• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 148
  • 33
  • 7
  • 7
  • 7
  • 6
  • 5
  • Tagged with
  • 232
  • 232
  • 48
  • 41
  • 38
  • 31
  • 29
  • 28
  • 28
  • 27
  • 27
  • 24
  • 22
  • 22
  • 17
  • 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.
201

Root morphology, photosynthesis, water relations and development of jarrah (Eucalyptus marginata) in response to soil constraints at restores bauxite mines in south-western Australia

Szota, Christopher January 2009 (has links)
Bauxite mining is a major activity in the jarrah (Eucalyptus marginata Donn ex Sm.) forest of south-western Australia. After mining, poor tree growth can occur in some areas. This thesis aimed to determine whether soil constraints, including reduced depth and compaction, were responsible for poor tree growth at low-quality restored bauxite mines. In particular, this study determined the response of jarrah root morphology, leaf-scale physiology and growth/development to soil constraints at two contrasting (low-quality and high-quality) restored bauxite-mine sites. Jarrah root excavations at a low-quality restored site revealed that deep-ripping equipment failed to penetrate the cemented lateritic subsoil, causing coarse roots to be restricted to the top 0.5 m of the soil profile, resulting in fewer and smaller jarrah trees. An adjacent area within the same mine pit (high-quality site) had a kaolinitic clay subsoil, which coarse roots were able to penetrate to the average ripping depth of 1.5 m. Impenetrable subsoil prevented development of taproots at the low-quality site, with trees instead producing multiple lateral and sinker roots. Trees in riplines, made by deep-ripping, at the high-quality site accessed the subsoil via a major taproot, while those on crests developed large lateral and sinker roots. Bauxite mining is a major activity in the jarrah (Eucalyptus marginata Donn ex Sm.) forest of south-western Australia. After mining, poor tree growth can occur in some areas. This thesis aimed to determine whether soil constraints, including reduced depth and compaction, were responsible for poor tree growth at low-quality restored bauxite mines. In particular, this study determined the response of jarrah root morphology, leaf-scale physiology and growth/development to soil constraints at two contrasting (low-quality and high-quality) restored bauxite-mine sites. Jarrah root excavations at a low-quality restored site revealed that deep-ripping equipment failed to penetrate the cemented lateritic subsoil, causing coarse roots to be restricted to the top 0.5 m of the soil profile, resulting in fewer and smaller jarrah trees. An adjacent area within the same mine pit (high-quality site) had a kaolinitic clay subsoil, which coarse roots were able to penetrate to the average ripping depth of 1.5 m. Impenetrable subsoil prevented development of taproots at the low-quality site, with trees instead producing multiple lateral and sinker roots. Trees in riplines, made by deep-ripping, at the high-quality site accessed the subsoil via a major taproot, while those on crests developed large lateral and sinker roots.
202

Local adaptation and genetic variation in south-western Australian forest trees : implications for restoration

O'Brien, Eleanor K January 2007 (has links)
[Truncated abstract] Spatial structuring of genetic variation is commonly observed in plant species due to limited dispersal and local adaptation. Intraspecific genetic variation has significant implications for ecological restoration because the source of seed or plants influences patterns of gene flow, and may affect performance if there is adaptive divergence among source populations. This study assessed quantitative trait variation, local adaptation and molecular variation within three common, widespread, long-lived forest tree species from south-western Australia to understand the distribution of intraspecific genetic variation and predict the consequences of seed transfer for restoration. The geographic distribution of quantitative trait variation of jarrah Eucalyptus marginata was assessed through measurement of 15-year-old trees grown in a provenance trial. Survival of trees from the northern jarrah forest was significantly higher than that of trees from southern jarrah forest provenances, where mean annual rainfall is much higher, but stem diameter at breast height (d.b.h.) of southern jarrah forest trees was greater, implying faster growth. D.b.h. of trees from within the northern jarrah forest also exhibited a positive relationship with mean annual rainfall, with maximum d.b.h. observed in trees from provenances in the high rainfall zone. These patterns may reflect selection for faster growth under high rainfall conditions or environmentally-induced parental effects. The percentage of trees bearing buds and flowers varied among latitudinal divisions. ... Neither genetic variation within nor among populations of any species could explain variation of emergence and establishment in reciprocal transplant trials. Collectively, the findings of this study suggest structuring of genetic variation in these species at a broad, rather than a very local, scale. This is expected for widespread, long-lived species, where extensive gene flow and temporal variation are likely to favour high within, relative to among, population genetic variation. However, there is evidence that the source of seed may have a significant influence on the success of restoration of these species, whether as a result of genetic variation among populations or due to other factors affecting seed quality. These results highlight the importance of integrating studies of molecular and adaptive trait variation when seeking to understand the causes and consequences of genetic variation within plant species and contribute to the development of seed sourcing practices for improved restoration success.
203

