1,720,989 research outputs found
Shrub encroachment of temperate grasslands: effects of plant biodiversity and herbage production
No full textIn Europe, semi-natural grasslands are an important resource of biodiversity and are, therefore, of high conservation interest. They are often invaded by shrubs, and they are threatened by under-utilization or abandonment which leads to further shrub encroachment. A gradient analysis of shrub-invaded temperate grasslands (from shrub-free to pioneer forest) in Germany was carried out to study the effect of shrub encroachment on plant biodiversity, herbage mass and nutritive value of herbage, as well as the effect on seed bank-vegetation similarity. The latter was driven by the question of the role of the soil seed bank for ecological restoration (Bossuyt & Honnay 2008). Our hypotheses are: (1) An initial shrub invasion leads to enhanced habitat diversity and according to the habitat heterogeneity hypothesis (MacArthur & Wilson 1967) thereby to higher species diversity. (2) Shrub encroachment leads to a loss of similarity between vegetation and soil seed bank. (3) Herbage mass and variables describing nutritive value of herbage decrease with increasing shrub encroachment.The selected 30 plots (10 m x 10 m) covered a wide gradient of shrub encroachment. Canopy height of the shrubs was between 15 and 500 (1000) cm, and the canopy cover ranged from less than 1 % to nearly 100 %. We recorded a total of 203 vascular plant species in the vegetation. Number of species per plot ranged between 27 and 68 (mean = 44.5), maximum species number per square meter was 41. Highest species diversity was found at medium shrub invaded sites, which is in line with our hypothesis of a hump-back relation between shrub encroachment and plant biodiversity. Similarity between seed bank and aboveground vegetation (Jaccard s coefficient of community) ranged between 7.5 and 36.4 %. Highest similarity was found in intermediate shrub invaded grasslands. We have to reject our hypothesis of decreasing seed bank-vegetation similarity with increasing shrub encroachment, but we found evidence for decreasing similarity with changing vegetation composition from grassland to shrub and forest vegetation. The following plant functional types were positively correlated with Jaccard index: therophytes (life form), annual plants (life span), and proportion of forbs. We found a reduction of herbage mass of DM from 3570 to 210 kg ha-1 with increasing shrub encroachment. Metabolizable energy concentration of herbage ranged from 8.9 to 10.2 MJ kg-1 DM and crude protein concentration from 72 to 171 g kg-1 DM, both measures being positively correlated with shrub occurrence. Increasing shrub occurrence was associated with a decrease in water-soluble carbohydrates concentration (from 151 to 31 g kg-1 DM) and a reduction in the indicator forage value . The results are in line with our hypothesis of decreasing herbage mass, but are contradictory to the hypothesis of decreasing nutritive value of herbage with increasing shrub encroachment.Our results emphasise the importance of semi-natural grasslands as a resource of biodiversity. Conserving these grasslands is closely connected to continuous agricultural use. Our results indicate a potentially large agronomic value for shrub-encroached temperate grasslands and suggest its utilization for livestock production
Shrub encroachment of temperate grasslands: effects of plant biodiversity and herbage production
No full textIn Europe, semi-natural grasslands are an important resource of biodiversity and are, therefore, of high conservation interest. They are often invaded by shrubs, and they are threatened by under-utilization or abandonment which leads to further shrub encroachment. A gradient analysis of shrub-invaded temperate grasslands (from shrub-free to pioneer forest) in Germany was carried out to study the effect of shrub encroachment on plant biodiversity, herbage mass and nutritive value of herbage, as well as the effect on seed bank-vegetation similarity. The latter was driven by the question of the role of the soil seed bank for ecological restoration (Bossuyt & Honnay 2008). Our hypotheses are: (1) An initial shrub invasion leads to enhanced habitat diversity and according to the habitat heterogeneity hypothesis (MacArthur & Wilson 1967) thereby to higher species diversity. (2) Shrub encroachment leads to a loss of similarity between vegetation and soil seed bank. (3) Herbage mass and variables describing nutritive value of herbage decrease with increasing shrub encroachment.The selected 30 plots (10 m x 10 m) covered a wide gradient of shrub encroachment. Canopy height of the shrubs was between 15 and 500 (1000) cm, and the canopy cover ranged from less than 1 % to nearly 100 %. We recorded a total of 203 vascular plant species in the vegetation. Number of species per plot ranged between 27 and 68 (mean = 44.5), maximum species number per square meter was 41. Highest species diversity was found at medium shrub invaded sites, which is in line with our hypothesis of a hump-back relation between shrub encroachment and plant biodiversity. Similarity between seed bank and aboveground vegetation (Jaccard s coefficient of community) ranged between 7.5 and 36.4 %. Highest similarity was found in intermediate shrub invaded grasslands. We have to reject our hypothesis of decreasing seed bank-vegetation similarity with increasing shrub encroachment, but we found evidence for decreasing similarity with changing vegetation composition from grassland to shrub and forest vegetation. The following plant functional types were positively correlated with Jaccard index: therophytes (life form), annual plants (life span), and proportion of forbs. We found a reduction of herbage mass of DM from 3570 to 210 kg ha-1 with increasing shrub encroachment. Metabolizable energy concentration of herbage ranged from 8.9 to 10.2 MJ kg-1 DM and crude protein concentration from 72 to 171 g kg-1 DM, both measures being positively correlated with shrub occurrence. Increasing shrub occurrence was associated with a decrease in water-soluble carbohydrates concentration (from 151 to 31 g kg-1 DM) and a reduction in the indicator forage value . The results are in line with our hypothesis of decreasing herbage mass, but are contradictory to the hypothesis of decreasing nutritive value of herbage with increasing shrub encroachment.Our results emphasise the importance of semi-natural grasslands as a resource of biodiversity. Conserving these grasslands is closely connected to continuous agricultural use. Our results indicate a potentially large agronomic value for shrub-encroached temperate grasslands and suggest its utilization for livestock production
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
The nature of interaction between Israeli entrepreneurs and investment capital available within and from outside Israel
