1,720,956 research outputs found
Managing European beech (Fagus sylvatica L.) forests for construction wood
No full textWhile the demand for construction wood is increasing, and Norway spruce faces declining area shares and increased climate-related risks, European beech has proven to offer adequate stiffness and bending strength for construction wood out of glued laminated timber (GLT). This study aims to identify the most suitable stand treatment for maximizing beech construction wood production. The research was conducted across a unique dataset of 19 long-term permanent plots, characterized by very contrasting and modern thinning methods (intense (A) and moderate (B)) and an extremely long running time (starting 1968–1971). Continuous measurements up to 2009 enabled an empirical analysis of construction timber yield during the thinning and in the remaining stands 2009. Additionally, growth and timber assortments by intended use and diameter classes were modelled based on crown projection area and diameter at breast height (DBH). A quality-based sorting, however, was neither feasible due to the available data nor required by the world’s leading manufacturer of beech construction timber (Pollmeier Massivholz GmbH & Co.KG). Results indicate that moderate thinning, combined with moderate annual diameter increment and relatively long rotation periods, maximizes the production of beech construction wood with a mid-diameter of the trunks of at least 30 cm. In contrast, intense thinning is only suitable for achieving higher target diameters. Following these recommendations the study suggests that the number of target trees could exceed current practice. These findings challenge existing literature recommendations and provide alternative management strategies for beech stands, although they contrast with guidelines for ensuring climate-stable stands
Quantifying and mapping the ready-to-use veneer volume of European beech trees based on terrestrial laser scanning data
No full textUsing 3D point clouds obtained with terrestrial laser scanning (TLS), we automatically and non-destructively quantified and mapped the estimated veneer wood volume of standing trees in differently structured beech stands. To mitigate climate change, we need to utilise wood for long-term carbon storage in products like construction wood and for substituting building materials based on fossil fuels. As the supply of wood from Norway spruce decreases, alternative species like beech must be considered for construction purposes. We present an approach to quantify and map the volume available for veneer production in beech forests. Our method is based on point clouds derived from TLS. We studied three forest plots, each with two different treatments (moderate vs. heavy thinning), resulting in varying stand basal areas ranging from 25 m2 to 36 m2 per hectare. We fitted different configurations of veneer rolls into point clouds of tree stems, choosing the configuration that yielded the highest volume of veneer wood. Our automatic optimisation algorithm ensured no misplaced veneer rolls. At the tree level, veneer wood volume was higher in intensely thinned stands. At the stand level, overall veneer volume was higher in moderately thinned stands, whereas the overall veneer share was higher in the heavily thinned stands. The veneer volume of a tree depended on diameter at breast height, crown base height, taper and curvature depth. Our approach detects all trees in a forest potentially ready for veneer production and shows the direct volumetric outcome under bark. This enables the planning of tree selection for harvest based on adaptable requirements for the veneer 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
Abschätzung der Produktivität verschiedener Baumarten für ausgewählte Standorte auf der Grundlage von Höhenanalysen
