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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.
81

Arctic Soils in a Warming Climate: Plot-scale Changes of CO2 Fluxes after Five Years of Experimental Warming.

Schröer, Cosima January 2020 (has links)
Terrestrial arctic ecosystems store large amounts of carbon (C). With global warming, this C might be released into the atmosphere as CO2 by stimulation of soil microbial degradation. At the same time, CO2 uptake in plants is enhanced, which might, in parts, offset CO2 losses. Yet, the future balance of these two contrasting feedbacks remain uncertain. This study aimed to better understand changes of input and output CO2 fluxes in an arctic tussock tundra ecosystem in response to global warming, with a special focus on the contrast between two sub-ecosystem habitats, the tussocks and the space between tussocks.  An experimental setup was used, where snow fences simulated winter warming by increasing snow depth, and open top chambers simulated summer warming. Daytime ecosystem respiration (ER), reflecting the outward CO2 flux, gross ecosystem production (GEP), reflecting the inward CO2 flux, and net ecosystem exchange (NEE), reflecting the net balance of both, were measured in the summer 2019 in the tussock and the intertussock habitat. In the tussock, both ER and GEP were as twice as high compared to the intertussock and increased with summer warming in a similar magnitude, resulting in an unchanged NEE. Fluxes in the intertussock were not altered with summer warming. Winter warming had no significant effects on ER and GEP in neither of the habitats. However, winter warming increased NEE and green biomass in the intertussock, indicating that in this habitat, plants benefit from warmer winter soil temperatures. Interaction effects of winter and summer warming underline the role of ecological processes outside the summer season, which are to date poorly understood. Contrasting responses of the two sub-ecosystem habitats highlight the challenges in predicting future C balances that are caused by small-scale spatial and temporal heterogeneity of C dynamics.
82

Exploring nature's benefits through tourism and eudaimonic well-being : a case study of the Jurassic Coast, Dorset

Willis, Cheryl Ann January 2013 (has links)
This research is concerned with advancing understanding of human-nature relationships and the ways in which people benefit from interactions with nature. This is important since economic accounts of the value of natural resources are most often used to determine priorities for action, leaving the more deep-felt and intangible ways that people experience and value nature largely excluded from decision making processes. The imperative to understand the more nuanced ways that people benefit from and value nature has gained traction in recent years most notably through high-profile analysis of natural resources which have made explicit their links to human well-being. This study aims to capture these wider values of the Jurassic Coast, Dorset and the ways in which it comes to resonate as significant and valuable to people. It uses both quantitative and qualitative techniques to gain rich insights into what this World Heritage Site really means to visitors and how experiences here underpin psychological well-being. A methodological innovation is presented in the human needs framework which is used to test the extent to which human needs thought to be important for psychological well-being are satisfied through interactions in the landscape. Moreover, it is hypothesised that this satisfaction leads to eudaimonic well-being which is concerned with positive psychological functioning and ‘flourishing’ (Ryan & Deci, 2001). This research has implications for tourism planning and management to ensure opportunities are created or maintained for human needs to be met in the landscape and for optimal visitor experiences to result. More widely, this research also has implications for understanding environmental value from a broad perspective and for using innovative methodologies to reveal these values, and to incorporate them in decision making processes in diverse policy areas.
83

Human behaviour and ecosystem services in sustainable farming landscapes : an agent-based model of socio-ecological systems

Guillem, Eléonore E. January 2012 (has links)
Agricultural areas represent around 40% of the earth surface and provide a variety of products and services essential to human societies. However, with policy reforms, market liberalisation and climate change issues, continuous land use and cover change (LUCC) brings uncertainty in the quantity and quality of ecosystem services supplied for the future generations. The processes of LUCC have been explored using top-down approaches at global and regional level but more recent methods have focused on agents’ interactions at smaller scale. This approach is better suited to understanding and modelling complex socio-ecological systems, which emerge from individual actions, and therefore for developing tools which improve policy effectiveness. In recent years, there has also been increasing interest in gaining more detailed understanding of the impacts of LUCC on the range of ecosystem services associated with different landscapes and farming practices. The objectives of this thesis are: 1/ to understand and model the internal processes of LUCC at local scale, i.e. farmer behaviour, 2/ to explore heterogeneous farmer decision making and the impacts it has on LUCC and on ecosystem services and 3/ to inform policy makers for improving the effectiveness of land-related policies. This thesis presents an agent-based modelling framework which integrates psycho-social models of heterogeneous farmer decisions and an ecological model of skylark breeding population. The model is applied to the Lunan, a small Scottish arable catchment, and is empirically-grounded using social surveys, i.e. phone interviews and choice-based conjoint experiments. Based on ecological attitudes and farming goals, three main types of farmer agents were generated: profit-oriented, multifunctionalist, traditionalist. The proportion of farmer types found within the survey was used to scale-up respondent results to the agent population, spatially distributed within a GIS-based representation of the catchment. Under three socio-economic scenarios, based on the IPCC-SRES framework, the three types of farmers maximise an utility function, which is disaggregated into economic, environmental and social preferences, and apply the farm strategy (i.e. land uses, management style, agri-environmental measures) that best satisfies them. Each type of agents demonstrates different reactions to market and policy pressures though farmers seem to be constrained by lack of financial opportunities and are therefore unable to fully comply with environmental and social goals. At the landscape level, the impacts on ecosystem services, in particular the skylark local population, depend strongly on policy objectives, which can be antagonist and create trade-offs in the provision of different services, and on farmer socio-environmental values. A set of policy recommendations is offered that encompasses the heterogeneity of farmer decision-making with the aim of meeting sustainable targets. Finally, further improvements of the conceptual and methodological framework are discussed.
84

