• Korean Journal of Environment and Ecology
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• v.21 no.4
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• pp.336-346
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• 2007

This study was conducted to evaluate the vegetation structure of 34 plots for inspection(plot unit: $100m^2$)of evergreen broad-leaved forest in Dongbaekdongsan(Mt.), Jeju-do, Korea. In accordance with the results of TWINSPAN and mean importance percentage analysis, the target forest was aged $28{\sim}52$, and classified into seven community types in total: Ilex rotunda community, Castanopsis sieboldii community, Castanopsis sieboldii-Quercus glauca community, Quercus glauca-Castanopsis sieboldii community, Quercus glauca community, Quercus glauca-Camellia japonica community, and Quercus glauca-Styrax japonica community. According to the results of importance percentage analysis and DBH class distribution of major woody species, the vegetational aspects showed that the dominant species were Castanopsis sieboldii and Quercus glauca in the canopy layer and Camellia japonica in the subordinate layer. Ilex rotunda and Quercus glauca-Styrax japonica community were damaged vegetation in the canopy layer. According to the index of Shannon's diversity in the six communities including the dominant species - Quercus glauca and Castanopsis sieboldii, their species diversity degree was $0.8745{\sim}1.3018$ and that of Ilex rotunda community was the lowest 0.7619. Camellia japonica, Eurya japonica, Ilex rotunda, Trachelospermum asiaticum var. intermedium, Ardisia crenata appeared in all the seven communities. In addition, Litsea coreana and Cinnamomum japonicum as well as Neolitsea serica presumed as climax species in the warm temperate climate also appeared and the constancy ratio of Cinnamomum japonicum was more than 80%. As a result, the target forest in Dongbaekdongsan(Mt.) was mainly compose of Castanopsis sieboldii and Quercus glauca in the canopy layer as a mixed vegetational pattern, and Cameliia japonica was dominant in the subordinate layer. Continuous monitoring was required, since Camellia japonica was strong in the subordinate layer in contrast to the weakness of Litsea coreana and Neolitsea serica reported as the species of climax stage in the forest with Evergreen Broad-leaved Vegetation at a viewpoint of successional direction.

• Journal of Korea Water Resources Association
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• v.45 no.3
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• pp.301-316
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• 2012

Two models, TANK and SWAT (Soil and Water Assessment Tool) were compared for simulating natural flows in the Paldang Dam upstream areas of the Han River basin in order to understand the limitations of TANK and to review the applicability and capability of SWAT. For comparison, simulation results from the previous research work were used. In the results for the calibrated watersheds (Chungju Dam and Soyanggang Dam), two models provided promising results for forecasting of daily flows with the Nash-Sutcliffe model efficiency of around 0.8. TANK simulated observations during some peak flood seasons better than SWAT, while it showed poor results during dry seasons, especially its simulations did not fall down under a certain value. It can be explained that TANK was calibrated for relatively larger flows than smaller ones. SWAT results showed a relatively good agreement with observed flows except some flood flows, and simulated inflows at the Paldang Dam considering discharges from upper dams coincided with observations with the model efficiency of around 0.9. This accounts for SWAT applicability with higher accuracy in predicting natural flows without dam operation or artificial water uses, and in assessing flow variations before and after dam development. Also, two model results were compared for other watersheds such as Pyeongchang-A, Dalcheon-B, Seomgang-B, Inbuk-A, Hangang-D, and Hongcheon-A to which calibrated TANK parameters were applied. The results were similar to the case of calibrated watersheds, that TANK simulated poor smaller flows except some flood flows and had same problem of keeping on over a certain value in dry seasons. This indicates that TANK application may have fatal uncertainties in estimating low flows used as an important index in water resources planning and management. Therefore, in order to reflect actually complex and complicated physical characteristics of Korean watersheds, and to manage efficiently water resources according to the land use and water use changes with urbanization or climate change in the future, it is necessary to utilize a physically based watershed model like SWAT rather than an existing conceptual lumped model like TANK.

