• Journal of Korean Society of Forest Science
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• v.112 no.2
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• pp.209-216
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• 2023

This study aimed to use national forest inventory data to develop a forest productivity index and yield prediction model of a Tilia amurensis stand. The site index displaying the forest productivity of the Tilia amurensis stand was developed as a Schumacher model, and the site index classification curve was generated from the model results; its distribution growth in Korea ranged from 8-16. The growth model using age as an independent variable for breast height and height diameter estimation was derived from the Chapman-Richards and Weibull model. The Fitness Indices of the estimation models were 0.32 and 0.11, respectively, which were generally low values, but the estimation-equation residuals were evenly distributed around 0, so we judged that there would be no issue in applying the equation. The stand basal area and site index of the Tilia amurensis stand had the greatest effect on the stand-volume change. These two factors were used to derive the Tilia amurensis stand yield model, and the model's determination coefficient was approximately 94%. After verifying the residual normality of the equation and autocorrelation of the growth factors in the yield model, no particular problems were observed. Finally, the growth and yield models of the Tilia amurensis stand were used to produce the makeshift stand yield table. According to this table, when the Tilia amurensis stand is 70 years old, the estimated stand-volume per hectare would be approximately 208 m³ . It is expected that these study results will be helpful for decision-making of Tilia amurensis stands management, which have high value as a forest resource for honey and timber.

• Journal of Korean Society of Forest Science
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• v.103 no.3
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• pp.439-445
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• 2014

In this study, we developed a dynamic stand yield model to estimate the baseline carbon stock, which is essentially required for a forest carbon offset project based on forest management. For developing the yield model, the data was acquired from the databases of the $5^{th}$ National Forest Inventory. The model was validated by comparing its estimations with field measurements that were conducted from 4 study sites (14 plots with thinning treatments) located in Hong-chun, Hoeng-sung, Yang-yang Daechi and Yang-yang Jungja. The difference between the estimations and the field measurements was less than 5%. Using the dynamic stand yield model, we estimated the changes in stand yield volume and carbon stocks for each species according to the baseline scenarios. As the results, we found that baseline carbon stock was the highest at Quercus acutissima stand (83.01tC/ha), while the lowest at Pinus rigida stand (32.17tC/ha) and Pinus densiflora stand of central region (39.09tC/ha). Hence, a project provider could get more carbon emission credits from an improved forest management project when considering the project with Pinus rigida stand or Pinus densiflora stand (central region). The baseline carbon stock and the dynamic stand yield model developed from this study would be useful for designing carbon offset projects based on improved forest management.

• Journal of Korean Society of Forest Science
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• v.98 no.6
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• pp.646-651
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• 2009

In this study, it was intended to prepare a stem volume table (with or without bark) and a stand yield table for Juglans mandshurica, plantations in Chungju, located in Chungcheongbuk-do, Korea. For the calculation of stem volume, we applied Kozak's growth model, which showed the best fitness index (97%). With this model, it was able to prepare the first yield table for Juglans mandshurica in Korea. Site index model, an indicator of forest productivity, was derived by using the Chapman-Richard model, in which the basic stand age was set to 30 years. The resulted site index ranged between 16 and 22. Based on the yield table of Juglans mandshurica resulted from this study, the volume for a 70-year-old stand with a midium site index class was estimated to be $238m^3/ha$, which is $100m^3/ha$ higher than the volume estimated from the yield table of Quercus acutissima. The yield table of oak trees has been used in the estimation of most broadleaf stands in Korea. However, the result of this study indicated that it is necessary to generate a stand yield table for each broadleaf species. The annual $CO_2$ removals of 30-year-old Juglans mandshurica plantations in the ChungJu region was estimated to be $5.84tCO_2/ha$. The stem volume and stand yield table of Juglans mandshurica plantation resulted from this study would provide a good information in decision making for forest management in ChungJu region.

