• Korean Journal of Remote Sensing
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• v.35 no.1
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• pp.179-193
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• 2019

Landslides are one of the most damaging geological hazards worldwide, threating both humans and property. Hence, there have been many efforts to prevent landslides and mitigate the damage that they cause. Among such efforts, there have been many studies on mapping landslide susceptibility. Geographic information system (GIS)-based techniques have been developed and applied widely, and are now the main tools used to map landslide susceptibility. We reviewed the status of landslide susceptibility mapping using GIS by number of papers, year, study area, number of landslides, cause, and models applied, based on 776 articles over the last 20 years (1999-2018). The number of studies published annually increased rapidly over time. The total study area spanned 65 countries, and 47.7% of study areas were in China, India, South Korea, and Iran, where more than 500 landslides, 27.3% of all landslides, have occurred. Slope (97.6% of total articles) and geology (82.7% of total articles) were most often implicated as causes, and logistic regression (26.9% of total articles) and frequency ratio (24.7% of total article) models were the most widely used models. We analyzed trends in the causes of and models used to simulate landslides. The main causes were similar each year, but machine learning models have increased in popularity over time. In the future, more study areas should be investigated to improve the generalizability and accuracy of the results. Furthermore, more causes, especially those related to topography and soil, should be considered and more machine learning models should be applied. Finally, landslide hazard and risk maps should be studied in addition to landslide susceptibility maps.

• Journal of the Korean Geotechnical Society
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• v.38 no.4
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• pp.5-20
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• 2022

To analyze the flow and density variations in debris flows, a two-phase finite volume model simplified with momentum equations was constructed in this study. The Hershel-Buckley rheology model was employed in this model to account for the internal and basal friction of debris flows and was utilized to analyze complex topography and entrainments of basal soil beds. In order to numerically solve the debris flow analysis model, a finite volume model with the Harten-Lax-van Leer-Contact method was used to solve the conservation equation for the debris flow interface. Case studies of circular dam failure, non-Newtonian fluid dam failure, and multiple debris flows were analyzed using the proposed model to evaluate shock absorption capacity, numerical isotropy, model accuracy, and mass conservation. The numerical stability and correctness of the debris flow analysis of this analysis model were proven by the analysis results. Additionally, the rate of debris flow with various rheological properties was systematically simulated, and the effect of debris flow rheological properties on behavior was analyzed.

• Journal of The Geomorphological Association of Korea
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• v.18 no.4
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• pp.97-126
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• 2011

This paper has identified the Quaternary Environmental research trend of the Korea that has become the center of physical geographers and analyzed its performance by topic. As a result, we could see that most studies are accepted as research topics of restoring topography-climate-vegetation-sea level-soil environment during 'Last Interglacial ~Holocene' targeting the Korean Peninsula and the surrounded area. However, the situation is that it is difficult to restore the Quaternary Environment of the Korea in general only with their study performance. In the future, I hope the Quaternary Environmental research of the Korea would play more leading role than the researchers of other field by selecting more wide ranged and in-depth study topics in terms of the Quaternary Environmental research to furthermore introduce a new analytic technique.

• Korean Journal of Agricultural and Forest Meteorology
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• v.9 no.3
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• pp.188-194
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• 2007

The relationships between pine mushroom emergence and meteorological factors were analyzed with three years (from 2003 to 2005) of measurement data at Yangyang site, in order to evaluate the effect of micrometeorological environment on pine mushroom production. fine mushroom was daily monitored and collected in the survey area during the its producing period (approximately one month). Pine mushroom production was highest in 2005 with the meteorological conditions of high temperature and frequent rainfalls in October. The production was lowest in 2004 due to dry conditions from mid September to late October, The meterological factors related to humidity (i.e., relative humidity, soil water content, and precipitation) were better correlated than those related to temperature (i.e., air and soil temperature, soil heat flux and solar radiation) with pine mushroom production. However, all of the correlation coefficients were statistically insignificant with values ranging from 0.15 to 0.46. Such poor correlations may be attributed to various other environmental conditions (e.g., topography, soil, vegetation, other fungi, the relationship between pine mushroom and pine forest) affecting pine mushroom production. We found that a mycelium requires a stimulation of low temperature (of three-day moving average) below $19.5^{\circ}C$, in order to farm a mushroom primordium which grows to pine mushroom after 16 days from the stimulation. We also found that the pine mushroom production ended when the soil temperature (of three-day moving average) fell below $14.0^{\circ}C$.