• Journal of the Korean Association of Geographic Information Studies
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• v.13 no.4
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• pp.111-124
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• 2010

To monitor the environment of land surface change is considered as an important research field since those parameters are related with land use, climate change, meteorological study, agriculture modulation, surface energy balance, and surface environment system. For the change detection, many different methods have been presented for distributing more detailed information with various tools from ground based measurement to satellite multi-spectral sensor. Recently, using high resolution satellite data is considered the most efficient way to monitor extensive land environmental system especially for higher spatial and temporal resolution. In this study, we use two different spatial resolution satellites; the one is SPOT/VEGETATION with 1 km spatial resolution to detect coarse resolution of the area change and determine objective threshold. The other is Landsat satellite having high resolution to figure out detailed land environmental change. According to their spatial resolution, they show different observation characteristics such as repeat cycle, and the global coverage. By correlating two kinds of satellites, we can detect land surface change from mid resolution to high resolution. The K-mean clustering algorithm is applied to detect changed area with two different temporal images. When using solar spectral band, there are complicate surface reflectance scattering characteristics which make surface change detection difficult. That effect would be leading serious problems when interpreting surface characteristics. For example, in spite of constant their own surface reflectance value, it could be changed according to solar, and sensor relative observation location. To reduce those affects, in this study, long-term Normalized Difference Vegetation Index (NDVI) with solar spectral channels performed for atmospheric and bi-directional correction from SPOT/VEGETATION data are utilized to offer objective threshold value for detecting land surface change, since that NDVI has less sensitivity for solar geometry than solar channel. The surface change detection based on long-term NDVI shows improved results than when only using Landsat.

• The Korean Journal of Ecology
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• v.24 no.5
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• pp.281-288
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• 2001

The relationships between the growths of Abies koreana W. and climatic factors were analyzed by the use of tree-ring analysis at the subalpine belt of Mt. Halla National Park. The four cores were extracted from each 21 trees at north-facing slope (1,900m a.s.1.). The site chronology was established on the periods from 1912 to 1999. The growth of A. koreana was very poor, in particular in the years of 1982, 1988 and 1996. Simple correlation was employed to analyze the relationship between the growth of A. koreana and climatic factors. The result of simple correlation indicates that the growth of A. koreana represent positive correlations both with the mean temperatures of April and previous November, and the precipitation of previous December and January. The presence of large number of frost-damaged scars in the individual trees of A. koreana implies that local freezing temperature conditions at Mt. Halla have occurred in 1964, 1965 and 1966. The correlations between the fir chronology SOI(Southern Oscillation Index) of previous January, February and November were significantly positive. The growth ratio of A. koreana demonstrates that this species is sensitive to seasonal variations. As the winter temperature rises, the growth ratio of A. koreana decreases, on the other hand, the increase of autumn temperature accelerates the growth ratio of A. koreana. The growth decline of A. koreana was observed from 51 cores out of the 54 cores, and the overall growth declines have initiated at 1978, 1982 and 1988. Distinct growth decline of A. koreana in the range of 70% is noticed at 34 cores out of the 51 cores. The decline of, A. koreana growth appears to be related to the winter temperature which has increased since mid-1970s.

• Korean Journal of Environment and Ecology
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• v.28 no.2
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• pp.182-196
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• 2014

In this study, for the forest vegetation classification and the quantitative analysis of the Picea jezoensis and Abies hollophylla stand, the type classification of the vegetation structure was performed with Z-M phytosociological method, and as a result, it was classified into the Picea jenoensis community and the Abies holophylla community in the community unity. The Picea jezoensis community was subdivided into the Rosa koreana group and the Acer ukurunduense group in the group unity and the Abies holophylla community was subdivided into the Acer mandshuricum group and the Lindera obtusiloba group. In the results of estimating the importance value based on the classified vegetation unity, it was deemed that the dominance of the Picea jezoensis would be continued for a while as the importance value from the tree layers of vegetation unity 1 and 2 represented relatively high with 30.73% and 20.25%. In addition, in the results of analyzing the species diversity to estimate the maturity of the community, the species diversity index of the vegetation unity 4 was the lowest with 0.6976 and that of vegetation unity 2 was the highest with 1.1256. As in the similarity between the communities, the vegetation unit 1 and 4 and the vegetation unit 2 and 4 represented low with 0.2880 and 0.3626, respectively, and the similarity between the vegetation unit 1 and 2 and between 2 and 4 represented 0.5411 and 0.5041, respectively, it was deemed that they were the communities that the difference in the composition species between the communities was not big. In the results of analyzing the Chi-square matrix and the catalog of constellations for the interspecific, they were divided mainly into two types, and type 1 plant species were mostly differential species and the characteristic species, which appeared in the Picea jezoensis community classified phytosociologically, and type II plant species were mostly the species appearing in the Abies holophylla community growing in the relatively damp places. Such results is deemed that the positive (+) correlation is recognized among the species, of which growing environments are similar, and the negative (-) correlation .represents among the species, of which preferential environments are different.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.63 no.3
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• pp.257-264
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• 2018

