1,721,014 research outputs found
Development of stand density management diagrams for Chinese fir plantations
No full textStand density management diagrams (SDMDs) are powerful tools for the design, display and evaluation of different density management regimes derived without long-term thinning trials in the field. The SDMDs can be used to predict future stand development based on specific thinning schedules and to optimize forest management. Even though Chinese fir (Cunninghamia lanceolata [Lamb.] Hook) covers the largest area in China’s plantations with an area of 8.54 million ha, there is no management tool for optimization of different management regimes. In this study, SDMDs, generated from common one-time inventory data, provided information about the evolution of quadratic mean diameter, stand volume, stem and above ground biomass with stand development for the widely planted Chinese fir plantations in southern China. A system of four equations was fitted simultaneously to data collected from 74 inventory plots. Relative spacing index was used to characterize the growing stock. These SDMDs can be easy tools for local forest managers to estimate the stand volume, stem and above ground biomass and could be the reference to determine optimum thinning schedules
Estimation of stand-level aboveground biomass dynamics using tree ring analysis in a Chinese fir plantation in Shitai County, Anhui Province, China
No full textChinese fir [(Cunninghamia lanceolata (Lamb.) Hook] is one of the most important plantation tree species in subtropical China, accounting for about 21 % of China’s total forest plantation area. Although many studies have been conducted in Chinese fir plantations, uncertainties remain regarding its potential and dynamics to sequestrate carbon as a function of stand type, stand age and management. In this study, we applied tree ring analysis as a retrospective tool to study tree- and stand-level aboveground biomass (AGB) dynamics in a 17-year old Chinese fir plantation in Shitai County, Anhui Province, China. A total of 18 trees from different dominance classes were felled for the stem analyses: 6 dominant, 6 co-dominant and 6 suppressed trees. The stem analyses showed that as expected the annual increments of dbh and AGB were significantly higher for dominant trees than those for co-dominant and suppressed trees. Total stand-level AGB increased from 1.85 t ha−1 at age 3 years to 108.12 t ha−1 at age 17 years. Splitting the stand into dominance classes, tree analysis was useful to explain variation of the stand-level AGB and provided more detailed information about the growth dynamics of the stands. Tree ring analyses offer a viable and efficient approach to retrospectively study tree growth and AGB accumulation dynamics in Chinese fir plantations. In the studied stand under the given management regime, a rotation period of 17 years would optizimise AGB productivity
On the site-level suitability of biomass models
No full textTree biomass estimates in environmental studies are based on allometric models, which are known to vary with species, site, and other forest characteristics. The UNFCCC published a guideline to evaluate the appropriateness of biomass models before application, but it misleads the concept of model suitability and does also allow the selection of models with systematic deviations in the predictions. Here we present an alternative approach based on non-parametric techniques. The approach was tested for pure stands, but this methodology is likewise applicable to mixed forests. The proposed tests perform well in rejecting a model if the predictions for the targeted population are systematically deviant. It is demonstrated that the suitability of an allometric model is a matter of accuracy. The proposed method also allows localizing the model. The presented approach can improve the transparency of global forest monitoring systems and can be implemented with relatively small effort. © 2015 Elsevier Ltd
Improving precision of field inventory estimation of aboveground biomass through an alternative view on plot biomass
No full textAbstract We contrast a new continuous approach (CA) for estimating plot-level above-ground biomass (AGB) in forest inventories with the current approach of estimating AGB exclusively from the tree-level AGB predicted for each tree in a plot, henceforth called DA (discrete approach). With the CA, the AGB in a forest is modelled as a continuous surface and the AGB estimate for a fixed-area plot is computed as the integral of the AGB surface taken over the plot area. Hence with the CA, the portion of the biomass of in-plot trees that extends across the plot perimeter is ignored while the biomass from trees outside of the plot reaching inside the plot is added. We use a sampling simulation with data from a fully mapped two hectare area to illustrate that important differences in plot-level AGB estimates can emerge. Ideally CA-based estimates of mean AGB should be less variable than those derived from the DA. If realized, this difference translates to a higher precision from field sampling, or a lower required sample size. In our case study with a target precision of 5% (i.e. relative standard error of the estimated mean AGB), the CA required a 27.1% lower sample size for small plots of 100 m2 and a 10.4% lower sample size for larger plots of 1700 m2. We examined sampling induced errors only and did not yet consider model errors. We discuss practical issues in implementing the CA in field inventories and the potential in applications that model biomass with remote sensing data. The CA is a variation on a plot design for above-ground forest biomass; as such it can be applied in combination with any forest inventory sampling design
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
Models for estimating biomass and carbon in biomass and soils in Pinus radiata (D. Don), Eucalyptus globulus (Labill) and Eucalyptus nitens (Deane & Maiden) Maiden plantations established in former agricultural lands in northwestern Spain
Full text linkThe aim of this work is to discuss modelling and estimation of C evolution in forest plantations. The study focused on the three levels at which C can be estimated: tree, stand and landscape level. The study involved evaluation of a dynamic process, i.e. the afforestation of former pasture land
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
- …
