• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 91
  • 11
  • 6
  • 3
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 124
  • 124
  • 19
  • 16
  • 15
  • 14
  • 13
  • 11
  • 11
  • 10
  • 9
  • 9
  • 9
  • 8
  • 8
  • 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.
91

Habitats online: A collaborative telecommunications project

Sudyka, Tracee Dee 01 January 1997 (has links)
This project develops a collaborative telecommunications project called Habitats Online. Review of the literature indicates that collaborative telecomunication projects, like Habitats Online, engage students in rich learning experiences and establish a network of future citizens who have a greater understanding of our environment and global communications. This master's project specifically addresses these issues.
92

Ruffed grouse (Bonasa umbellus) habitat ecology in the central and southern Appalachians

Whitaker, Darroch M. 15 January 2004 (has links)
Ruffed grouse populations are low in Appalachian forests, possibly because low habitat quality negatively affects survival, condition, and reproduction. Through the Appalachian Cooperative Grouse Research Project (ACGRP) researchers tracked >1500 radioed grouse at 10 study sites (1996__2002). To improve our understanding of Appalachian grouse habitat ecology, I carried out two primary analyses of this database. First, grouse should be under selective pressure to minimize movements, so I studied factors associated with variation in home range size. Second, importance of a habitat is affected by an individual's resource needs, and I investigated factors associated with variation in selection of "preferred" habitats. Both approaches yielded important insights into the species' regional habitat ecology. As elsewhere, clearcuts, which afford escape cover, formed the cornerstone of grouse habitat in the region. However, a number of other factors were also important. At the root of this was a divergence in habitat ecology between grouse inhabiting the two major forest types in the region. In oak-hickory forests nutritional constraint strongly influenced habitat use. Grouse home ranges increased 2.5x following poor hard mast crops, and at these times grouse increased use of alternate foraging habitats. Grouse, especially females and broods, made extensive use of mesic bottomlands and forest edges, which in oak-hickory forests support relatively abundant soft mast and herbaceous forages. In contrast, grouse inhabiting mixed mesophytic forests were insensitive to hard mast, did not select bottomlands, reduced use of forest edges, and increased use of clearcuts. I feel that greater abundance of birch, cherry, and aspen, buds of which are a high quality winter food, relieves nutritional stress on grouse inhabiting mesophytic forests. A general inference was that grouse attempted to balance competing strategies of maximizing either survival or condition, and the expression of this tradeoff was mediated by forest composition. Also presented here were studies of radiotelemetry error, roost site selection, and suitability of prescribed burning as a habitat improvement technique. In the closing chapter I make recommendations for managing Appalachian forests for grouse, which focus on improving winter foraging habitat, brood habitat, and escape cover, all of which are limiting in Appalachian forests. / Ph. D.
93

The Vegetation and Habitat Factors of Rockwall County, Texas

Smith, W. Desby 08 1900 (has links)
This paper consists of a study of the soils and vegetation found in Rockwall County, Texas. This county is located in the northeastern part of the state. Rockwall County lies in the northeastern part of the Black Waxy Belt of the Coastal Plains province.
94

Applications of GIS and Remote Sensing for the Characterization of Habitat for Threatened and Endangered Species

Shaw, Denice Marie, 1958- 12 1900 (has links)
Geographic Information Systems (GIS) and remote sensing technologies were used to identify and describe potential habitat for three species endemic to the Southwestern United States; the Golden-cheeked Warbler (Dendroica chrysoparia), the Black-capped Vireo (Vireo atricapillus), and the Texas kangaroo rat (Dipodomys elator). For each species, the computerized classification of digital satellite imagery was integrated with ancillary spatial information (e.g. soils, geology, and land use) to construct a data base to be used for ecological evaluation as well as habitat protection and management measures.
95

Modeling the Distribution of Bobcats and Areas of Reintroduction for Fisher in the Southern Washington Cascades