The effect of different management strategies on the dynamics of saproxylic insect habitats

ŠEBEK, Pavel January 2016 (has links)
The thesis concerns studies on habitats utilized by insects associated with deadwood. It presents a review of current issues in the conservation of saproxylic biodiversity. The effects of active intervention on temperate lowland woodland habitats, such as pollarding or coppicing, are evaluated in terms of their suitability for saproxylic communities and other groups. Further, the importance of open-grown trees for saproxylic diversity is assessed.
204

Geomorphic response to restoration and disturbance: Grazing, fire, and flooding on the Middle Fork John Day River, OR / Grazing, fire, and flooding on the Middle Fork John Day River, OR

Michelsen-Correa, Stephani 03 1900 (has links)
xii, 64 p. : ill. (some col.), maps / Salmon habitat restoration is ongoing at a Nature Conservancy preserve on the Middle Fork John Day River in the Columbia River Basin in north-central Oregon. The site has a long history of disturbance including dredge mining upstream, channelization, grazing, logging, fire, and floods. Using historic aerial photos, habitat unit surveys, and cross sectional profiles, this thesis shows how the channel morphology, particularly habitat unit diversity, has changed since 1939, just before placer mining began. Results show that the dominant influence on present day channel morphology is channelization from the 1930's. Other changes including dredge mining in the late 1930's to early 1940's, cessation of cattle grazing in 1991, and a fire followed by a flood in the winter of 1996-1997, had less impact because of the straightened, stabilized channel morphology. / Committee in charge: Patricia McDowell, Chairperson; W. Andrew Marcus, Member / 10000-01-01
205

Planejamento ambiental da bacia hidrográfica do Rio Guapi-Macacu: estudo da paisagem e qualidade ecológica / Environmental planning river basin Guapi-Macacu, RJ: study of landscape and ecological quality

