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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

The Effectiveness of Wildlife Corridors in Facilitating Connectivity: Assessment of a Model System from the Australian Wet Tropics

Horskins, Kerrilee January 2005 (has links)
Wildlife corridors have become a widely adopted management strategy for the conservation of species in fragmented habitats. Fragmentation reduces the size of habitat patches and increases the isolation of the populations within them, potentially resulting in extinction due to stochastic processes. The provision of a corridor between habitat patches is believed to increase the level of connectivity through the integration of populations into a single demographic unit, thus increasing the probability of survival. This assumption remains largely untested due to both a lack of investigation, and design limitations in some of the few studies performed. Connectivity is often assumed to occur simply from the presence of individuals within the corridor. Design criteria essential for the rigorous assessment of connectivity were identified and a landscape meeting these criteria selected. The vegetation within the corridor was found to be comparable in both structure and species composition to that of the patches that it connected. Two target species (Melomys cervinipes and Uromys caudimaculatus) were shown to occur along the corridor but not within the surrounding matrix. The combination of these factors indicated that the corridor was suitable for use as a model system and ensured that any subsequent results truly reflected the capacity of the corridor to function in the desired manner. The population structure was similar within the corridor and the connected patches for both species. Weights of individuals, sex ratios and the percentage of juveniles were consistent between the two system components, suggesting that the corridor contained breeding populations. Connectivity was therefore possible via generational gene flow for both species, while long distance movement events for U. caudimaculatus also indicated that direct movement between habitat patches may be possible for this larger species. Despite all ecological parameters indicating that connectivity was likely, genetic markers (mtDNA and nDNA) revealed significant population differentiation between the connected patches for both species. Populations linked by the corridor and those in isolated habitats were found to show the same level of genetic differentiation. Sampling at a finer spatial scale within connected patches and a continuous control habitat showed that population differentiation was common for M. cervinipes. Given the continuity of suitable vegetation, and the presence of individuals of breeding age along the corridor system, this was attributed to social structuring. U. caudimaculatus populations also showed evidence of genetic differentiation within a connected patch and along the corridor, despite panmixia within the continuous habitat. Having investigated a model system, the data from this study has implications for other wildlife corridor studies and for landscape managers. Firstly, the advantages of using an integrated ecological and genetic approach have been demonstrated. While genetic data determined the level of connectivity, the ecological data provided an understanding of the processes operating within the system. Secondly, the level of scale at which wildlife corridor studies are conducted may need addressing. Most studies currently treat a fragmented landscape in a binary manner and consider the connected patch to be the finest "grain". However, the processes responsible for the lack of connectivity were found to operate at the much finer within-patch scale. Finally, this study clearly indicated that not all wildlife corridors will provide connectivity between the connected populations and that connectivity cannot be inferred from the presence of individuals within the corridor. Given that social behaviour such as territorial defence and philopatry are common in many species, especially small mammals, a lack of connectivity via a wildlife corridor may be more common than currently assumed. The successful use of wildlife corridors as a management strategy, and the accurate assessment of their effectiveness therefore requires careful consideration of not only structural attributes of the corridor, but also behavioural, demographic and genetic parameters of the target species.
2

Projektet Livslinjen- världens längsta slåtteräng : En inventering med åtgärdsförslag för att gynna biologisk mångfald längs ett cykelstråk i en storstadskommun

Wedrén, Malin January 2015 (has links)
Den biologiska mångfalden har det senaste seklet utarmats i Sverige. Det beror till stor del på moderniseringen av jord- och skogsbruk som medfört drastiska habitatminskningar. En av de artrikaste biotoperna är den traditionellt hävdade slåtterängen. Projektet Livslinjen har initierats för att återskapa en sammanhängande slåtteräng genom en hel kommun. Den ska vara cykelbar med pedagogiska inslag för allmänheten och samtidigt fungera som en spridningskorridor för flora och fauna. Denna studie har inventerat örtskikt och övergripande struktur längs med tänkta sträcka. Utifrån de olika områdenas förutsättningar har åtgärder för restaurering och nyetablering föreslagits för att återskapa slåtterängslika miljöer samt generellt verka för en ökad biodiversitet. Merparten av det drygt 10 km långa stråket är präglad av kvävetillförsel och igenväxning. Några områden innehåller arter som indikerar slåtterängslika förhållanden. Äldre grova träd, sandiga marker, stenmurar och andra småbiotoper har noterats. Lämpliga skötselregimer måste implementeras på de flesta områdena. Ett estetiskt förhållningssätt bör finnas med i restaureringsprocessen speciellt i de urbana områdena. De ytor som huserar populationer av ängsvegetation måste fortsätta skötas med traditionella metoder för att kunna bevaras. Att starta med informationsförmedling till allmänheten i början av projektet är viktigt för att skapa förståelse. Uppföljning och nya inventeringar för att utvärdera effekterna av åtgärder tillråds. / Over the past century biodiversity has declined in Sweden as in all other western countries. Mainly due to modernization of agriculture and forestry which has resulted in drastic habitat losses for many species when rural areas have become less diverse and more fragmented. One of the most species-rich habitat is the traditional hay meadow. The Project Livslinjen (the “Lifeline”) has been initiated to re-create a coherent meadow trough a municipality. The public should be able to bike along it the whole way and it should also feature educational elements. At the same time, it should work as a wildlife corridor. In this study an inventory of forbes and the overall structure of the area is performed. This to identify potential actions to re-create meadow-like vegetation and generally increase biodiversity along the route. The study has found that the 10 km long route passes varied grounds with a city center in the middle. Most areas are influenced by nitrogen surplus and overgrowth. Though some areas hosts species that indicates meadow like conditions. Old large trees, sandy slopes, stonewalls and other microhabitats are noted as well. The initial stage of the restoration will focus on depleting nitrogen surpluses in the ground and selectively clear trees and shrubs. Appropriate management regimes must be implemented in most areas. An esthetics eye should be involved in the restoration process since it is recommended that biodiversity should not look untidy. Landscape variation should be a keyword in the process. Gradually, different parts of the route can start to be managed with traditional methods. Then active re-establishment of desirable species can commence. The areas which still house preserved meadow vegetation must continue to be managed accordingly. It is advised to commence with information to the public already at the start of the project to create understanding for what they see. Follow-ups and new inventories to evaluate the effects of measures is advised.
3

Predicting the Spatial Distribution of Forest Harvests in Mississippi from Landsat TM Data: Accuracy and Characterization

Jackson, Michael Bryan 30 April 2011 (has links)
Methods are needed to predict the spatial distribution pattern(s) of forest harvests to improve large-scale timber inventories through the incorporation of spatial distribution information. In this study, land cover type change detection methods were carried out using information from 1972 thru 2005 east-central Mississippi Landsat TM data to detect the spatial distribution of clearcut forest harvests. A random pattern was observed for clearcut harvests and this and other statistical data gathered in the study will be integrated into an existing forest inventory and transportation network database. The resulting harvested and forested area predictions generated by the database will assist with determining the sustainability and availability of forest resources for existing and future forest product mills and the creation of transportation networks needed to supply raw materials and distribute end products. Other implications include assessment of the quality and spatial components of wildlife habitat and a tool for forest certification programs.
4

Landscape Structure of Acacia-Commiphora Bushland in Southeastern Kenya

Mutiti, Christine Mango 28 July 2010 (has links)
No description available.
5

Trail Impacts on Movement in Wildlife Corridors: A Cleveland Metroparks Case Study

Escalambre, Michelle 10 July 2020 (has links)
No description available.

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