• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1235
  • 323
  • 157
  • 112
  • 73
  • 40
  • 18
  • 15
  • 15
  • 13
  • 12
  • 11
  • 9
  • 8
  • 7
  • Tagged with
  • 2423
  • 707
  • 517
  • 422
  • 422
  • 249
  • 245
  • 216
  • 203
  • 198
  • 177
  • 160
  • 157
  • 157
  • 153
  • 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.
131

Functional attributes of biodiversity in decomposer communities

Dickens, Helen Elizabeth January 2000 (has links)
No description available.
132

Stakeholder process within limestonequarrying and potential impacts onbiodiversity and ecosystem services. Case study of Bunge Ducker,Northern Gotland, Sweden

Shirnina, Elena January 2014 (has links)
Mining has always played an important role in human development. The growing demand for miningnowadays puts under threat biodiversity and ecosystem services, which leads to many conflicts based on choicebetween environment protection and social and economical development. Studying a case of a limestone quarryon Northern Gotland as one of the most representative cases of such conflict, gave an opportunity to investigateand analyze the cost of the decision-making in mining as well as interaction between stakeholders affecting andbeing affected by the decision from the perspective of the group opposing to mining. The research showedweakness of communication between the stakeholders; the weakness of the argument supporting social andeconomical development and giving it higher priority than the environment; and the best possible solution whichwould be turning the whole area of interest into a national park, even though such solution would not fulfilltheinterests of the mining company.
133

Ekosystemstödjande och multifunktionella växtval i urban miljö : En fallstudie med utgångspunkt i Nacka stadsbildning

Åshage, Anna January 2014 (has links)
This study has investigated how urban vegetation can be used in a multifunctional way to support ecosystem services in urban environments. Nacka municipality is in the start-up phase of building what is to become Nacka city. This provides a unique possibility to study and analyse what role the vegetation play in making the city a healthy living environment and how it needs to be adapted in order to be resilient against changing climate conditions and how the effects of those changes can be regulated. The study further investigates how airborne pollution, caused by urbanization processes, can be regulated or reduced by vegetation or species selection. Methods used in this study were a combination of qualitative interviews and literature studies, seeking to answer the questions: Which specific ecosystem functions are needed in the urban environment and which aspects will influence the ecosystems ability to deliver the functions in demand? And which plant species have the right mechanisms needed to deliver those functions? These questions have been studied and analysed in a local based context where the local conditions ands site specific needs of Nacka define criteria for plant selection. Based on those criteria, a plant list is presented that seeks to find synergies and effectiveness in plant selection with the aim to find plants that support and/or produce multiple ecosystem functions.
134

Interdisciplinarity in ecosystem management

Pujadas Botey, Anna 11 1900 (has links)
Global environmental deterioration demands the involvement of the academic community. Ecosystem management is a discipline within ecology that is especially concerned about doing interdisciplinary research in order to solve environmental problems. However, it is not clear what interdisciplinary work means, what its purpose is, and how it is practiced among ecosystem management researchers. The research presented in this dissertation has the goal of understanding ecosystem management researchers perspectives and practices concerning interdisciplinarity. It uses a pragmatic framework and a sequential mixed-methods research design to accomplish three particular objectives. First, it investigates the use of the term interdisciplinarity in the ecosystem management literature by evaluating citations and abstracts of 129 peer-reviewed, English language, journal articles via bibliometric analysis. Second, it explores the definition of interdisciplinarity among ecosystem management researchers by surveying 119 individuals using on-line questionnaires. Finally, it examines interdisciplinary perspectives among ecosystem management researchers by interviewing 15 key informants using semi-structured telephone interviews. Results show that ecosystem management researchers share a common understanding of what interdisciplinarity is. However, they are not especially concerned about discussing theoretical considerations of the concept of interdisciplinarity and its practice. In the context of the opportunities and challenges interdisciplinary work presents for the ecosystem management field, the research discusses the role of a deeper engagement with theories of interdisciplinarity. It encourages theoretical discussions of interdisciplinary work among ecosystem management researchers in order to enhance effective interdisciplinary research efforts and promote further contributions of ecosystem management to solving environmental problems.
135

The evolution of the latitudinal gradient in species richness

Cardillo, M. Unknown Date (has links)
No description available.
136

Using models to explore copper bioaccumulation in the Sydney Rock Oyster (Saccostrea glomerata) in a large coastal embayment