Andréa Franco de Oliveira 01 July 2011 (has links)
Os estudos de relação entre a paisagem e a água doce vêm sendo aprofundados pela comunidade científica e pelos propositores de políticas públicas, principalmente, para atender às demandas sobre as maneiras que este sistema ambiental pode ser alterado e na identificação das implicações políticas e ecológicas destas mudanças. Quanto mais se torna intenso e diversificado o uso dos corpos hídricos e da paisagem em bacias hidrográficas maior é a necessidade de se definir formas de planejamento, gerenciamento e gestão ecológica desses ecossistemas. O completo entendimento do funcionamento e dos processos ecológicos que ocorrem em uma bacia hidrográfica exige conhecimento simultâneo de seus sistemas aquáticos e terrestres, da biodiversidade, da fisiografia, da geologia e de sua conservação, temporal e espacial. Este entendimento e conhecimento da área de interesse são vitais para proposições de instrumentos ambientais legais, como Unidades de Conservação (UCs). É muito importante que a fundamentação destas propostas tenha como eixo principal o funcionamento dos ecossistemas e das paisagens, de forma a garantir uma maior conectividade e integração entre água (doce, salobra e salgada) e terra, e seus múltiplos usos. A presente tese foi desenvolvida com base neste contexto, apresentando e aplicando metodologias integradoras, seja na ecologia de paisagem (EP), seja na relação entre os ambientes dulcícola e terrestre. O objetivo principal deste trabalho foi o desenvolvimento de processos para planejamento ambiental em BHs, através do diagnóstico, compreensão e análise do funcionamento e dinâmica da paisagem e de ecossistemas de rios e córregos, apoiados no uso de geotecnologias. De acordo com os resultados obtidos, a BHGM ocupa uma área de 1260,36 km e 204,69 km de perímetro. É uma bacia com forma mais alongada que circular (KC = 1,6144e IC =0,4747 km/km) que indica uma menor susceptibilidade a enchentes em condições normais de precipitação exceto em eventos de intensidades anômalas. O mapeamento base (2007) realizado indicou que a bacia possuía 34,86% de uso antrópico e 64,04 % de remanescente florestal. Os dados de fitofisionomia potencial indicaram predominância da classe Florestas Ombrófila Densa Submontana (40%) e de Terras Baixas (39%). Foram estabelecidas para bacia 269 unidades de paisagem (integração da geomorfologia, geologia, fitofisionomia e uso da terra e cobertura vegetal (2007)) que junto com os dados de métrica de paisagem constituíram a proposta integrativa da tese para ecologia de paisagem. Em relação à qualidade ambiental foram adotados o índice de avaliação visual (IAV), o índice multimétrico físico-químico bacteriológico e o índice biótico estendido (IBE). A comparação entre estes índices demonstrou a confirmação entre os seus resultados para a maioria dos pontos amostrados nas áreas de referência e de pelo menos dois índices para os pontos intermediários e impactados. Foram propostos também dois cenários para a bacia: um considerando as condicionantes e medidas compensatórias vinculadas à licença prévia do complexo petroquímico do Estado do Rio de Janeiro (COMPERJ); e outro, sem considerar estas condições. O primeiro indicou a realização da restauração ecológica, seguindo as diretrizes do mapa síntese, integrada para restauração da paisagem. / Studies about relation between landscape and freshwater have been enhanced by the scientific community as by the proponents of public policies, in order to meet the demands generated from the discussion on the ways this environmental system can be modified and the identification of political and ecological implications of these changes. The stronger and more diversified uses of watercourses and landscape in their watersheds, the greater the need to define ways of planning, supervision and ecological management of these ecosystems. The complete understanding of the functioning and ecological processes that occur in a watershed requires simultaneous knowledge of their aquatic and terrestrial systems, biodiversity, physiography, geology as temporal and spatial preservation. Knowledge and understanding on the area of interest is vital for proposals of environmental legal instruments, such as Protected Areas (UCs1). It is preeminent that the rationale of these proposals has as its main axis ecosystems and landscapes functioning in order to ensure greater integration and connectivity between water (freshwater, brackish and saltwater) and land in its multiple uses. This thesis has been developed based on this context, proposing and implementing integrative methodologies, whether in landscape ecology (EP) or the interrelation between the freshwater and terrestrial environments. The study main objective was the development of processes for environmental planning in BHs by diagnosing, understanding and analyzing the landscape and ecosystems of rivers and streams functioning and dynamics, supported by geotechnologies. According to gathered results, BHGM occupies an area of 1260.36 km with 204.69 km of perimeter. It is a more oblong than circular basin (KC = 1.6144 and IC = 0.4747 km / km) indicating a lower susceptibility to flooding during normal rainfall events, except in anomalous intensities. The base mapping conducted indicated that the basin had 34.86% of anthropic use and 64.04% of remaining forest. The data indicated a predominance of the potential vegetation type of dense umbrageous sub-montane rain forest class (40%) and lowlands class (39%). There has been established 269 units for basin landscape which represents the data integration with geomorphology, geology, vegetation type and land use, and vegetation co ver (base year) which joined to the landscape metrics data formed the integrative thesis proposal for ecology landscape. This has been used as a planning tool in the proposition of ecological corridors and areas for potential sampling water quality in the basin. Regarding the environmental quality index were adopted visual rate index (IAV), the physical-chemical bacteriological multimetric index and biotic extended index (IBE). The comparison among indexes have confirmed results for most points showed in the reference areas, and at least for two indexes on intermediate and impacted points. There have also been proposed two scenarios for the basin, one considering conditions and compensatory measures concerned to the prior license for the petrochemical complex of the State of Rio de Janeiro (COMPERJ) and other without any consideration of the above mentioned. The first indicated the completion of restoration projects following the guidelines of the synthesis map for integrated landscape restoration.
206

Porovnání diverzity spontánně zarostlých a technicky rekultivovaných výsypek na Mostecku / The comparison of diversity on spontaneously re-vegetated and technically reclamed dumps from coal mining in the Most region

MÁLKOVÁ, Lucie January 2011 (has links)
Sites left to spontaneous vegetation succession and those technically reclamed were studied and compared on dumps in the Most Region, NW Czech Republic. Data were sampled in summer 2008 and 2010. Species composition and species diversity were analyzed using phytosociological reléves arranged along 100m transects. Alfa- and beta-diversity were evaluated. There were significant differences between sites in alfadiversity. Beta-diversity was highest in the spontaneously re-vegetated sites. There were also differences in species composition among the studied sites. I consider using spontaneous succession as appropriate in restoration of land disturbed by brown coal mining. It is a good alternative to expensive technical reclamation.
207