• Journal of Korean Society of Forest Science
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• v.111 no.1
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• pp.115-124
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• 2022

This study was conducted to obtain basic data that could help prevent damage caused by slow-moving landslides (land-creep). Specifically, the geological, topographic, and physical characteristics of land-creep were analyzed in Jiphyeon-myeon, Jinju-si. The first and second analyzed land-creeps occurred in 1982 and 2019, respectively. The area damaged in the second land-creep was about 11.5-fold larger than that damaged in the first land-creep. The dominant constituent rock in the land-creep area was sedimentary rock, which seems to be weakly resistant to weathering. The areas that collapsed due to land-creep were related to the presence of separated rocks between the bedding plane in the estimated activity surface over the slope direction and the vertically developed joint surface. Thus, surface water and soil debris were introduced through the gaps of separated rocks. Additionally, the areas collapsed due to the combination of the bedding plane and joint surface shale and sandstone showed an onion structure of weathered outcrop from the edge to inner part caused by weathering from ground water. Consequently, core stones were formed. The study area was a typical area of land-creep in a mountain caused by ground water. Land-creep was classified into convex areas of colluvial land-creep. The landslide-risk rating in the study area was classified into three and five classes. The flow of ground water moved to the northeast and coincided with the direction of the collapse. Soil bulk density in the collapsed area was lower than that in ridge area, which was rarely affected by land-creep. Thus, soil bulk density was affected by the soil disturbance in the collapsed area.

• Journal of Biosystems Engineering
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• v.30 no.1 s.108
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• pp.45-55
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• 2005

Knowledge of the relationship between crop yield and yield-limiting factors is essential for precision farming. However, developing this knowledge is not easy because these yield-limiting factors are interrelated and affect crop yield in different ways. In this study, data for grain yield and yield-limiting factors, including crop chlorophyll content, soil chemical properties, and topography were collected for a small (0.3 ha) rice paddy field in Korea and a large (36 ha) upland corn field in the USA, and relationships were investigated with path analysis. Using this approach, the effects of limiting factors on crop yield could be separated into direct effects and indirect effects acting through other factors. Path analysis provided more insight into these complex relationships than did simple correlation or multiple linear regression analysis. Results of correlation analysis for the rice paddy field showed that EC, Ca, and $SiO_2$ had significant (P<0.1) correlations with rice yield, while pH, Ca, Mg, Na, $SiO_2,\;and\;P_2O_5$ had significant correlations with the SPAD chlorophyll reading. Path analysis provided additional information about the importance and contribution paths of soil variables to rice yield and growth. Ca had the highest direct effect (0.52) and indirect effect via Mg (-0.37) on rice yield. The indirect effect of Mg through Ca (0.51) was higher than the direct effect (-0.38). Path analysis also enabled more appropriate selection of important factors limiting crop yield by considering cause-and-effect relationships among predictor and response variables. For example, although pH showed a positive correlation (r=0.35) with SPAD readings, the correlation was mainly due to the indirect positive effects acting through Mg and $SiO_2$, while pH not only showed negative direct effects, but also negatively impacted indirect effects of other variables on SPAD readings. For the large upland Missouri corn field, two topographic factors, elevation and slope, had significant (P<0.1) direct effects on yield and highly significant (P<0.01) correlations with other limiting factors. Based on the correlation analysis alone, P and K were determined to be nutrients that would increase corn yield for this field. With the help of path analysis, however, increases in Mg could also be expected to increase corn yield in this case. In general, path analysis results were consistent with published optimum ranges of nutrients for rice and com production. We conclude that path analysis can be a useful tool to investigate interrelationships between crop yield and yield limiting factors on a site-specific basis.

• Geophysics and Geophysical Exploration
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• v.13 no.1
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• pp.24-30
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• 2010

This study utilises repeated numerical tests to understand the effects of variable near-surface conditions on time-lapse seismic surveys. The numerical tests were aimed at reproducing the significant scattering observed in field experiments conducted at the Naylor site in the Otway Basin for the purpose of $CO_2$ sequestration. In particular, the variation of elastic properties of both the top soil and the deeper rugose clay/limestone interface as a function of varying water saturation were investigated. Such tests simulate the measurements conducted in dry and wet seasons and to evaluate the contribution of these seasonal variations to seismic measurements in terms of non-repeatability. Full elastic pre-stack modelling experiments were carried out to quantify these effects and evaluate their individual contributions. The results show that the relatively simple scattering effects of the corrugated near-surface clay/limestone interface can have a profound effect on time-lapse surveys. The experiments also show that the changes in top soil saturation could potentially affect seismic signature even more than the corrugated deeper surface. Overall agreement between numerically predicted and in situ measured normalised root-mean-square (NRMS) differences between repeated (time-lapse) 2D seismic surveys warrant further investigation. Future field studies will include in situ measurements of the elastic properties of the weathered zone through the use of 'micro Vertical Seismic Profiling (VSP)' arrays and very dense refraction surveys. The results of this work may impact on other areas not associated with $CO_2$ sequestration, such as imaging oil production over areas where producing fields suffer from a karstic topography, such as in the Middle East and Australia.

