• Korean Journal of Environment and Ecology
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• v.24 no.6
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• pp.708-722
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• 2010

This study was carried out to classify vegetation structure of the Hyangjeokbong in the Deogyusan National Park using the gradient analysis and phytosociological method. The vegetation was classified into Quercus mongolica community(Rhododendron schlippenbachii subcommunity, typical subcommunity), Q. serrata community, Q. variabillis community, Pinus densiflora community, Cornus controversa community, Fraxinus mandshurica community and Taxus cuspidata community. Ecological characteristics such as species composition, layer structure, vegetation ratio, and the distribution of individual trees by DBH(diameter at breast height) were significantly different among communities. The order of important value of the forest community with DBH 2cm above plants was Q. mongolica(81.2), F. mandshurica, Q. serrata, P. densiflora, Acer pseudosieboldianum, Q. variabillis, Rhododendron schlippenbachii, C. controversa, T. cuspidata. Distribution of DBH of Q. mongolica and Q. serrata had suggesting a continuous domination of these species over the other species for the time being. In contrast, F. mandshurica appeared limited to the valley of the sheet and a higher frequency of young individuals, suggesting a continuous domination of these species the development of a climax forest terrain. P. densiflora and T. cuspidata had suggesting a continuous domination of these species over the other species for the time being in maintain. Q. variabilis and C. controversa had a formality distribution, suggesting a continuous domination of these species over the other species for the time being. This study examined the correlation between each community and the environment according to DCCA ordination. The Q. mongolica community and T. cuspidata community predominated in the highest elevation habitats which had few moisture, Ca and in the low pH. The Q. serrata community mainly occurred in the low elevation habitats which had many moisture. P. densiflora community predominated in the middle elevation and south-facing slope habitats which had few moisture, Ca and in the low pH. F. mandshurica community predominated in the low elevation habitats which had many moisture, Ca and pH.

• Korean Journal of Soil Science and Fertilizer
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• v.39 no.5
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• pp.259-267
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• 2006

Hydraulic conductivity is the rate of water flux on hydraulic gradient. The van Genuchten Mualem (VGM) model is frequently used for describing unsaturated state of soils, that is composed with the function of soil water potential and soil water content and requests various parameters. This study is to get the value of VGM parameters used Rosetta computer program based on neural network analysis method and to calculate VGM parameters. VGM parameters included Ko(effective saturated hydraulic conductivity), ${\theta}r$(residual soil water content), ${\theta}s$(saturated soil water content), L, n and m. The unsaturated hydraulic conductivity at 10 kPa was calculated by using Rosetta program. Unsaturated hydraulic conductivities of 17 soil series at 1, 3, 5, 7 kPa were also obtained by applying saturated hydraulic conductivity by disk tension infiltrometer based on Gardner and Wooding's equation. Water flow at the water potential of 3 kPa was very low except Namgye, Hagog, Baegsan, Sangju, Seogcheon, Yesan soil series. Unsaturated hydraulic conductivity at 1 kPa showed the highest value for Samgag soil series and was in order of Yesan, Hwabong, Hagog and Baegsan soil series. Those of Gacheon, Seocheon and Ugog soil series were very low. When the value by VGM was compared with the value by disc tension infiltrometer, there was a tendency with exponential function to soils without gravel but there was no tendency to soils including gravel. Conclusively, it would be limited that VGM model for unsaturated hydraulic conductivity analysis applies to Korean agricultural land including gravel and having steep slope, shallow soil depth.