Studies on dune rehabilitation techniques for mined areas at Richards Bay, Natal

Moll, John Bingham January 1993 (has links)
Rehabilitation is a dynamic process influenced by factors related to more than one field of ecology. It is therefore necessary to consider all these components when assessing the rehabilitation, although in the initial stages the successful revegetation of the disturbed areas is the most important criterion. Richards Bay Minerals, on whose mining site this project was carried out, is dredge mining heavy minerals on the north coast of Natal, where they have rehabilitated mined areas since 1978. This project has been carried out to establish: 1) The success of their dune forest rehabilitation using quantitative techniques. 2) The available seed bank in their rehabilitation stands. 3) The similarities in the succession taking place in rehabilitation stands compared to the revegetated stands in the vicinity of Richards Bay. 4) The best methods for creating alternative vegetation communities, especially grasslands, with a high species diversity on the mined tailings. This study reviews only the success of rehabilitation of the natural vegetation but other studies focusing on the insect, reptile, mammal and bird populations are also being undertaken by other researchers. No particular method of determining the success of vegetation rehabilitation has been chosen by restoration ecologists. Therefore in this study a broad range of quantitative techniques were used to show whether successional changes are occurring in the vegetation and physical environment. The results obtained from sampling the rehabilitated vegetation have shown that both the species richness and diversity are increasing as the returned vegetation matures. Levels of soil properties such as Sodium, Phosphate, Calcium and percentage organic matter have also risen with increasing stand age. Community complexity is also increasing with stand age, and TWINSPAN and DECORANA plots have separated out the differently aged stands based on their differences. A "pilot" study was done on the seed bank present in the rehabilitation stands. This has shown the presence of large amounts of early successional, mostly herbaceous species. Seeds of later successional and woody species were scarce which may be a result of the sampling intensity used. However seeds of late successional ground cover species were found in the older stands. Comparisons between the natural revegetation of disturbed areas in the vicinity of Richards Bay and the rehabilitation stands revealed similarities in both species composition and complexity. Species richness and diversity values are comparatively similar for the younger revegetated and older rehabilitation stands, and lWlNSPAN and DECORANA analysis techniques clustered the samples recorded from these areas in close proximity on their relative plots. The oldest revegetated sites contain a number of species found in the rehabilitated vegetation but as Acacia karroo has thinned-out in these stands many of these other species are now mature individuals. Attempts at rehabilitating an area of grassland at Richards Bay Minerals has not produced satisfactory species diversity and experimental manipulations were used to try and increase the diversity of the existing Eragrostis curvula dominated community. Of the several treatments used for the manipulation, a combination of burning and further topsoiling was the most successful in reducing Eragrostis importance and in increasing the species richness. Grassland topsoil spread directly onto the bare tailings produced an extensive vegetation covering over a short period but species richness was not significantly greater than for the existing Eragrostis dominated grassland, and further treatments and management needs to continue if this technique is to be employed. Only a limited amount of alien infestation of the rehabilitated areas was evident from the sampling undertaken during this research. As the removal of alien plants is an ongoing process and the rehabilitation stands are continuously monitored to identify any new invaders, this is not expected to become a problem. From the results of work done overseas and the rehabilitation carried out in South Africa it appears that it is possible to return natural vegetation communities on mined areas. That this is a lengthy process is to be expected but by manipulating the vegetation and continuously monitoring the process it may be possible to speed up development. Areas in need of further research have been identified based on the findings of this project. This will help to reinforce the undertaking of management proposals that will enhance the vegetation recovery and the success of the rehabilitation programme.
208

Diverzita znaků žahadlových blanokřídlých na stanovištích s jemným substrátem / Diversity of traits of aculeatan hymonopterans in habitats with finely-grained substrate

