• Journal of Korean Society of Forest Science
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• v.97 no.6
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• pp.561-564
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• 2008

Pinus densiflora(red pine) stands in Korea have been faced with the serious threat by pine wilt disease caused by Bursaphelenchus xylophilus (nematodes). It is not easy to early detect and prevent the infected trees because those cannot be visually identified during the initial phase of infection. Red pine is usually infected by B. xylophilus from May to July and can be just visually detected in October or November. While the infected trees are wilted, the spectral value of Near Infrared (NIR) is supposed to be decreased. Based on this phenomena, in this paper, the vegetation vitality change of infected trees was analyzed using vegetation indices. Spectral values of Red, Green and NIR had been acquired monthly by a portable NIR camera in the same place of red pine stands infected by pine wilt disease. It could be proven that the vegetation index, or vegetation vitality of damaged trees starts to decrease from June, in the early infecting phase.

• Journal of Korea Water Resources Association
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• v.56 no.11
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• pp.721-728
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• 2023

Agricultural drought is triggered by a depletion of moisture content in the soil, which hinders photosynthesis and thus increases carbon dioxide (CO₂) concentrations in the atmosphere. The aim of this study is to analyze the relationship between soil moisture (SM) and vegetation activity toward quantifying CO₂ concentration in the atmosphere. To this end, the MODerate resolution imaging spectroradiometer (MODIS), an optical multispectral sensor, was used to evaluate two regions in South Korea for validation. Vegetation activity was analyzed through MOD13A1 vegetation indices products, and MODIS gross primary productivity (GPP) product was used to calculate the CO₂ flux based on its relationship with respiration. In the case of SM, it was calculated through the method of applying apparent thermal inertia (ATI) in combination with land surface temperature and albedo. To validate the SM and CO₂ flux, flux tower data was used which are the observed measurement values for the extreme drought period of 2014 and 2015 in South Korea. These two variables were analyzed for temporal variation on flux tower data as daily time scale, and the relationship with vegetation index (VI) was synthesized and analyzed on a monthly scale. The highest correlation between SM and VI (correlation coefficient (r) = 0.82) was observed at a time lag of one month, and that between VI and CO₂ (r = 0.81) at half month. This regional study suggests a potential capability of MODIS-based SM, VI, and CO₂ flux, which can be applied to an assessment of the global view of the agricultural drought by using available satellite remote sensing products.

• Journal of The Korean Society of Agricultural Engineers
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• v.53 no.3
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• pp.75-82
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• 2011

This study refers to the derivation of simple crop yield prediction equation by using KOMPSAT-2 derived vegetation index. For a 1.25 ha small farm area located in the middle part of South Korea, the KOMPSAT-2 panchromatic and multi-spectral images of 31th August 2008, 17th November 2008, and 10th September 2009 were used. The field spectral reflectance during growing period for the 6 crops (rice, potato, corn, red pepper, garlic, and bean) were measured using ground spectroradiometer and the yield was investigated. Among the 6 vegetation indices (VI), the NDVI and ARVI between measured and image derived showed high relationship with the coefficient of determination of 0.85 and 0.95 respectively. Using the 3 years field data, the NDVI and ARVI regression curves were derived, and the yields were tried to compare with the maximum VIs value.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.9 no.6
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• pp.1-12
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• 2006

Remote sensing cannot provide a direct measurement of vegetation index (VI) but it can provide a reasonably good estimate of vegetation index, defined as the ratio of satellite bands. The monitoring of vegetation in nearby urban regions is made difficult by the low spatial resolution and temporal resolution image captures. In this study, enhancing spatial resolution method is adapted as to improve a low spatial resolution. Recent studies have successfully estimated normalized difference vegetation index (NDVI) using improved resolution method such as from the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard EOS Terra satellite. Image enhancing spatial resolution is an important tool in remote sensing, as many Earth observation satellites provide both high-resolution and low-resolution multi-spectral images. Examples of enhancement of a MODIS multi-spectral image and a MODIS NDVI image of Cheongju using a Landsat TM high-resolution multi-spectral image are presented. The results are compared with that of the IHS technique is presented for enhancing spatial resolution of multi-spectral bands using a higher resolution data set. To provide a continuous monitoring capability for NDVI, in situ measurements of NDVI from paddy field was carried out in 2004 for comparison with remotely sensed MODIS data. We compare and discuss NDVI estimates from MODIS sensors and in-situ spectroradiometer data over Ochang plain region. These results indicate that the MODIS NDVI is underestimated by approximately 50%.

