• The Korean Journal of Ecology
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• v.18 no.4
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• pp.503-512
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• 1995

The present paper describes partial results of the study on the activities of microbes in the soil of Quercus mongolica forest from July, 1994 to April, 1995. To determine the relationship between structure and function of soil microbial ecosystem, the author investigated the seasonal change of physical environmental factors, microbial population and soil enzyme activities. The changes of pH was not significant and the temperature of surface soil was 2℃ higher than lower soil through out the year. Moisture contents (％) of soil samples ranged from 7.64％ to 42.11％. However, soils of site 3 at Mt. Komdan in which vegetation is successional have higher moisture content than the others. The bacterial population increased in summer, but continuously decreased in autumn and winter, and then reincreased again in spring. Bacterial population of surface soil was higher than those of 30 cm depth all the year round. Dehydrogenase activity (DHA) was about two-fold higher throughout in surface soil compared to those of lower soil. And the correlation coefficient between DHA and bacterial population size was 0,713, It was suggested that DHA could be used as a primary index of soil microbial population and activity in soil ecosystem.

• Journal of the Korean Association of Geographic Information Studies
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• v.23 no.3
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• pp.26-67
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• 2020

Synthetic Aperture Radar(SAR) is able to photograph the earth's surface regardless of weather conditions, day and night. Because of its possibility to search for hydrological factors such as soil moisture and groundwater, and its importance is gradually increasing in the field of water resources. SAR began to be mounted on satellites in the 1970s, and about 15 or more satellites were launched as of 2020, which around 10 satellites will be launched within the next 5 years. Recently, various types of SAR technologies such as enhancement of observation width and resolution, multiple polarization and multiple frequencies, and diversification of observation angles were being developed and utilized. In this paper, a brief history of the SAR system, as well as studies for estimating soil moisture and hydrological components were investigated. Up to now hydrological components that can be estimated using SAR satellites include soil moisture, subsurface groundwater discharge, precipitation, snow cover area, leaf area index(LAI), and normalized difference vegetation index(NDVI) and among them, soil moisture is being studied in 17 countries in South Korea, North America, Europe, and India by using the physical model, the IEM(Integral Equation Model) and the artificial intelligence-based ANN(Artificial Neural Network). RADARSAT-1, ENVISAT, ASAR, and ERS-1/2 were the most widely used satellite, but the operation has ended, and utilization of RADARSAT-2, Sentinel-1, and SMAP, which are currently in operation, is gradually increasing. Since Korea is developing a medium-sized satellite for water resources and water disasters equipped with C-band SAR with the goal of launching in 2025, various hydrological components estimation researches using SAR are expected to be active.

• Journal of Ecology and Environment
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• v.41 no.10
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• pp.281-289
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• 2017

Background: In this study, the growth and reproductive response of seedlings, grown in plastic pots with sand, to moisture and nutrients were analyzed in order to study the environmental conditions required to create an alternative habitat for Epilobium hirsutum L., an endangered plant. Results: Vegetative and reproductive growths of Epilobium hirsutum L. are accelerated with increase in moisture and organic matter content in the soil. Among vegetative organs, the number of runners related to asexual reproduction was the highest when the moisture content was over 25% and nutrient content between 7 and 14% in the soil. But the number of flowers related to flowering responses, among reproductive organs, was the highest when the moisture content was maintained at 75% and when nutrient content was 21% in the soil. The number of seeds, related to sexual reproduction, was the highest when the moisture content was over 25% and nutrient content between 14 and 21%. Conclusions: The study results show that a place with high moisture and nutrient content in the soil is advantageous to asexual and sexual reproduction of Epilobium hirsutum L. Therefore, we must serve periodically nutrient and seeds to sustain population in in situ conservation. Furthermore, it is advisable to create in riverside where abundant nutrient content have, making alternative habitat of Epilobium hirsutum L. Also, we must find species that have high contribution degree index through vegetation survey.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.2
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• pp.157-167
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• 2016