Wofková, Gabriela January 2016 (has links)
Natural habitats of aculeate hymenopterans are rapidly decreasing and strictly specialized species are thus going to be endangered or extinct. However, in the last decades the conservation potential of postindustrial sites has been found. There were many endangered and nationally extinct species recorded along with the drift sand specialists. However, one unclear thing remains - on postindustrial sites there were still no recordings of species that have similar biological traits to the species that are colonizing these sites. The main target of my thesis was to find traits which make it possible for the insects to colonize postindustrial sites. A matrix of 79 traits was made to describe aculeate hymenopterans biotope preferences, phenology, morphology, biogeographical area, nest, food and life history strategies. With these traits I describe 351 species systematically collected on twenty-one localities with finely - grained substrate found in Polabi and South Bohemia. These traits were tested with weighted mean abundances on type of substrate (artificial vs. sandy) with GEE analysis and the type of locality (dumping ground of coal combustion, ore and sand sludge vs. sandpits vs. natural sand) with PCoA analysis. A phylogenetic correction was incorporated in both analyzes. My results show that on...
209

Lifeblood of the Earth: Nuwuvi (Southern Paiute) Hydrological Knowledge and Perceptions of Restoration in Two Southern Nevada Protected Areas

Wendel, Kendra Lesley 20 March 2014 (has links)
In the arid landscapes of the southern Great Basin and northern Mojave Desert, issues surrounding water resource management are often politically contentious. Nuwuvi (Southern Paiute) have known and managed these resources for thousands of years prior to Euro-American arrival in the region. A variety of factors, including federal policies that resulted in the creation of reservations and forced placement in boarding schools, as well as contemporary resource commodification, have influenced Nuwuvi knowledge and practice. In this thesis, I examined the character of Nuwuvi ethnohydrological knowledge, including management knowledge, of two protected areas: Spring Mountains National Recreation Area (SMNRA), managed by the U.S. Forest Service (USFS) and Desert National Wildlife Refuge (DNWR), managed by the U.S. Fish and Wildlife Service (USFWS). In addition, I investigated perceptions of water health and restoration among participants from the two managing agencies and six Nuwuvi Nations. I addressed these topics using the theoretical framework of political ecology and a methodology that included semi-structured interviews and demographic questionnaires with 16 Nuwuvi knowledge holders and four federal agency participants. I conducted text analysis of partial interview transcripts using the inductive coding method in order to identify recurring themes and concepts related to hydrology, management, and restoration. My results illustrated that Nuwuvi ethnohydrological knowledge, which developed incrementally over time, conceptualized water as a sentient being that required human interaction to remain healthy. There was also evidence that Nuwuvi knowledge of water was changing as a result of political, economic, and social forces. Furthermore, these findings suggest that Nuwuvi and agency approaches to hydrological management and restoration were built upon differing epistemologies, though there was convergence among specific management and restoration techniques. Based on these results, a report of findings from the Nuwuvi Knowledge-to-Action project, including recommendations for collaborative stewardship approaches, was delivered to participants in August 2013.
210

A study of high school biology students engaged in a Science-Technology-Society (STS) landfill restoration project

Taylor, Beatrice Dietering 26 February 2007 (has links)
The purpose of this study was to observe high school students as they progressed through a Science-Technology-Society (STS) project that involved the closing of a landfill. In this STS project, students investigated the best vegetation for reseeding a closed landfill. This project was initiated because a highway was to be built across the landfill to Explore Park. The director of Explore Park requested an experimental vegetation instead of the standard vegetation mixture. He wanted a vegetation that was aesthetically pleasing and environmentally acceptable. The study investigated the involvement of students in the construction of knowledge of local environmental issues. Students shared their perceptions about the STS process through interviews, journal entries, a questionnaire, field notes, and written artifacts. All data were transcribed and coded for themes. Ethnographic methods were used to tell this story in twelve vignettes. The results of this study are important because they show how educators can use local issues to build classroom curriculum. Students became actively involved in the learning process as they advanced through identified STS instructional goals. The first goal was the Foundations Level. Basic content associated with landfill management and revegetation issues were introduced. Facts about garbage and the need for reducing, reusing, and recycling were investigated. The second goal was the Issue Awareness Level. This goal included becoming involved, identifying the players, and investigating values and beliefs. The third goal was the Investigation and Evaluation Level. Students were exposed to concepts and strategies necessary to investigate and analyze the issues and evaluate alternative solutions. This level encompassed designing plant experiments. The fourth goal was the Citizenship Responsibility Level. Students were introduced to strategies necessary for making responsible decisions concerning solutions to the issues. The conclusions of this study suggest that for many students, the teaching of science through local technological and societal issues allowed them to become actively engaged in the learning process. Students who took ownership of their investigations created opportunities to enhance self-esteem, made connections, and enhanced their knowledge of scientific investigations and scientific content in the context of real life issues. / Ph. D.

Page generated in 0.1383 seconds