• 한국환경복원기술학회지
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• 제16권5호
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• pp.59-69
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• 2013

Global warming also has effects on the phenology. The limitation of phenology study is an acquisition of phenology data. Satellite images analysis can make up limitation of monitering data. This study is to analyze spatial distribution and characteristics of phenology changes using MODIS images. Research data collected images of 16 day intervals of 11 years from year 2001 to 2010. The data analyzed 228 images of 11 years. It can figure out changes of phenology by analyzing enhanced vegetation index of MODIS image. We made a comparison between changes of phenology and flowering of cherry blossoms. As a results, Startup of season spatially was getting late from southern area to north area. Startup of Phenology was foreshortened 13 days during 11 years, and change ratios of cherry blooming was getting more faster from 0.18 dat to 0.22 day per year during that same period.

• 대한원격탐사학회지
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• 제40권2호
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• pp.179-190
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• 2024

This study aims to compare supervised classification methods with phenology-based approaches, specifically pixel-based and segment-based methods, for accurate crop mapping in agricultural landscapes. We utilized Sentinel-2A imagery, which provides multispectral data for accurate crop mapping. 31 normalized difference vegetation index (NDVI) images were calculated from the Sentinel-2A data. Next, we employed phenology-based approaches to extract valuable information from the NDVI time series. A set of 10 phenology metrics was extracted from the NDVI data. For the supervised classification, we employed the maximum likelihood (MaxLike) algorithm. For the phenology-based approaches, we implemented both pixel-based and segment-based methods. The results indicate that phenology-based approaches outperformed the MaxLike algorithm in regions with frequent rainfall and cloudy conditions. The segment-based phenology approach demonstrated the highest kappa coefficient of 0.85, indicating a high level of agreement with the ground truth data. The pixel-based phenology approach also achieved a commendable kappa coefficient of 0.81, indicating its effectiveness in accurately classifying the crop types. On the other hand, the supervised classification method (MaxLike) yielded a lower kappa coefficient of 0.74. Our study suggests that segment-based phenology mapping is a suitable approach for regions like South Korea, where continuous cloud-free satellite images are scarce. However, establishing precise classification thresholds remains challenging due to the lack of adequately sampled NDVI data. Despite this limitation, the phenology-based approach demonstrates its potential in crop classification, particularly in regions with varying weather patterns.

• 대한원격탐사학회지
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• 제34권2_1호
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• pp.267-282
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• 2018

인공위성 영상을 활용한 식생 계절 추정 연구의 지속적 발전에도 불구하고 현장 자료와의 비교를 통한 검증은 다소 미흡한 실정이다. 특히, 다양한 형태로 패치화 되어 있는 우리나라 산림의 경우, 인공위성 영상과 해상도가 일치하지 않는 한계가 존재하여 위성 영상만으로 개엽일을 추정하는데 어려움이 따른다. 본 연구는 식생 계절 추정의 신뢰도를 향상시키기 위해 대축적 임상도(1:5,000)를 MODIS 픽셀 해상도에 맞게 재구성하여 MODIS의 NDVI와 EVI 두 식생지수들로부터 시계열 식물계절 곡선을 생산하여 현장 자료를 바탕으로 우리나라의 산림에 적합한 식생 지수와 개엽일 추출 방법을 비교 및 평가하였다. 또한 각 픽셀의 임상 구성비율과 식생지수로부터의 식물계절 추출 간의 상관관계를 분석하였다. 국립수목원에서 실측된 개엽일을 바탕으로 NDVI와 EVI를 비교하였을 때 우리나라의 산림에는 EVI가 더 적합하였고, 식생지수 계절 곡선으로는 일차도함수가 개엽일 추출에 가장 적합하였다. 현장 개엽일이 조사된 7개의 활엽수종이 속한 픽셀과(중앙픽셀) 이웃한 8개의 픽셀을 실측 개엽일과 비교하였을 때, 실측과 가장 높은 상관관계를 보이는 베스트 픽셀을 구성하는 임상은 활엽수림 67.9%, 침엽수림 14.3%, 혼효림 7.7% 구성을 보였고 평균 결정계수($R^2$)는 0.64으로 나타나 높은 상관관계를 보였다. MODIS EVI로 추출한 전국 평균 개엽일은 최소 112.9일(2014년)에서 최대 129.1일(2010년)으로 2003년 이래로 약 0.16일 빨라졌다. 향후 연구에서는 활엽수림과 혼효림의 개엽일 분석 외에도 다양한 기후 및 지형 인자들의 영향을 파악하기 위해 침엽수림의 개엽일 추출까지 확장할 필요가 있으며 우리나라 산림 생태계의 다양성을 고려한 종합적인 연구가 진행되어야 할 것이다.