• The Korean Journal of Ecology
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• v.26 no.5
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• pp.281-287
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• 2003

We present the first analysis of moor vegetation on the Moojechi of Ulsan including syntaxonomy and syndynamics. We classified plant communities according to the Braun-Blanquet approach. In order to better understand ecological alteration processes and changing species compositions along successional gradients we also examined synecological differences using Principal Coordinate Analysis(PCoA) in terms of moisture gradient, species richness, and community structure. Classification resulted in one association and five plant communities occupying distinct moor habitats: Hypericum laxum-Eleocharis acicularis for. longiseta community, Drosera rotundifolia-Eleocharis congesta community, Platanthero-Molinietum japonicae ass. nova hoc loco, Molinia japonica-Alnus japonica community, Miscanthus sinensis-Pinus densiflora community, and Convallaria keiskei-Quercus serrata community. Due to synecological correspondences and floristic similarities in supraregional perspective, Platanthero-Molinietum can be assigned to existing higher syntaxonomic units of Molinion and Molinietalia in Braun-Blanquet system, established in Japan. We propose to extend their range and designate the new class Molinietea japonicae representative to the intermediate moor (Zwischenmoor) vegetation in Northeast Asia. PCoA resulted in four types showing a sequencess of succession: Needle spike-rush type, moor-grass type (incl. alder forest type), eulalia type, and oak forest type. A combination of edaphic conditions (soil eutrphication and soil moisture) and hydrologic patterns of moor ecosystem related to topography, occurring as result of external geophysical forces, controls inter alia spatial patterns and floristic compositions of moor plant communities.

• Journal of Ecology and Environment
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• v.43 no.2
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• pp.117-128
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• 2019

Background: Cliffs are a major plant habitat around the coastal area, but in contrast to sand dunes and salt marshes, they have been little investigated in Korea. There are simple descriptions of cliff vegetation in studies on island vegetation, but there is no published paper, which addressed sea cliff vegetation synthetically. Furthermore, the coastal area where this study was carried out was designated as a conservation reserve. Even though, this area is exposed to intense recreational use such as trekking in these days. This study aims to clarify spatial distribution and structure of vegetation along the environmental gradient on coastal cliff and plateau in the Janggi peninsula (Homigot) located on southeastern Korea. Further, this study has also another objective to prepare a restoration plan to protect this conservation reserve from intense human disturbance. Results: Landscape elements were arranged in the order of sea cliff risen directly on the sea, seashore, coastal cliff, and plateau covered with relatively deep soil in a coastal area of the Janggi peninsula (Homigot), southeastern Korea. Vegetation was sampled at 59 plots arranged from the sea cliff through the seashore and coastal cliff to plateau. The sea cliff, seashore, and coastal cliff, which compose the coastal landscape, were dominated by the seashore spatulate aster (Aster spathulifolius Maxim.) community, dwarf sand sedge (Carex pumila Thunb.) community, and seashore spatulate aster (Aster spathulifolius Maxim.) community. On the plateau corresponding to the ridge of the coastal cliff, black pine (Pinus thunbergii Parl.) community, golden rain tree (Koelreuteria paniculata Laxmann) community, east Asian hackberry (Celtis sinensis Pers.) community, sawleaf zelkova (Zelkova serrata Makino) community, and Korean oak (Quercus dentata Thunb.) community were established in the mentioned order along distance from the sea. Stand ordination showed a vegetation sequence from the seashore through the cliff to the plateau, consistent in its overall pattern among sites. This was dominated by topography. There is evidence for the importance also of salinity, drought and of soil depth. Conclusion: The lack of scientific interest in cliffs to date is in striking contrast to the commonness of cliffs around the whole national territory and to the attraction cliffs have had for humans throughout history. Cliffs provide a unique habitat, rarely investigated from an ecological viewpoint. Cliffs may represent an invaluable type of ecosystem, consisting of some of the least disturbed habitats on earth and contributing more to the biodiversity of a region than their surface coverage would indicate. Although this coastal area where this study was carried out was designated as a conservation reserve, this area is in danger of severe disturbance due to excessive recreational use. We recommended a restoration plan to protect this area from such a disturbance.

• Journal of Korea Water Resources Association
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• v.30 no.6
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• pp.777-785
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• 1997

This study was conducted to clarify the hydrological characteristics of subsurface flow through a soil matrix and macropores. The research facility was set up in a 20m-1ong trench excavated down to bedrock at the base of a hillslope in the Panola catchment under USGS Georgia district. 13 macropores were found on the trench face and 6 major macropores were monitored. Matrix and macropore flow were measured during 95.5mm rainfall on March, 6 to 7. 1996. Macropore flow had great influence on formation of peak flow because the delivery time to Peak flow of macropore flow were faster about 10hrs than those of matrix flow. Matrix flow continued to recess for 3 days. On the other hand, macropore flow stopped within 12hrs after the event ceased. This means that matrix flow controls the recession part. The spatial variations of matrix and macropore flow between each trough and collector were very large by a wide range of 8,655.3 $\ell$ to 17.8 $\ell$ . The bed rock surface topography relates closer with the spatial variations of the flow than the surface one.