The interspecific estimation for tolerance capacities of upland crop species to excessive soil water stress in paddy field is significant in agricultural practices. Most of upland crops can be damaged by either excessive soil water or capillary rise of the water table during rainy season in paddy fields. The major objective of this study was to evaluate water stress of upland crops under different drainage classes in converted paddy field. This experiment was carried out in poorly drained soil (PDS) and imperfectly drained soil (IDS) of alluvial sloping area located at Toero-ri, Bubuk-myeon, Miryang-si, Gyeongsangnam-do. The soil was Gagog series, which was a member of the fine silty, mixed, nonacid, mesic family of Aeric Endoaquepts (Low Humic-Gley soils). Two drainage methods, namely under Open ditch drainage methods (ODM) and, Closed pipe drainage methods (PDM) were installed within 1-m position at the lower edge of the upper paddy fields. The results showed that sum of excess water days ($SWD_{30}$), which was used to represent the moisture stress index, was 42 days (the lowest) in the PDM compared with 110 days in the ODM. Most of upland crops were more susceptible to excessive soil water during panicle initial stage on more PDS than on IDS. Yield of upland crops in the PDM was continuously increased by the rate of 15.1% on sorghum, 15.4% foxtail millet, 53.6% proso millet, 49.6% soybean and 47.9% adzuki bean as compared in the ODM. The capacity for tolerance by excessive soil water based on yield of each upland crop in the poorly drained sloping paddy fields was the order of sorghum, soybean, foxtail millet, proso millet and adzuki bean. Therefore, Sorghum is relatively tolerant to excessive soil water conditions and, may be grown successfully in converted paddy field.

• Journal of Korea Water Resources Association
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• v.36 no.6
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• pp.961-969
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• 2003

Formulation of quasi-dynamic wetness index was derived to predict the spatial and temporal distribution of the soil moisture. The algorithm of dynamic wetness index was developed through introducing the convolution integral with the rainfall input. The spatial and temporal behaviors of the wetness index of the Sulmachun Watershed was calculated using the digital elevation model(DEM) and the rainfall data for two years. The spatial distribution of the dynamic wetness index shows most dispersive feature of flow generation among the three assumptions of steady, quasi-dynamic and dynamic. The statistical distribution of the quasi-dynamic wetness index and the dynamic wetness index approximate to the steady state wetness index as the time step is increased. The dynamic wetness index shows mixed distribution of the normalized probability density function.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.19 no.1
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• pp.73-83
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• 2016

Forest degradation reduces ecosystem services provided by forest and could lead to change in composition of species. In North Korea, there has been significant forest degradation due to conversion of forest into terrace fields for food production and cut-down of forest for fuel woods. This study analyzed the phenological changes in North Korea, in terms of vegetation and moisture in soil and vegetation, from March to Octorber 2013, using MODIS (MODerate resolution Imaging Spectroradiometer) images and indexes including NDVI (Normalized Difference Vegetation Index), NDSI (Normalized Difference Soil Index), and NDWI (Normalized Difference Water Index). In addition, marginal farmland was derived using elevation data. Lastly, degraded terrace fields of 16 degree was analyzed using NDVI, NDSI, and NDWI indexes, and marginal farmland characteristics with slope variable. The accuracy value of land cover classification, which shows the difference between the observation and analyzed value, was 84.9% and Kappa value was 0.82. The highest accuracy value was from agricultural (paddy, field) and forest area. Terrace fields were easily identified using slope data form agricultural field. Use of NDVI, NDSI, and NDWI is more effective in distinguishing deforested terrace field from agricultural area. NDVI only shows vegetation difference whereas NDSI classifies soil moisture values and NDWI classifies abandoned agricultural fields based on moisture values. The method used in this study allowed more effective identification of deforested terrace fields, which visually illustrates forest degradation problem in North Korea.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.1
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• pp.130-136
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• 2020

There are many problems that occur currently in agriculture industries. The problems such as unexpected of changing weather condition, lack of labor, dry soil were some of the reasons that may cause the growth of the plants. Condition of the weather in local area is inconsistent due to the global warming effect thus affecting the production of the crops. Furthermore, the loss of farm labor to urban manufacturing jobs is also the problem in this industry. Besides, the condition for the plant like air humidity, air temperature, air quality index, and soil moisture are not being recorded automatically which is more reason for the need of implementation system to monitor the data for future research and development of agriculture industry. As of this, we aim to provide a solution by developing IoT-based platform along with the irrigation for increasing crop quality and productivity in agriculture field. We aim to develop a smart garden system environment which the system is able to auto-monitoring the humidity and temperature of surroundings, air quality and soil moisture. The system also has the capability of automating the irrigation process by analyzing the moisture of soil and the climate condition (like raining). Besides, we aim to develop user-friendly system interface to monitor the data collected from the respective sensor. We adopt an open source hardware to implementation and evaluate this research.