• Journal of Korean Society of Forest Science
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• v.99 no.1
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• pp.9-15
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• 2010

This study was conducted to develop a stand growth model and a stand yield table for Eucalyptus pellita and Acacia mangium plantations in Kalimantan, Indonesia. To develop a stand growth model, Weibull robability density function, a diameter class model, was applied in this study. In the development of stand growth model by site index and stand age, a hierarchy is generally required - estimation, recovery and prediction of the diameter class model. A number of grow equations were also involved in each process to estimate diameter, height, basal area, minimum or maximum diameter. To examine whether the grow equations are adequate for Eucalyptus pellita or Acacia mangium plantations, a fitness index was analyzed for each equation. The results showed that fitness indices were ranged from 65 to 89% for Eucalyptus pellita plantations and from 72 to 95% for Acacia mangium plantations. As being highly adequate for the plantations, a stand yield table was developed based on the resulted growth model, and applied to estimate the stand growth with midium site index for 10-year period. The highest annual stand growth of Eucalyptus pellita plantations was estimated to be 21.25 $m^3$/ha, while that of Acacia mangium plantations was 27.5 $m^3$/ha. In terms of annual stand growth, Acacia mangium plantations appeared to be more beneficial than Eucalyptus pellita plantations. Also, to estimate commercial timber volume available from the plantations, an assumption that a log would be cut by 2.7 m in length and the rest of the log would be cut by 1.5m was involved. The commercial timber volume available from Eucalyptus pellita plantations was 68.0 $m^3$/ha, 33% from the total stand volume, 203.2 $m^3$/ha. Also 96.7 $m^3$/ha of commercial timbers were available from Acacia mangium plantations, which was 42% from the 232.9 $m^3$/ha in total. Presenting a good information about the stand growth in Eucalyptus pellita and Acacia mangium plantations, this study might be useful for whom proceeds or considers an abroad plantation for merchantable timber production or carbon credit in tropical regions.

• Journal of Korean Society of Forest Science
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• v.84 no.1
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• pp.63-70
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• 1995

This paper discusses applications of neural network to stand stocking control problems. The scope of this research was to develop a neural network model for finding optimal stand management regimes and examining the performance of the model for field application. Performance was analyzed in consideration of the number of training examples and structural aspects of neural network. Research on network performance was based on extensive optimization studies for pure longleaf pine(Pinus palustris) stands. For experimental purposes. an existing nonlinear even-aged stand optimization model with a whole-stand growth and yield simulator was used to generate data samples required for the performance analysis.

• Journal of Forest and Environmental Science
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• v.27 no.3
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• pp.135-141
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• 2011

The present study was carried out from September 2007 to February 2008 in Umfakarin natural forest reserve, South Kordofan, Sudan. The objective was to analyze the effect of different management strategies on yield of gum talha from Acacia seyal. A total of 493 single target trees were selected, based on their diameters, and assigned to tapping treatments in three different stand densities (making a total of nine treatments per stand density). The treatments are as follows: tapping date with three levels (first of October, 15 October and first of November) and two levels of local tapping tools (sonki, and makmak). Untapped trees were used as control. The first picking of gum was started fifteen days after tapping while the subsequent pickings were done in intervals of fifteen days. Yield per tree throughout the season was obtained by summing up the gum yield from all pickings. Yield throughout the season (from first to the last picking) were analyzed. General linear model (GLM) was used to test the effect of different tapping treatments on the yield of gum talha. Post hoc test after analysis of variance (ANOVA) based on Scheffe test was performed to examine the differences in gum yield as a result of different management strategies. The results showed that tapping has a significant influence on gum yield. Analysis of pick-to-pick yield indicated that only three treatments in dense stand density showed a decreasing pattern while the rest of treatments either have constant or unclear patterns. The results of the present study were based on a single season data and that may underscore the real effect of Acacia seyal stands' management strategies on gum talha yield. Conducting gum yield experiments in permanent trial plots are highly recommended in order to analyze gum yield of seasonal time series.

