• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 138
  • 58
  • 21
  • 10
  • 7
  • 6
  • 5
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 278
  • 52
  • 32
  • 31
  • 28
  • 28
  • 27
  • 27
  • 24
  • 24
  • 19
  • 19
  • 18
  • 17
  • 15
  • 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.
11

Plant recruitment across alpine summits in south-eastern Australia /

Venn, Susanna Elizabeth. January 2007 (has links)
Thesis (Ph.D.) -- La Trobe University, 2007. / Research. "A thesis submitted in total fulfillment of the requirements for the degree of Doctor of Philosophy, Department of Botany, School of Life Sciences, Faculty of Science, Technology and Engineering, La Trobe University, Bundoora". Includes bibliographical references (leaves 173-187). Also available via the World Wide Web.
12

The 3500-year-long lake-dwelling tradition comes to an end: what is to blame?

Menotti, Francesco January 2015 (has links)
No
13

Restaurering för störda områden i kalfjällsmiljö : Utvärdering av pilotförsök för återvegetering av området kring den nedlagda underjordsgruvan i Stekenjokk / Restoration of a disturbed area in an alpine environment : Evaluation of the revegetation projects of the area around the abandoned underground mine in Stekenjokk

Ögren, Amanda January 2016 (has links)
The aim of this study was to evaluate restoration methods used in a revegetation project for the heavily disturbed area around the abandoned underground mine Stekenjokk, located in an alpine area in Västerbotten County, Sweden. The studies were initiated in 2013 by Enetjärn Natur AB on behalf of Boliden Mineral AB and several methods were adopted in the purpose of investigating the feasibility of different restoration methods. Seeding, plantation of adult plants and transplantation of vegetation turfs were performed in combination with addition of organic matter. In addition, ‘safe sites’ were created either by addition of cobbles to the surface, creation of holes in the ground or by putting out coconut mats. All plant material, e.g. seeds, plantation of adult plants and transplantation of vegetation turfs, resulted in new establishment of plants in the area. Spontaneous establishment of plants was also observed in several of the examined plots. Several of the methods used are probably suitable for restoration of the old industrial area in Stekenjokk. However, the success varied among different methods and there was a tendency for higher survival of plants in experimental plots to which soil had been added. A combination of addition of plant material (seeds or adult plants), addition of organic matter and creation of ‘safe sites’ seemed most effective in accelerating revegetation in the heavily degraded area in Stekenjokk. However, sample sizes were small and more studies should be conducted to confirm the generality of this conclusion.
14

Precipitation distribution in the Lake Pukaki Catchment, New Zealand

Kerr, Timothy Ross January 2009 (has links)
Mountain precipitation, as a major component of global ecology and culture, requires diverse observation-based distribution studies to improve process characterisation and so enhance environmental management and understanding. Analysis of data from an array of precipitation gauges within the nationally important, and internationally extreme, mountainous Lake Pukaki catchment in New Zealand has been undertaken in an effort to provide such a study, while also improving local hydrological understanding. An objective observation based undercatch-corrected 1971-2000 average annual precipitation distribution has been prepared for the mountainous Lake Pukaki catchment, New Zealand. Precipitation records from 58 gauges at 51 sites, augmented with 10 new gauges, were used in preparation of the distribution. The assessed undercatch correction of 17 % across the catchment indicates that mountain hydrological investigations in New Zealand that use precipitation data and yet do not consider undercatch will be in considerable error. The average annual distribution confirms the existence of high precipitation magnitudes and horizontal gradients in the catchment in comparison with other mountain regions around the world. The high magnitude is unusual when its position in the lee of the principal orographic divide is considered indicating rare precipitation distribution processes occur in the region. Consideration of river flows, glacial change and evaporation led to a confirmation of the gauge derived average catchment precipitation. Precipitation to wind direction relationships identified the predominant westerly wind to be the primary precipitation generating direction with large magnitude events biased towards the northerly direction. All directions from the eastern side of the mountain divide had the lowest frequency and daily precipitation magnitude. Derivation of wind-classed precipitation distributions identified a distinctive south east to north west precipitation gradient for all wind directions, most severe for the north west direction and least severe for the easterly direction. Precipitation extent was greatest for the northerly direction and least for the south south westerly. The wind-classed distributions enable the estimation of daily precipitation likelihood and magnitude at any location in the catchment based on knowledge of the synoptic wind flow direction and precipitation at just one reference site. Improved river flow and lake inflow estimates resulted from the use of wind classed daily precipitation estimates validating the quality of the wind classed distributions. From 1939 to 2000 there has been no statistically significant trend in precipitation magnitudes, frequencies, or extremes in the catchment. At Aoraki/Mt Cook village, in the upper catchment, there have been significant increases in magnitude, frequency and extremes associated with the phase change of the Interdecadal Pacific Oscillation (IPO) in 1978. This change can be explained by the increase in strength of westerly winds for the different IPO phases but not by a change in frequency of different wind directions. In the lower catchment the IPO relationship is of an opposite sense to that observed in the upper catchment, indicating that the areas operate under two different climate regimes with different precipitation controls. The significant relationship to the IPO phase indicates that it is more important than climate warming in terms of future precipitation distribution in the Lake Pukaki catchment, and by extension the Southern Alps. The distributions prepared provide a valuable tool for operational and academic hydrological applications in the region. In addition, they provide a valuable characterisation of the precipitation in a Southern Hemisphere mid-latitude lee to predominant westerlies glacierized mountain catchment. From this standpoint they highlight the contrast to Northern Hemisphere mountain precipitation distributions commonly used in model validation studies, thereby providing an extension of locations with which to refine orographic precipitation process understanding.
15

