1,721,056 research outputs found
Stand Density Management Diagrams for Three Exotic Tree Species in Smallholder Plantations in Vietnam
No full textWhen smallholder farmers establish tree plantations to sell wood to the wood industry, they may run into problems when the plantations are mature and to be marketed because these farmers usually (1) do not know how to estimate the growing stock and (2) do not have sufficient knowledge of the wood markets. In this study, we tackle problem (1) and present stand density management diagrams (SDMDs) as a simple tool that allows rapid estimation of standing volume from data that stem from very basic inventory. Our data come from smallholder plantations in Vietnam, from four communes in the provinces of Binh Dinh and Phu Tho. Immense afforestation activities have been taken place in the country during the past two decades and it is special to Vietnam that a large share of these afforestations are under smallholder management with the goal to generate an additional source of income for these rural poor. A certain type of SDMDs is elaborated for three important exotic tree species commonly used for establishing industrial tree plantations (Acacia hybrid, Acacia mangium and Eucalyptus urophylla). They can be used for volume estimation and are also a tool to guide stand management and silvicultural treatments in general. Both implementation of the inventory and usage of the SDMDs are straightforward and simple so that this tool may be well suited to support smallholders in a better informed marketing of their wood, as well as, a better informed silvicultural management of their plantations
Estimating growth in beech forests: a study based on long term experiments in Switzerland
No full text• This contribution presents a dynamic stand growth model for Beech (Fagus
sylvatica L.) forests, based on a dataset provided by the Swiss Federal
Institute for Forest, Snow and Landscape Research WSL, Birmensdorf. The dataset includes
143 research plots, covering a wide range of growing sites and providing up to 16 interval
measurements per research plot.
• The objective of this research is to complement the range of existing beech growth
models by bridging the gap between the historical yield tables and the single tree growth
models. The specific aim is to develop transition functions which will project three state
variables (dominant height, basal area and number of trees per hectare) at any particular
time, in response to any arbitrary silvicultural treatment.
• Two of the transition functions were derived using the generalized algebraic difference
approach (GADA), the third one was derived with the algebraic difference approach (ADA).
All the functions were fitted simultaneously using iterative seemingly unrelated
regression and a base-age-invariant method. The influence of thinnings on basal area
growth was included by fitting different transition functions for thinned and unthinned
stands.
• The overall model provides satisfactory predictions for time intervals up to 20 years.
The new model is robust and its relatively simple structure makes it suitable for economic
analysis and decision support
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
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
Estimation of biomass, volume and growth of subtropical forests in Shitai County, China
Full text linkGeneral abstract
Global climate change caused by increased carbon dioxide (CO2) and other greenhouse gases has become one of the most urgent worldwide environmental topics of the 21st century and alleviating climate change has become a core research interest. Forests cover 30% of total global surface and their role in alleviating global climate change has been highlighted because forests act as a continuous carbon sink of 1.9-2.6 Pg C (1 Pg = 1015 g) per year.
China is one of the biggest countries worldwide with large area of forests, and China’s forests act as an important role in alleviating climate change. Plantation forests, as one important forest type in China, have reached an area of 61.7 million ha until 2008 due to massive plantation establishment activities in the past several decades, which amount to 29% of the global plantation area. From 1950 to 2011, plantations in China sequestered 1.686 Pg C by net uptake into biomass and soil organic carbon. Therefore, China’s plantations have made a considerable contribution to reduce atmospheric carbon. However, the stand quality of plantations is relatively low due to the short rotations and a lack of appropriate management. Mean standing volume in plantations is 49 m3 ha-1, which is much lower than the world average of 130.7 m3 ha-1 according to 7th national forest inventory in China. This suggests a huge potential to increase carbon sequestration in China’s plantations through forest management and thereby alleviate future climate change.
To improve the management of China’s plantations, the objectives of this thesis, as a case study, were to provide a methodological basis for stand management of Chinese fir plantations and to develop a method to efficiently estimate regional biomass in Shitai County, China in context of carbon forestry. This thesis contains five main chapters that are prepared as manuscripts. Specifically, firstly, the aboveground biomass (AGB, including stem, branch and leaf biomass) and its dynamics were estimated in a Chinese fir plantation (Cunninghamia lanceolata) and a Castanoposis sclerophylla forest using the generalized algebraic difference approach (GADA) and biomass allometric models. GADA models were developed for both Chinese fir and Castanoposis sclerophylla to predict the diameter at any age of each individual tree. Secondly, a compatible taper function based on Fang et al. (2000) and a stand-level merchantable volume model were developed for Chinese fir plantations to estimate merchantable and total volume at the tree- and stand-levels. Thirdly, stand density management diagrams (SDMDs) were proposed to optimize stand management of Chinese fir plantations for different management purposes. Fourthly, soil organic carbon was analysed to examine the effects of land use change from secondary forest to Chinese fir and Moso bamboo plantations on soil organic carbon (SOC) and nitrogen (N) stocks. Finally, regional biomass was estimated based on inventory data using five different methods, which is expected to contribute to optimize the selection of methods for efficient regional biomass estimation.