• Journal of Korean Society of Forest Science
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• v.78 no.4
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• pp.333-344
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• 1989

The objectives of this study were to investigate the growth of Gyrophora esculanta and to establish a method of tissue culture of the plant. The results obtained were as follows : 1. The Gyrophora esculanta was found growing mostly on the rock slopes of 722 m to 1915 min elevation on mountains in Korea. 2. Trees growing in the vicinity of the G. esculanta were mainly Quercus spp., Pinus thunbergii, Acer spp. and Lespedeza spp, Especially Quercus spp. was found growing in all of the study site. 3. The average Length of the rock slopes with G. esculanta growing on was 14 m and their aspects were mostly south. 4. The G. esculanta were found growing on rocks of Crystalline Schist, Quartz, Liparite, Granite, ete. Particularly they were mostly found on granites. The gradient of the rock slopes was in the range of 22-90 degrees. 5. The mean number of individuals of G. esculanta per one rock slope ranged from 14 at Mt. Bukhan to 70 at Mt. Jrri. Their mean diameter ranged from 1.8cm at Mt. Munsu to 4.6cm at Mt, Sokri. 6. The average percentage of G. esculanta with fruit body was 17.6%. The highest value was found at Mt. Cheonhwang (24.0%). 7. When the 100 segments of rhizoid of Gyrophora esculanta cultured in Detmer's medium supplemented with kinetine 5mg/l and 2, 4-D 3mg/l, n callus of microspore origins were induced from about 20% of the segments. As the induced n callus was transplanted on the six different types of rocks, it was observed that the juvenile G. esculanta grew best on granite and the development rate of G. esculanta on the granite was about 55%.

• Journal of the Korean Geotechnical Society
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• v.34 no.2
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• pp.19-32
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• 2018

During the process of gas hydrate extraction in the deep seabed, fine diatom particle migration occurs, which causes the seabed slope failure and the productivity deterioration of the gas hydrate. Therefore, a study related with the changes of the ground characteristics due to the fine particle migration is required. The objective of this study is to investigate the change of hydraulic properties of sand due to the migration of fine diatom particle in sandy soils. In order to simulate the sediments of the Ulleung basin gas hydrate in the East Sea, fifteen sand-diatom mixtures that have different diatom volume fractions (DVF) are prepared. During the falling head permeability tests, the coefficients of permeability are measured according to the DVF. In addition, for the simulation of the fine diatom particle migration, constant head permeability tests are conducted by applying the hydraulic pressures of 3 kPa, 6kPa, and 9 kPa on a specimen composed of two layers: a specimen with 50% DVF in upper layer and a specimen with 0% DVF in lower layer. Furthermore, the coefficient of permeability and the electrical resistivity of the migration zone are measured during the constant head permeability test. The falling head permeability tests show that the coefficient of permeability decreases as the DVF of the specimen increases. In addition, the gradient of the coefficient of permeability curve decreases in the DVF range of 10%~50% compared with that of 0%~10%, and increases above 50% in DVF. The result of constant head permeability tests shows that the coefficient of permeability decreases and electrical resistivity increases in the migration zone due to the fine diatom particle migration. This study demonstrates that fine diatom particle migration reduces the permeability of the soils and the behavior of the migration zone due to the fine diatom particle migration may be estimated based on the reversal relationship between the coefficient of permeability and the electrical resistivity.

• Korean Journal of Soil Science and Fertilizer
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• v.34 no.1
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• pp.1-7
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• 2001

Total upland area for cultivating the vegetable crops in the Alpine soils of Northeastern South Korea has been extending its limit to meet the increasing demand of vegetable food in recent decades. About 70% of these alpine soils are located in over 7% of the slope and most of vegetable crops have been cultivated intensively without practicing the best management systems. Thus, soil erosion and continuous cropping system have degenerated the soil fertility and shown detrimental effects on water quality. We initiated an intensive and extensive investigation to characterize the fertility problems encountered in these uplands. Objectives of this paper were to characterize the fertility status in the Alpine soils cultivated with vegetable crops for many years and to provide the recommendations for adequate soil management measures including fertilization and erosion control. Soils in general have good drainage with textural classes of loam or sandy loam. Their topographical characteristics tended to lead them to shallow plow layers, and the steepness of the terrain created erosion hazard. Of the soils examined, about 11% of uplands over 30% gradient was found in need of an urgent reforestation. A high content of gravel and firm hardness of soil attributed to inhibit the utilization of farm machinery and plant-root development. The average soil pH 5.6 was slightly low relative to pH 5.70 of the national average. Organic matter content was high compared with 2.0% of national average, but decreased with the prolonged cultivation periods. Available $P_2O_5$ concentration was unusually high due to the consequence of over dose application with chemical and organic fertilizers. Exchangeable cations as Ca, Mg, and K were appeared to be decreased in these regions with prolonging the cultivation periods. There were no significant differences in cation exchange capacity (CEC) and electrical conductivity (EC) among locations. Heavy metal contents were mostly lower than the threshold of danger level designated by Soil Environment Conservation Law of South Korea. Results indicated that a proper countermeasure and the best management practice should be immediately implemented to conserve the top soil and fertility in the Alpine regions.