No full textDie Optimierung der Produktivität von Wäldern ist ein wichtiges Thema. Während die Optimierung des Reinertrages schon seit Langem im Fokus steht, rückt auch die Optimierung der Volumenproduktion und der CO2-Sequestrierung zunehmend in den Mittelpunkt der Aufmerksamkeit. Die vorliegende Studie sollte dazu mit Berechnungen zu ausgewählten Standorten im Beispielwaldbetrieb Forstgut Sattelmühle im Pfälzerwald einen Beitrag leisten. Datengrundlage der Arbeit war neben den eigenen Erhebungen die aktuelle Forsteinrichtung und Standortskartierung des Forstgutes für die naturale Produktion sowie die durchschnittlichen Holzpreise, durchschnittlichen Holzerntekosten und die Standardkosten-Kalkulationsbasis des Forstamtes Johanniskreuz für die ökonomischen Berechnungen.Nach Auswahl von drei für den Betrieb repräsentativen Standortseinheiten („frische Sande“, „mittlere mäßig arme Sande“, „trockene arme Sande“) und Erhebung der relevanten waldwachstumskundlichen Daten für die Kiefer (Pinus sylvestris L.), Fichte (Picea abies L.), Douglasie (Pseudotsuga menziesii Mirb.), Buche (Fagus sylvatica L.) und Traubeneiche (Quercus petraea (Matt.) Liebl.) vor Ort, wur-den auf Grundlage traditioneller Ertragstafeln standortspezifische Bonitierungen durchgeführt und mit Hilfe von Höhenanalysen unter Verwendung der Sloboda-Funktion aktualisierte Höhenwachstumsfächer erstellt. Auf deren Basis und unter zur Hilfenahme moderner Produktionsprogramme konnten aktualisierte, den gegenwärtigen Höhenwachstumsverlauf und die aktuelle Bestandesbehandlung besser darstellende, Ertragstafeln erzeugt werden. Zur Bestimmung des ausscheidenden Bestandes und der zu verkaufenden Sortimente wurden diese neuen Ertragstafeln und die Bestandessortentafel nach SCHÖPFER & DAUBER (1989) verwendet. Hiermit konnten die jährlichen Reinerträge aus der Holzproduktion je Hektar für die betrachteten Baumarten bei Zinssätzen von 0, 1, 2 und 3 % errechnet und verglichen werden. Unter Verwendung baumartenspezifischer Raumdichten konnten für die einzelnen Baumarten und Standorte die Kohlenstoffaufnahme im Derbholz errechnet und untereinander verglichen werden. Auf dem Standort „frische Sande“ sind bei höchsten Zuwächsen und C-Speicherungsraten auch die größten Reinerträge, auf „trockenen armen Sanden“, begründet durch schlechte Ertragsklassen, bei geringem Zuwachs und geringer C-Speicherung die niedrigsten Reinerträge aus der Holzproduktion zu erzielen. Bei allen Baumarten war bei Verwendung der traditionellen Ertragstafeln eine Bonitätsdrift erkennbar, die bei Kiefer und Buche am geringsten ausfiel. Die deutlichsten Bonitätsveränderungen zeigte die Douglasie. Beim Vergleich der Volumenzuwächse der einzelnen Baumarten schnitten Buche (4,5-7,8 Vfm/ha/a) und Kiefer (5,0-8,0 Vfm/ha/a) am schlechtesten ab. Die Eiche (5,6-11,7 Vfm/ha/a) wies gerade auf mittleren mäßig armen Sanden höhere Zuwächse auf. Die Douglasie (13,7-23,7 Vfm/ha/a) zeigte ihre Überlegenheit auf allen Standortseinheiten deutlich, wobei sie auf den frischen Sanden das größte Ausmaß erreichte und bis zu den trockenen armen Sanden kontinuierlich absank. Die Fichte (12,8-15,8 Vfm/ha/a) nahm eine Zwischenstellung zwischen Douglasie und Eiche ein. Die gemittelte dGz100-Bonität über alle drei Standortseinheiten bei aktueller Baumartenverteilung lag bei 8,7 Vfm/ha/a.Auch bei der Betrachtung der zu erwartenden Reinerträge aus der Holzproduktion zeigen Buche und Kiefer auf allen Standorten die geringsten Werte. Die höchsten Reinerträge – etwa 9- bis 10-mal so hoch wie bei Buche – sind durch die Douglasie zu erzielen. Die mit Fichte zu erzielenden Gewinne liegen in etwa bei 47 % (auf frischen Sanden) bzw. 62 % (auf mittleren mäßig armen Sanden) der Douglasien-Werte. Für Eiche, die bei 0 % Zins in der Lage ist, sehr hohe Gewinne zu erzielen (auf mittleren mäßig armen Sanden die höchsten), wirkt sich durch hohe Kosten zu Beginn des Bestandeslebens die Verzinsung sehr stark aus, sodass sie schon bei unter 2 % Verzinsung nicht mehr als wirtschaftlich sinnvolle Alternative zu den beiden Nadelholzarten Douglasie und Fichte zu betrachten ist. Der durchschnittliche Reinertrag aus der Holzproduktion ohne Zinsberücksichtigung liegt für die betrachteten Standorte und die aktuelle Baumartenverteilung bei rund 341 €/ha/a. Auch ohne Berücksichtigung der betrieblichen Fixkosten liegt der interne Zinsfuß für alle Baumarten außer Douglasie (2,4 bis 4,0 %) und Fichte (2,2 bis 2,7 %) mehr oder weniger deutlich unter oder gleich 2 %, sodass davon ausgegangen werden muss, dass bei höheren Zinssätzen unter aktuellen Bedingungen kein positives Betriebsergebnis zu erzielen ist. Die Fähigkeit Kohlenstoff zu speichern unterscheidet sich bei den Baumarten aufgrund ihrer unter-schiedlichen Raumdichten und des Zuwachsverhaltens. Während auch hier auf allen Standorten die Douglasie aufgrund des hohen Volumenzuwachses und einer, mit Fichte verglichen, relativ hohen Raumdichte sehr hohe Werte verzeichnet, zeigt die Kiefer das geringste Potential (standortabhängig 35 – 38 % der