Tectonometamorphic studies in the crustal envelope of mantle peridotites in the western Betic Cordillera, southern Spain

Argles, Tom January 1996 (has links)
No description available.
16

Statistical inference on evolutionary processes in Alpine ibex (Capra ibex) : mutation, migration and selection

Aeschbacher, Simon January 2011 (has links)
The thesis begins with a general introduction to population genetics in chapter 1. I review the fundamental processes of evolution - mutation, recombination, selection, gene flow and genetic drift - and give an overview of Bayesian inference in statistical population genetics. Later, I introduce the studied species, Alpine ibex (Capra ibex ), and its recent history. This history is intimately linked to the structured population in the Swiss Alps that provides the source of genetic data for this thesis. A particular focus is devoted to approximate Bayesian computation (ABC) in chapter 2, a method of inference that has become important over the last 15 years and is convenient for complex problems of inference. In chapter 3, the biological focus is on estimating the distribution of mutation rates across neutral genetic variation (microsatellites), and on inferring the proportion of male ibex that obtain access to matings each breeding season. The latter is an important determinant of genetic drift. Methodologically, I compare different methods for the choice of summary statistics in ABC. One of the approaches proposed by collaborators and me and based on boosting (a technique developed in machine learning) is found to perform best in this case. Applying that method to microsatellite data from Alpine ibex, I estimate the scaled ancestral mutation rate (THETA anc = 4Neu) to about 1:288, and find that most of the variation across loci of the ancestral mutation rate u is between 7.7*10 -4 and 3.5*10 -3. The proportion of males with access to matings per breeding season is estimated to about 21%. Chapter 4 is devoted to the estimation of migration rates between a large number of pairs of populations. Again, I use ABC for inference. Estimating all rates jointly comes with substantial methodological problems. Therefore, I assess if, by dividing the whole problem into smaller ones and assuming that those are approximately independent, more accuracy may be achieved overall. The net accuracy of the second approach increases with the number of migration rates. Applying that approach to microsatellite data from Alpine ibex, and accounting for the possibility that a model without migration could also explain the data, I find no evidence for substantial gene flow via migration, except for one pair of demes in one direction. While chapters 3 and 4 deal with neutral variation, in chapter 5 I investigate if an allele of the Major Histocompatibility Complex (MHC) has been under selection over the last ten generations. Short- and medium-term methods for detecting signals of selection are combined. For the medium-term analysis, I adapt a matrix iteration approach that allows for joint estimation of the initial allele frequency, the dominance coefficient, and the strength of selection. The focal MHC allele is shared with domestic goat, and an interesting side issue is if this reflects an ancestral polymorphism or is due to recent introgression via hybridization. I find most evidence for asymmetric overdominance (selection coefficient s: 0.974; equilibrium frequency: 0.125) or directional selection against the `goat' allele (s: 0.5) with partial recessivity. Both scenarios suggest a disadvantage of the `goat' homozygote, but differ in the relative fitness of the heterozygotes. Overall, two aspects play a dominating role in this thesis: the biological questions and the process of inference. They are linked, yet while the proximate motivation for the biological component is given by a specific system - the structured population of Alpine ibex in the Swiss Alps - the methods used and advanced here are fairly general and may well be applied in different contexts.
17

Social behaviour and activity patterns of the African ice rat Otomys sloggetti robertsi