Effectiveness of protected areas and implications for conservation of biodiversity and ecosystem services

Duran, America Paz January 2014 (has links)
Protected areas (PAs) are considered a key strategy to ensure the in situ persistence of biodiversity and the ecosystem services (ES) that this provides. The coverage of PAs has exponentially expanded in the last 25 years, and they now account for approximately 13% of the Earth's surface. Alongside this expansion, PA research literature has also increased seeking to identify and assess the main factors that influence the effectiveness of PAs in sheltering biodiversity and ES from anthropogenic pressures. Spatial distribution, spatial design, management strategy and threats, have been widely acknowledged as key factors. However, despite significant progress, several aspects of these factors remain poorly explored. This thesis aims to identify and address some of the gaps, which I detail below. The second chapter contributes to understanding of how the distribution of PAs affects the representation of biodiversity and ES. To this end, the Chilean PA system was used as a case study as this has never been previously assessed in terms of ES. I found that the strong bias in Chilean PAs distribution toward southern areas, which contain mainly ice and bare rock, hampers the PA system in achieving effective representativeness. The third and fourth chapters address some gaps in PA spatial design. The third assesses for the first time the spatial design of the global PA system and provides new methodologies to achieve this at such a large scale. Focusing on the size, shape, level of fragmentation, occurrence of buffer zones and proximity to the closest PA, I demonstrate that PAs tend to be small, irregularly shaped and fragmented. However, they are often close to one another and generally have buffer zones. Using the methodology generated on third chapter, I explicitly test in the fourth chapter the combined and interactive effects of PA spatial features on their ability to represent biodiversity, which has never been tested before. Using South America as a model for study I show that the spatial design largely explains biodiversity representation and that the interaction between spatial features affects the latter. The fifth chapter focuses on threats to PAs, assessing the extent to which metal mining activities represent an actual conflict with the global PA system. Evidence suggests that the global terrestrial PA system has been effective at displacing metal mining activities from within its bounds. However, given the high proportion of mines found in the close surroundings of PAs, and the distances over which mining activities can have influences, it is highly likely that the conservation performance of a significant proportion of PAs is being affected. So far I have demonstrated that PAs are not always optimally distributed and they can compete with other land uses, which can undermine their functionality. In this regard, in the final analytical chapter I explore how using spatial conservation prioritization (SCP) tools it is possible to optimize the representation of conservation features by minimizing competition with other land uses. Specifically, I assess the consequences for biodiversity and ES representation of incorporating land use trade-offs in SCP analyses. I show that the dichotomist decision of treating a land use as a trade-off or not can have enormous consequences on biodiversity and ES representation, and the implications of such decisions have to be considered before policy recommendations. This thesis shows that distribution, spatial design and threats play an important role in PA representativeness, and that SCP techniques can make a significant contribution to balancing biodiversity and ES conservation with human activities, when trade-offs are treated comprehensively. Finally, I discuss the importance of prioritising the interactions between, rather than just individual effects of, factors in order to optimise PA effectiveness and the distribution of scarce conservation resources.
85

What hope for the suffering ecosystems of our planet? : the contextualization of Christological perichoresis for the contemporary ecological crisis

Sahinidou, Ioanna January 2012 (has links)
No description available.
86

Getting engaged with Incubators : The Case of Startplatz

Stock, Ingmar January 2016 (has links)
In modern, fast moving business environments it is crucial for established corporations to find new sources of innovativeness in order to secure their competitiveness and long-term survival. Startups could be such a new source of innovativeness. Unfortunately, it is difficult for startups and corporations to cooperate. Mostly, this is because of the companies’ organization and the different way they operate. To overcome this gap, corporations started to get engaged with business incubators. Even though this phenomenon can be observed in practice already, little research has been done to better understand the forms this collaboration could have or the motives leading to such a cooperation. By studying an incubator that is engaged with established companies in many different ways, various forms of relationships could be identified. Moreover, based on the descriptions of those types of collaboration and in depth interviews, the motives leading corporations and incubators to get involved in various ways could be identified. The empirical contribution of this thesis is to better understand how established corporations can get engaged with entrepreneurial activity and startups in particular.
87