The recent global climate change induced the drought, flooding, and insect pest outbreaks. These caused the severe damage to crop yield in the domesticated field and occurrence change of insect pest species. The sap-sucking insect pest, aphids are common in soybean [Glycine max (L.) Merr.] and cause serious yield losses. Thus, developing resistance cultivars is promising and efficient strategy to prevent the significant yield losses by aphid and screening germplasm is the essential procedure to achieve this goal. We tried to establish a resistance test indicator for foxglove aphid, Aulacorthum solani (Kaltenbach), in soybean and found that plant damage degree or infested plant damage is most suitable one. Also we screened around 1,200 of soybean germplasm including wild and cultivated species for its resistance to foxglove aphid from the various origins, and 67 soybeans, including PI 366121, showed antixenosis resistance, 31 germplasms among 67 antixenosis germplasms were showed antibiosis to foxglove aphid with non-choice test. The identified foxglove aphid resistant soybean resources showed significantly low rate in survival test. Furthermore, resistance type, (i.e., antibiosis or antixenosis) of each candidate were varied. In this research, we established the screening index for foxglove aphid resistance in soybean, and identified the resistance varieties. This result could be useful resources in breeding for new foxglove aphid resistance soybean cultivars, and provide fundamental information to investigate the resistance mechanism in soybean.

• Korean Journal of Agricultural and Forest Meteorology
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• v.1 no.1
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• pp.1-11
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• 1999

Rice yield and primary productivity (NPP) are dependent upon the variability of climate and soil. The variability and regionality of the rice yield and net primary productivity were evaluated with the meteorological data collected from Korea Meteorology Administration and the actual rice yield data from the Ministration of Agriculture and Forestry, Korea. The estimated NPP using the three models, dependent upon temperature(NPP-T), precipitation(NPP-P) and net radiation(NPP-R), ranged from 10.87 to 17.52 Mg ha$^{-1}$ with average of 14.69 Mg ha$^{-1}$ in the South Korea and was ranged 6.47 to 15.58 Mg ha$^{-1}$ with average of 12.59 Mg ha$^{-1}$ in the North Korea. The primary limiting factor of NPP in Korea was net radiation, and the secondary limiting factor was temperature. Spectral analysis on the long term change in air temperature in July and August showed periodicity. The short periodicity was 3 to 7 years and the long periodicity was 15 to 43 years. The coefficient of variances, CV, of the rice yield from 1989 to 1998 ranged 3.23 percents to 12.37 percents which were lower than past decades. The CV's in Kangwon and Kyeongbuk were high while that in Chonbuk was the lowest. The prediction model based on th e yield index and yield response to temperature obtain ed from the field crop situation showed reasonable results and thus the spatial distributions of rice yield and predicted yield could be expressed in the maps. The predicted yields was well fitted with the actual yield except Kyungbuk. For better prediction, modification should be made considering radiation factor in further development.

• Korean Journal of Remote Sensing
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• v.20 no.2
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• pp.77-89
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• 2004

The spatial and temporal variations of aerosol optical depth (AOD) over Northeast Asia regions have special importance in the aerosol research for estimation of aerosol radiative forcing parameters and climate change. Aerosol optical and physical properties (AOD and ${\AA}$ngstrom parameter) have been investigated by using Moderate Resolution Imaging Spectroradiometer (MODIS) and Total Ozone Mapping Spectrometer (TOMS) Aerosol Index (AI) to estimate aerosol characteristics over the study region during 2001. Additionally, aerosol characteristics over the Korean peninsular during Aerosol Characteristic Experiment in Asia (ACE-Asia) Intensive Observation Period (IOP) have been investigated by using satellite observations. The results showed that the daily-observed aerosol data indicate seasonal variations with relatively higher aerosol loading in the spring and very low during the winter. The typical Asian dust case showed higher AOD (>0.7) with lower Angstrom exponent (<0.5) and higher AI (>0.5) that is mainly due to the composition of coarse particles in the springtime. Mean AOD for 2001 at 4 different places showed 0.65$\pm$0.37 at Beijing, 0.31$\pm$0.19 at Gosan, 0.54$\pm$0.26 at Seoul, and 0.38$\pm$0.19 at Kwangju, respectively. An interesting result was found in the present study that polluted aerosol events with small size dominated-aerosol loading around the Korean peninsular are sometimes observed. The origin of these polluted aerosols was thought to East China. Aerosol distribution from satellite images and trajectory results shows the proof of aerosol transport. Therefore, aerosol monitoring using satellite data is very useful.

