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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.
1241

Macroecological patterns of plant species and anthropogenic activities

Correa Cano, María Eugenia January 2015 (has links)
The study of macroecology not only identifies patterns in the distribution and abundance of species at large spatial and temporal scales, it also gives insight into the processes underlying those patterns. The contribution of this work is not limited to helping develop the field of ecology per se, but also provides important insights into the understanding of large scale processes like climate change, the spread of introduced species, pest control and how increasing pressure from anthropogenic activities threatens biodiversity and ecosystem services. During the first decade following its formal inception, most of the progress in macroecology was made through studies of animal species, and research into plant species continues to lag far behind. This thesis contributes to the study of the macroecology of plant species by examining some selected macroecological patterns that have been studied only for animal species and by including an important issue that might have significant effects on diverse macroecological patterns, namely anthropogenic activities. The second and third chapters of the thesis address the generalised individuals-area relationship (GIAR) and the patch individuals-area relationship (PIAR), two macroecological relationships not previously explored for plant species. I show for the first time the existence of negative GIARs at the intraspecific and interspecific levels in plant species, similar to those documented for animal species. Unlike animal species, I did not find a broadly consistent intraspecific PIAR in plant species; more than half of the tested species showed negative PIARs. The resource concentration hypothesis may help explain those positive PIARs that were observed. The fourth chapter considers the effect of past human activities on current patterns of plant species richness at a landscape scale. Using a detailed database on the historical anthropogenic activities for Cornwall, U.K., I examine the relationship between species richness and the area covered by each historical land-use at two different spatial resolutions (10km x 10km and 2km x 2km). I find that at the 10km x10km scale human activities carried out since the 17th and 19th centuries explain an important proportion of the variation in current plant species richness. In contrast, a model at 2km x 2km scale with upland woods and the total land area of a grid cell explain only 5% of the variation. The fifth and sixth chapters focus on how artificial light at night (ALAN), which has increasingly come to attention as a significant anthropogenic pressure on species, is interacting with the distributions of plant species. In the fourth chapter, I consider the plant family Cactaceae to determine the proportion of the global distribution ranges of species that is being influenced by ALAN, and how this changes with the size of these distribution ranges and over a 21-year period (1992 to 2012). I found that >80% of cacti species are experiencing ALAN somewhere in their distribution range, and that there is a significant upward trend in ALAN in the ranges of the vast majority of species. For the sixth chapter, I consider similar issues for the threatened plant species of Britain, exploiting new remote sensing imagery of nighttime lighting at a very fine spatial resolution (c.340x340m2). Only 8% of Britain is free of artificial light at night and in consequence a high number of threatened plant species have a high proportion of their range under some influence of ALAN.
1242

Ecological knowledge towards sustainable forest management:habitat requirements of the Siberian flying squirrel in Finland

Hurme, E. (Eija) 18 November 2008 (has links)
Abstract Maintaining biodiversity in boreal forest landscapes in conjunction with forestry is a challenging task. This requires ecological understanding that is based on empirical research. In this thesis, I examined spatial and temporal occupancy patterns as well as predictability of the occurrence of the Siberian flying squirrel (Pteromys volans L.) in Finland. I used thematic maps which matched habitat requirements of the flying squirrel in forested landscapes and data on species presence and absence, which were gathered in suitable forest habitats. The results of this thesis provide applications for landscape management. First, the preferred habitat characteristics of the flying squirrel were linked to available forest data. In addition, some predictive habitat models could be used to estimate the distribution of the flying squirrel within a region. Second, based on a five year study the forests were classified as continuously occupied, continuously unoccupied and variable-occupancy patches. The dynamic occupancy pattern emphasizes the need for repeated surveys to also locate the seldom-used suitable habitats in a landscape. Third, a comparison of simulated future scenarios in long-term forest planning suggested that flying squirrel habitat might be maintained without considerable loss of timber in a landscape. Thus, a combination of ecological and economic goals in forestry planning is an encouraging alternative. Fourth, there were more polypore species in forests occupied by the flying squirrel. This suggests that conservation of the flying squirrel habitats would protect other naturally co-occurring species, and thus the flying squirrel could be assigned as an umbrella species in mature spruce-dominated forests. Based on these findings, I suggest that the flying squirrel could be used as one of the target species for forest management in boreal forest landscapes. Further research challenges are related to the examination of habitat thresholds and to the projection of future scenarios where ecological, economic and social aspects are combined to assist in complex decision making processes.
1243

Ant (Hymenoptera: Formicidae) Assemblages in Three New York Pine Barrens and the Impacts of Hiking Trails