Russell Geoffrey Richards Unknown Date (has links)
No description available.
137

Soft systems analysis of ecosystems

Shanmuganathan, Subana Unknown Date (has links)
This research is a case study evaluation of the use of self-organising map (SOM) techniques for ecosystem modelling to overcome the perceived inadequacies with conventional ecological data analysis methods. SOMs provide an analytical method within the connectionist paradigms of artificial neural networks (ANNs), developed from concepts that evolved from late twentieth century neuro-physiological experiments on the cortex cells of the human brain. The rate and extent at which humans influence environmental deterioration with commensurate biodiversity loss is a cause for major concern and to prevent further degradation by human impact, parsimonious models are urgently needed. Indeed, the need for better modelling techniques has never been so great. Ecologists and many national and international bodies see the situation as 'significantly critical' for the conservation of our global ecosystem to foster the continued wellbeing of humanity on this earth.The thesis investigates and further refines SOM based exploratory data analysis methods for modelling naturally evolving, highly diverse and extremely complex ecosystems. Earlier studies provide evidence on SOM ability to analyse complex forest and freshwater biological community structures at limited scales. On the other hand, growing concerns over conventional methods, their soundness and ability to model large volumes of data are seen as of little use, leading to arguments on the results derived from them. Case study chapters illustrate how SOM methods could be best applied to analyse often 'cryptic' ecosystems in a manner similar to that applied in modelling highly complex and diverse industrial system dynamics. Furthermore, SOM based data clustering methods, used for financial data analysis are investigated for integrated analysis of ecological and economic system data to study the effects of urbanisation on natural habitats.SOM approaches prove to be an excellent tool for analysing the changes within physical system variables and their effects on the biological systems analysed. The Long Bay-Okura Marine Reserve case study elaborates on how SOM based approaches could be best applied to model the reserve's intertidal zone with available numeric data. SOM maps depicted the characteristic microclimate within this zone from ecological monitoring data of physical attributes, without any geographical data being added. This kind of feature extraction from raw data is found to be useful and is applied to two more case studies to study the slow variables of ecosystems, such as population dynamics, and to establish their correlation with environmental variations. SOM maps are found to be capable of distinguishing the human induced variations from that of natural/ global variations, at different scales (site, regional and global) and levels using regional and global data. Hence, SOM approaches prove to be capable of modelling complex natural systems incorporating their spatial and temporal variations using the available monitoring data, this is a major advantage observed with SOM analyses.In the third case study, potential use of SOM techniques to analyse global trends on the effects of urbanisation in environmental and biological systems are explored using the World Bank's statistical data for different countries. Many state and international institutions, concerned over global environmental issues, have made attempts to develop indicators to assess the conditions of different ecosystems. The enhancements with SOM approaches against the currently recommended indicator system based on information pyramid and pressure-state-response (PSR) models are elaborated upon.The research results of SOM methods for ecosystem modelling, similar to that applied to industrial process modelling and financial system analysis show potential. SOM approaches (i.e. cluster, dependent component, decision system and trajectories/ time series analyses) provide a means for feature extraction from the available numeric data at different levels and scales, fulfilling the urgent need for modelling tools to conserve our global ecosystem. They can be used to bridge the gap in converting raw data into knowledge to inform sustainable ecosystem management. Increasingly, traditional methods based on Before-After-Control-Impact (BACI) designs and Analysis of Variance (ANOVA) are seen to be unsuitable for ecological data analysis, as they are unable to detect human induced environmental impacts from that of a natural cause. This thesis proves that SOM techniques could be applied to modelling not only a natural systems complexity but also its functioning and dynamics, incorporating spatial as well as temporal variations, to overcome the constraints with conventional methods as applied in other stated disciplines.
138

Using models to explore copper bioaccumulation in the Sydney Rock Oyster (Saccostrea glomerata) in a large coastal embayment

Russell Geoffrey Richards Unknown Date (has links)
No description available.
139

Agricultural intensification and ecosystem function in a brigalow (Acacia harpophylla)landscape: implications for ecosystem services

Collard, Stuart J. January 2007 (has links)
[Abstract]: Agricultural intensification, involving habitat fragmentation and modification, typically leads to a decline in biodiversity and ecosystem function. While most studies concentrate on remnant patches, the less intensively managed components of agricultural landscapes may also provide biodiversity values and ecosystem services. This study examines the contribution of different categories of land management to biodiversity and ecosystem function along a gradient of agricultural intensification. Differences within these land management categories are also examined. Research results are interpreted in the broad context of ecosystem services and their resilience in agro-ecosystems.
140

Ecology and Hydrology of a Threatened Groundwater-Dependent Ecosystem:The Jewel Cave Karst System in Western Australia

