1,720,959 research outputs found
Management options for the conversion of allochthonous coniferous forest patches towards more natural species composition in the Vorpommersche Boddenlandschaft National Park, NE Germany
No full textThe conversion of coniferous tree plantations towards natural self-regenerating forests is one of the targets of forestry in Europe and particularly desirable in national parks. The aim of this study was to evaluate the effectiveness of different conversion approaches (conducted once) on natural forest development in man-made spruce plantations. We studied the effects of three distinct management options (partial-cutting [PC], clear-cutting with timber removal [CC] and clear-cutting with timber remaining [CCr]) six years after application on tree regeneration (sapling identity, abundance, height, browsing intensity) and understorey species composition in former spruce plantations within the Vorpommersche Boddenlandschaft National Park in Northeastern Germany. An unmanaged spruce [M] and near-natural beech [N] stands were considered as local references. The sites differed significantly in tree regeneration and understorey species composition. The abundance of native tree saplings was highest at site CCr, their height did not differ among sites, while browsing intensity was most pronounced at site CC. Understorey species composition of all management options was equally dissimilar to site N. However, site CCr contained more species that are typically abundant in local beech forests. Clear-cutting of spruce plantations with dead wood remaining on site favoured the natural regeneration of native trees and understorey vegetation compared to clear-cutting with timber removal, partial-cutting and no management. Herbivore browsing detrimentally affected tree regeneration independent of the treatment. Clear-cutting with timber removal promoted the dominance of competitive herbaceous species that may hamper long-term forest regeneration. We conclude that progression of site CCr appears to proceed fastest towards natural forest conditions. Further long-term data is required to derive clear trends regarding time and direction of forest regeneration. Keywords: forest conversion, spruce plantations, beech forest, natural tree regeneration, understorey species composition, deer browsin
Changes of vegetation in coniferous monocultures in the context of conversion to mixed forests in 30 years – Implications for biodiversity restoration
No full textDrivers of tree regeneration in coniferous monocultures during conversion to mixed forests in Central Europe – Implications for forest restoration management
No full texthttp://dx.doi.org/10.13039/501100010269 Bavarian Ministry of Food Agriculture and Forestryhttp://dx.doi.org/10.13039/501100003385 University of GöttingenOpen-Access-Publikationsfonds 202
Diversification of coniferous monocultures in the last 30 years and implications for forest restoration: a case study from temperate lower montane forests in Central Europe
No full textPlanted monocultures of even-aged coniferous tree species are abundant worldwide but increasingly damaged by biotic and abiotic stressors and disturbances. In Central Europe, a fundamental goal of ecologically oriented forest management is thus the conversion of pure and often even-aged coniferous stands into structurally more diverse and mixed broad-leaved forests. This conversion is often achieved by single-tree selection resulting in small canopy openings that promote artificial or natural regeneration. Consequently, forest conversion aims at altering stand structure and tree communities. In order to describe the status quo of forest conversion and derive implications for forest management, we investigated changes of tree composition and forest structure in the Bavarian Spessart mountains in southwest Germany. We conducted a resurvey of 108 semi-permanent plots in four different coniferous stand types of Norway spruce, Scots pine, Douglas fir, and European larch about 30 years after the initial survey. We found significant differences in the stratification and cover of respective forest layers between the two sampling periods that indicated an increase in stand structural heterogeneity. While species richness of the overstorey remained constant, species richness and diversity of the shrub and lower canopy layer increased significantly. Regenerating “winner” species included late-successional broad-leaved (e.g., European beech, sessile oak), pioneer broad-leaved (e.g., silver birch, rowan) and shade-tolerant coniferous (e.g., silver fir, Douglas fir) species. Although Norway spruce was significantly reduced in the overstorey, it regenerated in parts extensively in the understorey. We conclude that the forest conversion in the Spessart mountains was overall successful in terms of diversifying forest structure and tree species. Its effects are, though, still emerging and the stands are in a transitional phase. Besides the preferred natural regeneration of target tree species, forest management may consider active measures to guide the facilitated diverse tree community of previously pure and even-aged coniferous stands towards stand maturity.Bayerisches Staatsministerium für Ernährung, Landwirtschaft und Forsten http://dx.doi.org/10.13039/501100010269Georg-August-Universität Göttingen 50110000338
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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