• Journal of the Korean Wood Science and Technology
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• v.30 no.3
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• pp.97-103
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• 2002

This study was carried out to obtain basic information on racking resistance of shear walls and the factors affecting racking resistance of shear walls. Shear walls constructed by larch lumber nominal 50 mm × 100 mm framing and various sheathing materials were tested by applying monotonic and cyclic load functions. Shear walls with various stud spacing such as 305 mm, 406 mm, and 610 mm were tested under both of monotonic and cyclic loads and shear walls with various aspect (height-width) ratios were tested under cyclic load functions. The effect of hold-down connectors in shear walls was also tested under cyclic load functions. Racking resistance of shear walls has very close linear relation with stud spacing and width of shear walls. The ultimate racking strength of shear walls was reached at around or before the displacement of 20 mm. It was proposed in this study that the minimum racking strength and minimum width for shear wall be 500 kgf and 900 mm, respectively. Load-displacement curves obtained by racking tests under monotonic load functions can be represented by three straight line segments. Under cyclic load functions, envelope curves can be divided into three sections that can be represented by straight lines and the third section showed almost constant or decreasing slope.

• Journal of the Korean Wood Science and Technology
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• v.51 no.5
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• pp.345-357
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• 2023

The present study conducted a stem analysis to trace growth information of Japanese larch (Larix kaempferi) and predict the future changes in growth volume. For this purpose, six L. kaempferi trees over 47 years old were cut at 1-2 m intervals from a height of 0.2 m, and circular plates of 5 cm thickness were collected for stem analysis. The analysis indicated that approximately 1-8 years are required to grow up to chest height. The annual height and diameter growth increased rapidly until the trees are 15 years old and gradually decreased after 20 years. The volume of 30-year-old trees in Oegam-ri forests, which were well-managed after artificial reforestation, was 0.4837 m³, whereas that in unmanaged Singi-ri forests was 0.1956 m³. Although the volume of individual trees differed greatly depending on the forest management status, it was found that the volume increased by 1.67-1.76, 2.49, and 3.49 times at 40, 50, and 60 years age, respectively, compared to the legal harvesting age 30. Therefore, factors such as the carbon dioxide reduction effect, forest management benefits, and the condition of trees at the site should be considered before harvesting trees.

• Journal of Plant Biology
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• v.25 no.1
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• pp.37-53
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• 1982

Pollen analysis from lake districts, Youngnangho, Wolhamji and Bangeojin, revealed vegetational patterns in Korea. The pollen stratigraphy was divided into five zones, zone L, I, II, IIIa and IIIb for the past 15,000 years. During zone L (earlier than 10,500 yr BP), late-glacial period, Youngnangho was vegetated with a coniferous forest dominated by spruce, larch, haploxylon pine and fir with considerable amount of herbs. Zone I(10,500~7500 yr BP) was predominantly herbaceous vegetationj with significant amount of oak and diploxylon pine. It suggests that the overall environment became milder and drier than late-glacial period. Zone II(7,500~4,000 yr BP), hypsithermal period, showed significant warming condition, indicated by high pollen concentrations of oak, diploxylon pine and hornbeam, and by more diverse flora of deciduous broad-leaved trees than before. Herbs were not an important part of vegetation. Zone III$^a$(4,000~1,500 yr BP) had pine and oak as main elements. Birch increased slightly while hornbeam decreased in this time. It indicates cooling condition. Zone III$^b$(1,5000-present) which can be called pine period showed obvious human interference. Following forest clearance, agriculture was intensified. The beginning of logging and agriculture was discernible by a sudden decline of arboreal species and by considerable amount of rice, buckwheat, sorrel and plantain. Numerous charcoal fragments were observed in zone I and zone III$^b$.