This thesis was a part of the Lin4carbon project, which aimed to develop and optimize integrated methodological approaches for the estimation of biomass and carbon stock and improve forest management in China. Forest inventories were conducted to deliver actual estimates of volume, biomass and carbon stock and provide information about the feasibility and costs of sampling and plot designs. To achieve these objectives, three different inventory scales were established: (1) a land use and forest inventory (LUI/FI) that produced information over the whole extent of the sampling frame based on a 3×3 km systematic grid; (2) a forest management inventory (FMI) for those stands with forest management information with a 500×500 m systematic grid, and (3) a stand inventory of selected stands (SI) with a 100×100 m systematic grid. A nested plot design with an inner radius of 6 m and outer radius of 10 m was used. A total of 258 plots were established, 74 of which were dominated by Chinese fir plantations.
In the SI plots, a total of 103 trees of different dominance classes of the five main species were felled for stem analysis and biomass allometric model construction. This included 46 Chinese fir trees. The stems were cut into sections at heights of 0.3 m, 1.3 m, 3 m and 2 m intervals thereafter up to the treetop. Cross-sectional stem discs (about 5 cm thick) were collected at each of these heights, as well as one disc at ground level.
In chapter III, GADA models based on stem analysis of 18 C. lanceolate and 15 C. sclerophylla trees were developed. The application of the GADA model yielded a very good performance in terms of diameter prediction for each individual tree. Combining the allometric models, estimated AGB increased with stand age, increasing from 69.4 ± 7.7 (mean ± standard error) in 2010 to 102.5 ± 11.4 Mg ha-1 in 2013 for Chinese fir plantations, compared to 136.9 ± 7.0 in 2010 to 154.8 ± 8.0 Mg ha-1 in 2013 for C. sclerophylla forests. AGB increment was 10.6 ± 1.2 for 2010-2011, 11.0 ± 1.2 for 2011-2012 and 11.5 ± 1.3 Mg ha-1 a-1 for 2012-2013 for C. lanceolate, respectively. They were significantly higher than those of C. sclerophylla forests with 5.8 ± 0.3, 5.9 ± 0.3 and 6.3 ± 0.4 Mg ha-1 a-1. Stems contributed 76% to total AGB and AGB increment, highlighting the importance of stems in ecosystem biomass stocks. By combining biomass allometric models, stand-level AGB dynamics were successfully estimated, which can contribute to our understanding of net primary production and carbon sequestration dynamics in these forest ecosystems.
Based on a statistical sample of n = 46 non-forked Chinese fir trees, a compatible taper function proposed by Fang et al. (2000) and a stand-level merchantable volume model were developed for Chinese fir plantations in chapter IV. A second-order continuous autoregressive error structure corrected the inherent serial autocorrelation of different observations in a given tree. The taper function and volume equations were fitted simultaneously after autocorrelation correction. The model developed by Fang et al. (2000) fitted the data well and had a very good performance in terms of diameter and individual tree volume prediction. The stand-level merchantable volume equation based on the ratio approach was developed using basal area, dominant height, quadratic mean diameter and top diameter (ranging from 0 to 30 cm) as independent variables. The high correlation between measured and predicted total and merchantable stand volume from this model highlighted the efficiency of stand-level merchantable model in stand-level merchantable volume and total stand volume estimation. Lastly, a total stand-level volume table using stand basal area and dominant height was proposed for local forest managers to simplify the stand volume estimation.
To provide a simple tool that guide the stand management for different management purposes, SDMDs for stand volume, stem biomass and total AGB were developed for Chinese fir plantations in chapter V. The number of the trees per ha was set on the y-axis and dominant height was set on the x-axis, while stand volume, stem biomass or AGB was presented on the isolines. To develop the SDMD, a system of four equations was fitted simultaneously using the data collected from 74 inventory plots. The relative spacing index was used to characterize the growing stock. Two practical examples with the same management target were also proposed to explain the use of SDMD for stand management optimization. The proposed SDMDs can be an easy tool for local forest managers to estimate the stand volume, stem biomass and AGB, and could be a reference to determine optimum thinning schedules. It is an effective planning tool based on relatively low input with reliable data.
Conversion of secondary forests to Chinese fir and Moso bamboo plantations represents an important land use change in subtropical China. The effects of this conversion on soil organic carbon (SOC) and nitrogen (N) stocks have been examined in chapter VI. Soil samples were collected from six plots in the Castanopsis sclerophylla forest, five plots in the Chinese fir and three plots in the Moso bamboo plantations. Three profiles starting from the north direction, lying at 0°, 120° and 240°, and 3 m from the plot center, were sampled in each plot. Soil samples were collected down to 50 cm in four layers: 0-10 cm, 10-20 cm, 20-30 cm and 30-50 cm. Mineral soil was air-dried at room temperature and sieved through 2-mm and 0.15-mm sieves for total SOC and N concentration analysis. Over 0-50 cm, SOC and N stocks in the secondary forests were significantly higher than those of Chinese fir and Moso bamboo plantations with values of 203.68, 127.34 and 118.25 Mg ha-1 for SOC stock and 9.24, 5.10 and 6.35 Mg ha-1 for N stock. The results indicated that converting the secondary forests to Chinese fir and Moso bamboo plantations significantly decreased the SOC and N stocks at a depth of 0-50 cm. These reductions were associated with prescribed burning, site preparation, belowground metabolism and stand age. Therefore, it is expected that increasing the rotation age (and improving establishment techniques) could not only increase the AGB accumulation, but also increase SOC stock in the Chinese fir plantations
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
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