1,720,962 research outputs found
Herbivore Communities and Plant Diversity as Key Drivers of Savanna Ecosystem Resilience in a Changing Climate - A Model Assessment
Get PDFSavannas play a crucial role in providing essential ecosystem services, including carbon sequestration, biodiversity conservation, and water regulation. However, these ecosystems face threats from changing climatic conditions and unsustainable rangeland practices. Intensive livestock grazing has led to widespread degradation of savanna systems, characterised by shrub encroachment and loss of ecosystem functions. Shifting rangeland use from cattle grazing to native herbivores is proposed to reverse these negative trends, but the consequences for ecosystem properties and processes are not yet clear. Climate change and extreme events such as droughts exacerbate the challenges faced by savannas, potentially affecting the provision of essential ecosystem services on which local people’s livelihoods depend. Ensuring savanna resilience to environmental stressors, especially increased aridity, is essential for sustaining these vital services. This resilience largely depends on the interaction between herbivores, vegetation composition, and climate. Unfortunately, our understanding of this interaction is limited, and current research has not addressed how savannas will respond to uncertain future climate conditions under different rangeland management practices.
In this thesis, I used the ecohydrological simulation model EcoHyD to investigate the effects of different rangeland practices on vegetation and water resources of a semi-arid savanna under current and future climate. This research makes two important contributions, first by examining the impacts of different future climate projections at a regional scale, which has not been the case in previous studies, and second by modelling rangeland types beyond grazing. In Chapter II of the study, I examined the impacts of grazing and browsing herbivores on plant diversity and ecosystem functioning. The results showed that intensive grazing negatively affects grass cover and water availability, whereas browsing herbivores increased vegetation cover, plant functional diversity, and water use. However, these outcomes may depend on herbivore community composition and climate contexts, especially when extreme events
Summary
like prolonged droughts occur. In Chapter III, I addressed these context-dependencies by investigating how different rangeland management options (i.e., grazer-dominated, mixed- feeders or browser-dominated herbivore communities) impact savanna ecosystems during droughts of varying durations. I found that diverse herbivore communities with a higher proportion of browsers combined with high plant functional diversity improve plant community resistance to drought and recovery after drought events, thus leading to enhanced ecosystem functioning and resilience. However, to fully understand ecosystem responses to climate change, temperature increases, precipitation changes and droughts need to be considered together. In Chapter IV, I therefore analysed the potential use of wild herbivore communities in regional climate adaptation plans to ensure the long-term resilience of savanna rangelands to the impacts of all aspects of uncertain climate change. My results have shown that while climate change alone does not necessarily lead to ecosystem degradation, in combination with poor management practices such as intensive grazing it can quickly lead to critical thresholds being exceeded. On the other hand, I have found that reducing the density of grazers and including mixed herbivores and browsers can promote ecosystem stability and resilience. Crossing tipping points can thus be delayed, or even avoided.
In conclusion, my research suggests that utilising diverse herbivores and functionally diverse plant communities in rangeland management strategies can improve ecosystem resilience, minimise the risk of irreversible degradation, and better manage uncertainties associated with climate change
Data from: Savanna resilience to droughts increases with proportion of browsing wild herbivores and plant functional diversity
No full text<p><span>1. Maintaining the resilience and functionality of savannas is key to sustaining the ecosystem services they provide. This maintenance is largely dependent on the resilience of savannas to stressors, such as prolonged droughts. The resilience to drought is largely determined by the interaction of herbivores and the functional composition of vegetation. So far, our understanding and ability to predict the response of savannas to drought under different types of rangeland use and as a function of vegetation composition are still limited.</span></p>
<p><span>2. In this study, we used the ecohydrological, spatially-explicit savanna model EcoHyD to determine if the resilience of a savanna rangeland towards prolonged droughts can be enhanced by the choice of rangeland use type (grazer-dominated, mixed-feeders or browser-dominated) and animal density. We evaluated the ability of a Namibian savanna system to withstand droughts and to recover from droughts based on its perennial grass cover and the overall species composition. </span></p>
<p><span>3. Generally, we determined a low resilience under high grazer densities.</span> <span>Most importantly, we found that functional diversification of herbivores and plants acted as resilience insurance against droughts, leading to greater resistance and recovery of perennial grasses. In particular, a higher proportion of herbivores allowed for higher resilience, probably also due to a short-term switch to more drought-resistant or unpalatable species. </span></p>
<p><span>4. In this case, herbivore diversification was of high self-regulatory value </span><span>by reestablishing trophic complexity</span><span>, reducing the need for additional management interventions. </span></p>
<p><span>5. <strong>Synthesis and applications</strong></span><span><strong>. </strong>Savanna systems will be more resistant to drought if (i) a dense perennial grass cover is maintained, protecting the topsoil from heat-induced water losses and erosion, encompassing functionally important species that are particularly well adapted to water stress and that are palatable, if (ii) the grazing pressure is adjusted to the productivity of the system, and (iii) the herbivore community includes browsers. </span></p><p>Funding provided by: Bundesministerium für Bildung und Forschung<br>Crossref Funder Registry ID: http://dx.doi.org/10.13039/501100002347<br>Award Number: FKZ 01LL1804A</p><p>Funding provided by: Bundesministerium für Bildung und Forschung<br>Crossref Funder Registry ID: http://dx.doi.org/10.13039/501100002347<br>Award Number: FKZ 01LL1804B</p>
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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