Douglasie). Dies liegt begründet in geringen Volumenzuwächsen und verglichen mit den Laubbaumarten geringer Raumdichte. Aufgrund ihrer sehr hohen Raumdichten im Vergleich zu den Nadelhölzern, zeigen die Baumarten Eiche (56 – 101 % der Douglasie) und Buche (43 – 44 % der Douglasie), verglichen mit Fichte (61 – 75 % der Douglasie) und Kiefer, ein höheres Potential der jährlichen Kohlenstoffbindung. Die Sensitivitätsanalyse zeigte für alle drei untersuchten Größen, wie sich durch Umverteilung der Baumartenanteile auf den Standorten, Steigerung des Douglasienanteils bei gleichzeitiger Verringerung des Kiefernanteils oder durch eine Kombination beider Maßnahmen die Werte verbessern las-sen. So steigert sich die jährliche Kohlenstoffbindung im Derbholz und der Volumenzuwachs pro Hektar durch eine Steigerung des Douglasienanteils um 10 % und bei gleichzeitiger Umverteilung der Baumarten um beinahe ein Viertel im Vergleich zum aktuellen Zustand. Bei Betrachtung des Reinertrags aus der Holzproduktion wirken sich die Veränderungen noch deutlicher aus. Die Auswirkungen einer veränderten Bewirtschaftungsweise der Bestände (z.B. veränderte Ästung bei Douglasie, veränderte Bestandebegründung) wurden ebenfalls betrachtet und dargestellt.Die Ergebnisse stellen einen wichtigen Erkenntniszugewinn hinsichtlich der Produktivitätsunterschiede, der betriebswirtschaftlichen Ergebnisse und der Kohlenstoffaufnahme fünf wichtiger Baumarten auf verschiedenen Standortsausprägungen auf Sandstein dar. Ohne qualitative Beurteilung der ökologischen Auswirkungen können aus Sicht des Reinertrags, des Volumenzuwachses und der Kohlenstoffspeicherung folgende Empfehlungen gegeben werden: Eine angemessene Ausweitung des Douglasienanbaus fördert die Volumenproduktion, die ökonomische Leistungsfähigkeit und die C-Sequestrierung im Wald. Ein Zurückdrängen der ohnehin deutlich überwiegenden Kiefernbestände wird sich in gleicher Weise positiv auswirken. Dabei sollten die Douglasienbestände zur optimalen Ausnutzung ihrer Überlegenheit auf den wüchsigsten Standorten angesiedelt sein.Optimising the productivity of forests is an important issue. While the optimisation of the net yield has long been the focus, the optimisation of volume production and CO2-sequestration are increasingly becoming the focus of attention. The present study contributes to this with calculations for selected locations in the forest estate “Forstgut Sattelmühle” in the Palatinate Forest. In addition to own sur-veys, the data basis of the work was the current forest management plan and site mapping of the forest estate for natural production. Economic calculations were based on average timber prices, timber harvesting costs and the calculation basis of standard costs from the forest district administra-tion “Johanniskreuz”.After the selection of site units, which are representative for the estate an based on specific soil properties (“fresh sands”, “medium moderately poor sands”, “dry poor sands”), the relevant forest growth-related data were collected on site. Site-indices were carried out on the basis of traditional yield tables and measured data. Additionally, it was possible to create updated height growth curves with the help of height analyses based on the Sloboda-function. With these height growth curves and with the help of modern production programs, updated yield tables could be generated that better depict the current height growth and stand treatment. The resultant yield tables alongside the stand level assortment table from SCHÖPFER & DAUBER (1989) were used to determine the harvesting volume and the assortments to be sold. Thereafter, it was possible to calculate and compare the annual net yields from wood production per hectare for Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies L.), Douglas fir (Pseudotsuga menziesii Mirb.), European beech (Fagus sylvatica L.) and sessile oak (Quercus petraea (Matt.) Liebl.) for interest rates of 0, 1, 2 and 3 %. Using tree species-specific wood densities, it was possible to calculate the carbon uptake in the rough wood for the individual tree species and site units and to compare them with one another. On the fresh sands site, the highest net yields are obtained in conjunction with the highest increments and C storage rate, while on dry poor sands, warranted by poor yield classes, the lowest net yields from timber production are obtained in conjunction to low increments and low C