1,721,075 research outputs found
negative diversity effect, dominant influence of management regime
No full textBackground: Agricultural intensification has transformed most grasslands of Central Europe from non-intensive to highly intensive management during the last 50 years, resulting in large reductions of species diversity. This impoverishment has raised concern with regard to ecosystem functions. Positive diversity effects on productivity have been found in experiments with synthetic grasslands but were rarely confirmed in semi-natural grasslands in the field. Aims: Our objective was to investigate the diversityproductivity relationship independently from management effects in mature grassland. Methods: We conducted a three-factorial experiment (fertilisation, mowing frequency, diversity; n?=?6) in a permanent grassland to disentangle effects of management intensity and diversity on above-ground biomass (AGB), fine root biomass and root distribution patterns. Herbicides were applied to increase the diversity gradient across the plots. Results: While fertilisation had a strong positive effect on AGB and the cutting frequency a minor one, AGB was negatively related to species richness. Root biomass and distribution gave no indication of below-ground complementary resource use. Conclusions: The N-driven productivity increase since the 1950s is by far more influential on above-ground productivity than any diversity effect. Field manipulation studies in mature communities are needed to understand the productivitydiversity relationship in grasslands under changing land use.Ministry of Science and Culture of Lower Saxon
Root trait responses of six temperate grassland species to intensive mowing and NPK fertilisation: a field study in a temperate grassland
No full textBackground and aims Plant traits may characterize functional ecosystem properties and help to predict community responses to environmental change. Since most traits used relate to aboveground plant organs we aim to explore the indicative value of root traits. Methods We examined the response of root traits (specific root length [SRL], specific root surface area [SRA], root diameter [RD], root tissue mass density [TMD], root N concentration) in six grassland species (3 grasses, 3 herbs) to four management regimes (low vs. high mowing frequency; no fertilization vs. high NPK fertilization). The replicated experiment in temperate grassland with long continuity simulated the increase in grassland management intensity in the past 50 years in Central Europe. Results Increasing mowing frequency (one vs. three cuts per year) led to no significant root trait changes. NPK fertilization resulted in considerable trait shifts with all species responding in the same direction (higher SRL, SRA and N concentration, lower TMD) but at different magnitude. Fertilization-driven increases in SRA were mainly caused by lowered tissue density while root diameter reduction was the main driver of SRL increases. Conclusion We conclude that root morphological traits may be used as valuable indicators of environmental change and increasing fertilization in grasslands
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
Management alters interspecific leaf trait relationships and trait‐based species rankings in permanent meadows
No full textQuestion Plant functional traits have the potential to characterize species ecological strategies and predict ecosystem responses to environmental changes. (1) Do trait responses to land‐use intensification alter trait‐based species rankings, and (2) does land‐use intensification alter relationships among interrelated leaf traits? Location Solling Mountains, Central Germany (Grassland management experiment, GrassMan). Methods Over the course of 2 yr with differing weather conditions, we analysed the specific leaf area (SLA) of eight grassland species and related it to leaf nitrogen per mass (Nmass) or area (Narea) in an old‐growth grassland with two fertilization levels (none vs NPK fertilization, 180‐30‐100 kg·ha−1·yr−1) and two cutting frequencies (one vs three cuts per season). Results NPK fertilization led to an expected increase in SLA, Nmass and Narea, while the effect of altered cutting frequency on leaf traits was more species‐specific. Species‐specific responses to management significantly altered trait‐based species rankings. A significant SLA–Nmass relationship occurred in unfertilized plots, whereas the SLA–Narea relationship was stronger in fertilized plots. This was mostly caused by a decrease in the among‐species variation in Nmass upon fertilization. Conclusions Although our results reflect only short‐term community responses, they indicate that trait‐based species ranking and the relationships between plant functional traits are not always consistent across different management regimes. Hence, trait values used to characterize species and communities should never be discussed without consideration of the set of environmental conditions under which they were measured
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