An exploration of new methods to assess energy availability in the English oak (Quercus robur)

Bracewell, Kathryn Vanessa January 2000 (has links)
No description available.
88

A soil-based assessment of the sustainability of a zero-input alternative to shifting cultivation in the tropical moist forest of Alto Beni, Bolivia

Robison, D. M. January 1987 (has links)
No description available.
89

Historical perspectives on the evolution and ecology of Hawaiian birds : part I: phylogeny of the Hawaiian finches (Fringillidae: Drepanidini); part II: palaeoecology of terrestrial communities

James, Helen Frances January 1998 (has links)
No description available.
90

Intensive agriculture to semi-natural grassland : evaluating changes in ecosystem service provision to help determine costs and benefits of agri-environment schemes

Horrocks, Claire Alice January 2013 (has links)
Intensive agriculture has led to an increase in production; however this has often coincided with a decline in the provision of other Ecosystem Services (ES). ES affected include those regulated by soil chemical, physical and biological properties such as biodiversity provision and the regulation of nutrient cycling, water quality and rates of greenhouse gas emissions. A growing awareness of the value of nonproduction ES to human health and wellbeing has encouraged the funding of agrienvironment schemes in the UK, through which farmers receive funding to alter management practices to increase the provision of certain ES. One particular management change encouraged through agricultural payments is the creation of species rich grassland (SRG) on former intensively managed (IM) arable or grassland sites. Under these schemes farmers are required to carry out an extensification of management practices by reducing or ceasing fertiliser application, grazing and cultivation, or removing the existing crop or sward and sowing a specified seed mix of desired grassland species. Despite the commitment of substantial sums of money and land to extensification schemes, there has been little research into the extent to which they enhance provision of multiple ES and the potential for the legacy of intensive agriculture to limit ES provision and greatly reduce the value of extensification. This study aimed to: 1) compare soil properties between sites remaining under intensive management and those that had undergone extensification; 2) relate soil properties to; fluxes of the greenhouse gas nitrous oxide (N2O), plant diversity, soil microbial diversity and concentrations of nutrients in leachate from intensively and extensively managed sites in order to determine potential benefits of extensification. Paired field plots were established on working farms in south east Scotland and at Rothamsted Research North Wyke in south west England. Each of the four plot pairs in Scotland consisted of a newly created SRG on former arable land and an adjacent IM plot. The SRG plots ranged in age from 3 to nine years old in 2010. Soil samples were collected from the Scottish sites twice yearly in 2010 and 2011, alongside regular measurements of N2O fluxes from soil and assessment of plant diversity. At North Wyke four replicated SRG plots, forming part of an existing experiment on former intensive grassland, were each paired with an IM plot. Soil samples were analysed for their chemical and physical properties and for the concentration of certain phospholipid derived fatty acids (PLFA) biomarkers to compare the composition and size of the soil microbial community. Soil N2O fluxes and the nitrogen (N) and phosphorus (P) concentrations of soil water samples measured in 2010 and 2011. Results from more intensive N2O flux measurements, conducted in 2012, were compared to model output from the UK-DNDC model to assess its potential for predicting changes in N2O emissions following extensification. No significant difference was found in any soil chemical or physical properties between paired IM and SRG plots in Scotland, although soil bulk density tended to be lower in the older SRG plots relative to the paired IM plots. Nitrous oxide emissions were low from all plots with only an occasional emissions peak being recorded and overall there was no significant effect of management intensity on soil N2O fluxes. The UK-DNDC model outputs were generally of a similar order of magnitude but poorly correlated with measured N2O fluxes and soil water and available N content. Botanical diversity was enhanced in the SRGs compared to the IM plots, though plant species were mostly of low conservation value and indicative of a high nutrient environment and the diversity of the SRG plots was low, compared to long-established semi-natural grassland elsewhere in Europe. Total soil PLFA concentration was significantly higher in the IM plots but the fungal concentration and the ratio of Gram positive:Gram negative bacteria were no greater in the SRG, suggesting it had begun to resemble long-term unimproved grassland. Despite limited success at obtaining soil water samples, at North Wyke concentrations of mineral N in soil water were lower from the SRG plots than the IM plots, although there were no consistent differences in total P or organic N concentrations, organic N contributed over 80% of the total N in soil water samples from the SRG plots. This study has shown that the legacy of intensive agriculture continues to affect soil properties for at least 10 years following extensification. The results suggest that the potential for newly created SRGs to provide enhanced ES’ could be limited and may not justify the reduction in productivity and the financial input associated with shortterm extensification schemes.

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