• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 21
  • 15
  • 2
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 53
  • 9
  • 8
  • 8
  • 7
  • 7
  • 7
  • 7
  • 6
  • 6
  • 6
  • 6
  • 5
  • 5
  • 5
  • 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.
21

Amphibian monitoring in Kakamega Forest, Kenya

Wairimu, Vincent Muchai January 2007 (has links)
Magister Scientiae (Biodiversity and Conservation Biology) / Since the late 1970 there has been increased concern of amphibian decline and extinction. Several causes for the worldwide declines have been suggested and include ultraviolet radiation, predation, pollution, climate change, diseases and habitat modification. To counter this, more research on the subject has been encouraged of which long term monitoring has been suggested as a research method. The study was conducted in Kakamega Forest in Kenya, which is the country's remnant of the once vast Guineo-Congolian forest. A rectangular transect whose sides measured 600 m in total was established and transect walks were carried out every two weeks for two consecutive days between 2002 and 2006. 24 species were targeted in the study and were sampled through VES and AES and data recorded in a GPS and later downloaded. In this study I examined the influence of rainfall, temperature, habitat and moon phases on the activity of frogs in Kakamega Forest. I also determined under which weather conditions sampling was more efficient. When monitoring was carried out by two observers I tested whether their data were similar. Data were analysed using non-parametric methods (Kruskal-wallis and Tukey test), species abundances analysed using EstimateS..Out of the 24 targeted species only 14 were recorded, with a total of 535 specimens being counted mostly at night. Most frogs in Kakamega Forest were more active in temperatures between 20 and 25oC. There was not much variation and there was no frog activity when the temperature was extremely high. There was rainfall throughout the year and there was no significant differences in the number of frogs counted in rainfall above 200 mm or below 200 mm. There was no significant difference in the number of specimens found in the different vegetation segments in the forest. More amphibians were caught under cloudy, rainy and clear conditions at night than under any weather condition during the day. During the day, more amphibians were caught during cloudy conditions than when it rained or when there was no cloud cover. There was no difference in catch among night conditions and there was no difference between clear and rainy days In Kakamega Forest, night is the best time to sample amphibians. In terms of weather it is best to sample when it is cloudy both during the day and at night. There were no differences in sampling abilities between two observers tested under similar weather conditions.
22

Environmental sustainability through participatory approaches : socio-geographic assessment of the Mathenjwa tribal authority landscape, Northern KwaZulu-Natal

Alexander, Patrick James 21 June 2013 (has links)
Development, environmental sustainability, agriculture and livelihoods are dimensions that are often considered antagonistic. By thinking at the landscape level however, innovative opportunities arise for simultaneity as these entities manifest spatially and require communication across disciplines. Trans-frontier Conservation Areas (TFCAs) embrace this thinking. These are large areas that cut across two or more international boundaries, include within them at least one Protected Area (PA) and other multiple resource use areas, including human dwellings and cultivated areas. Similarly, ecoagriculture is an innovative approach to land use management as it seeks to spatially synergise agriculture, livelihoods and biodiversity conservation across space and requires an awareness of landscape-level issues by land users, a condition which is not necessarily met. Such landscape thinking stems from the fact that if a piece of land is subject to rigorous conservation, it will fail if the surrounding areas are degraded. Additionally, it has been shown that agriculture often benefits from the nearby presence of natural areas for ecosystem services such as pollination, pest management, and erosion control. As such, multifunctional landscape mosaics together with small scale farmers, not large scale monocultures, are the key to global food security, as the former more effectively links agricultural intensification to hunger reduction. In order to ascertain an integrated understanding of the landscape concept, necessary for the formalisation of ecoagriculture, this study assessed the landscape perceptions and understandings held by local people residing within a TFCA. We employed participatory methods within the Mathenjwa Tribal Area (MTA), an area falling within the Lubombo TFCA and identified as holding ecoagriculture potential. Results revealed that local people perceive landscape as a function of subsistence utility. Local people perceive land-use multifunctionality, necessary for the formalisation of ecoagriculture, but at a smaller scale than expected depending on both social and biophysical interpretations. Landscape scale projects should incorporate local landscape understandings. / Dissertation (MA)--University of Pretoria, 2013. / Geography, Geoinformatics and Meteorology / MA / Unrestricted
23

Population estimation and landscape ecology of the Puerto Rican Nightjar

Gonzalez, Rafael 01 May 2010 (has links)
The Puerto Rican Nightjar Caprimulgus noctitherus is an endangered species found in forest of southern Puerto Rico. I documented density of nightjars in Guánica Forest, the region of Guayanilla-Peñuelas, and Susúa Forest. The geographic range of the species was expanded because of this study and presence documented in a number of new localities. Stand level habitat model indicated forest type and midstory visual obscurity best predicted nightjar habitat. Landscape model predicted considerably more suitable nightjar habitat exists than had been previously estimated (> 30%) and highlighted several areas of importance for the species. I evaluated nightjar population estimation techniques and found use of point transects with lures (playback) and moon phase covariates generated best estimates. My results highlighted several sites currently under private ownership that should be protected or acquired. Establishment of new protected areas for the nightjar represents highest priority for conservation and eventual delisting of the species.
24