• 한국지리정보학회지
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• 제17권3호
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• pp.20-38
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• 2014

식물계절은 기후변화와 관련된 생태계의 중요한 지표로서 지속적인 모니터링을 필요로 한다. 본 연구에서는 Moderate Resolution Imaging Spectrometer(MODIS) 위성영상을 기반으로 구름이나 기타 영향에 의한 오류를 보정한 식생지수를 통해 국내 산림의 식물계절학적 특성을 분석하였으며, 이에 Harmonic Analysis of NDVI Time-Series(HANTS) 알고리즘을 이용하였다. 그 결과, 위성영상 기반 식생지수의 노이즈를 효과적으로 감소시킬 수 있었으며, 고도에 의한 식물계절 변화 및 경향을 파악할 수 있었다. 식물계절시기는 고도에 따른 변화경향이 뚜렷하게 나타났으며, 침엽수의 경우 생육개시일과 생육종료일, 생육기간은 각각 +0.71일/100m, -1.33일/100m, -2.04일/100m, 활엽수의 경우 +1.50일/100m, -1.54/100m, -3.04/100m, 혼효림의 경우 +1.39일/100m, -2.04일/100m, -3.43일/100m로 분석되었다. 고도에 따른 식물계절시기의 변화는 기온과 관련된 것으로 판단되며, 활엽수림이 침엽수림보다 변화에 대한 민감도가 더 높은 것으로 나타났다.

• Journal of Ecology and Environment
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• 제34권2호
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• pp.149-156
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• 2011

Phenological variables derived from remote sensing are useful in determining the seasonal cycles of ecosystems in a changing climate. Satellite remote sensing imagery is useful for the spatial continuous monitoring of vegetation phenology across broad regions; however, its applications are substantially constrained by atmospheric disturbances such as clouds, dusts, and aerosols. By way of contrast, a tower-based ground remote sensing approach at the canopy level can provide continuous information on canopy phenology at finer spatial and temporal scales, regardless of atmospheric conditions. In this study, a tower-based ground remote sensing system, called the "Phenological Eyes Network (PEN)", which was installed at the Gwangneung Deciduous KoFlux (GDK) flux tower site in Korea was introduced, and daily phenological progressions at the canopy level were assessed using ratios of red, green, and blue (RGB) spectral reflectances obtained by the PEN system. The PEN system at the GDK site consists of an automatic-capturing digital fisheye camera and a hemi-spherical spectroradiometer, and monitors stand canopy phenology on an hourly basis. RGB data analyses conducted between late March and early December in 2009 revealed that the 2G_RB (i.e., 2G - R - B) index was lower than the G/R (i.e., G divided by R) index during the off-growing season, owing to the effects of surface reflectance, including soil and snow effects. The results of comparisons between the daily PEN-obtained RGB ratios and daily moderate-resolution imaging spectroradiometer (MODIS)-driven vegetation indices demonstrate that ground remote sensing data, including the PEN data, can help to improve cloud-contaminated satellite remote sensing imagery.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.405-407
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• 2003

An attempt has been in this study to delineate the characteristics of spectral signatures of the vegetation in terms of various VIs, particularly made the Normalized Difference Vegetation Index(NDVI), Modified Soil Adjusted Vegetation Index2(MSAVI2) and Enhanced Vegetation Index(EVI). Multitemporal SPOT-4 VEGETATION data from 1998 to 2002 have been used for the analysis. They have been compared with each other for their similarities and differences. The correlations between the vegetation indices observed at various degree of vegetation coverage during their different stages of growth were examined. All of the VIs have shown qualitative relationships to variations in vegetation. Apparently, the NDVI and MSAVI2 are highly correlated for all of the temporal changes, representing the different stages of phenology.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.420-422
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• 2003

• 대한원격탐사학회지
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• 제25권5호
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• pp.399-409
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• 2009

