• Korean Journal of Ecology and Environment
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• v.43 no.1
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• pp.150-160
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• 2010

The objective of this study was to analyze long-term temporal trends of water chemistry and spatial heterogeneity for 7 sampling sites of the Hyeongsan River watershed using water quality dataset during 1999 to 2008 (obtained from the Ministry of Environment, Korea). The water quality, based on eight physical and chemical parameters, varied largely depending on the years, seasons and sampling sites. Seasonal and annual means of conductivity, used as a key indicator for a ionic dilution declined during the monsoon season and TN, based on overall mean of all sites, showed marked declines during the monsoon, compared to those of the premonsoon. In the mean time, BOD and COD had no significant relations with a precipitation, in spite of some differences in the sampling sites. In contrast, major input of SS occurred during the period of summer monsoon season. Spatial trend analyses of all parameters, except for DO and temperatures, showed that gyeongju city acted as a point source, and thus, water quality at the location of Site 4 declined abruptly, compared to locations of Site 1~2. Based on overall dataset, efficient water quality management in the point source tributary streams is required for better water quality of the main Hyeongsan River.

• Korean Journal of Ecology and Environment
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• v.37 no.4 s.109
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• pp.378-384
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• 2004

We investigated the variations of epilithic diatom community and assessed water quality of the water system of Ulleung Island by DAIpo in April, May, July, August, October, and November of 2003, and January and February of 2004. Samples were collected from four sampling stations. Total 95 taxa were identified from this study and dominant species were Nitzschia inconspicua, Achnanthes minutissima, Gomphonema angustum and Cocconeis placentuja var. lineata. The variation of DAIpo values was ranged from 51.14 to 77.77 and the water quality by DAIpo was estimated between ${\alpha}-oligosaprobic$ and ${\beta}- oligosaprobic$ states.

• Journal of Korean Society of Forest Science
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• v.85 no.3
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• pp.372-380
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• 1996

This study was carried out to study the resistant substances to pine needle gall midge and seasonal variation of phenolic compounds in pine needles among susceptible and resistant species to pine needle gall midge. Free and water soluble phenolic compounds contained in pine needles showed seasonal variations among pine species. But, catechol, vanillic acid and syringic acid including phenolic compounds showed no variation between pine species, even the amount of those component varied by the seasons. Salicylic acid in pine needles showed 140ppm in Pinus virginiana, 35ppm in Pinus thunbergii and 72ppm in hybrid pine, Pinus thunbergii${\times}$P. virginiana, but traces in Pinus densiflora on May and June, hatching season in larvae of pine needle gall midge. There was high level of salicylic acid in resistant species to pine needle gall midge but traces in susceptible species. As our previous researches, the necrosis rate of larvae of pine needle gall midge showed high level on the solution of phenolic compounds extracted from needles of P. virginiana and salicylic acid, and there was no gall formation in P. virginiana, so that salicylic acid in pine needles seems to have relation with those results. Therefore, it is estimated that salicylic acid is resistant substance to pine needle gall midge.

• Journal of Wetlands Research
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• v.22 no.2
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• pp.73-80
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• 2020

Polygonatum stenophyllum Maxim. is a native perennial herb to Korea belonging to family Liliaceae. Although it was removed from the endangered species list, since it inhabits the riverside, it has been threatened with damage to its populations due to frequent disturbances. In order to reveal the basic ecological characteristics of P. stenophyllum, This study was identified the life cycle of the aboveground part and was measured the number of flowers and fruits, which are reproductive organs of P. stenophyllum in riverside in Paju - si during the two years. As a result, aboveground part of P. stenophyllum appeared and grew rapidly until the end of May to about 1m. In early May, two buds per one peduncle were formed up to six pairs per floor. The flowers bloomed in turn from the base of the stem and to the top floor and the blooming occurred when the number of leaves was at least three. Fruits were formed in mid-June and matured by the end of September. The numbers of flowers and fruits were revealed that flowers bloomed in turn from the bottom of the stem to the top floor, the most intensively bloomed in the center part of the stem, and did not bloom from the floor closest to the ground and above the highest 5th node. This basic ecological characteristics of the P. stenophllyum grown in riverside identified in this study will be useful as basic data for their conservation.

• Korean Journal of Environmental Agriculture
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• v.19 no.1
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• pp.75-79
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• 2000

To investigate seasonal variations of soil solution chemistry, samples were collected from zero tension lysimeters in O, A, and B horizons of 26-year-old Larix leptolepis. Pinus koraiensis and Quercus mongolica stands in Kwangju, Kyunggi Province from September, 1996 through June. 1999. Potassium, $Mg^{2+}$, $Cl^-$, and $No_3\;^-$ concentrations increased in October and November concurrent with inputs of fresh litterfall and twigs. Sodium, $Ca^{2+}$, $K^+$, and $Mg^{2+}$ concentrations increased in March and April concurrent with the yellow sand effect. Potassium concentration showed the highest variation among ions, and $Cl^-$ concentration showed positive correlations with $K^+$ and $Mg^{2+}$ concentrations. Soil solution pH decreased while $Al^{3+}$ and $K^+$ concentrations increased during the study period. If our data reflects long term trends. then $Al^{3+}$ concentration in the O horizon will reach the toxic level (0.180 meq/l) within 10-20 years depending on species.

• The Korean Journal of Zoology
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• v.39 no.3
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• pp.325-336
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• 1996

Community organization of the drosophilid flies was investigated with respect to the seasonal variation in species abundance and vertical microdistribution on the basis of the trapped collections in the two natural forests on Cheju-do from May to October 1994. The dominant species were Drosophila bizonata, D. curviceps, D. lutescens, D. angu leris, D. tsigana and D. immigrans in the annual collections. The pattern in seasonal changes of the dominant species was similar at the two survey sites. Seasonal fluctuation in the species diversity was more affected by evenness than by species richness (number of species). The seasonal variation of abundance showed an unimodal pattern in all of the dominant species. The seasonal patterns of vertical microdistribution revealed difference in some of the dominant species between the two survey sites. These results suggest that the predominant species in the forest avoid niche overlap by means of seasonal separation of breedings and that the vertical microdistribution is strongly affected by factors associated with season and vertical site in the deep wooded forests.