Trends in Benthic Algal Community Response to a Small-Scale Gradient of Current Velocities Along a Streambed Transect

Song, Xiaozhao 25 June 2007 (has links)
No description available.
25

Spatial Analysis of Transect Zone and Land Surface Temperature: A Case Study on Hamilton County, Ohio

Jahan, Kazi Nusrat 24 October 2013 (has links)
No description available.
26

BUNDLE HEIGHTS VARIATION IN THE ANTERIOR AND POSTERIOR TRANSECTS OF TURTLE UTRICLE

Yi, Lin 30 September 2007 (has links)
No description available.
27

The Biodiversity Mirage: the Effects of Habitat Degradation and Exotic Predators on Ground-Dwelling Forest Birds, Tenrecs and Lemurs in Northeastern Madagascar

Murphy, Asia J. 03 June 2015 (has links)
Madagascar is one of the world's top conservation priorities due to the intense anthropogenic pressures on its diverse and endemic wildlife. There have been very few studies conducted in the largest protected area complex in Madagascar, the Masoala-Makira landscape (northeastern Madagascar). My goal was to examine the response of ground-dwelling forest birds, tenrecs (Lipotyphla: Tenrecidae) and lemurs to habitat degradation and the presence of exotic predators, and monitor population trends at resurveyed sites from 2008 to 2013. Using camera trap surveys and distance sampling, we observed 26 bird species (n = 4,083 observations), three spiny tenrec species (n = 244 observations) and 12 lemur species (n = 1,172 observations). Out of 13 focal species (seven bird, three tenrec and three lemur species), seven had higher point estimates of occupancy or density at intact forests when compared to intermediately degraded or degraded forest sites. Common tenrecs (Tenrec ecaudatus) and cathemeral lemurs changed their activity patterns, becoming more nocturnal in degraded forests. Feral cat (Felis sp.) trap success was negatively related to the detection of three bird species (red-breasted coua, Coua serriana; scaly ground-roller, Geobiastes squamiger; and Madagascar crested ibis, Lophotibis cristata). At two resurveyed sites (S02 and S05), out of 19 and 17 species, only four and eight species did not show consistent declines in occupancy or encounter rates, respectively, over a six-year period. This research highlights the urgent need for immediate conservation action in the Masoala-Makira protected area complex in order to protect one of the world's biodiversity hotspots. / Master of Science
28

Caractérisation et suivi des états de surfaces éolisés en Tunisie pré-saharienne : approches stationnelle et spatiale / Characterization and monitoring of surfaces prone to wind erosion in Southern Tunisia : site and space approaches

Bouzaida, Dalel 17 March 2012 (has links)
Suite aux changements climatiques, de nouveaux paysages reflétant les interactions entre les processus naturels et les activités humaines inappropriées sont apparus en Tunisie Méridionale. L’érosion éolienne en est l’une des manifestations les plus remarquables. Au cours de cette thèse, une méthodologie opérationnelle et validée (méthode du transect permanent) a été mise au point pour la caractérisation des états de surfaces éolisés et la quantification du bilan sédimentaire d’un transect d’environ 500m de longueur sur une période de deux ans. A l’échelle spatiale, la cartographie des Unités Eoliennes : zones de départ, transit et dépôt de sable a été élaborée. Un essai de caractérisation radiométrique des zones de dépôt ensablées a été ensuite tenté pour l’analyse diachronique des changements survenus durant plus de 35 ans. A l’échelle stationnelle, la méthode du transect permanent permet le calcul diachronique des bilans sédimentaires et la comparaison simultanée des changements des Complexes d’Etat de Surface. La seule observation des états de surface éolisés est insuffisante pour déterminer le fonctionnement éolien précis d’une région, elle induit à des erreurs d’interprétation sur les processus sédimentaires en cours.A l’échelle spatiale, les cartes des Unités Eoliennes permettent de déterminer la vulnérabilité du milieu face aux processus de déflation, transport et dépôt. De plus, la caractérisation des zones ensablées par des indices radiométriques n’est pas évidente avec des images de 30 m de résolution. Les analyses statistiques effectuées ont montré que l’indice de couleur est le plus indiqué pour ce genre d’étude. Le calcul des taux de changement entre deux images de dates successives permet d’estimer l’évolution temporelle des espaces ensablés et la distribution spatiale des zones nouvellement ensablées sur plus de 35 ans. / Under the effect of climate change, new landscapes reflecting the interactions between natural processes and human inappropriate activities appeared in Southern Tunisia. Wind erosion is one of the most important events. In this thesis, operational and validated methodology (the permanent transect method) has been developed for the characterization of Surfaces States and quantification of the sediment balance of a 500 m length transect over a period of two years. On spatial scale, mapping of the Aeolian units of deflation, transit and sand deposit was developed. Radiometric characterization of sand accumulations was then tried for the detection of changes that occurred within more than 35 years.At the site level, the permanent transect method enabeled the diachronic sedimentary balance calculation and the comparison of the Surface states changes. The single observation of these areas is insufficient to determine the real eolian process of a region ; moreover it induces to errors of interpretation on the sedimentary process.At the spatial scale, maps of the Aeolian units enabeled to determine the vulnerability of the environment to the process of deflation, transport and deposition. In addition, the characterization of sand accumulations by radiometric indices is not obvious within 30 m resolution images. The statistical analyses have shown that Color Index is the most indicated for this type of study. The calculation of the rates of change between two successive dates images allows to estimate the sandy spaces evolution and their spatial distribution for more than 35 years.
29