NDVI(Normal Difference Vegetation Index)는 식생의 광합성량과 직접적인 상호관련성이 있기 때문에 생태학적인 목적으로 이러한 지수들의 수많은 응용 가능성이 있다. 본 연구에서는 시계열 MODIS(Moderate Resolution Imaging Spectroradiometer) NDVI 자료를 이용하여 9년 동안 (2000~2008)의 북한 북부고원지대 아고산 고산 식생의 생물계절 특징을 모니터링 하였다. 5월 초순의 급격한 성장 이후 6월부터 8월까지 NDVI값은 0.8이상 지속적으로 유지되었고 최대 식생 생산량과 시기는 각 각 0.86, 7월 28일 이었다. 식생 성장의 시작과 쇠퇴는 평균적으로 각각 5월 9일, 9월 30일이었고, NDVI 값은 각각 0.51,0.54이었다. 식생 성장 기간은 2003년에 128일로 가장 짧았고 2000년과 2005년은 176일로 가장 길었다. 그리고, 동일한 수직적 산림 식생 환경을 가지고 있는 남한의 설악산과 지리산의 생물계절 특성과 비교하였다. 남북한의 아고산 고산 식생대는 약 30일 이상의 식생 생육 기간의 차이가 있었고 남한지역이 MODIS 자료의 합성 주기인 16일만큼 개서시기가 빨랐다. 본 연구는 북한 고원지대 산림 식생의 시계열 및 생물계절적인 변화를 정량적으로 분석한 연구로서 그 의의가 클 뿐만 아니라 북한 지역의 산림 식생 라이브러리 작성 및 통일을 대비한 북한 자연환경계획 수립에 기초 베이스맵으로 활용될 수 있다.

• 대한원격탐사학회지
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• 제38권1호
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• pp.57-72
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• 2022

In this paper, we aimed to examine the flowering dates of cherry blossom and the peak dates of maple leaves in South Korea, by the combination of temperature observation data from ASOS (Automated Surface Observing System) and NDVI (Normalized Difference Vegetation Index) from MODIS (Moderate Resolution Imaging Spectroradiometer). The more recent years, the faster the flowering dates and the slower the peak dates. This is because of the impacts of climate change with the increase of air temperature in South Korea. By reflecting the climate change, our statistical models could reasonably predict the plant phenology with the CC (Correlation Coefficient) of 0.870 and the MAE (Mean Absolute Error) of 3.3 days for the flowering dates of cherry blossom, and the CC of 0.805 and the MAE of 3.8 for the peak dates of maple leaves. We could suppose a linear relationship between the plant phenology DOY (day of year) and the environmental factors like temperature and NDVI, which should be inspected in more detail. We found that the flowering date of cherry blossom was closely related to the monthly mean temperature of February and March, and the peak date of maple leaves was much associated with the accumulated temperature. Amore sophisticated future work will be required to examine the plant phenology using higher-resolution satellite images and additional meteorological variables like the diurnal temperature range sensitive to plant phenology. Using meteorological grid can help produce the spatially continuous raster maps for plant phenology.

• Journal of Ecology and Environment
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• 제34권3호
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• pp.295-305
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• 2011

Many studies have suggested the positive effects of grazing by large herbivorous mammals on seed dispersal, but little is known about how herbivores could affect the fate of ingested seeds. This study examined the effects of seed ingestion by sika deer (Cervus nippon) on seed fate in a temperate grassland established in an urban park long resided by high densities of sika deer. I compared species composition and seasonal traits of seed abundance and maturity in the grassland community with those in deer fecal pellets. In total, 27 herbaceous species were observed, including the predominant Zoysia japonica. Seed phenology and production differed among the three dominant species (Z. japonica, Digitaria violascens, and Hydrocotyle maritima). Pellets contained at least 26 species of herbaceous seeds, and their abundance differed among species. Of the 26 species, 15 were observed in the vegetation at the study site. The peak of seed abundance in pellets for the dominant species appeared 1 month after the peak of inflorescence production (but most of the inflorescences were immature and susceptible to digestion) and consequently corresponded to the peak of mature inflorescence. Because sika deer are likely to ingest seeds at any maturity stage in the grassland and immature seeds are less hardened, ingested immature seeds can suffer great losses. The results suggested that the survival of germable seeds with great losses of immature seeds may be a factor determining which plant species can be successfully dispersed by herbivores.