Hinze, Andrea 16 November 2006 (has links)
Faculty of Science School of Biology 9410199j TEL: 011 673 8139 / I studied the sociality and activity patterns of free-living ice rats Otomys sloggetti robertsi. The ice rat is a medium-sized, diurnal, herbivorous rodent, endemic to the alpine habitats of the southern Drakensberg and Maluti Mountains in southern Africa. These environments are characterized by sub-zero temperatures in winter and high levels of solar radiation in summer, and snow can be expected at any time of the year. Previous research by other scientists indicated that the physiology of ice rats is more similar to congeners living at lower altitudes, and, instead the taxon has morphological and behavioural adaptations for coping with the temperature extremes in its environment. Predator pressure on ice rats was negligible in my study site, making the ice rat an ideal model for testing how environmental factors influence sociality and activity patterns. Sociality was investigated by using direct observations and through experimental manipulations. Colonies comprised 4-17 individuals with several reproductively active males and females. Colony members had a high degree of home range overlap, whereas interactions between colony members were rare and usually resulted in agonistic behaviour. Ice rats responded aggressively to experimentally-caged colony members positioned in different parts of their own colony and these were treated with the same level of aggression as were strangers. Moreover, colony members competed aggressively for better-quality introduced food, particularly in winter. From direct observations of male-female interactions, it appeared that ice rats mate promiscuously, which is most likely a consequence of the multi-male and multi-female colonies. Females spent long periods of time belowground with unweaned young which emerged aboveground independently at four weeks of age. The first litter born in a season dispersed at sexual maturity (males±14 weeks; females±9 weeks), but, since I did not observe the behaviour of litters born later in the breeding season, I was not able to tell if these dispersed as well. I excavated the burrow systems of ice rats and found an intricate interlinking underground tunnel system with sometimes more than 25 entrance holes and 1-2 nesting chambers, which would provide a thermoneutral refuge for the ice rats at night as well as during adverse weather conditions. Because the ratio of the number of animals in the colony to III the number of nest chambers exceeded one, I predicted that huddling occurs belowground, which was confirmed by video recordings of nest chambers. Diurnal aboveground activity patterns of ice rats were influenced by prevailing environmental conditions, which resulted in synchronous aboveground appearance of members in a colony. The summer activity pattern was bimodal, dominated by foraging and sun basking behaviour aboveground, with animals retreating belowground to escape high temperatures and radiation levels prevalent around midday. Ice rats utilized the warmer temperatures throughout the day in winter for aboveground foraging and basking. Otomys s. robertsi displays a spatial shift in its social system: colony members huddle belowground but display temporal territoriality aboveground. Such a social system is contrary to predictions previously made for this taxon (i.e. they live as family groups). Ice rat relatives living at lower altitudes mainly occur as non-social aggregations and one relative, the vlei rat O. irroratus, also displays temporal territoriality. Although sociality is common in rodents inhabiting temperate environments in the northern hemisphere, these rodents do not show territoriality at other times. I conclude that the social system of ice rats, in the absence of significant predation pressure, is determined by a combination of 1) environmental factors driving communal thermoregulation and 2) phylogenetic constraints imposed by competition for limited food resources.
18

Franchising jako metoda vstupu na trh / Franchising as a market entry strategy

Hovorková, Petra January 2011 (has links)
This diploma thesis is focused on franchising and a practical application of a theory. The theoretical part describes basic principles of franchising, its advantages and disadvantages and franchise agreement. I put more emphasis on development and current state of franchising in the Czech Republic. I describe and evaluate franchising in the company Alpine Pro in the practical part of the thesis. I show that a purely Czech franchise concept is able to succeed in stiff competition - and not only in the Czech Republic. The aim is to evaluate franchisor - franchisee relationship (on the basis of the questionnaire research) and to suggest some measures and recommendations that would lead to improvement of the weak points of the franchise concept Alpine Pro.
19

Climate, grazing and plant interactions : Does climate and grazing shape plant interactions in alpine environments?

