• Journal of the Korean Wood Science and Technology
• /
• v.32 no.6
• /
• pp.67-73
• /
• 2004

The influence of liquefied wood (LW) on the mechanical and thermal properties of liquefied wood-polymer composites (LWPC) was investigated in this study. The thermal behaviors of LWPC were characterized by means of thermogravimetric (TGA) and differential scanning calorimetric (DSC) analyses. LW showed significant effects on the mechanical strength properties. The increase of flexural MOE and Young's modulus was related to the increase of stiffness of LWPC. The effect of LW was also significant on the flexural and tensile MOR. The impact strength decreased with the increase of LW application level. With the increased stress concentration by the poor bonding between LW and polymer, the impact strength of LWPC decreased, compared with that of high-density polyethylene (HDPE). The thermal stability of LWPC decreased with the increase of LW content up to 40%. The melting temperature of HDPE decreased with the increase of LW loading level. Enthalpy of HDPE also decreased with the addition of LW. This study proves the thermal stability necessary for the consolidation of composition materials.

• Journal of Forest and Environmental Science
• /
• v.38 no.4
• /
• pp.290-301
• /
• 2022

Increasing life expectancy leads to a rise in the prevalence of aging-related mental diseases and a concomitant increase in the financial and societal pressures related to their prevention and management. This issue is attracting increasing attention from researchers. Therefore, this study aimed to determine whether a healing program in a forest environment is effective for improving cognitive function, depression, anxiety, and stress in elderly people. A nonequivalent control group pretest-posttest design was used. The experimental group consisted of 18 males and females aged 60 to 80 years who participated in a forest healing program for seven days, while the comparison group comprised 10 people with similar demographics. For the process of data analysis, this study performed a cross-analysis to determine the homogeneity of the data and carried out the Wilcoxon signed-rank test, a nonparametric statistical test, to verify the significance of each group. Participation in the forest healing program led to a significant improve-ment in cognitive function (p=0.030). The levels of depression decreased, but this result was not statistically significant. The levels of anxiety decreased significantly (p=0.004). The mean cortisol score, a measurement of stress, decreased, but it was not statistically significant. These findings confirmed the effectiveness of this program for improving certain mental conditions of elderly people, and affirmed that the use of long-term forest healing programs can be expected to alleviate national pressures created by aging societies.

• Journal of Forest and Environmental Science
• /
• v.28 no.4
• /
• pp.263-267
• /
• 2012

Characteristics of charcoals manufactured in each temperature as 400, 600 800, 1,000 and $1,200^{\circ}C$ were examined. Sapwood and heartwood of Quercus variabilis that one of major species in charcoal materials were used for this experiment. Charcoal density was decreased highly 38-60% compared with wood density and density of sapwood was slightly decreased but heartwood was not changed with increasing carbonization temperature increase. Weight loss of sapwood and heartwood charcoal increased as carbonization temperature increases, and there is no difference between sapwood and heartwood charcoal. Refining degree of sapwood and heartwood charcoal was zero in charring over $800^{\circ}C$. Moisture and ash of sapwood and heartwood charcoal in each carbonization temperature were not differed between sapwood and heartwood. Volatile of sapwood charcoal was slightly higher than that of heartwood, and decreased as carbonization temperature increases. As the carbonization temperature increased, fixed carbon of sapwood and heartwood charcoal increased. Calorific values of charcoal prepared at $600^{\circ}C$ were 7,200-7,300 cal/g and then decreased slightly as carbonization temperature increased.

• Journal of Forest and Environmental Science
• /
• v.30 no.2
• /
• pp.226-232
• /
• 2014

To understand transition characteristics from wood to charcoal the dimensional changes of carbonized woods at low temperature from $300^{\circ}C$ to $350^{\circ}C$ at the intervals of $10^{\circ}C$ were investigated. Three species of hardwoods and two species of softwoods were used in this study. Measurements of dimensional changes of cells were observed by stereoscopic microscope and an image analyzer. The apparent volume of each specimen decreased greatly with increasing temperature. Severe cracks and collapse were observed frequently in hardwoods and hardly in softwoods. Vessel diameter and tracheid cell wall thickness of the wood samples were decreased with increasing carbonization temperature. Contraction of vessel diameter in tangential direction was greater than that in radial direction. Cell wall thickness of tracheids decreased with increasing carbonization temperature. Consequently, even though it was small range of carbonization temperature, dimensions of wood components were changed considerably.