• Korean Journal of Plant Resources
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• v.11 no.3
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• pp.296-300
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• 1998

When medicinal mushroom, Poria cocos, is cultured , inoculation method of spawn is cross slice inoculation of which the both sides of pine tree were peeled and spawn of P.cocos was inoculated. However, this method required lots of inoculation amount. This study was carried out to improve the culturing method of P. cocos. A good growth of P.cocos was observed in MCM(mushroom complete medium), showing proper mycelia growth and density. In inoculation amount, conventional method(cross slice inoculation) requires 20 bottles of spawn. In contrast, short log method required 8 bottles of spawn and drilling inoculation method 2~3 bottles, which could save by 60% and 85-90% respectively. In the selectrion of tree species, pine and larch had better condition for spawn culture and sclerotia formation condition.In terms of yield , pine was 33.7kg/3.3$m^2$. In the yield of pine, conventional method was 23.4kg/3.3$m^2$, drilling inoculation 29.4kg/3.3$m^2$, short log inoculation 31.7kg/3.3$m^2$, therefore drilling inoculation could increase by 25% and short log inoculation 35%, In addition, management cost was also saved.

• Journal of the Korean Wood Science and Technology
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• v.47 no.3
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• pp.265-276
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• 2019

In our previous study, the LeNet3 model successfully classified images from the transverse surfaces of five Korean softwood species (cedar, cypress, Korean pine, Korean red pine, and larch). However, a practical limitation exists in our system stemming from the nature of the training images obtained from the transverse plane of the wood species. In real-world applications, it is necessary to utilize images from the longitudinal surfaces of lumber. Thus, we improved our model by training it with images from the longitudinal and transverse surfaces of lumber. Because the longitudinal surface has complex but less distinguishable features than the transverse surface, the classification performance of the LeNet3 model decreases when we include images from the longitudinal surfaces of the five Korean softwood species. To remedy this situation, we adopt ensemble methods that can enhance the classification performance. Herein, we investigated the use of ensemble models from the LeNet and MiniVGGNet models to automatically classify the transverse and longitudinal surfaces of the five Korean softwoods. Experimentally, the best classification performance was achieved via an ensemble model comprising the LeNet2, LeNet3, and MiniVGGNet4 models trained using input images of $128{\times}128{\times}3pixels$ via the averaging method. The ensemble model showed an F1 score greater than 0.98. The classification performance for the longitudinal surfaces of Korean pine and Korean red pine was significantly improved by the ensemble model compared to individual convolutional neural network models such as LeNet3.

• Journal of the Korean Wood Science and Technology
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• v.45 no.6
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• pp.797-808
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• 2017

Automatic wood species identification systems have enabled fast and accurate identification of wood species outside of specialized laboratories with well-trained experts on wood species identification. Conventional automatic wood species identification systems consist of two major parts: a feature extractor and a classifier. Feature extractors require hand-engineering to obtain optimal features to quantify the content of an image. A Convolutional Neural Network (CNN), which is one of the Deep Learning methods, trained for wood species can extract intrinsic feature representations and classify them correctly. It usually outperforms classifiers built on top of extracted features with a hand-tuning process. We developed an automatic wood species identification system utilizing CNN models such as LeNet, MiniVGGNet, and their variants. A smartphone camera was used for obtaining macroscopic images of rough sawn surfaces from cross sections of woods. Five Korean softwood species (cedar, cypress, Korean pine, Korean red pine, and larch) were under classification by the CNN models. The highest and most stable CNN model was LeNet3 that is two additional layers added to the original LeNet architecture. The accuracy of species identification by LeNet3 architecture for the five Korean softwood species was 99.3%. The result showed the automatic wood species identification system is sufficiently fast and accurate as well as small to be deployed to a mobile device such as a smartphone.

• Journal of the Korean Wood Science and Technology
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• v.45 no.4
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• pp.409-418
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• 2017