storage. For all tree species, when the traditional yield tables were used, a site index drift was apparent, with pine and beech displaying the least drift. Douglas fir showed the most significant changes in site index. When comparing the increases in volume of the individual tree species, beech (4.5-7.8 m3 ha-1 yr-1) and pine (5.0-8.0 m3 ha-1 yr-1) performed the least favorably. Oak showed a higher rate of growth (5.6-11.7 m³ ha-1 yr-1). Douglas fir (13.7-23.7 m3 ha-1 yr-1) clearly showed its superiority on all sites, which was highest on fresh sands and decreased continuously to dry, poor sand sites. Productivity of Norway spruce (12.8-15.8 m3 ha-1 yr-1) was located between Dougals fir and oak. The averaged dGz100-site index across all three site units with the current tree species distribution was 8.7 m³ ha-1 yr-1.When looking at the expected net yield from wood production, beech and pine show the lowest values on all site units. The highest net yields - about nine to ten times higher than beech - can be achieved with Douglas fir. The profits that can be achieved with spruce are around 47 % (on fresh sands) and 62 % (on medium, moderately poor sands) of the Douglas fir values. For the oak, which is able to achieve very high profits at 0 % interest (on medium, moderately poor sands even the highest), the high costs at stand establishment present a strong effect when interest rates are considered, so far that it can no longer be regarded as an economically viable alternative to Douglas fir and spruce, even with interest rates around 2 %. The average net yield from wood production over all studied site units and with the current tree species distribution without taking interest into account is around 341 € ha-1 yr-1. Even without taking operational fixed costs into account, the internal rate of return for all tree species except Douglas fir (2.4 % to 4.0 %) and Norway spruce (2.2 % to 2.7 %) is distinctly below or equal 2 %, so that it must be assumed that with higher interest rates under current conditions no positive operating result can be achieved.The ability to store carbon differs between tree species due to their different spatial densities and growth behavior. While Douglas fir shows very high values at all locations due to the high volume growth and a relatively high spatial density compared to spruce, pine shows the lowest potential for C-sequestration (depending on the location 35 – 38 % of the Douglas fir). This is due to the small increase in volume and, compared to the deciduous tree species, lower spatial density. Due to their very high density compared to conifers, oak (56-101 % of Douglas fir) and beech (43-44 % of Douglas fir) show a higher potential for annual carbon sequestration compared to spruce (61 – 75 % of Douglas fir) and pine. Within the sensitivity analysis, all three examined variables showed how the values can be improved by redistributing the proportion of tree species on the sites, increasing the proportion of Douglas fir while reducing the proportion of pine, or by combining both actions. The annual carbon sequestration in the rough wood and the volume growth per hectare increases by increasing the Douglas fir proportion by 10 %. When redistributing the tree species at the same time it increases by almost a quarter compared to the current state. When looking at the net yield from wood production, the changes have an even more pronounced effect. The effects of changed management methods (e.g. modified pruning of Douglas fir, improved stand foundation) were also considered and presented. The results represent an important gain in knowledge with regard to the productivity differences, the economic results and the carbon uptake of five important tree species at various locations on sand-stone. Without a qualitative assessment of the ecological effects, from the point of view of the net yield, the increase in volume and the carbon storage the following recommendations are given. An appropriate expansion of Douglas fir cultivation promotes volume production, economic efficiency and C-sequestration in the forest. Reducing area of the already clearly predominant Scots pine stands will have a positive effect in the same way. The Douglas fir stocks should be located in the most vigorous locations in order to optimally exploit their superiority
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
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