Stefan@calm.wa.gov.au, Stefan Eberhard January 2004 (has links)
Groundwater is a significant component of the world's water balance and accounts for >90 % of usable freshwater. Around the world groundwater is an important source of water for major cities, towns, industries, agriculture and forestry. Groundwater plays a role in the ecological processes and 'health' of many surface ecosystems, and is the critical habitat for subterranean aquatic animals (stygofauna). Over-abstraction or contamination of groundwater resources may imperil the survival of stygofauna and other groundwater-dependent ecosystems (GDEs). In two karst areas in Western Australia (Yanchep and Leeuwin-Naturaliste Ridge), rich stygofauna communities occur in cave waters containing submerged tree roots. These aquatic root mat communities were listed as critically endangered because of declining groundwater levels, presumably caused by lower rainfall, groundwater abstraction, and/or forest plantations. Investigation of the hydrology and ecology of the cave systems was considered essential for the conservation and recovery of these threatened ecological communities (TECs). This thesis investigated the hydrology and ecology of one of the TECs, located in the Jewel Cave karst system in the Leeuwin-Naturaliste Ridge. A multi-disciplinary approach was used to explore aspects pertinent to the hydrology and ecology of the groundwater system. Thermoluminescence dating of the limestone suggested that development of the karst system dates from the Early Pleistocene and that caves have been available for colonisation by groundwater fauna since that time. Speleogenesis of the watertable maze caves occurred in a flank margin setting during earlier periods of wetter climate and/or elevated base levels. Field mapping and leveling were used to determine hydrologic relationships between caves and the boundaries of the karst aquifer. Monitoring of groundwater levels was undertaken to characterise the conditions of recharge, storage, flow and discharge. A hydrogeologic model of the karst system was developed. The groundwater hydrograph for the last 50 years was reconstructed from old photographs and records whilst radiometric dating and leveling of stratigraphic horizons enabled reconstruction of a history of watertable fluctuations spanning the Holocene to Late Pleistocene. The watertable fluctuations over the previous 50 years did not exceed the range of fluctuations experienced in the Quaternary history, including a period 11,000 to 13,000 years ago when the watertable was lower than the present level. The recent groundwater decline in Jewel Cave was not reflected in the annual rainfall trend, which was above average during the period (1 976 to 1988) when the major drop in water levels occurred. Groundwater abstraction and tree plantations in nearby catchments have not contributed to the groundwater decline as previously suggested. The period of major watertable decline coincided with a substantial reduction in fire frequency within the karst catchment. The resultant increase in understorey vegetation and ground litter may have contributed to a reduction in groundwater recharge, through increased evapotranspiration and interception of rainfall. To better understand the relationships between rainfall, vegetation and fire and their effects on groundwater recharge, an experiment is proposed that involves a prescribed burn of the cave catchment with before-after monitoring of rainfall, leaf-area, ground litter, soil moisture, vadose infiltration and groundwater levels. Molecular genetic techniques (allozyrne electrophoresis and mitochondria1 DNA) were used to assess the species and population boundaries of two genera and species of cave dwelling Amphipoda. Populations of both species were largely panrnictic which was consistent with the hydrogeologic model. The molecular data supported the conclusion that both species of amphipod have survived lower watertable levels experienced in the caves during the Late Pleistocene. A mechanism for the colonization and isolation of populations in caves is proposed. Multi Dimensional Scaling was used to investigate patterns in groundwater biodiversity including species diversity, species assemblages, habitat associations and biogeography. Faunal patterns were related to abiotic environmental parameters. Investigation of hydrochemistry and water quality characterized the ecological water requirements (EWR) of the TEC and established a baseline against which to evaluate potential impacts such as groundwater pollution. The conservation status of the listed TEC was significantly improved by increasing the number of known occurrences and distribution range of the community (from 10 m2 to > 2 x lo6 m2), and by showing that earlier perceived threatening processes (rainfall decline, groundwater pumping, tree plantations) were either ameliorated or inoperative within this catchment. The GDE in the Jewel Cave karst system may not have been endangered by the major phase of watertable decline experienced 1975-1987, or by the relatively stable level experienced up until 2000. However, if the present trend of declining rainfall in southwest Wester,,Australia continues, and the cave watertable declines > 0.5 m below the present level, then the GDE may become more vulnerable to extinction. The occurrence and distribution of aquatic root mat communities and related groundwater fauna in other karst catchments in the Leeuwin-Naturaliste Ridge is substantially greater than previously thought, however some of these are predicted to be threatened by groundwater pumping and pollution associated with increasing urban and rural developments. The taxonomy of most stygofauna taxa and the distribution of root mat communities is too poorly known to enable proper assessment of their conservation requirements. A regional-scale survey of stygofauna in southwest Western Australia is required to address this problem. In the interim, conservation actions for the listed TECs need to be focused at the most appropriate spatial scale, which is the karst drainage system and catchment area. Conservation of GDEs in Western Australia will benefit fi-om understanding and integration with abiotic groundwater system processes, especially hydrogeologic and geomorphic processes.

Page generated in 0.0301 seconds