This work attempted to manufacture glued-laminated timber (Glulam) bonded with melamine-urea-formaldehyde (MUF) resin adhesives at various melamine contents from 20% to 50% under high frequency (HF) heating for a very short time. Two preparation methods were employed to prepare MUF resin adhesives with different melamine contents: one-batch method of synthesizing MUF resins in a single batch, and two-batch method of mixing urea-formaldehyde (UF) resin with melamine-formaldehyde (MF) resin that had been synthesized separately. As the melamine content increased, the gelation time and peak temperature of MUF resins decreased. The adhesion performance of plywood showed that the one-batch MUF resin adhesive with 50% melamine content only satisfied the standard requirement of water resistance. Thus, the one-batch MUF resin adhesive with 50% melamine content was applied for bonding wood lamina from four softwood species such as Japanese larch, Korean red pine, Korean pine and Japanese cedar to manufacture Glulam under HF heating. All Glulam samples bonded with the one-batch MUF resin adhesives with 50% melamine content except those from Korean Red Pine satisfied the requirement in water soaking or boiling water delamination test as an exterior grade Glulam. The presence of rosin in Korean Red Pine was believed to be responsible for its poor adhesion. These results showed that the one-batch MUF resin adhesives with 50% melamine content provided acceptable water resistance with exterior grade Glulam manufactured under HF heating.

• Journal of Korean Society of Forest Science
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• v.74 no.1
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• pp.82-87
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• 1986

Noticed that large number of the Korean white pine (Pinus koraiensis S. et Z.) has lost its typical excurrent tree from by removal of apical shoot in the process of cone harvesting, the investigation and analysis for the species were made on the basis of the relationship among DBH, total height, merchantable height, and merchantable volume, compared with normally grown Japanese larch (Larix leptolepis Gordon). One hundred sample trees for each species were selected in the same aged stands for the study. Results have indicated that the pine has shown abnormal height growth pattern mainly by the disturbance of external artificial force. The pine's forked and/or crooked stems by the reason lave led the result of less merchantable volume in the same DBH classes. Consequently, the pine would have undesirable tree form in terms of timber production, unless free from apical shoot disturbances. Considered to the merit of the Korean white pine that can produce timber and pine nuts, management alternatives for the pine stand were suggested to achieve maximum rate of return for the silvicultural investment.

• Journal of Korean Society of Forest Science
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• v.108 no.3
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• pp.405-417
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• 2019

We analyzed the profitability of Korea's forestry by evaluating stumpage prices of the main economic tree species. Stumpage prices are evaluated with a market value formula, subtracting logging and transporting costs from market prices of logs. If trees are sold at the current cutting age, the stumpage price of larch is about 4.5 million KRW per hectare and that of Korean pine is about 3.7 million KRW per hectare. The stumpage prices do not cover reforestation cost, which is about 6.1 million KRW per hectare. If government subsidies did not support the cost of reforestation and silviculture, there would be no profits at all. The cost of forestry is very high in terms of planting and silviculture. In the future, the prices of logs are not predicted to rise and the wages for labor are not predicted to fall. Without reforming the current forestry regime, Korean forestry is, thus, not sustainable. Therefore, low-cost forestry efforts like natural regeneration should be adopted to make forestry viable. Investments in forestry infrastructure like forest roads are also required to decrease the timber logging and transporting costs.

• Korean Journal of Environment and Ecology
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• v.21 no.4
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• pp.356-365
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• 2007

This study was conducted to evaluate the changed vegetational community structure according to vegetational succession in Chiaksan National Park of Korea by applying ordination and classification method of floristic composition along with the actual vegetation by correlation. As for the ratio of actual vegetation, Mongolian oak forest(33.1%) was the highest, followed by mixed forest(16.2%), Japanese larch forest(15.6%), deciduous broad-leaved forest(14.7%), red pine forest(11.1%), Korean pine forest(2.3%) and Pitch pine forest(0.1%), respectively. The vegetation was classified into Acer pseudosieboidianum-Quercus mongolica community, Cornus controversa-Carpinus cordata community, Quercus sonata community, Pinus densiflora community and afforestation. The Acer pseudosieboldianum-Quercus mongolica community-a subordinately ranked community-was divided into Carpinus laxiflora-Sassa borealis community, Fraxinus rhynchophylla community and Symplocos chinensis for. pilosa-Carex siderosticta community. The results of community classification using by ordination and classification method of floristic composition were similar to each other. The vegetational succession, with the combination of Quercus mongolica, Acer pseudosieboldianum and Rhododendron schlippenbachii, was predicted to form a climax forest from above the hillside.