• Korean Journal of Remote Sensing
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• v.38 no.6_3
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• pp.1847-1859
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• 2022

Wildfires in North Korea can have a directly or indirectly affect South Korea if they go south to the Demilitarized Zone. Therefore, this study calculates the regional optimized Forest Fire Danger Index (FFDI) based on Local Data Assessment and Prediction System (LDAPS) weather data to obtain forest fire risk in North Korea, and applied it to the cases in Goseong-gun and Cheorwon-gun, North Korea in April 2022. As a result, the suitability was confirmed as the FFDI at the time of ignition corresponded to the risk class Extreme and Severe sections, respectively. In addition, a qualitative comparison of the risk map and the soil moisture map before and after the wildfire, the correlation was grasped. A new forest fire risk index that combines drought factors such as soil moisture, Standardized Precipitation Index (SPI), and Normalized Difference Water Index (NDWI) will be needed in the future.

• The Korean Journal of Ecology
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• v.21 no.5_3
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• pp.695-702
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• 1998

This study was carried out to investigate to determine seasonal variation of dehydrogenase activity, phosphatase activity, adenosine tri-phosphate content and some physicochemical properties, such as soil pH, moisture content, organic matter and several heavy metal concentrations from Apr. 1997 to jan. 1998 in Pinus densiflora and Quercus mongolica forest in Mt. Nam, to explain a relationship between enzyme activity and the soil factors. There were ranges of 4.03-4.65 in soil pH, 18.65-51.09% in moisture content and 6.69-95.95% in orgainc matter. The organic matter content decreased with soil horizon, showing the higher values in Q. mongolica forest. In comparison to the results of Kawngneung site as control area, there were slightly differences due to a development level of forest ecosystem and microbial degradation of organic matter. The heavy metal concentrations showed 32.50-75.55 ${\mu}g/g$ in Cu, 69.33-134.84 ${\mu}g/g$ in Zn, 57.02-150.32 ${\mu}g/g$ in Pb, and 0.36-1.00 ${\mu}g/g$ in Mt. Nam. These values are higher than in Kwangneung site because of long-term exposure to air pollutants from central city. On the other hand, ATP contents in Mt. Nam were lower than in Kawngneung site in relation to soil organic matter, moisture content and relatively high heavy metal concentrations. ATP contents per soil weight was largest in F+H layer and in spring time of other seasons. Dehydrogenase activity as an index of soil microbial activity had a ranges of 170.67-1,221.66 ${\mu}g$ TPF/g that showed lower values than in Kawngneung site. However, phophatase activity had a contray tendency due to P fertilization for a continuous management. Those values increased through spring to a maximum in the summer and fall in autumn. This is basically caused by metabolic state of soil on the biological activity and several and several factors, such as aeration, soil temperature, vegetation and microflora.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.2
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• pp.127-134
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• 2012

Microwave remote sensing can help monitor the land surface water cycle, crop growth and soil moisture. A ground-based polarimetric scatterometer has an advantage for continuous crop using multi-polarization and multi-frequencies and various incident angles have been used extensively in a frequency range expanding from L-band to Ka-band. In this study, we analyzed the relationships between L-, C- and X-band signatures and soil moisture content over the whole soybean growth period. Polarimetric backscatter data at L-, C- and X-bands were acquired every 10 minutes. L-band backscattering coefficients were higher than those observed using C- or X-band over the period. Backscattering coefficients for all frequencies and polarizations increased until Day Of Year (DOY) 271 and then decreased until harvesting stage (DOY 294). Time serious of soil moisture content was not a corresponding with backscattering over the whole growth stage, although it increased relatively until early August (R2, DOY 224). We conducted the relationship between the backscattering coefficients of each band and soil moisture content. Backscattering coefficients for all frequencies were not correlated with soil moisture content when considered over the entire stage ($r{\leq}0.50$). However, we found that L-band HH polarization was correlated with soil moisture content (r=0.90) when Leaf Area Index (LAI)<2. Retrieval equations were developed for estimating soil moisture content using L-band HH polarization. Relation between L-HH and soil moisture shows exponential pattern and highly related with soil moisture content ($R^2=0.92$). Results from this study show that backscattering coefficients of radar scatterometer appear effective to estimate soil moisture content.