1,721,028 research outputs found
Invertebrate communities in adjacent Douglas fir and native beech forests in New Zealand
Full text linkNon-native trees profoundly alter the structure and resilience of native forest ecosystems through direct or indirect effects on ecosystem processes, e.g. by altering invertebrate communities, but such effects are poorly understood in New Zealand. We sampled adjacent stands of the non-native tree Douglas fir (Pseudotsuga menziesii) and native beech (Nothofagaceae) forests and tested whether the overall invertebrate communities varied across forest types. We then assessed whether natural enemies, both trophic-generalist predators and more trophic-specialist parasitoids, differed across forest types. We found a trend for lower overall invertebrate family diversity in Douglas fir plantations compared to native beech forests. Parasitoid abundance was lower in Douglas fir forests compared to native beech forests, although we could not tease apart whether these effects were due to differences in forest age, forest type, or a combination of these factors. Our findings suggest that there are subtle shifts in invertebrate community composition from native forests to non-native forests, and that trophic specialisation might play a key role in determining which natural enemies can inhabit non-native forests in New Zealand. Nevertheless, our small sample size calls for further exploration of these patterns.Fil: Evans, Alison M.. Department Of Conservation; Nueva ZelandaFil: Peralta, Guadalupe. University of Canterbury; Nueva Zelanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: van Beest, Floris M.. Department Of Conservation; Nueva ZelandaFil: Klijzing, Krista. Department Of Conservation; Nueva ZelandaFil: Peltzer, Duane. Crown Research Institutes. Landcare Research; Nueva Zeland
Influence of environmental drivers on the movement behaviour of harbour porpoises in the North Sea
Full text linkDissertação de Mestrado, Estudos Integrados dos Oceanos, 18 abril de 2019, Universidade dos Açores.O boto e um pequeno predador marinho com um elevado estatuto de conservação nas águas europeias. Para uma proteção eficaz desta espécie é importante ter conhecimentos detalhados das respostas comportamentais as mudanças das condições ambientais. Neste estudo, investiguei a influência das condições ambientais sobre a variação do comportamento de deslocação de grande escala da população de botos no Mar do Norte. Foram analisados dados de deslocações de 57 indivíduos rastreados por satélite num período de 19 anos. Para cada relocalização, estimou-se o estado comportamental subjacente do indivíduo (residência ou em deslocação) recorrendo a processos de modelação do estado espacial (State-space modelling, SSM). Estes estados comportamentais foram então correlacionados com variáveis ambientais estáticas e dinâmicas através de regressões logísticas. Estimou-se que os botos estão cerca de 81% do seu tempo em áreas circunscritas, passando apenas uma pequena parte do seu tempo (6%) em rápidas deslocações de longa distância, classificadas como estado de deslocação. Esses movimentos de curta duração e longas distâncias refletem provavelmente deslocações entre áreas de procura de alimentação. As restantes relocalizações (13%) não puderam ser atribuídas sem ambiguidade a nenhum destes estados comportamentais. Foram encontradas diferenças individuais consideráveis na extensão destas deslocações, com máximos variáveis entre 24 km e 867 km, relativamente à posição inicial. Consequentemente, a proporção de tempo gasto no estado de deslocação rápida (variando de 0,5% até 20,0%) e no estado residente (variando de 50,5% ate 99,5%) foi altamente variável entre indivíduos. O estado residente foi associado com baixos níveis de salinidade, temperatura e velocidade da corrente; com altas concentrações de clorofila-a em relação à media sazonal; e com declives intermédios do fundo. Estes resultados indicam indiretamente que as presas dos botos provavelmente se agregaram em áreas com as condições ambientais referidas, servindo, portanto, como área de alimentação. Estudos anteriores sobre a distribuição e abundância dos botos suportam a importância desses fatores ambientais. Os conhecimentos adquiridos neste estudo podem ser usados para melhorar os modelos populacionais espaciais que estão atualmente a ser desenvolvidos para estudar o impacto do ambiente marinho em mudança, e com as crescentes perturbações antrópicas, que afetam a dinâmica da população de botos.ABSTRACT: The harbour porpoise is a small marine predator with a high conservation status in European waters. In order to protect the species effectively, it is crucial to acquire detailed knowledge on behavioural responses to changing environmental conditions. Here, I investigated the influence of environmental conditions on variation in large-scale movement behaviour of the harbour porpoise population in the North Sea. The movement tracks of 57 satellite- tracked individuals tagged over a total period of 19 years were analysed. For each relocation, the underlying behavioural state (area-restricted or transient state) of the individual was estimated using a state-space modelling (SSM) approach. The behavioural states were then modelled as a function of multiple static and dynamic environmental variables by means of a logistic regression. Harbour porpoises were estimated to spend about 81% of their time in area-restricted state (i.e. movements within feeding areas), while they spent only a small amount of their time (6%) in making fast and long-ranging movements, classified as transient state. These short movement bursts over long distances