1,721,000 research outputs found
Do endogeic earthworms change plant competition? A microcosm study
No full textPlants compete for limited resources. Although nutrient availability for plants is affected by resource distribution and soil organisms, surprisingly few studies investigate their combined effects on plant growth and competition. Effects of endogeic earthworms (Aporrectodea jassyensis), root-knot nematodes (Meloidogyne incognita) and the spatial distribution of N-15 labelled grass litter on the competition between a grass (Lolium perenne), a forb (Plantago lanceolata) and a legume (Trifolium repens) were investigated in the greenhouse. Earthworms promoted N uptake and growth of L. perenne. Contrastingly, shoot biomass and N uptake of T. repens decreased in the presence of earthworms. P. lanceolata was not affected by the earthworms. We suggest that earthworms enhanced the competitive ability of L. perenne against T. repens. Nematodes increased the proportion of litter N in each of the plant species. Litter distribution (homogeneous vs. patch) did not affect the biomass of any plant species. However, P. lanceolata took up more N-15, when the litter was homogeneously mixed into the soil. The results suggest that endogeic earthworms may affect plant competition by promoting individual plant species. More studies including decomposers are necessary to understand their role in determining plant community structure
Earthworms and litter distribution affect plant-defensive chemistry
No full textStudies on plant-defensive chemistry have mainly focused on plants in direct interaction with aboveground and occasionally belowground herbivores and pathogens. Here we investigate whether decomposers and the spatial distribution of organic residues in soil affect plant-defensive chemistry. Litter concentrated in a patch ( vs. homogeneously mixed into the soil) led to an increase in the aucubin content in shoots of Plantago lanceolata. Earthworms increased total phytosterol content of shoots, but only when the litter was mixed homogeneously into the soil. The phytosterol content increased and aphid reproduction decreased with increasing N concentration of the shoots. This study documents for the first time that earthworms and the spatial distribution of litter may change plant-defensive chemistry against herbivores
Effects of earthworms and organic litter distribution on plant performance and aphid reproduction
No full textHuman management practices and large detritivores such as earthworms incorporate plant litter into the soil, thereby forming a heterogeneous soil environment from which plant roots extract nutrients. In a greenhouse experiment we investigated effects of earthworms and spatial distribution of N-15-labelled grass litter on plants of different functional groups [Lolium perenne (grass), Plantago lanceolata (forb), Trifolium repens (legume)]. Earthworms enhanced shoot and root growth in L. perenne and P. lanceolata and N uptake from organic litter and soil in all plant species. Litter concentrated in a patch (compared with litter mixed homogeneously into the soil) increased shoot biomass and N-15 uptake from the litter in L. perenne and enhanced root proliferation in P. lanceolata when earthworms were present. Growth of clover (T. repens) was rather independent of the presence of earthworms and organic litter distribution: nevertheless, clover took up more nitrogen in the presence of earthworms and exploited more N-15 from the added litter than the other plant species. The magnitude of the effects of earthworms and organic litter distribution differed between the plant species, indicating different responses of plants with contrasting root morphology. Aphid (Myzus persicae) reproduction was reduced on P. lanceolata in the presence of earthworms. We suggest that earthworm activity may indirectly alter plant chemistry and hence defence mechanisms against herbivores
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
- …