Halsey, Shiloh Michael 16 August 2013 (has links)
The fisher (Martes pennanti) is a medium sized member of the mustelid family that once roamed the forests of Washington and whose historic range in the western United States once spread throughout the northern Rocky Mountains, the Cascade and Coast Ranges, and the Sierra Nevada (Carroll, Zielinski, and Noss 1999; Powell 1993, Spencer et al. 2011). Due to pressures from trapping and habitat fragmentation, the abundance of the species in the western United States has decreased dramatically and is thought to be limited to several small, isolated populations. In 2008, fishers were reintroduced to the Olympic Peninsula; however, bobcat (Lynx rufus) predation in the first years is thought to have killed off a significant portion of the released fisher hindering their ability to establish a self-sustaining population (Lewis et al. 2011). Other studies in the western United States have shown that bobcats can be a dramatic force on small or isolated fisher populations. The coniferous forest of the southern Washington Cascades is the possible site of a release of currently extirpated fishers. My research examines the distribution of bobcats in the region and explores the implication this and the habitat variables of the area have for a future reintroduction of fisher. The workflow of the research was a stepwise process of: 1) surveying forested areas in the southern Washington Cascades for the presence and absence of bobcat and acquiring previously completed survey data 2) using a classification tree to model the correlation of bobcat presence or absence with forest variables and 3) applying these relationships to spatial analysis the creation of maps showing areas of high ranking fisher habitat. The classification tree modeled the correlation between the forest variables and the results of the surveys, which included 145 bobcat absence observations and 39 presence observations. The model highlighted a 95% probability of absence above 1,303 m in elevation, 73% probability of absence in areas under 1,303 m in elevation and with a tree diameter value under 43.45 cm, 57% probability of absence in areas between 1,070 m and 1,303 m in elevation and with a tree diameter value above 43.45 cm, and an 89% probability of bobcat presence in areas under 1,070 m in elevation with a tree diameter value above 43.45 cm. I applied an upper elevation limit of 1,676 meters as a threshold for suitable habitat and only considered habitat suitable in cells with a tree diameter above 29 cm. The three locations highlighted as the most suitable areas for reintroduction due to a large amount of the highest ranking habitat and the largest aggregations of suitable habitat cells were around the William O. Douglas Wilderness that straddles the border of the Gifford Pinchot National Forest (GPNF) and the Wenatchee National Forest, another location in the Norse Peak Wilderness northeast of Mount Rainier, and a third location in Indian Heaven Wilderness in the southern portion of the GPNF.
96

O efeito da heterogeneidade de habitats sobre as interações planta-polinizador em uma região da bacia do Rio Corumbataí - SP /

Patricio, Gleiciani Bürger. January 2007 (has links)
Resumo: Estudos realizados em ambientes fragmentados revelam que vários processos ecológicos são afetados pelo tamanho, forma e grau de isolamento dos remanescentes de vegetação nativa. A abundância local de polinizadores pode ser explicada pela relação de atratividade planta - polinizador e pela disponibilidade de sítios de nidificação e recursos florais. Este trabalho teve como objetivo geral, avaliar o efeito da heterogeneidade de habitats sobre a interação planta - polinizador em áreas com forte influência antrópica. A hipótese testada foi a de que a heterogeneidade de habitats afeta a disponibilidade de polinizadores e, conseqüentemente, a produção de frutos e sementes. Para isso, a espécie seleciona foi S. viarum. Foram selecionadas 12 áreas dentro da região da Bacia do Rio Corumbataí - SP, sendo 6 áreas mais homogêneas, com H’ < 0,9, e 6 mais diversificadas, com H’ > 1,4. Os pontos amostrais foram distribuídos nas áreas centrais desses habitats segundo as possibilidades de acesso. Para cada ponto amostral foi estabelecida uma estação de coleta de dados, onde foram instaladas as plantas para os estudos sobre polinização. Foram realizados 4 períodos de coletas de dados. Em um mesmo período, tanto áreas de alta como de baixa heterogeneidade foram observadas quanto à fenologia e à visitação por abelhas. Em relação à porcentagem de frutos formados de S. viarum Dun., evidenciando seu sucesso reprodutivo, houve diferença significativa entre as áreas localizadas na região de Rio Claro e as localizadas na região de Ipeúna, mas não entre as áreas de alta e baixa heterogeneidade. A análise da paisagem na escala de 600m mostrou que essas duas regiões diferem significativamente quanto à porcentagem de cobertura de mata. Isso pode, em parte, explicar a diferença encontrada entre as duas regiões, mas não entre áreas de alta e baixa heterogeneidade... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Studies carried through in fragmented environments disclose that some ecological processes are affected by the size, form and degree of isolation of the remainders of native vegetation. The local abundance of pollinators can be explained by the relation of plant-pollinator attractiveness and the availability of nest site and floral resources. This study it aimed to evaluate the effect of the heterogeneity of habitats on the interaction plant-pollinator in areas with strong antropogenic influence. The tested hypothesis was of that the heterogeneity of habitats affects the availability of pollinators and, consequently, the production of fruits and seeds. 12 areas inside of the region of the Basin of Rio Corumbataí - SP had been selected, being 6 more homogeneous areas, with H' < 0,9, and 6 more diversified, with H' > 1,4. The sampling points had been distributed in the central areas of these habitats according to access possibilities. For each sampling point, a period of collection of data was established, where the plants had been installed for pollination studies. Four periods of data collecting had been carried through. In a same period, as many areas of high as of low heterogeneity had been observed according the phenology and the visitation for bees. The percentage of formed fruits of S. Viarum Dun., evidencing the reproductive success, had significant difference between the located areas in the region of Rio Claro and the located ones in the region of Ipeúna, but not between the areas of high and low heterogeneity. The analysis of the landscape in the scale of 600m showed that these two regions differ significantly as for the percentage of bush covering. This can, in part, to explain the difference found between the two regions, but not between areas of high and low heterogeneity. A very small number of bees were collected in the flowers... (Complete abstract click electronic access below) / Orientador: Maria José de Oliveira Campos / Coorientador: Osmar Malaspina / Banca: José Chaud Netto / Banca: Isabel Alves dos Santos / Mestre
97

An experimental investigation of the effects of supplementary food and ground cover on small mammal population dynamics and community structure in a Swaziland grassland.