likely reflected transient movements between foraging grounds. The remaining relocations (13%) could not be assigned unambiguously to either state. Considerable individual differences in the extent of movements were found, with the maximum net displacement from the first location ranging from 24 km to 867 km. Accordingly, the proportion of time spent in transient state (ranging from 0.5% to 20.0%) and resident state (ranging from 50.5% to 99.5%) was highly variable among individuals. The area-restricted state was associated with low levels of salinity, temperature and current velocity; with high levels of chlorophyll a concentrations relative to the seasonal mean; and with intermediate sea bottom slopes. These results indirectly indicate that prey species may aggregate in areas where such environmental conditions are found, therefore serving as feeding grounds to harbour porpoises. Earlier studies on harbour porpoise distribution and abundance support the importance of these environmental drivers. The findings from this study can be used to better inform spatially explicit population models that are currently being developed to study the impact of a changing marine environment with increasing anthropogenic disturbance on harbour porpoise population dynamics
Factors affecting the spatiotemporal distribution of moose, with a special emphasis on supplementary feeding
Full text linkDoktorgradsavhandling ved Universitetet i Oslo ved det matematisk- naturvitenskapelige fakultet, nr 1016.Large herbivores constitute an important natural resource and are actively managed to
meet economic, conservation and environmental objectives. To alleviate the potential of
resource limitation and damage to commercially important habitats in areas with high
population densities, the provisioning of artificial or supplementary forage has become a
popular wildlife management intervention throughout Europe and North America.
However, the usefulness of supplementary feeding is equivocal and little is known about
how it affects spatiotemporal distribution patterns of large herbivores.
The main aim of this thesis is to quantify the effect of supplementary feeding on
the spatiotemporal distribution of moose (Alces alces L. 1758) living in southern Norway.
I used locations of free-ranging GPS (global positioning system) collared moose (N = 26
in summer and N = 32 in winter) with access to supplementary feeding stations to
estimate habitat selection and home range size as a function of feeding status (i.e. feeding
station users vs. non-users), variation in browse quantity and quality, and also in terms of
local climate and individual characteristics. To evaluate fine-scale distribution patterns
and foraging decisions around supplementary feeding stations I employed 2 independent
datasets (GPS data and browsing estimates) from two study areas (in Telemark and
Hedmark counties) that differ in the length of their feeding history. I apply central-place
foraging theory to explain the observed patterns.
My results indicate that supplementary feeding affects the spatiotemporal
distribution of moose only at intermediate to fine spatial scales during winter, with
feeding station users behaving as central-place foragers. However, feeding station users
did not differ in their large-scale habitat selection patterns or home range size compared
to non-users. Instead, moose habitat selection was driven by a scale-dependent trade-off
between browse quantity (landscape-scale) and browse quality (within-home rangescale).
Moreover, depletion of high quality browse during winter lead moose to increase
selection for lower quality browse within their home range. Variation in home range size
was affected by several extrinsic (i.e. climate and natural browse) and intrinsic variables
(i.e. individual characteristics) and their effects varied between and within spatiotemporal
scales. After 6 years of feeding, moose that used feeding stations selected for
commercially valuable browse (i.e. Scots pine) within their home range to the same
extent as non-users, which questions the effectiveness of winter feeding in reducing
browsing pressure over large spatial scales. In addition, as the time scale of feeding
increased from 5-10 to 15-20 years, browsing pressure on commercially valuable browse
(i.e. Scots pine and Norway spruce) was amplified at a fine spatial scale. At the same time, resource depletion in the vicinity of feeding stations lead moose to forage at
increasing distances from feeding stations and browsing damage occurred at least up to 1
km from feeding stations. These findings suggest that when supplementary feeding is
practised over longer time scales (more than 20 years) there is the potential for a trade off
to occur between the energetic cost of returning to the central-place (i.e. feeding station)
and the energetic benefits it provides.
Evaluating management actions is important to determine whether the objectives
and desired effects are realized. I have shown how supplementary feeding can affect the
spatiotemporal distribution of moose and how subsequent browsing pressure around
feeding stations can change over time. However, there are a variety of direct and indirect
effects that follow the provisioning of supplementary forage that have not yet been
adequately assessed. A holistic evaluation of the effectiveness of supplementary feeding
as a wildlife management tool is required and needs to consider all the associated benefits
and costs, especially considering long-term developments and potential ecosystem-level
effects
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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