Marberg, Mikael January 2013 (has links)
Increased knowledge of plant interactions is important for our understanding of how ecosystems will respond to climate changes. Using four common low-herb and three tall- herb species as phytometers I measured the net outcome of plant interactions in an alpine environment by a neighbour removal experiment. Grazing and climate were tested as explanatory factors for differences in the outcome of plant interactions, with two altitudes representing different climates. The most important finding in this experiment is that competition is the dominating interaction among plants in this habitat, regardless of plant size, climate and grazing. Climatic exposure and grazing only influenced tall-herb species while low-herbs were mainly limited by competition, presumably for light. These results are important since facilitative interactions and net facilitation in plant communities are often reported to become more common in severe climates.
20

Personality and vigilance behaviour in alpine marmot (Marmota marmota)

Ferrari, Caterina 05 1900 (has links) (PDF)
De plus en plus d'études démontrent la notion que le comportement des individus diffère selon les situations et à travers le temps. Ce phénomène se nomme personnalité de l'individu. Il est fort probable que les traits de personnalité jouent un rôle pertinent dans l'écologie de l'individu et les chercheurs tentent de comprendre quelles sont les causes de ces différences individuelles. À cette fin, il est nécessaire d'avoir diverses approches et on procède actuellement, en laboratoire et sur le terrain, à des recherches effectuées selon l'approche de l'optimalisation afin de vérifier si les variations, la répétabilité et l'hérédité ont une incidence sur les traits de personnalité. Les mesures biologiques de réponses physiologiques et endocriniennes peuvent nous aider à comprendre les mécanismes qui sont à la base des variations comportementales. L'étude de la personnalité réalisée avec des contraintes dans l'utilisation du temps nous permet de vérifier comment certains traits de personnalité influencent l'histoire de vie des individus. Nous avons étudié la personnalité dans un contexte d'anti-prédation où l'animal doit faire face à un compromis entre se nourrir ou rester vigilant car il risque d'être attaqué à tout moment. La présente recherche vise à déterminer si la personnalité de la marmotte Alpine (Marmota marmota) diffère d'un individu à l'autre et si, compte tenu de leur personnalité, les marmottes utilisent différentes stratégies contre les prédateurs. La marmotte Alpine constitue un bon modèle afin d'étudier les stratégies anti-prédateurs et les comportements de prises de risques. Les marmottes vivent en groupes et ces derniers habitent des terriers interreliés possédant plusieurs points d'accès. Les marmottes cherchent leur nourriture à l'extérieur de leur terrier et pendant qu'elles s'alimentent, elles surveillent l'environnement afin de s'assurer qu'il n'y a pas de risques d'attaques de la part de prédateurs. Notre recherche a été effectué dans une zone où habitent un grand nombre de marmottes Alpines ainsi que deux espèces de leurs prédateurs naturels, soit l'aigle royal (Aquila chrysaetos) et le renard roux (Vulpes vulpes). Au cours des étés 2007, 2008 et 2009, nous avons étudié 12 groupes familiaux habitant deux secteurs situés à diverses latitudes au sein du Parc National Gran Paradiso (Italie). Nous avons capturé et marqué 122 individus d'âges et de sexes différents et nous avons procédé à des tests d'open-field sur 105 de ces individus. Dans la plupart des cas, les tests ont été effectués au moins à deux reprises au cours d'années différentes. Grâce à ces tests d'open-field, nous avons pu mesurer le niveau d'activité pour chacun des individus et nous avons découvert une très forte incidence d'habituation sur ce trait. Les mesures des paramètres physiologiques lors de la manipulation nous ont fourni une mesure biologique de la pro-activité pour chacun des individus ce qui nous a permis de constater qu'un individu dominant avait un rythme cardiaque plus élevé que celui proposé dans la théorie. On a également noté que l'âge, le poids et leur interaction avaient une incidence sur la pro-activité des individus mais que cette tendance diffère selon la classe d'âge. Grâce à ces mesures, nous avons obtenu un indice fiable sur la personnalité des individus ainsi que des preuves permettant d'affirmer que cette espèce possède une stratégie d'adaptation (coping style): les individus plus actifs avaient un rythme cardiaque plus élevé. Nous avons effectué d'autres analyses en utilisant ces valeurs individuelles de personnalité. Le deuxième objectif visé par la présente étude était de valider les résultats sur la personnalité au sein du cadre écologique du comportement antiprédateur. À cette fin, nous avons effectué sur le terrain des observations focales lorsque des marmottes marquées faisaient preuve de vigilance en s'alimentant et nous avons considérer la fréquence et la durée des cas de vigilance comme constituant des paramètres du comportement de vigilance. Nous avons constaté que la personnalité jouait un rôle sur le comportement de vigilance mais que certains des résultats allaient à l'encontre de la théorie; nous suggérons que de contrôler pour l'indice du risque pourrait clarifier nos résultats. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : activité, comportement antiprédateur, openfield, personnalité, Marmota marmota.

Page generated in 0.0235 seconds