A New Method for Ground-Based Assessment of Farm Management Practices

Jeffrey T Bradford (11203395) 29 July 2021 (has links)
The research uses cameras mounted to a vehicle to capture geotagged images while conducting a transect survey. The images from two capture dates were manually classified into different classes of previous crop, tillage systems, residue cover, and cover crop utilization. The raw data was compared against the Indiana Cropland Transect Survey and the USDA-NASS Cropland Data Layer. The symmetric Kullback-Liebler divergence method was used to compared the distributions looking for similarities. <div><br></div><div>The manually classified data was then used to build satellite segmentation models using artificial neural networks , decision trees, k nearest neighbors, random forests, and support vector machine methods. The models were compared using overall accuracy, kappa coefficient, specificity, sensitivity, positive prediction value, and negative prediction value. The best model for each category of previous crop, tillage system, residue cover, and cover crop was used to segment a Sentenial-2 imagery downloaded from Copernicus Open Access hub. The results of the segment were compared by looking at the agreement at individual pixel locations from the segmented raster to the manually classified data and the Indiana Cropland Transect Survey. </div><div><br></div><div>Finally, all the images captured were used to being the development of a automated image classifier using nested convolutional neural networks (CNN). A small set of images was used to build the CNN. That model when then make prediction on new unclassified images. The predictions were manually checked. The check images were used to the to build the training and validation pools for the models. The first network divided the images into field or not field.</div><div>The second branch was field images divided in to images containing green growing plants of brown dead plants or residues. The final branch was determining the amount of surface cover left on a field. The results from each run of the training process were saved and used to assess model performance looking at accuracy and loss.</div>
30

Estimation Of Demography And Seasonal Habitat Use Patterns Of Anatolian Mouflon (ovis Gmelinii Anatolica) In Konya Bozdag Protection Area Using Distance Sampling

Ozdirek, Lutfiye 01 September 2009 (has links) (PDF)
The Anatolian mouflon (Ovis gmelinii anatolica) is an endemic ungulate subspecies and of IUCN Vulnerable status that inhabits Konya-Bozdag region located in Central Anatolia. In this thesis, the demography and habitat use of the only natural population of Anatolian mouflon at Konya-Bozdag Provice is studied. Throughout the study, distance sampling techniques, specifically line transect sampling, are used to estimate density, size and growth rate of this population. Sex, age and count data are used to estimate relevant parameters. Changes in population structure and seasonal area use are monitored for two years. Data is collected during repeated random line transects from May 2007 to July 2009. Line transect method is preferred since it requires less effort and is less expensive when compared to the complicated techniques that need animal marking or radio tagging. In total, 78 transect lines were surveyed during the time which covers 3 lambing periods. In spite of the paratuberculosis epidemics in the fenced area which has affected the population adversely in the previous years, a rather stable population trend is observed. The post-breeding population size in 2007, 2008 and 2009 were estimated to be 883+-241, 939+-136, 972+-243 (average+-satndard error) and densities as 27.227, and 28.186 individuals per sq km, respectively. Growth rate of population is found using the ratio of the population size estimates of consecutive years from 2007 to 2009, average 1.0495+-0.0203. Habitat use patterns of the Anatolian mouflon throughout the study period are investigated according to seasons and sex groups. There is sexual segregation in the Anatolian mouflon population in Konya Bozdag Province, with the females using the western part and males using the eastern part of Bagderesi. Seasonal patterns affect on the area use of animals, group formation and compositions and the relationship between them are searched throughout the study. The movements of the individuals and groups followed seasonal patterns as centers of activities changed according to seasons.

Page generated in 0.0659 seconds