• Korean Journal of Environmental Biology
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• v.41 no.3
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• pp.283-290
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• 2023

The Republic of Korea reclaimed land to increase its food self-sufficiency rate, but the yield was reduced due to abnormal climate. In this study, it was hypothesized that rapid and continuous monitoring technology could help improve yield. Using the vegetation index (VI) analysis, the drought stress index was calculated and the drought stress for corn grown in Hwaong, Saemangeum, and Yeongsan River reclaimed tidal land was predicted according to drying treatment. The vegetation index of corn did not decrease during the last 20 days of irrigation when soil moisture rapidly decreased, but decreased rapidly during the 20 days after irrigation. The reduction rate of the vegetation index according to the drying treatment was in the order of Saemangeum>Yeongsan River>Hwaong reclaimed tidal land, and normalized difference vegetation index(NDVI) decreased by approximately 50% in all reclaimed tidal lands, confirming that drought stress occurred due to the decrease in moisture content of the leaves. In addition, structure pigment chlorophyll index (SIPI) and photochemical reflectance index (PRI), which are calculated based on changes in light use efficiency and carotenoids, were reduced; drought stress caused a decrease in light use efficiency and an increase in carotenoid content. Therefore, vegetation index analysis was confirmed to be effective in evaluating and predicting drought stress in corn growing on reclaimed tidal land corn.

• Korean Journal of Environment and Ecology
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• v.30 no.6
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• pp.1009-1021
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• 2016

The community structure and abundance of epilithic biofilm were bimonthly examined to know spatial and temporal patterns of biofilm biomass and taxonimical composition at the two study sites, Gosapo and Gyeokpo with different degrees of wave exposure levels from November 2010 to September 2011. Biomass was estimated by using chlorophyll a contents (Chl a), normalized difference vegetation index (NDVI), and vegetation index (VI). Cyanobacteria such as Aphanotece spp. predominated in the proportion of 57.53% at Gosapo and of 61.12% at Gyeokpo and they are abundant in mid shore and in summer at both study sites. The diatoms Navicula spp., Achnanthes spp. and Licmophora spp. were common species and they showed an increasing trend from high to low shore. NDVI, VI, and chl a contents were the greatest at mid shore for Gosapo (0.44, 3.05, $24.56{\mu}g/cm^2$) and at low shore for Gyeokpo (0.41, 2.73, $17.98{\mu}g/cm^2$). NDVI, VI, and chl a content were all maximal in January and minimal in March at the both sites. Average NDVI, VI, and chlorophyll a contents of biofilms were greater at Gosapo (0.43, 2.89, $22.84{\mu}g/cm^2$) than Gyeokpo (0.38, 2.48, $15.48{\mu}g/cm^2$).Of three shore levels(high, mid, and low) Chl a contents were positively correlated with NDVI and VI at the two study sites indicating that non-destructive NDVI and VI values can be used in stead of destructive Chl a extraction method. In conclusion, epilithic biofilm was more abundant seasonally in winter, vertically in mid and low intertidal zone, and horizontally at wave exposed shore than in summer, at high and sheltered shore in Korea.

• Korean Journal of Environment and Ecology
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• v.27 no.5
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• pp.579-591
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• 2013

This study was carried out to investigate the actual vegetation, the structure of plant community, and ecological succession sere of forest ecosystem in temperate northern climate zone, Daegwallyeong Ranch, Gangwon-do (Province) and to offer the basic data for planning of the forest managemant. As a result of analysis of actual vegetation, vegetation types divided into 56types and the area of survey site was $19,397,361m^2$. The ratio of vegetation type dominated by Quercus mongolica forest was 39.1%, primary grassland was 24.7%, Quercus mongolica-Deciduous broad-leaved forest was 11.3%. Twenty eight plots (size is $20m{\times}20m$) were set up and the results analyzed by DCA which in one of the ordination technique showed that the plant communities were divided into six groups which area community I (Pinus densiflora-Quercus mongolica community), community II (Quercus mongolica-Pinus densiflora community), community III (Quercus mongolica community), community IV (Quercus mongolica-Deciduous broad-leaved community), community V (Deciduous broad-leaved community), community VI (Sorbus alnifolia community). The age of community Iwas ranged from 57 to 62 years old, that of community IIwas ranged from 41 to 77 years old, community III was ranged from 47 to 108 years old, community IV was ranged from 47 to 82 years old, community V was 47 years old, community VI was 55 years old, thus we supposed that the age of the study site is about from 41 to 108 years old. The Ecological succession is predicted from Pinus densiflora community to Quercus mongolica community and Deciduous broad-leaved were distributed in the center of the valley in Daegwallyeong Ranch. According to the index of Shannon's diversity (unit: $400m^2$), community IV was ranged from 0.8203 to 1.1439, community III was ranged from 0.8019 to 1.1375, community V was 1.0993, community I was ranged from 0.9475 to 1.0797, community II was ranged from 0.6896 to 1.0324, community VI was 0.9909.