• Journal of the Society of Disaster Information
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• v.17 no.4
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• pp.694-709
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• 2021

Purpose: In this study, earthquake-induced landslide risk assessment was conducted to provide basic data for efficient and preemptive damage prevention by selecting the erosion control work before the earthquake and the prediction and restoration priorities of the damaged area after the earthquake. Method: The study analyzed the previous studies abroad to examine the evaluation methodology and to derive the evaluation factors, and examine the utilization of the landslide hazard map currently used in Korea. In addition, the earthquake-induced landslide hazard map was also established on a pilot basis based on the fault zone and epicenter of Pohang using seismic attenuation. Result: The earthquake-induced landslide risk assessment study showed that China ranked 44%, Italy 16%, the U.S. 15%, Japan 10%, and Taiwan 8%. As for the evaluation method, the statistical model was the most common at 59%, and the physical model was found at 23%. The factors frequently used in the statistical model were altitude, distance from the fault, gradient, slope aspect, country rock, and topographic curvature. Since Korea's landslide hazard map reflects topography, geology, and forest floor conditions, it has been shown that it is reasonable to evaluate the risk of earthquake-induced landslides using it. As a result of evaluating the risk of landslides based on the fault zone and epicenter in the Pohang area, the risk grade was changed to reflect the impact of the earthquake. Conclusion: It is effective to use the landslide hazard map to evaluate the risk of earthquake-induced landslides at the regional scale. The risk map based on the fault zone is effective when used in the selection of a target site for preventive erosion control work to prevent damage from earthquake-induced landslides. In addition, the risk map based on the epicenter can be used for efficient follow-up management in order to prioritize damage prevention measures, such as to investigate the current status of landslide damage after an earthquake, or to restore the damaged area.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.25 no.4
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• pp.81-96
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• 2020

Berthlot's reaction spectrophotometric method is generally used for the analysis of dissolved ammonium in seawater, but in recent years, a fluorescence method using an orthophthaldialdehyde-sulfite (OPA) fluorescent reagent is actively used internationally. In this study, we investigated the effects of the detection limit between the analysis methods, the reagent refractive index inherent in the spectrophotometric method, and the use of different calibration curves to understand the cause of the difference in dissolved ammonium concentration (about 0.31 𝜇M) observed in the seawater samples and a nutrient reference material between two institutions (KIOST (spectrophotometric method, one-order linear regression gradient only), Australia CSIRO (fluorescence method, quadratic formula)) conducted onboard the Australian R/V Investigator in 2017. The method detection limit (0.063 𝜇M) and the reagent refractive index background value (0.054 𝜇M) of the spectrophotometric method measured in this study could explain the difference in dissolved ammonium concentration values of the two institutes about 20% and 17%, respectively. However, when the concentration of the calibration curve of the spectrophotometric method was calculated using the same quadratic as the fluorescence method or the slope and intercept of linear regression, the difference in the dissolved ammonium concentration between the two institutions was reduced to less than the detection limit of the spectrophotometric method. Therefore, the difference in the concentration of dissolved ammonium between the two institutions, found in the nutrient reference materials and the seawater field sample during the international onboard nutrient inter-comparison experiment, may be attributed to be the effect of the different calibration curves used in the two methods rather than the effect of the difference in two analytical methods. When comparing the dissolved ammonium data from seawater samples in the future, it is recommended to pay attention to the information on the baseline, number of standard solutions, and calibration curve used in the analysis.