• Journal of the Korean Institute of Landscape Architecture
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• v.50 no.1
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• pp.68-77
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• 2022

The human thermal environment in an apartment complex located in Seoul was quantitatively analyzed to devise methods to modify human heat-related stresses in landscape and urban planning. Microclimatic data (air temperature, relative humidity, wind speed, and short- and long-wave radiation) were collected at 6 locations [Apt-center, roof (cement), roof (grass), ground, playground, and a tree-lined road] in the late spring and summer, and the data were used to estimate the human thermal sensation, physiological equivalent temperature (PET) and universal thermal climate index (UTCI). As a result, the playground location had the highest thermal environment, and the roof (grass) location had the lowest. The mean difference between the two locations was 0.8-1.1℃ in air temperature, 1.8-4.0% in relative humidity, and 7.5-8.0℃ in mean radiant temperature. In open space locations, the wind speed was 0.4-0.5 ms-1 higher than others. Also, a wind tunnel effect happened at the Apt-center location during the afternoon. For the human thermal sensation, PET and UTCI, the mean differences between the playground and roof (grass) locations were: 5.2℃ (Max. 11.7℃) in late spring and 5.4℃ (Max. 18.1℃) in summer in PET; and 3.0℃ (Max. 6.1℃) in late spring and 2.6℃ (Max. 9.8℃) in summer in UTCI. The mean differences indicated a level change in PET and 1/2 level in UTCI, and the maximum differences showed greater changes, 2-3 levels in PET, and 1-1.5 levels in UTCI. Moreover, the roof (grass) location gave 4.6℃ PET reduction and a 2.5℃ UTCI reduction in late spring, and a 4.4℃ PET reduction and a 2.0℃ UTCI reduction in the summer when compared with the roof (cement) location, which results in a 2/3 level change in PET and a 1/3 level in UTCI. Green infrastructure locations [roof (grass), ground, and a tree-lined road] were not statistically significant in the reduction of PET and UTCI in thermal environment modifying effects. The implementation of green infrastructure, such as rooftop gardens, grass pavement, and street tree planting, should be adopted in landscape planning and be employed for human thermal environment modification.

• Journal of Korea Water Resources Association
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• v.55 no.10
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• pp.761-774
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• 2022

Accurate hydrologic prediction is essential to analyze the effects of drought, flood, and climate change on flow rates, water quality, and ecosystems. Disentangling the uncertainty of the hydrological model is one of the important issues in hydrology and water resources research. Hydrologic data assimilation (DA), a technique that updates the status or parameters of a hydrological model to produce the most likely estimates of the initial conditions of the model, is one of the ways to minimize uncertainty in hydrological simulations and improve predictive accuracy. In this study, the two ensemble-based sequential DA techniques, ensemble Kalman filter, and particle filter are comparatively analyzed for the daily discharge simulation at the Yongdam catchment using airGRdatassim. The results showed that the values of Kling-Gupta efficiency (KGE) were improved from 0.799 in the open loop simulation to 0.826 in the ensemble Kalman filter and to 0.933 in the particle filter. In addition, we analyzed the effects of hyper-parameters related to the data assimilation methods such as precipitation and potential evaporation forcing error parameters and selection of perturbed and updated states. For the case of forcing error conditions, the particle filter was superior to the ensemble in terms of the KGE index. The size of the optimal forcing noise was relatively smaller in the particle filter compared to the ensemble Kalman filter. In addition, with more state variables included in the updating step, performance of data assimilation improved, implicating that adequate selection of updating states can be considered as a hyper-parameter. The simulation experiments in this study implied that DA hyper-parameters needed to be carefully optimized to exploit the potential of DA methods.