• Korean Journal of Environmental Agriculture
• /
• v.42 no.2
• /
• pp.121-130
• /
• 2023

The RGB (red, green, and blue) imagery analysis is an important remote sensing tool, which estimates the effect of environmental stress on turfgrass growth and physiology. Therefore, this study investigated the effect of continuous wear stress treatment on Zoysia japonica through RGB imagery analysis. The results of the growth measurement showed that the plant height substantially decreased, after nine hours of treatment with no considerable difference thereafter. Dry weight measurement showed a substantial difference in the morphological growth characteristics of the aerial part of the turfgrass, but none in the stolon and root zone. This could be attributed to the short period of compaction treatment. The ROS (reactive oxygen species) analysis showed that ROS rapidly increased due to wear stress treatment. The MDA content increased during the traffic process, whereas the green pixels increased and decreased repeatedly; however, overall, the trend declined but the overall trend decreased. Thus, this study confirmed that MDA was effective in reflecting the wear stress of turfgrass; however, it could through RGB image analysis.

• Journal of Environmental Science International
• /
• v.29 no.9
• /
• pp.915-924
• /
• 2020

The purpose of this study was to conduct a forest healing program for victims affected by the large forest fires of 2017 in Gangneung and to investigate its effects on the stress and physical health promotion of the victims. From January to March 2019, three forest therapy programs were conducted on 49 residents of four villages that suffered forest fires in the National Center for Forest Therapy, Daegwallyeong. The results showed that the degree of stress of forest fire victims decreased significantly by means of these programs. Furthermore, autonomic nerve activity, stress resistance, stress index, and fatigue decreased significantly and average heart rate and heart stability also improved.

• Journal of Korean Society of Forest Science
• /
• v.98 no.5
• /
• pp.609-617
• /
• 2009

This study was conducted to investigate ecological indicators of forest degradation after forest fire and clear-cutting in the Siberian larch (Larix sibirica Ledeb.) stand of Mongolia. The species abundance and biodiversity indices were higher in burned and clear-cut stands than those of reference stand, but boreal understory species, such as Vaccinium vitis-idaea, Pyrola incarnata, Linnea borealis and Maianthemum bifolium, completely disappeared and was replaced by sedge species, such as Carex duriuscula, C. lanceolata, C. pediformis, Poa attenuata and P. pratensis. During the research period, temperature increased by an average of $1.6^{\circ}C$ in burned stand and $1.7^{\circ}C$ in clear-cut stand compared to reference stand, but RH sharply decreased up to 15.7% in clear-cut stand. This result indicates that Larix sibirica stand became warmer and drier after forest fire and clear-cutting, and contributed to the abundance of sedge and grass species in the understory. Moreover, intense occupation of tall sedge grass after forest fire and clear-cutting had a vital role as obstacle on natural regeneration of Larix sibirica. The similarity of species composition between reference and burned stands was higher (73.6%) than between reference and clear-cut stands (63.8%). Soil moisture significantly decreased after forest fire and clear-cutting, and the extent of decrease was more severe in the clear-cut stand. The chemical properties at soil organic layer were significantly affected by forest fire and clear-cutting but not the mineral horizons. Inorganic nitrogen of the forest floor significantly decreased in the clear-cut stand ($1.1{\pm}0.4mg{\cdot}kg^{-1}$) than that of the burned ($4.5{\pm}2.3mg{\cdot}kg^{-1}$) and reference stands ($5.0{\pm}2.3mg{\cdot}kg^{-1}$). Available P of the forest floor significantly increased after fire, whereas it decreased after clear-cutting. These results indicate that existence of boreal understory vegetation, and changes in soil moisture and available P are distinct attributes applicable as ecological indicators for identifying forest degradation in Mongolia.

