Chapter 1.5 --- Organization of the Thesis --- p.11 / Chapter Chapter 2 --- Literature Review --- p.13 / Chapter 2.1 --- Landscape Ecology --- p.13 / Chapter 2.1.1 --- Definition --- p.13 / Chapter 2.1.2 --- Applications --- p.16 / Chapter 2.1.3 --- Landscape Metrics --- p.18 / Chapter 2.1.4 --- Applications of Landscape Metrics --- p.24 / Chapter 2.1.5 --- Sensitivity of the Metrics --- p.29 / Chapter 2.2 --- Feng Shui woodlands --- p.34 / Chapter 2.2.1 --- General Characteristics --- p.34 / Chapter 2.2.2 --- Physical and Spatial Characteristics --- p.37 / Chapter 2.2.3 --- Ecological Importance --- p.41 / Chapter 2.2.4 --- Functions of Feng Shui Woodlands --- p.43 / Chapter 2.2.5 --- Threats to Feng Shui Woodlands --- p.46 / Chapter 2.3 --- Summary --- p.48 / Chapter Chapter 3 --- Methodology --- p.49 / Chapter 3.1 --- Introduction --- p.49 / Chapter 3.2 --- Study Site Description --- p.51 / Chapter 3.3 --- Identification of Feng Shui Woodlands --- p.53 / Chapter 3.3.1 --- Acquisition and Pre-processing of Remote Sensing Data --- p.53 / Chapter 3.3.2 --- Identification of Feng Shui Woodlands --- p.57 / Chapter 3.4 --- Extraction of Landscape Metrics and Landuse composition --- p.62 / Chapter 3.4.1 --- Landscape Metrics of Feng Shui Woodlands --- p.62 / Chapter 3.4.2 --- Estimation of Landuse Composition in Feng Shui Woodlands' Neighbourhood --- p.66 / Chapter 3.5 --- Construction of a Geographical Information System (GIS) Database --- p.68 / Chapter 3.6 --- Analysis of Landscape Ecology of Feng Shui Woodlands --- p.68 / Chapter 3.7 --- Summary --- p.70 / Chapter Chapter 4 --- Results and Discussion (I)´ؤPhysical Characteristics of Feng Shui woodlands --- p.71 / Chapter 4.1 --- Introduction --- p.71 / Chapter 4.2 --- Identification of Feng Shui Woodlands --- p.71 / Chapter 4.3 --- Interpretation of Landscape Metrics --- p.79 / Chapter 4.4 --- Factor Analysis Results of Landscape Metrics --- p.95 / Chapter 4.5 --- Summary --- p.100 / Chapter Chapter 5 --- Results and Discussion (II)一Interaction between Landuse Composition and Feng Shui woodlands --- p.101 / Chapter 5.1 --- Introduction --- p.101 / Chapter 5.2 --- Estimation of Landuse Composition --- p.101 / Chapter 5.3 --- Change of Landuse Composition in Feng Shui Woodlands' Neighbourhood --- p.106 / Chapter 5.4 --- Factor Analysis of Landuse Composition --- p.115 / Chapter 5.5 --- Interaction Between Landuse Composition and Feng Shui Woodlands --- p.120 / Chapter 5.5.1 --- Correlation Analysis --- p.120 / Chapter 5.5.2 --- Cluster Analysis --- p.124 / Chapter 5.6 --- GIS Database --- p.133 / Chapter 5.7 --- Summary --- p.135 / Chapter Chapter 6 --- Conclusion --- p.137 / Chapter 6.1 --- Summary of The Study --- p.137 / Chapter 6.2 --- The Landscape Ecological Value of Feng Shui Woodlands --- p.138 / Chapter 6.3 --- Limitations of This Study --- p.142 / Bibliography --- p.144 / Appendix 1´ؤResults from Factor Analysis and Clustering Analysis --- p.153 / Appendix 2´ؤChange of Percentage of Landuse for Feng Shui Woodlands across 500 meters --- p.156
43