• Proceedings of the Korea Water Resources Association Conference
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• 1994.02a
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• pp.449-456
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• 1994

넓은 지역(Arkansas River Basin)에 대하여 토양 수분을 기본으로한 물 수지 모델이 계절별 년별 시간단위로 연구되었다. 지표면과 대기 수분사이의 상호 작용과 재순환 효과에 대한 연구가 유역의 매개 변수화 과정에서 수행되었으며 대규모의 지표면과 대기사이의 상호 작용에 의하여 넓은 지역의 지표 수문은 장기간의 확률분포함수에 있어서 두가지 즉 건조와 습한 안정상태의 영향을 받는다. 토양수분 균형 방정식에서 추계학적 변동은 주위환경 변동에 의하여 야기되는 안정상태 사이의 변이와 함께 분리된 선호하는 통계학적 안정상태를 초래한다. 과거의 자료를 바탕으로 비선형 물수지 모델이 Arkansas강 유역에 대하여 검정되었다. 모델에서 안정상태 사이의 평균 변이시간이 물리과정의 추계학적 표현과 검정된 모델변수들로부터 계산되었다. 본 연구는 안정상태 사이의 변이시간 혹은 거주시간, 즉 시스템이 주어진 안정상태에 머무는 시간(가뭄이나 홍수상태의 지속기간)의 예측과 밀접한 관계가 있다.

• Korean Journal of Ecology and Environment
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• v.45 no.1
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• pp.82-92
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• 2012

In this study, we identified spatial and temporal patterns of reservoir trophic state within Keum-river watershed and analyzed correlations between chlorophyll-$a$ (Chl-$a$) and water quality parameters including conductivity and total phosphorus (TP). The reservoirs were separated into three trophic categories by the criteria of TP: 2 oligotrophic (9.3~9.4 ${\mu}g\;L^{-1}$), 15 mesotrophic (10.3~19.2 ${\mu}g\;L^{-1}$), and 14 eutrophic reservoirs (38.9~117.1 ${\mu}g\;L^{-1}$). Water quality parameters such as conductivity, TP, and Chl-$a$ reflected rainfall patterns, and the patters of annual mean TP were similar to the variation of annual mean Chl-$a$. Empirical models of Chl-$a$ against TP in reservoirs showed that statistical significance ($p$ <0.05) occurred in only some seasons and the trophic relations were modified by a washing-out effect or high non-algal light attenuation.

• Journal of Wetlands Research
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• v.13 no.2
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• pp.275-289
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• 2011

We investigated the hydrological and geomorphological characteristics of small irrigation ponds in civilian control zone of Paju city in Korea. Among 85 small irrigation ponds, water level of 52 ponds changed seasonally and that of 33 was constant. Water sources of 12 ponds were surface water, 29 surface water and ground water, and 44 ground water. 4 ponds locate in the edges of forests, 33 in flat-lands, and 48 in valleys. Water in 45 ponds was exchanged with paddy fields and 40 ponds were isolated from paddy fields. Endangered or endemic species were inhabited in 26 ponds, which have ground water as water source and constant water level. Based on these characteristics, we suggested 4 types of small irrigation ponds: spring, water exchanging, stagnant/spring, stagnant water. This classification system will help ecosystem managers to investigate ponds systematically and manage them based on pond type.

• Korean Journal of Ecology and Environment
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• v.39 no.1 s.115
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• pp.73-84
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• 2006

The objective of this study was to analyze long-term temporal trends of water chemistry and spatial heterogeneity for 10 sampling sites of the Yeongsan River watershed using water quality dataset during 1995 to 2004 (obtained from the Ministry of Environment, Korea). The water quality, based on multi-parameters of biological oxygen demand (BOD), chemical oxygen demand (COD), conductivity, dissolved oxygen (Do), total phosphorus (TP), total nitrogen (TN) and total suspended solids (TSS), largely varied depending on the sampling sites, seasons and years. Largest seasonal variabilities in most parameters occurred during the two months of July to August and these were closely associated with large spate of summmer monsoon rain. Conductivity, used as a key indicator for a ionic dilution during rainy season, and nutrients of TN and TP had an inverse function of precipitation (absolute r values> 0.32, P< 0.01, n= 119), whereas BOD and COD had no significant relations(P> 0.05, n= 119) with rainfall. Minimum values in conductivity, TN, and TP were observed during the summer monsoon, indicating an ionic and nutrient dilution of river water by the rainwater. In contrast, major inputs of total suspended solids (TSS) occurred during the period of summer monsoon. BOD values varied with seasons and the values was closely associated (r=0.592: P< 0.01) with COD, while variations of TN were had high correlations (r=0.529 : P< 0.01) with TP. Seasonal fluctuations of DO showed that maximum values were in the cold winter season and minimum values were in the summer seasons, indicating an inverse relation with water temperature. The spatial trend analyses of TP, TN, BOD, COD and TSS, except for conductivity, showed that the values were greater in the mid-river reach than in the headwater and down-river reaches. Conductivity was greater in the down-river sites than any other sites. Overall data of BOD, COD, and nutrients (TN, TP) showed that water quality was worst in the Site 4, compared to those of others sites. This was due to continuous effluents from the wastewater treatment plants within the urban area of Gwangju city. Based on the overall dataset, efficient water quality management is required in the urban area for better water quality.