Barber, Grace W 18 March 2015 (has links)
Ants are ecologically important, environmentally sensitive, widespread, and abundant, yet ant assemblages of many habitats remain poorly understood. Ants in inland barrens of New York State (NY) barely have been studied, but the limited data suggest such habitats are likely to support uncommon ant species and high species density for the region. To increase knowledge of these assemblages, I systematically collected ants from three inland barrens systems in NY, to create species lists and measure species density. I also investigated how hiking trails — a common man-made disturbance — may be impacting ant assemblages in these early-successional, disturbance-dependent ecosystems. My data strongly indicate uncommonly high densities of ant species in NY pine barrens, including the most northern known occurrences of some species, and show that ant assemblage composition and species density are altered on hiking trails relative to managed barrens habitat bordering the trails. I conclude that monitoring ants on hiking trails could provide valuable information, particularly on disturbance-tolerant species, and an opportunity for visitor participation and citizen science programs that could detect additional rare species.
1244

Charakterizace a aplikace mikrovlnného plazmatu pro hojení ran / Characterization and application of microwave plasma on wound healing

Truchlá, Darina January 2020 (has links)
Non-thermal plasma has a lot of ways for using in nowadays medicine. It presents many useful actions like charged particles, UV light, electric field, radicals, excited atoms and molecules. That complicated chemistry directs to uncountable synergistic interaction between cold plasma and biological systems, involve cells and tissues. This thesis is about effects of cold plasma to wound healing. Two different microwave plasma systems were used for the presented study. The first one was argon plasma torch generated by surface wave using the quartz capillary, the second one was plasma torch with reverse vortex argon flow. Diagnostics of plasma jet by optical emission spectroscopy shown the presence of active particles, which are responsible for a lot of impact of plasma treatment. Concentrations of active particles generated by plasma are dependent on conditions of plasma generation like power of generator and gas flow. For visual evidence of effects on skin caused by active particles was created simulation of skin tissue. Interaction between plasma jet and artificial skin tissue shown that UV light and temperature are not responsible for all observed effects which are noticed after plasma treatment. Some part of experiments was realized in collaboration with Medical University of Sofia in Bulgaria. The theory of positive effect to wound healing was supported by experiments based on treating artificially created wounds on laboratory mice by cold plasma. It was proved, that process of wound healing is significantly shorter after using plasma treatment in comparison with normal wound healing. Plasma treating of wound for 10 seconds in two consequent days seems like more effectively than application of plasma only one day. This Thesis was carried out as a part of international project PLASMABORDER that was supported by European commission under cohesion funds; programme INTEREG SK-CZ under contract No. 304011P709.
1245

Modulation der Candida albicans Biofilmbildung und Expression von Pathogenitätsfaktoren durch Lactobacillus spp.

Dreßel, Tilmann 19 June 2014 (has links)
Lactobacillus- Spezies, die zur Gattung der Milchsäurebakterien gehören, haben bereits hemmende Eigenschaften gegen Candida albicans gezeigt. Dieser dimorphe Hefepilz ist einer der bedeutendsten Erreger von Pilzinfektionen beim Menschen und einer der häufigsten Verursacher Katheter- assoziierter Infektionen. Eine bedeutende Rolle bei der Pathogenität von C. albicans spielt die Biofilmbildung, die sowohl die körpereigene Abwehr als auch die antimykotische Therapie einer invasiven Infektion erheblich erschwert. Zu den Virulenzfaktoren zählt eine Vielzahl von Genen, darunter auch die sekretorischen Aspartylproteasen (SAPs), die zur Infektion sowohl in vitro als auch in vivo beitragen. In der vorliegenden Arbeit wurde der Einfluss verschiedener Lactobacillus- Stämme auf die Biofilmbildung des invasiv pathogenen C. albicans SC 5314 und des in der Pathogenität abgeschwächten Stammes ATCC 10231 untersucht, sowohl phänotypisch als auch hinsichtlich der metabolischen Aktivität durch den semi- quantitativen XTT- Reduktions- Assay. Zudem erfolgten Expressionsanalysen ausgewählter Gene von C. albicans, deren Zusammenhang mit der Biofilmbildung und Pathogenität bekannt ist. Dabei konnte gezeigt werden, dass L. johnsonii DSM 10533 die metabolische Aktivität beider C. albicans- Stämme erheblich verringern kann (um bis zu 80%) und auch einen phänotypisch drastisch reduzierten Biofilm verursacht. In Anwesenheit dieses Stammes kam es zu stark verringerter Aktivität der beobachteten SAP- Gene vor allem des invasiven Stammes C. albicans SC 5314. Andere Pathogenitäts- assoziierte Gene wie Als 3 und Hwp 1 wurden dagegen eher hochreguliert. L. rhamnosus DSM 20021 und ein klinisches Isolat verursachten ebenfalls eine Verringerung der metabolischen Aktivität, sorgten phänotypisch aber eher für vermehrte Hyphenbildung des Pilzes. Ersterer verursachte eine deutlich reduzierte Aktivität von Hwp 1 und Ume 6 bei C. albicans ATCC 10231. L. reuteri DSM 20016 zeigte keinen signifikanten Einfluss auf Biofilmbildung, Aktivität und Genexpression der beobachteten C. albicans- Stämme. Diese Ergebnisse zeigen deutlich, dass unterschiedliche Lactobacillus- Stämme sich in ihrem Einfluss auf C. albicans erheblich unterscheiden. Auch die Reaktion verschiedener C. albicans- Stämme auf Lactobacillus- Spezies ist sehr verschieden. In dieser Arbeit zeigte L. johnsonii DSM 10533 ein deutliches Potential, C. albicans in der Biofilmbildung und Expression von Pathogenitätsfaktoren zu hemmen. Dieser Stamm erscheint damit für weiterführende Untersuchungen hinsichtlich probiotischen Potentials geeignet. Die Ergebnisse einer Lactobacillus Spezies können nicht generell auf andere Lactobacillus Spezies übertragen werden. Ob sich innerhalb einer Spezies alle Stämme gleichermaßen verhalten, bedarf ebenfalls der Überprüfung. Die Ergebnisse dieser Arbeit werfen auch die Frage auf, ob Lactobacillus Spezies sogar die Pathogenität von C. albicans erhöhen können.
1246