Vegetation succession on glacier forelands in the Jostedalsbreen region and Jotunheimen, south-central Norway

Grimm, Günter Albin January 2000 (has links)
In this study four different aspects of primary successions on glacier forelands in South-Central Norway are investigated. First, general vegetation and environment trends, which have been observed by other scientists, were studied on two forelands. It is shown that the two selected forelands (one low- and one high-altitude foreland, Nigardsbreen and Storbreen, respectively) differ in the speed of vegetation cover change and in the overall species richness developed over the last 250 years since deglaciation. This is attributed to differences in the severity of the environment between the two forelands. Some support for an early peak in the number of species was found for the Nigardsbreen foreland, whereas the Storbreen foreland shows no significant trend in the development of species richness. Life-forms and soil-depth change on both forelands in the predicted manner. A novel approach for the use of Ellenberg indicator values for the estimation of pH-values from the existent vegetation shows highly significant correlations between predicted pH values and trends measured for similar terrain ages from a study by Messer (1988). Investigation at two different scales indicated that small-scale disturbances (< 100 m) may influence the mosaic of the environment, which affects the results of the chronosequence approach. By using a strict geometrical sampling design more variable conditions entered the analyses than with the stratified random sampling schemes adopted by others, such as Matthews (1979b). Some loss in the power of analysing the data occurred, but the results are still consistent with hypotheses about primary succession on glacier forelands. Second, new aspects of the temporal development and successional change of plant communities were investigated on the same two forelands. There is some evidence of succession from a pioneer community to the local climax community of the surrounding area for both forelands. There is also support for the correlation of timedependent environmental variables with the successional development of plant communities. A new application of Ellenberg indicator values in ordinations was assessed for its value in estimating average environmental conditions derived from the vegetation. As with the previous analyses, investigation of community development at two different scales supported the importance of sampling scale on the analysis of succession data. Third, spatially explicit analyses of distribution patterns of dominant woody species was developed as a means to investigate processes and formulate hypotheses about primary succession on glacier forelands. The data for this part of the study was collected on five glacier forelands, three low-altitude (Nigardsbreen, Austerdalsbreen and Bødalsbreen) and two high-altitude (Storbreen and Høgvaglbreen). Pattern descriptors including perimeter/area index, autocorrelation measures and fractal dimensions, support the hypothesis of differential colonisation of wind and animaldispersed species. Even more convincing is the result that low- and high-altitude forelands show significant differences in the patterns exhibited by wind and animals dispersed species. This result is thought to be related to the differences in environmental severity affecting the establishment of colonising species. Finally, logit modelling of the distributions of dominant woody species provides insights into the sampling effort needed to gather enough data for meaningful analyses. It also leads to the identification of important factors influencing the distribution of those species.
44

Interacting Disturbances in the Boreal Forest and the Importance of Spatial Legacies at Multiple Scales

James, Patrick Michael Arthur 03 March 2010 (has links)
Forest disturbances and the spatial patterns they create affect ecosystem processes through their influence on forest vegetation from individual trees to landscapes. In the boreal and mixed-wood forests of eastern Canada the main agents of disturbance are logging, fire, and defoliation by the spruce budworm (SBW, Choristoneura fumiferana). These disturbances are similar in that they remove forest biomass and influence forest succession but also distinct in that logging creates patterns that are different than those created by natural disturbances. All disturbances are indirectly linked to each other through their mutual effects on forest spatial structure and succession. Through such feedbacks, spatial disturbance legacies can facilitate or constrain further disturbances, including forest management. Surprisingly, the long term spatial consequences of interactions among multiple natural and anthropogenic disturbances remain largely unexplored. This thesis investigates how, and at what spatial scale, legacies in forest composition and age structure influence natural disturbance dynamics, and how natural disturbances constrain forest management. I address four specific questions: (i) For how long do spatial legacies of different forest management strategies persist on the landscape? (ii) How do interactions among logging, fire, SBW, and succession affect timber availability and long term forest patterns in age and composition? (iii) How do these patterns differ from those created by each disturbance individually? And, (iv) How can management be used to reduce the extent and severity of fires and SBW defoliation through the manipulation of forest structure? The key scientific innovations of this thesis are: (i) Characterization of the duration and influence of spatial legacies on forest disturbances and sustainability; (ii) Development of a dynamic spatial forest simulation model that includes distinct successional rules that respond to different types of disturbance and shifts in disturbance regimes; and, (iii) Development and application of a wavelet-based significance testing framework to identify key scales of expression in forest spatial patterns. These innovations provide a scientific basis for landscape level forest management strategies designed to reduce the long term impacts of defoliating insects and to meet multiple objectives.
45