• Korean Journal of Environment and Ecology
• /
• v.3 no.1
• /
• pp.42-50
• /
• 1989

A valley and a ridge forest in Mt. Gaya area was studied to investigate forest structure in relation to altitude and part of slope. Sixty-three quadrats were set up in the valley forest along altitude of 600m to 1,000m and part of slope, and thirty-eight quadrats were set up in the ridge forest along altitude of 700m to 1,430m. According to the importance values, the valley forest was Quercus mongolica-Lespedeza maximowiczii community and the ridge forest was Pinus densiflora, Quercus mongolica-Rhododendron mucronulatum community. Similarity index between the valley forest community and the ridge forest community was 37.2%. Shannon's species diversities of the valley forest community and the ridge forest community were 1.3402 and 1.0098, respectively. According to importance values by crown stories and DCA ordination, successional trends of tree species may be from Pinus densiflora and Pinus koraiensis through Quercus mongolica to Quercus serrata and Carpinus laxiflora. As going from the lower part to upper part of the slope in the valley forest, the importance values of Quercus mongolica, Quercus aliena, Rhododendron mucronulatum and Lespedeza maximowiczii increased while those of Carpinus laxiflora and Fraxinus rhynchophylla decreased. With increasing elevation in the valley and ridge forest, the importance value of Pinus densiflora decreased while that of Quercus mongolica increased. In the valley forest, densities of canopy and shrubstratum increased as increasing elevation, and the number of species and species diversity decreased as increasing elevation and going from the lower part to the upper of slope. The range of similarity indices between parts of the slope, and the elevation belts of 100m in the valley forest were 66.6-69.2 and 25.9-79.8%, respectively. In the ridge forest, density and basal area of canopy tended to decreased as increasing elevation, and the range of similarity indices between elevation belts of 100m was 27.9-98.2%.

• Journal of Korean Society of Forest Science
• /
• v.98 no.5
• /
• pp.563-567
• /
• 2009

This study was conducted to clarify the characteristics of bird communities between before and after forest fire in tropical deciduous Dipterocarp forest of Mondulkiri protected forest of the northeastern Cambodia from January to April 2009. The DBH distribution of trees were different in each DBH class. Most of the trees (> 80%) were belong to < 30 cm DBH. After the forest fire, coverage of understory layers were dramatically decreased by the fire. Total 64 species of birds were recorded, and 64 and 46 species of birds were observed before and after the fire, respectively. Observed number of individuals of bee-eaters, treepies, kingfishers, lapwings, herons, junglefowl, peafowl, prinias and warblers were decreased after the fire. The decrease of those species would be related with the change of habitat condition, such as decrease of water amount and understory coverage. For the management and conservation of junglefowls, peafowls, prinias and warblers, understory vegetation should be maintained in Mondulkiri protected forest, northeastern Cambodia.

• Journal of Korean Society of Forest Science
• /
• v.98 no.5
• /
• pp.593-601
• /
• 2009

Forest disturbances including forest fire, insect pests and diseases, landslides, and forest conversion from 1976 to 2005 were investigated to trace the changes of major forest disturbance agents and their characteristics over time in accordance with changes in natural and social environment in South Korea. While the damaged area by insect pests and diseases continuously decreased for the past 30 years, damaged areas by forest fire and landslide were fluctuating through years. The interval of large forest fires has become shorter with increased tree volume. The precipitation between January and April were significantly correlated with large fire occurrences as Pearson's correlation coefficient -0.400 (P=0.029). The composition of major insect pests and diseases damaging Korean forests has been changed continuously, and become more diversified. While damages by pine caterpillar (Dendrolimus spectabilis) and pine needle gall midge (Thecodiplosis japonensis) decreased, damage by introduced pests has been more serious recently. The change of precipitation pattern that brought more localized heavy rain or powerful typhoon resulted in the recent increase in landslide areas. The major land uses to induce forest conversion have been changed, reflecting the changes in industrial structure in South Korea as agriculture and mining in 1970s, mining and golf ranges classified in pasture in 1980s, and road and housing construction in 1990s and 2000s. Changes in forest disturbance patterns in South Korea show that a country's industrial development is jointly working with global warming on forest stand dynamics. Altering energy structure and land use pattern induced by industrial development accumulates forest volume and reforms microenvironments on forest floor, interacting with climate change, inducing shorter interval of large forest fire and changes in major species composition of forest insect pests and diseases.