COMPARING THE COMPOSITION OF SAPROXYLIC BEETLE FAUNA ON OLD HOLLOW OAKS BETWEEN TWO TIME PERIODS

Kamboyi, Chipango January 2019 (has links)
Oak habitats are rich in saproxylic species, but the habitat is declining with loss of diversity due to encroachment which decrease the vitality of oaks. The present explorative study compared results from a study conducted in 1994, with present species communities to observe if there has been change in species composition and what factors that can explain species diversity and composition. The results revealed that the overall species composition between 1994 and 2018 has changed. There were 130 species recorded in 2018 compared to 108 species in 1994 (31 new species were recorded in 2018, and 9 species lost from the study in 1994). There was a high species turnover recorded per individual tree, and the species composition between the living and encountered dead trees did not differ. Species composition was affected by canopy cover, and trunk circumference (CCA P-value 0.001 and 0.014 respectively). Unlike 1994, there were no variables in 2018 that could explain the association with species numbers. Warmer conditions recorded during the sampling period have probably led to increased flight activity of beetles and therefore increasing chances of capturing more species and individuals. The warmer conditions possibly shadowed the effects of the explanatory variables in explaining the changes in species numbers. Perhaps the change in species composition could also be attributed to existing management interventions that may be supporting an increasing species number of saproxylic beetles, however no strong conclusions could be drawn. Management interventions such as the recruitment of new oaks should be encouraged and intensified in order to provide habitats and support stable populations as the loss of oaks may lead to increased risk of extinction of the saproxylic beetles in the study area.
1247

Afromontane avian assemblages and land use in the Bale Mountains of Ethiopia : patterns, processes and conservation implications

Mitiku, Addisu Asefa 11 1900 (has links)
Although protected areas have been used as principal conservation tools, most of them are suffering from human-induced threats. Consequently, a good understanding of such human-driven threats on biodiversity and identifying early warning systems for habitat change in protected areas is necessary for effective conservation of natural resources. To examine the impact of human disturbance on avifaunal assemblages and to assess the potential application of birds as bioindicators of forest health monitoring in the Afromontane forest of the Bale Mountains of Ethiopia, I recorded birds and habitat variables in three protected and three unprotected forests using a point transect method in 2009 and 2012. The two land use types differ in disturbance levels (higher in the unprotected areas), vegetation structure and bird assemblages. Species richness of entire bird guild, open woodland and open land habitat guilds, granivore and insectivore feeding guilds, and shrub layer and ground layer foraging substrate guilds of birds were significantly higher in the unprotected areas than the protected areas. Abundances of guilds of birds mostly followed a similar trend with species richness. However, densities of overall and forest-specialist bird guilds were higher in the protected area and vice versa for the other guilds. In general, the protected area assemblages were dominated by forest-specialist species, while those of the unprotected areas were dominated by openland and shrubland species. The implication is that disturbance had caused encroachment of non-native species (openland, open woodland and shrub land species) while negatively affecting native species (forest species, particularly tree canopy foragers). These assemblage differences are linked to changes in vegetation structure caused by disturbance. Thus, further forest degradation in the protected area should be avoided in order to maintain native/forest-specialist species. Given the differences in bird assemblages between the two land use types, there is a high likelihood that bioindicator species (i.e. indicator species - those 'characteristic' of a particular habitat - and detector species - those occurring in the different habitats considered but with moderate indication value) can be identified, therefore providing a useful tool to monitor ecosystem health of the forests. Four and nine species were identified as appropriate indicator species (i.e. species with indicator values > 60% and fulfilling biological and niche history criteria used in selection) in the protected and unprotected areas, respectively. In addition, nine species were identified as detectors of habitat change in the protected areas. These bioindicators provide a useful tool for managers of Afromontane forest in the Bale Mountains, as well as similar habitats elsewhere, for long term monitoring of ecosystem health of the forests. / Dissertation (MSc)--University of Pretoria, 2013. / DST/NRF Centre of Excellence / Zoology and Entomology / MSc / Unrestricted
1248