• Spatial Information Research
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• v.20 no.4
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• pp.47-55
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• 2012

Normalized Difference Vegetation Index (NDVI) has been used to measure and monitor plant growth, vegetation cover, and biomass from multispectral satellite data. It is also a valuable index in forest applications, providing forest resource information. In this research, an approach for monitoring forest change using MODIS NDVI time series data is explored. NDVI difference-based approaches for a specific point in time have possible accuracy problems and are lacking in monitoring long-term forest cover change. It means that a multi-time NDVI pattern change needs to be considered. In this study, an efficient methodology to consider long-term NDVI pattern is suggested using a harmonic model. The suggested method reconstructs MODIS NDVI time series data through application of the harmonic model, which corrects missing and erroneous data. Then NDVI pattern is analyzed based on estimated values of the harmonic model. The suggested method was applied to 49 NDVI time series data from Aug. 21, 2009 to Sep. 6, 2011 and its usefulness was shown through an experiment.

• Korean Journal of Remote Sensing
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• v.35 no.6_1
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• pp.883-893
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• 2019

In this study, crop coefficients were calculated in two different methods and the results were evaluated. In the first method, appropriateness of GLDAS-based evapotranspiration was evaluated by comparing it with observed data of Cheongmi-cheon (CMC) Flux tower. Then, crop coefficient was calculated by dividing actual evapotranspiration with potential evapotranspiration that derived from GLDAS. In the second method, crop coefficient was determined by using MLR (Multiple Linear Regression) analysis with vegetation index (NDVI, EVI, LAI and SAVI) derived from MODIS and in-situ soil moisture data observed in CMC, In comparison of two crop coefficients over the entire period, for each crop coefficient GLDAS K_c and SM&VI K_c, shows the mean value of 0.412 and 0.378, the bias of 0.031 and -0.004, the RMSE of 0.092 and 0.069, and the Index of Agree (IOA) of 0.944 and 0.958. Overall, both methods showed similar patterns with observed evapotranspiration, but the SM&VI-based method showed better results. One step further, the statistical evaluation of GLDAS K_c and SM&VI K_c in specific period was performed according to the growth phase of the crop. The result shows that GLDAS K_c was better in the early and mid-phase of the crop growth, and SM&VI K_c was better in the latter phase. This result seems to be because of reduced accuracy of MODIS sensors due to yellow dust in spring and rain clouds in summer. If the observational accuracy of the MODIS sensor is improved in subsequent study, the accuracy of the SM&VI-based method will also be improved and this method will be applicable in determining the crop coefficient of unmeasured basin or predicting the crop coefficient of a certain area.

• Proceedings of the KSRS Conference
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• 2008.03a
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• pp.14-19
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• 2008

소나무 재선충에 감염되어 고사하는 소나무의 증가는 우리나라 산림에 심각한 위협이 되고 있다. 재선충은 매개 후 고사단계에 이르기까지 진행과 확산이 빨라 감염목이 발견되면 곧바로 임내에서 벌채 및 훈증 처리해야 하며 5${\sim}$6월에 감염되어 10${\sim}$11월에 육안으로 고사를 확인할 수 있다. 재선충에 의해 소나무가 고사되는 과정에서 식생활력도가 크게 감소하며 이러한 현상은 근적외선 영역에서 분광반사의 감소를 수반한다. 따라서 본 연구는 근적외선영역의 분광감소를 이용하여 재선충 피해목의 조기진단이 가능할 수 있다는 것에 착안하여 수행하였다. 근적외선영상 취득 방법으로 휴대가 간편한 근적외선 카메라를 이용하여 재선충 피해지역의 소나무림을 5월부터 11월까지 매월 촬영하였다. 이렇게 수집된 분광반사값으로부터 식생지수(Vegetation Index: VI)의 변화를 분석하였고, VI의 감소율로부터 소나무 재선충 감염목을 조기에 발견할 수 있다는 결과를 도출하였다.