Monadjem, A. 23 December 2013 (has links)
The primary aim of this study was to investigate the role of food supply and ground cover on the community structure, population dynamics and demography of terrestrial small mammals in a subtropical grassland. This aim was achieved through a series of food supplementation and cover manipulation experiments conducted at eKundizeni Farm near Matsapha, Swaziland, over a 28 month period. The effects of five different diets on the rodent Mastomys natalensis were investigated in the laboratory, and the results showed that rolled oats and rabbit pellets were suitable for growth and reproduction in this species. The effects of supplementary food were investigated on two supplemented grids and one control over a twelve month period. Small mammal biomass increased significantly on the supplemented grids in relation to the control. This increase in biomass was the result of a twofold increase in the numbers of M natalensis. Food supplementation further affected M. natalensis by: extending the breeding season of females; increasing body weight; increasing survival; and decreasing home range area. Food supplementation had a weak positive effect on the density of another rodent Lemniscomys rosalia, but did not affect any other demographic feature of this species. Food supplementation did not have a demographic effect on any other species of small mammal captured. The effects of vegetative cover were investigated, over a twelve month period, on two control grids and four manipulated grids on which the vegetative cover was mechanically reduced. Supplementary food was added to two of the latter four manipulated grids. The biomass of small mammals, including M. natalensis, was lower on grids with reduced vegetative cover than on the controls. However, food supplementation resulted in a significant increase in the biomass of M. natalensis on one of the manipulated grids. Hence, M. natalensis was induced to shift to a habitat with reduced cover by the provision of supplementary food. Additional information on the population dynamics, age structure, reproduction and diet of M natalensis, L. rosalia, Mus minutoides and Steatomys pratensis is also presented. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1997.
98

Seasonal home range and foraging movements of the Wahlberg's epauletted fruit bat (Epomophorus wahlbergi) in an urban environment.

Rollinson, Dominic Paul. January 2012 (has links)
Urbanisation through the process of habitat loss and fragmentation has caused drastic changes in ecosystem dynamics around the world. Many species can no longer survive in these urban areas; however there are those species that have been able to survive and in fact thrive in the newly created habitats. With increasing urbanisation it is important that animals are able to adjust to a life in close association with humans. One such group of organisms which has adjusted well to urbanisation is the suborder Megachiroptera (Chiroptera). Some species from this suborder have benefited from increased food and roost resources in certain urban areas. Exotic fruiting plants (introduced purposely and accidentally) as well as increased cultivated gardens have provided additional food sources in some urban environments, while man-made structures, and increased suitable vegetation, have provided additional roosting opportunities. Although these urban dwelling species live in close association with humans, very little is known of their ecology in urban areas. Wahlberg's epauletted fruit bat Epomophorus wahlbergi is one such species of which little is known of its suburban ecology despite its increased presence in many urban areas. This study on the ecology of E. wahlbergi was conducted from February to October 2011 in the urban environment of Pietermaritzburg, South Africa. The aim was to examine foraging movements and habitat use of E. wahlbergi in this urban environment. The objectives were to determine seasonal differences in foraging movements and home range sizes in this urban environment. In addition the roosting dynamics and roost characteristics of E. wahlbergi in this urban environment were determined. In late summer, it was found that individual E. wahlbergi movements ranged considerably, with some bats making extensive flights to different parts of town while others stayed in particular areas throughout; no bats were recorded to have left the urban environment. Some of the larger distances covered in a single night's movements were two and five km. In late summer roosting fidelity varied between individual bats; all the individual bats changed their roosts at least once during late summer. Some individuals had as many as three known daytime roost sites. There was a difference in home range size between the sexes; with females occupying a larger home range size than males. This variation in movement patterns of individual bats suggests that their social interactions, roost site preferences, or dietary preferences vary between individuals in late summer. A significant difference in home range size and habitat use by E. wahlbergi was found between winter and spring, with home range sizes being larger in winter. The increased home range sizes and habitat use in winter were a consequence of bats feeding on the fruits of the alien invasive Syringa (Melia azedarch) with few other trees in fruit. Consequently bats had to move greater distances for food in winter. In spring, fruit availability was greater and more varied including both indigenous and exotic fruits. Consequently in winter, the bats were more reliant on a few fruiting species to meet their dietary requirements than during spring. Bats changed their roosts regularly in summer, winter and spring. There was considerable variation in roost temperatures however roost temperatures were higher than ambient temperatures. Roosts in man-made structures were higher in temperature than those in natural vegetation. This study suggests the importance of temperature in the selection of daytime roosts, however other factors such as predator avoidance and proximity to food resources are also considered in selection of daytime roosts. Within the order Chiroptera, species from the suborder Microchiroptera have generally not been well represented in urban areas, it is important that the reasons for this be better understood. Further research is still required to better understand the ecology of urban dwelling species as well as to understand the reasons why many species are not able to adjust to urban environments. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.
99