PREDICTING SITE SUITABILITY FOR KUDZU (PUERARIA MONTANA) IN THE GREAT LAKES BASIN AND SURROUNDING REGION

Ashley M Kovach-Hammons (12462825) 26 April 2022 (has links)
<p> Kudzu (Pueraria montana) is an invasive woody vine widespread throughout the  southeastern United States, with recent studies predicting that its habitat will expand northward.  New occurrences and recent studies using climatic parameters suggest that the Midwestern  region of the United States is at the greatest risk of kudzu invasion. As there have already been  25 reports of kudzu within the Great Lakes basin, and no previous landscape models exist for the  basin, I developed probability models from existing spatial data (land cover, hydrology, geology,  annual precipitation, elevation, aspect, and known kudzu locations) using generalized additive,  bioclimate envelope, and maximum entropy methods. I further expanded each model to include  the basin and a 2.25-degree buffer in order to include 193 reported kudzu sites. For each  predictive model, I determined the area under the curve (AUC) for a receiver operating  characteristic curve (ROC) comparing false positive and false negative rates. I performed field  surveys at eight known sites of kudzu presence in Michigan, Indiana, and Ohio. Each presence  site was paired with a control (known kudzu absence site). I collected environmental data  including canopy cover, volumetric soil moisture, soil pH, litter depth, midstory species diversity  and diameter at breast height (DBH), and overstory basal area. Each environmental measure was  compared between kudzu presence and control survey sites as well as between in-basin and out?of-basin survey sites using a two-way ANOVA. Maximum entropy models produced the highest  AUC in both the basin and buffer models during model development. These models showed that  urban and disturbed habitats resulted in the greatest probability of potential habitat for kudzu. I  found no statistically significant differences in environmental characteristics between kudzu  absent and presence sites or between in- and out-of-basin sites, suggesting kudzu might be  dispersal-limited rather than limited by environmental characteristics. Continuing existing  management and further monitoring of kudzu spread is likely necessary to limit further  introduction and to mitigate spread of kudzu within the Great Lakes region.  </p>
1249

Ecophysiology of Juniperus virginiana encroachment in Ohio

Hamati, Samia 28 April 2022 (has links)
No description available.
1250

Evaluating the Ecological Status of the Introduced Nile Monitor (Varanus niloticus) in Florida: Forecasting Presence and Population Expansion Using Computational Geographic Information Systems

Cohen, Noah G 17 November 2017 (has links)
The Nile monitor (Varanus niloticus) is a large, carnivorous lizard that has become a notorious invasive species in Florida, USA. Initially released in the 1980s from the pet trade, the species has since established at least three breeding populations and spread throughout much of southern Florida. While current control efforts have failed to eradicate V. niloticus, it is important to attain a better understanding of its invasive dynamics to guide and inform better control strategies. In this study, available georeferenced records of V. niloticus in Florida were compiled and linked to a habitat classification map to evaluate ecotype preferences. Factored with bioclimatic data, the regional spread of V. niloticus was modelled for contemporary and projected (i.e., in the year 2050) presence using Maxent and Mahalanobis Distance models. Study results indicate that V. niloticus maintains a strong presence in eastern Lee County on the southwestern coast. Populations in Palm Beach and Miami-Dade counties on the southeastern coast may be interconnected, contrary to current descriptions that they are separated from each another. Model forecasts of conditions for the year 2050 identify widespread expansion of V. niloticus in Florida, particularly northward with the establishment of a new population center in Pasco County in the western central peninsula. This is the first known modelling study of V. niloticus in Florida and identifies regions at greater risk for future population expansion.

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