Relative effects of landscape and local habitat characteristics on grassland songbird abundance and occurrence in southwestern Manitoba

Lockhart, Jessica 14 September 2016 (has links)
I investigated the relative effects of grassland cover and fragmentation per se, and the relative influence of landscape and local habitat characteristics on grasslands songbirds in the moist mixed-grass prairies of Manitoba. In 2013, 361 avian point counts were conducted across 47, 2.4-km radii landscapes in the southwest part of the province. I used an information-theoretic approach to rank and select models describing effects of landscape and local-scale habitat variables on grassland songbird abundance and occurrence. Overall, my results indicate that grassland amount, fragmentation and quality, and matrix composition had relatively small and variable effects on grassland songbird abundance and occurrence, but that abundance of obligate species when pooled showed a strong negative response to grassland fragmentation. While fragmentation through edge effects may contribute to obligate species declines, my results suggest that these factors alone are unlikely to explain ongoing declines of grassland birds in southwestern Manitoba. / October 2016
46

Investigations of pond metabolism in temperate salt marshes of Massachusetts

Yoo, Gyujong January 2018 (has links)
Thesis advisor: Tara Pisani Gareau / Salt marshes provide important ecosystem services, including carbon sequestration. Permanently inundated ponds are prominent features in the marsh landscape, encompassing up to 60% of the total marsh area, but they are rarely considered in biogeochemical assessments. I investigated two ponds in Plum Island Estuary, MA to measure and analyze their metabolism. The ponds varied in size and vegetation cover. Oxygen concentrations and pH values were recorded in 15-minute intervals during the entire study period. The ponds regularly become hypoxic or anoxic during night. This is a problem for the estimation of respiration rates which are based on nighttime measurements. To investigate this potential underestimation, several approaches to estimate respiration were used. First, additional measurements of surface water concentrations of dissolved inorganic carbon were made. A comparison of respiration estimates based on oxygen and DIC changes during tidal isolation revealed a reasonable agreement for the most time but not during periods of high productivity during the day or late at night. At this point, oxygen concentrations are so depleted that a change in concentration – the indicator of respiration – is barely detectable. However, DIC based respiration rates indicate that respiration is occurring under these hypoxic/anoxic conditions. This saturation changes during periods of tidal inundation, when a nighttime peak in oxygen concentrations indicates that the flood water is relatively enriched in oxygen compared to the pond water. On three days, it was tested whether under these conditions the oxygen-based respiration rate was higher than under hypoxic conditions (i.e., during tidal isolation). The rates were indeed higher than those under tidal isolation but still not in the range of DIC-based rates. Overall, metabolic rates differed between the two ponds in magnitude, which is likely caused by different vegetation cover, but may be influenced by size, sampling period, and duration as well. / Thesis (BS) — Boston College, 2018. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Departmental Honors. / Discipline: Earth and Environmental Sciences.
47

Distribution and biomass dynamics of the alpine treeline ecotone across the western United States