The utility of linear riparian rainforest for vertebrates on the Atherton and Evelyn Tablelands, North Queensland /

Hausmann, Franziska. January 2004 (has links)
Thesis (M.Phil.) -- Griffith University, 2004. / Facsimile of the author's original dissertation. Pagination of document: x, 121 leaves. Includes bibliographical references. Also available online via the World Wide Web.
100

O efeito da heterogeneidade de habitats sobre as interações planta-polinizador em uma região da bacia do Rio Corumbataí - SP

Patricio, Gleiciani Bürger [UNESP] 28 September 2007 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:30:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-09-28Bitstream added on 2014-06-13T20:20:37Z : No. of bitstreams: 1 patricio_gb_me_rcla.pdf: 2982674 bytes, checksum: de54c07500e9014cf1e6fb466fb9530c (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Estudos realizados em ambientes fragmentados revelam que vários processos ecológicos são afetados pelo tamanho, forma e grau de isolamento dos remanescentes de vegetação nativa. A abundância local de polinizadores pode ser explicada pela relação de atratividade planta - polinizador e pela disponibilidade de sítios de nidificação e recursos florais. Este trabalho teve como objetivo geral, avaliar o efeito da heterogeneidade de habitats sobre a interação planta - polinizador em áreas com forte influência antrópica. A hipótese testada foi a de que a heterogeneidade de habitats afeta a disponibilidade de polinizadores e, conseqüentemente, a produção de frutos e sementes. Para isso, a espécie seleciona foi S. viarum. Foram selecionadas 12 áreas dentro da região da Bacia do Rio Corumbataí - SP, sendo 6 áreas mais homogêneas, com H < 0,9, e 6 mais diversificadas, com H > 1,4. Os pontos amostrais foram distribuídos nas áreas centrais desses habitats segundo as possibilidades de acesso. Para cada ponto amostral foi estabelecida uma estação de coleta de dados, onde foram instaladas as plantas para os estudos sobre polinização. Foram realizados 4 períodos de coletas de dados. Em um mesmo período, tanto áreas de alta como de baixa heterogeneidade foram observadas quanto à fenologia e à visitação por abelhas. Em relação à porcentagem de frutos formados de S. viarum Dun., evidenciando seu sucesso reprodutivo, houve diferença significativa entre as áreas localizadas na região de Rio Claro e as localizadas na região de Ipeúna, mas não entre as áreas de alta e baixa heterogeneidade. A análise da paisagem na escala de 600m mostrou que essas duas regiões diferem significativamente quanto à porcentagem de cobertura de mata. Isso pode, em parte, explicar a diferença encontrada entre as duas regiões, mas não entre áreas de alta e baixa heterogeneidade... / Studies carried through in fragmented environments disclose that some ecological processes are affected by the size, form and degree of isolation of the remainders of native vegetation. The local abundance of pollinators can be explained by the relation of plant-pollinator attractiveness and the availability of nest site and floral resources. This study it aimed to evaluate the effect of the heterogeneity of habitats on the interaction plant-pollinator in areas with strong antropogenic influence. The tested hypothesis was of that the heterogeneity of habitats affects the availability of pollinators and, consequently, the production of fruits and seeds. 12 areas inside of the region of the Basin of Rio Corumbataí - SP had been selected, being 6 more homogeneous areas, with H' < 0,9, and 6 more diversified, with H' > 1,4. The sampling points had been distributed in the central areas of these habitats according to access possibilities. For each sampling point, a period of collection of data was established, where the plants had been installed for pollination studies. Four periods of data collecting had been carried through. In a same period, as many areas of high as of low heterogeneity had been observed according the phenology and the visitation for bees. The percentage of formed fruits of S. Viarum Dun., evidencing the reproductive success, had significant difference between the located areas in the region of Rio Claro and the located ones in the region of Ipeúna, but not between the areas of high and low heterogeneity. The analysis of the landscape in the scale of 600m showed that these two regions differ significantly as for the percentage of bush covering. This can, in part, to explain the difference found between the two regions, but not between areas of high and low heterogeneity. A very small number of bees were collected in the flowers... (Complete abstract click electronic access below)

Page generated in 0.0366 seconds