No full textIsrael is a small country that has rapidly become a global leader in production of high-tech goods. Supporting this industry is strong investment and high levels of entrepreneurship. Some scholars suggest a close similarity between the Israeli Venture Capital industry and that of Silicon Valley. To validate that claim I have closely replicated a network model developed for entrepreneur-venture capital interactions in Silicon Valley and applied it to Israel. This has been achieved through mapping the linkages with a 3D network modelling software (Pajek) between biotech firms created since 2000 and other players in the Israeli market such as venture capital funds, universities and government institutions. Information gathered on the entrepreneurs responsible for the biotech firms creation suggests that the majority are either professors at research institutes or hold a doctorate degree, suggesting strong linkages between the entrepreneurs and their research institutes. Many firms are also found to employ professional management teams. The matrix of inter-connections and supporting institutions suggests that biotech research institutions have a strong focus on fostering commercialization of new technologies. There is also abundant support for high-tech and venture capital from the Israeli government, which is a point of difference between Israel and Silicon Valley. Taken together the strong presence of institutions and of government support may explain,at least in part, the attractiveness of Israel for investors despite the country’s precarious and uncertain condition as one of the global war and conflict hot spots
Institutions as economic growth determinants: a comparative study of New Zealand and Argentina
No full textThrough the last two and a half decades academia has realised that viable explanations of the rise and decline of nations in a world in dramatic economic and political change requires more than a static neoclassical model. Among the flourishing research on institutions as economic growth determinants are the two distinct theories of Douglass North, the co-recipient of Nobel Prize in 1993, and Mancur Olson. Both scholars claim the universality of their approaches in explaining real world economic history. However, research on the differences in their theories and their applicability to small and remote countries, like New Zealand and Argentina, remains in its early stages. A more detailed investigation of conceptual differences may clarify particular economic growth parameters, and may provide more empirical support for each theory. Thus, the research question is: Can the economic growth patterns of New Zealand and Argentina of the last quarter century be explained either by Douglass North’s ‘cultural heritage’ hypothesis or by Mancur Olson’s ‘country-specific economic policy’ hypothesis? Firstly, an in-depth literature review of Douglass North’s and Mancur Olson’s latest academic work is conducted. Based on the examination of commonalities and differences in their terminologies and concepts, a conceptual framework for further empirical tests is derived. The framework is used to evaluate New Zealand’s and Argentina’s economic growth patterns in order to address the abovementioned research question. The assessment of the literature reveals that both scholars share the notion of the role of the state in providing well-defined individual property rights, low transaction cost levels, and well-developed national capital markets to achieve economic growth potential. They ascribe growth-fostering characteristics to institutions of Britain and other relating democracies, while they see obstacles for economic success for Latin American countries. On the other hand, their propositions differ substantially in the foundation of economic policy and its ability to adjust over time. The findings of the empirical research show that institutions play a major role. However, the proposed differences in the aforementioned indicators exist only to a limited extent. An enhanced understanding is obtained that New Zealand’s and Argentina’s economic growth patterns cannot be solely explained neither by North’s nor Olson’s theory. A combination of both theories and further amendments might account more accurately for the actual economic histories of the two countries
Institutions as economic growth determinants: a comparative study of New Zealand and Argentina
No full textThrough the last two and a half decades academia has realised that viable explanations of the rise and decline of nations in a world in dramatic economic and political change requires more than a static neoclassical model. Among the flourishing research on institutions as economic growth determinants are the two distinct theories of Douglass North, the co-recipient of Nobel Prize in 1993, and Mancur Olson. Both scholars claim the universality of their approaches in explaining real world economic history. However, research on the differences in their theories and their applicability to small and remote countries, like New Zealand and Argentina, remains in its early stages. A more detailed investigation of conceptual differences may clarify particular economic growth parameters, and may provide more empirical support for each theory. Thus, the research question is: Can the economic growth patterns of New Zealand and Argentina of the last quarter century be explained either by Douglass North’s ‘cultural heritage’ hypothesis or by Mancur Olson’s ‘country-specific economic policy’ hypothesis? Firstly, an in-depth literature review of Douglass North’s and Mancur Olson’s latest academic work is conducted. Based on the examination of commonalities and differences in their terminologies and concepts, a conceptual framework for further empirical tests is derived. The framework is used to evaluate New Zealand’s and Argentina’s economic growth patterns in order to address the abovementioned research question. The assessment of the literature reveals that both scholars share the notion of the role of the state in providing well-defined individual property rights, low transaction cost levels, and well-developed national capital markets to achieve economic growth potential. They ascribe growth-fostering characteristics to institutions of Britain and other relating democracies, while they see obstacles for economic success for Latin American countries. On the other hand, their propositions differ substantially in the foundation of economic policy and its ability to adjust over time. The findings of the empirical research show that institutions play a major role. However, the proposed differences in the aforementioned indicators exist only to a limited extent. An enhanced understanding is obtained that New Zealand’s and Argentina’s economic growth patterns cannot be solely explained neither by North’s nor Olson’s theory. A combination of both theories and further amendments might account more accurately for the actual economic histories of the two countries
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
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