1,720,958 research outputs found
Evaluation and optimization of the thinning phase in spruce stands
No full textThe aim of the present analysis of 38 spruce stands in the Winnefeld Sud Forest is to integrate the planning of the thinning phase at stand and at forest levels. Solution of the problem requires generation, evaluation and finally optimization of management options. A growth model and a thinning model were used to develop management options. Several options were generated for each stand with the management simulator Jakta. The economic criterion of forest value (BEW) was applied for option evaluation. Optimization involves evaluation of-multiple scenarios for the entire forest by determining the optimal space-time pattern of thinnings for all of the stands combined. For this purpose the software package JLP was used; Finally a sensitivity analysis was carried out to find the optimal solution under consideration of timber price and interest rate changes
About the evaluation of k-tree samples
No full textThe k-tree plot is a plot design in which the k trees nearest to a sample point are taken as sample trees. While field implementation is often stated to be fast and straightforward, the challenge of an unbiased estimator remains. A design-unbiased estimator has been developed but is not operational for practical application yet and it is common practice to employ empirical estimators. Applications can be found in ecological surveys above all, but also in some forest inventories even if it is known since long that the empirical estimators carry an unknown bias, depending on the spatial pattern of the stands. In this study we summarize recent findings on the sampling statistics of the k-tree plot design. This includes an overview of the inclusion zone approach as illustrated in Figures 1, 2 and 3. We carry out and describe a first illustrating sampling simulation oil an artificially generated small stand (as of Figure 1 and 2). Objective is to demonstrate the performance of the first design-unbiased estimator and establish a comparison to fixed area plots and Bitterlich plots. From this study results that the design unbiased estimator yields more precise results for both the estimation of basal area and stem density than fixed area plots or Bitterlich sampling. However, the field effort to implement that estimator is prohibitive. If estimation without bias is a serious issue in a particular forest inventory, the authors recommend resorting to more simply to handle plot designs such as of fixed area plots, thus avoiding the estimator challenge of k-tree plots
Evaluating management regimes for European beech forests using dynamic programming
Get PDFCITATION: Torres-Rojo, J.M., Vilcko, F. & Von Gadow, K. 2014. Evaluating management regimes for European beech forests using dynamic programming. Forest Systems, 23(3):470-482, doi:10.5424/fs/2014233-05296.The original publication is available at http://revistas.inia.es/index.php/fs/indexAim of study: This contribution describes a systematic search method for identifying optimum thinning regimes for beech forests (Fagus sylvatica L.) by using a combination of optimization heuristics and a simple whole stand growth prediction model.
Area of study: Data to build the model come from standard and management forest inventories as well as yield tables from the Northern and Western part of Germany and from southern and central Denmark. Material and methods: Growth projections are made from equations to project basal area and top height. The remaining stand variables are recovered from additional equations fitted from forest inventory data or acquired from other authors. Mortality is estimated through an algorithm based on the maximum density line. The optimization routine uses a two-state dynamic programming model. Thinning type is defined by the NG index, which describes the ratio of the proportion of removed trees and basal area with respect to the same proportion before thinning.
Main results: Growth equations fitted from inventory data show high goodness of fit with R2 values larger than 0.85 and high significance levels for the parameter estimates. The mortality algorithm converges quickly providing mortality estimates within the expected range.
Research highlights: The combination of a simple growth and yield model within a Dynamic Programming framework in conjunction with NG values as indicators of thinning type yield good estimates of practical thinning schedules compared to thinning recommendations provided by diverse authors.http://revistas.inia.es/index.php/fs/article/view/5296Publisher's versio
A case study of forest management planning using a new heuristic algorithm
No full textWe present an approach to generate and evaluate different silvicultural development paths and to optimize the development of a Norway spruce stand, using a long-term planning horizon. To generate a silvicultural path, the maximum stand density was applied. At each thinning event, three possible thinning intensities (10, 20,30% of the stem number per ha) were randomly chosen. A search algorithm known as modified Accelerated Simulated Annealing (mASA) was used to estimate the optimum combination of stand paths for a given forest as a whole. Production and economic management objectives were considered and then compared. The economic criterion was the Expected Stand Value (ESV) with a 4% discount rate. The generated data set of 38 Norway spruce stands (comprising a total of 123.8 ha) was used in the case study. The result with the best combination of paths was presented in a digitized forest map. Forest management simulation was performed using a specially developed computer program, for a planning horizon of 20 years. The mASA proved to be an effective search method for identifying optimum paths
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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