1,720,954 research outputs found
Seed conservation biology in the Hawaiian flora
No full textThe estimated rate of ongoing plant extinctions per year is up to 500 times the background extinction rate, and this is of even greater concern when the species at risk are endangered and endemic. Endemism-scaled richness of vascular plants is 9.5 times higher on oceanic islands than on continents, with land cover change being a primary threat. Hawaiʻi, the most isolated archipelago on Earth, has less than 1% of the land mass of the rest of the United States, it contains over half of all the federally listed endangered species, and has over 250 plant taxa with fewer than 50 individuals remaining in the wild. Therefore, the need for understanding plant conservation practices in Hawaiʻi and beyond are more urgent than ever. Fortunately, seed banking provides the most efficient and cost-effective means of ex situ plant conservation. However, not all species can be conserved by conventional seed banking methods and even in those that can, current genebank standards may not be maximizing seed longevity. Seed traits that lend to a species being able to be conserved long-term by conventional methods include desiccation (i.e. drying) and long-term freeze tolerance (i.e. orthodox seed storage behavior). Although many species of the Hawaiian flora produce desiccation tolerant seeds, some sensitivity to long-term freezing stress (reduced longevity) has been detected in Hawaiian Lobelioideae (Campanulaceae), Cyperaceae, Rubiaceae, and Urticaceae. To date, the Hawaiian flora is the largest reported with this curious intermediate “freeze-sensitive” storage behavior.Recently each of the 256 Kauaʻi endemic taxa were reviewed for the IUCN Red List of Threatened Species and in Chapter I our synthesis of these Red List Assessments showed that 95% were threatened by extinction and 5% were already extinct at least in the wild. This emphasized the need for urgent and effective seed banking intervention in support of global and local plant conservation strategies.Both seed banking efforts and restoration efforts can be challenged by lack of information on seed germination and dormancy, thus germination studies are especially relevant for seed accessions of rare plants where seed lot size is usually small. In order to answer the many questions pertaining to longevity and storage behavior, it is necessary to have a reliable estimate of viability, and this is usually quantified through germination testing. However, when seed dormancy is present, germination and viability are not necessarily of equal value. Thus, we need to first investigate seed dormancy and germination ecology to interpret seed survival data and improve seed banking and restoration outcomes. In Chapter II we found physiological dormancy (PD) in the majority of the 29 Hawaiian montane species studied. In Chapter III we found that Coprosma kauensis exhibited physiological dormancy (PD), and was desiccation tolerant, and initially freeze tolerant after six months of storage at the conventional (-20°C) temperature. In Chapter IV we studied six species of Hawaiian Lobelioids and found morphophysiological dormancy (MPD), but did not study the endemic genus Brighamia. We therefore examined Brighamia rockii in Chapter V and found the species to exhibit morphological (MD) or morphophysiological dormancy (MPD). B. rockii germinated in the dark, which is very rare for Campanulaceae, but also means that the species is unlikely to form a persistent soil seed bank. In Chapter VI we investigated the effect of environmental variables and seed zone on initial viability and found that there was no correlation with environmental variables, but there was with seed zone. With climate change comes increasing storm frequency and intensity, drought, and sea level rise, all of which increase salinity especially in coastal habitats. In Chapter VII we investigated the effects of increased salinity on 21 species of Hawaiian coastal plants and found varying levels of salinity tolerance among species.Germination modelling of rare species can be hindered by limited seed availability, which can severely restrict experimental design. Previously, a novel approach to model germination was developed for complex germination experiments that use fully parametric statistical models that are readily interpretable, produces biologically meaningful and important parameters, and accounts for random effects between replicates (Petri dishes). In Chapter VIII we propose an improved two-step analysis of germination data from complex experimental designs.Understanding the relative longevity between accessions, genotypes, species, or experimental treatments is relevant to anyone concerned retention of viability. In Chapter IX we explain why we consider p50, defined as the time during storage when seed lot viability, as measured through a germination test, has declined to 50%, is a suitable longevity trait parameter. Moisture content determination is one of the most important and common assessments made on seeds, and controlling the amount of moisture in seeds is one of the biggest factors that determine seed longevity. In Chapter X we review various methods for assessing the moisture status of seeds, and also discuss various ways to adjust the moisture content of seeds in preparation for longevity assessments or seed banking.In Chapter XI we targeted Kauaʻi species with fewer than 50 individuals remaining in the wild and harvested seeds from herbarium specimens and tested for viability and actual longevity. Only one of >2000 seeds sown germinated, thus we recommend that these types of “resurrection” projects be carried out sooner rather than later before seed viability further decreases under the suboptimal environmental conditions of herbaria. In Chapter XII, we used differential scanning calorimetry to generate lipid thermal fingerprints for Hawaiian and related Lobelioideae, and test several hypotheses relating to temperature sensitive seed storage traits. We found, among other things, large lipid melting events around the conventional seed banking temperature (-20°C) which could explain why desiccation tolerant “freeze sensitive” seed storage behavior is reported for this group in Hawaiʻi
Plant Ecology of Arid-land Wetlands; a Watershed Moment for Ciénega Conservation
Full text linkabstract: It’s no secret that wetlands have dramatically declined in the arid and semiarid American West, yet the small number of wetlands that persist provide vital ecosystem services. Ciénega is a term that refers to a freshwater arid-land wetland. Today, even in areas where ciénegas are prominent they occupy less than 0.1% of the landscape. This investigation assesses the distribution of vascular plant species within and among ciénegas and address linkages between environmental factors and wetland plant communities. Specifically, I ask: 1) What is the range of variability among ciénegas, with respect to wetland area, soil organic matter, plant species richness, and species composition? 2) How is plant species richness influenced locally by soil moisture, soil salinity, and canopy cover, and regionally by elevation, flow gradient (percent slope), and temporally by season? And 3) Within ciénegas, how do soil moisture, soil salinity, and canopy cover influence plant species community composition? To answer these questions I measured environmental variables and quantified vegetation at six cienegas within the Santa Cruz Watershed in southern Arizona over one spring and two post-monsoon periods. Ciénegas are highly variable with respect to wetland area, soil organic matter, plant species richness, and species composition. Therefore, it is important to conserve the ciénega landscape as opposed to conserving a single ciénega. Plant species richness is influenced negatively by soil moisture, positively by soil salinity, elevation, and flow gradient (percent slope), and is greater during the post-monsoon season. Despite concerns about woody plant encroachment reducing biodiversity, my investigation suggests canopy cover has no significant influence on ciénega species richness. Plant species community composition is structured by water availability at all ciénegas, which is consistent with the key role water availability plays in arid and semiarid regions. Effects of canopy and salinity structuring community composition are site specific. My investigation has laid the groundwork for ciénega conservation by providing baseline information of the ecology of these unique and threatened systems. The high variability of ciénega wetlands and the rare species they harbor combined with the numerous threats against them and their isolated occurrences makes these vanishing communities high priority for conservation.Dissertation/ThesisMasters Thesis Plant Biology 201
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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