• Journal of Korean Society of Forest Science
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• v.103 no.2
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• pp.264-269
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• 2014

The aim of this study was to determine the current distribution area of Robinia pseudoacacia habitat and to estimate its stand yield as well as its carbon stocks. In order to do so, the area of R. pseudoacacia distribution is obtained based on the large-scaled forest type map (1:5,000). Also, Weibull diameter distribution model is used to predict the yield of R. pseudoacacia stands. In addition, carbon emission factor is applied to calculate carbon stocks and removals. To obtain the stand yield of R. pseudoacacia, we developed estimation equation considering growth factors of the stand, e.g. mean diameter, the basal area, maximum and minimun diameter and etc. and tested it to ensure accuracy. Consequently, estimation equation derived from all growth factors have shown significance that could also be used for analysis. Site index was also established to determine the productivity of the forestland that later turned out to be ranging from 16 to 22. Based on these results, stand yield tables were drawn up. R. pseudoacacia is widely distributed in inland areas of Gyeongsang, Chungcheong and Gyeonggi provinces which covers total area of 26,770 ha. And when it is converted into carbon stocks, it amounts to 2,517,598tC with annual carbon uptake of 3.76tC/ha which is comparable to Querqus species that is known to storer large amounts of carbon. Therefore, R. pseudoacacia is also expected to serve as a viable carbon pool that would contribute to the mitigation of climate change. Furthermore, stand yield tables, an outcome of this survey would assist not only in proper management but also in sustainable management policy of R. pseudoacacia.

• Journal of Korean Society of Forest Science
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• v.101 no.4
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• pp.592-598
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• 2012

Forest stand yield and its changes along with 10 thinning scenarios were estimated using a forest stand yield model for six major tree species in Korea, such as Pinus densiflora in Gangwon province, Pinus densiflora in other regions, Pinus koraiensis, Larix leptolepis, Quercus acutissima Carruth, Quercus mongolica. The 10 thinning scenarios were generated based on a number of constraints and assumptions. For instance, it was assumed that thinning is implemented between 15 years and 40 years with 5 year period and its duration should be at least 10 years. Also, the overall removal rate from the thinning treatments was assumed to be not greater than 60%. Under the 10 scenarios, the overall stand yield volumes from thinning and final harvesting were estimated for each species and site index. The results showed that highest yield volumes were obtained for Pinus densiflora in Gangwon province, Pinus koraiensis and Quercus mongolica when 30% of basal areas were thinned at 20 and 40 years, while highest yield volumes were obtained for Pinus densiflora in other regions and Larix leptolepis when 20% of basal areas were thinned at 20, 30 and 40 years. Those two scenarios gave the same amount of highest yield volume for Quercus acutissima Carruth. Also the results indicated that thinning treatment is effective to increase overall stand yield volume and its effects are larger with a higher site index. The largest thinning effects were found in Pinus densiflora in Gangwon province (28%) and Larix leptolepis (25%), while limited in Pinus koraiensis (12%). The forest stand yield model, used in this research, could be an effective tool for estimating the stand dynamics with various thinning treatments, but it could be improved in a further research that validates its applicability in the field.

• Journal of Korean Society of Forest Science
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• v.101 no.2
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• pp.266-278
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• 2012

The objective of this study was developing dynamic stand growth model to predict diameter at breast height (DBH) growth by thinning intensity and cycle for major tree species of South Korea. The yield table, one of static stand growth models, constructed by Korea Forest Service was employed to prepare dynamic stand growth models for 8 tree species. In the process of model development, the thinning type was designated to thinning from below and equations for predicting the DBH change after thinning by different intensities was generated. In addition, stand density (N/ha), age and site index were adopted as explanatory variables for DBH prediction model. Thereafter, using the model, DBH growth under various silvicuture through integrating such equations considering thinning intensities, and cycles. The dynamic stand growth model of DBH developed in this study can provide understanding of effectiveness in forest growth and growing stock when thinning practice is performed in forest. Furthermore, results of this study is also applicable to quantitatively assess the carbon storage sequestration capability.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.3
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• pp.205-212
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• 2021

In this study, two types of thrust stand modeling were proposed for the design of a thrust stand using flexure. Type A model generate combined load for tangential (thrust) and axial compressive load (self weight). And type B generate combined load for tangential and axial tensile load. The research was done by comparing the influence of the load between the models through a 1D calculation and computational analysis. The 1D calculated value and the computational analysis value were compared for a total of 10 sections and the results were confirmed to be very similar. In order to prove the validity of the analysis results, the equivalent stress was confirmed from the computational analysis of the flexure, and the production of the Type B model was selected from the evaluation of the yield condition (Von-Mises Yield Criterion).