1,721,091 research outputs found
Changes in soil organic carbon stocks and fractions following forest expansion on subalpine grasslands
Full text linkThe abandonment of grasslands represents the dominant land-use change (LUC) and the main driver for the establishment of new forest areas in many regions of the European Alps. Fractions sensitive to LUC can be indicative of changes in soil organic carbon (SOC) and they can allow a better understanding of OC stabilization processes. Despite the key role played by physical OC fractions, it is still unclear how they respond to forest
expansion on abandoned grasslands. Our aim was therefore to explore the impact of LUC on SOC storage, focusing on the effect of grassland abandonment and forest expansion on physical OC fractions.
In a subalpine area of the Trentino region, Italy, four land use types were investigated: i) managed grassland, mown and fertilized for more than 100 years; ii) grassland abandoned around 10 years ago, with shrubs and Picea abies saplings; iii) early-stage forest, dominated by P. abies and established on a grassland abandoned
around 1970; iv) old forest, dominated by Fagus sylvatica and P. abies. For each land use type, three subplots were sampled with eight soil cores to 30 cm depth. SOC stocks were calculated after determination of bulk density, stoniness, root biomass and organic carbon content. Aggregate size fractions were obtained through wet-sieving using a series of sieves (2000, 250, 53 mm mesh size). In size-density fractionation, a silt and clay fraction 50 mm, after physical dispersion of aggregates. The fraction >50 mm was further separated at a density of 1.6 g cm-3 in sodium polytungstate, for the estimation of particulate organic matter (POM) and stable aggregates.
Especially in the top 10 cm, mineral soil OC stocks were lower in early-stage and old forest (-28%) than in managed and abandoned grasslands. Despite a tendency toward increasing mean size of aggregates according
to aggregate size fractionation, size-density fractionation revealed a significant decline in OC allocation to stable aggregates from grassland to forest. In 0-10 cm, the fraction of SOC stored in stable aggregates shifted from 78% in managed grassland to 59% in the old forest. Size-density fractionation also showed that a greater fraction of SOC was stored in POM in the old forest (18% of SOC stock) compared with the managed grassland (5%), but it
did not compensate for the decreased OC accumulation in stable aggregates. The OC allocation to silt and clay fractions remained unchanged, thus showing lower response to LUC. The decline in SOC storage in stable aggregate fractions was indicative of the decreasing total mineral SOC stocks after forest expansion on subalpine grasslands. Higher OC allocation to POM fraction in the mineral soil and changed carbon distribution between mineral and organic soil layers suggest an overall decrease in SOC stability and a concomitant shift to more labile OC fraction
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
Effects of forest expansion on mountain grassland: changes within soil organic carbon fractions
No full textBackground and Aims Grassland abandonment followed by forest succession is the dominant land-use change in the European Alps. We studied the impact of current forest expansion on mountain grassland on changes in physical soil organic carbon (SOC) fractions along a land- use and management gradient, focusing on changes in aggregate stability and particulate organic matter (POM).
Methods Four successional stages were investigated: managed grassland, two transitional phases in which grassland abandonment led to colonization by Picea abies (L.) Karst., and old mixed forest dominated by Fagus sylvatica L. and P. abies. Soil samples collected from the mineral soil (0-5 cm, 5-10 cm, 10-20 cm0-20 cm) were fractionated following two procedures: 1) aggregate size fractionation, separating aggregates based on their dimension, and 2) size-density fractionation, separating stable aggregates from non-occluded POM.
Results The dimension of aggregates assessed by aggregate -size fractionation tended to increase, whereas SOC allocation to stable aggregates assessed by size-density fractionation decreased following conversion of grassland to forest (e.g from 81 to 59% in the 0-5 cm layer). The amount of SOC stored in POM increased by 3.8 Mg ha-1 in the integrated 0-20 cm layer from managed grassland to old forest.
Conclusions The combination of two physical SOC fractionation procedures revealed that natural fForest succession on abandoned grasslands led to a decline in physical SOC stability in the mineral soil, suggesting that SOC can become more susceptible to management and environmental modifications as indicated by decreased amounts of stable aggregate C and increased amounts of POM-C
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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