Grafius, Darren Robert 01 May 2012 (has links)
The alpine treeline ecotone is primarily caused by climate at continental and regional scales, but at finer scales exhibits increasing complexity and linkages with abiotic factors. In order to better understand the dynamics and geographic properties of treeline, a three-pronged study was conducted. The study's first objective investigated what factors account for local treeline variation by comparing a climate-based predictive surface with actual treeline elevation. After finding that a mean growing season temperature of 10.27°C was the strongest predictor of treeline at continental scales, statistical analyses attempted to model the differences between predicted and actual treeline elevation based on local climatic and geomorphological controls. Site elevation and latitude were found to correlate most strongly. Roughness also exerted positive influences, as well as precipitation when coupled with certain terrain factors. The second objective explored the distribution of treeline carbon at site scales by analyzing field data gathered in August 2009 in Glacier National Park, Montana. This confirmed the expected relationship of upright trees containing the highest biomass density, tundra the lowest, and krummholz in the middle. A high degree of dead organic matter was discovered, which may have important implications for treeline as a carbon source or sink when considering treeline's slow decomposition rates, and how these will change under climate warming. An additional analysis investigated the potential for relative biomass gain with future treeline advance, based on site and regional differences in slope and environmental lapse rates. The third objective asked what the potential for change in treeline biomass is across the western United States is by using freeze-thaw days as a proposed indicator. This potential importance is based on existing knowledge of the facilitating relationships between solifluction, surface geomorphology, and seedling establishment and survival. Freeze-thaw days were found to be highly variable, but correlated most strongly with elevation, suggesting increased temperature variability at higher elevations. The concluding chapter synthesizes the findings and maps potential biomass gain and freeze-thaw days together to highlight treeline sites and regions with the greatest potential for advance in a warming climate.
48

Interacting abiotic and biotic factors affecting Jeffrey pine regeneration along an elevational gradient

Gworek, Jennifer R. January 2005 (has links)
Thesis (M.S.)--University of Nevada, Reno, 2005. / "(December 2005)." Includes bibliographical references (leaves 36-42). Online version available on the World Wide Web.
49

Historical land cover impacts on water quality in the Provo River watershed, 1975 - 2002 /

Donaldson, Fredric J. January 2005 (has links) (PDF)
Thesis (M.S.)--Brigham Young University. Dept. of Geography, 2005. / Includes bibliographical references (p. 71-78).
50

Factors affecting movement patterns of mule deer (<i>Odocoileus hemionus</i>) in southern Saskatchewan : implications for chronic wasting disease spread

Silbernagel, Erin Rae 08 April 2010
Chronic wasting disease (CWD) has been a known threat to Saskatchewans wild cervid populations for more than a decade. As host movements can affect the spread of a disease across the landscape, disease models and management strategies should incorporate information regarding movement patterns of the host population in question. I used radio telemetry to study mule deer (<i>Odocoileus hemionus</i>) captured between 2006 and 2008 in a CWD-endemic region of southern Saskatchewan. Using location data from 152 individuals, I investigated home range size and patterns of direct and indirect contact (measured using proximity and shared space use) in relation to sex, habitat, and landscape structure. <p>Home ranges (95% fixed kernel) of GPS-collared deer in this study averaged 21.4 km² (n = 94). Male home ranges (mean = 29.5 km², n = 56) were larger than those of females (mean = 16.1 km², n = 38), which could have implications for CWD prevalence differences between sexes. Of the landscape variables tested, topographic ruggedness was inversely related to home range size and Shannons diversity (a measure of both habitat richness and evenness) was positively related to home range size. <p>Potential direct contact events were identified when two deer were located within 25 m of each other at the same point in time. These events occurred more often between February and April, agreeing with the tendency of mule deer to aggregate into large groups during the late winter months, and suggesting that this may be an important time period for disease transmission. Contact also occurred more than expected in cropland, whereas areas of shared use occurred more than expected in grassland, shrub/wood habitat, and rugged terrain. Smaller home ranges and greater degree of shared space use within areas of rough topography may lead to greater risk of environmental contamination with the infectious CWD agent in these areas. In contrast, the relationship between cropland and probability of direct contact may imply greater risk of direct CWD transmission between deer occupying this habitat. <p>These results identify connections between particular landscape factors and risk of CWD transmission and will be used, in combination with results of related studies, to develop a model of CWD spread in Saskatchewan. This will in turn aid management agencies in developing methods to more effectively manage the disease and control its movement outside of affected regions.

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