• Korean Journal of Ecology and Environment
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• v.53 no.2
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• pp.208-219
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• 2020

Forest thinning brought the large variation to forest ecosystem including environment and animal. Our study was result of long-term monitoring for ground-dwelling arthropod communities after thinning in forest ecosystem. In this study, we conducted field study on plantation forest in Chuncheon, Korea in 2018, and compared with previous study data (2006 and 2008). We found that the effect of thinning was still existent 10 years later from thinning with difference of habitat environment(depth of ground organic matter, coverage rate of ground vegetation and canopy). And ground-dwelling arthropod communities showed changes of abundance and taxa at the study area and thinning conditions. Ground-dwelling arthropod communities in 2018 were dominant in the order of Diptera, Hymenoptera, Coleoptera (Insecta), Araneae (Arachnida) and Collembola (Collembola). Among the conditions of thinning, Araneae (Arachnida), Coleoptera and Hymenoptera (Insecta) showed amount of abundance in heavy thinning. And Collembola (Collembola) and Diptera (Insecta) were most common in area of light thinning. In 2018 ground-dwelling arthropod communities, abundance of Diptera and Coleoptera (Insecta) and Isopoda (Crustacea) were decreased although Hemiptera and Orthoptera (Insecta) were increased than 2008 arthropod communities. Arthropod communities in 2018 were more similar with those in 2008 (after thinning) than with those in 2006 (before thinning).

• Journal of the korean society of oceanography
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• v.38 no.3
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• pp.111-121
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• 2003

The seasonal succession of zooplankton communities in the coastal area off Incheon, Kyeonggi Bay, was investigated with the samples collected at intervals of 10 to 15 days from January 1999 to December 2000. Total abundance of zooplankton communities showed remarkable seasonal variations, ranged from 1,100 to $120,400{\;}indiv./\textrm{m}^3$, and annual mean abundance was $22,000{\;}indiv./\textrm{m}^3$. There were several times of the total abundance during a year, and the timing ofhigh abundances were about the same in 1999 and 2000. During the study period except summer, the abundance of dinoflagellate Noctiluca scintillans and copepod Acartia hongi contributed to the most part of total zooplankton. Whereas, during summer, smaller copepod Oithona davisae and Paracalanus crassirostris were dominant species. Zooplankton communities in the coastal waters off Incheon showed typical characteristics of coastal-estuarine communities, which were dominated by a few species, and abrupt seasonal variations in abundance. We suggest that the seasonal succession and abundance variations of zooplankton communities were caused by the seasonal variations in water temperature and by the seasonally varying phytoplankton biomass in the study area.

• Knowledge Management Research
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• v.11 no.2
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• pp.17-35
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• 2010

As the internet has been used widely, many online communities have been appeared. Initially, many users used online communities for communication and information sharing. Recently, users start using online communities for building, maintaining, and extending social networks which they did in offline environments previously. The importance of online community is considered by many scholars and also companies to use it strategically. Therefore many studies have focused on exploring characteristics of online communities. Most of them have emphasized the importance of online community. Few study focuses on dynamics within online community. By using social network analysis (SNA), this study tries to explore dynamics of online community. Specially, By measuring the centrality of online community and tracing its changes, this study investigates how the relationships among participants in online communities have been changed over the time. Findings of this study indicate that, as participants has joined in an online community over the time, an opinion leader is appeared, and her/his power is changed.

• Journal of Korean Society of Rural Planning
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• v.25 no.3
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• pp.103-114
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• 2019

The purpose of this study is to investigate the value perception changes of early adolescents, who are from 5th grades to 7th grades regarding to agriculture and rural communities through debate education. Since current education policy to educate agricultural value is limited in solving stereotypes and acquiring abundant relevant knowledge about agricultural values, this study tried to test the effect of debate education for the change of value perception of early adolescents about agriculture and rural communities. Through the two weeks of a debate education course, the differences of perception changes between the experimental group and control group were analyzed. As a result, education on agriculture and rural communities through debate has a great influence on the change of value perception and thus, it could be used as a supplementary educational method for literacy education and field trip learning. Lastly, limitations and implications for the study is discussed.

• Journal of Ecology and Environment
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• v.32 no.3
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• pp.197-206
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• 2009

Benthic macroinvertebrate communities were collected from six different sites in the Dobong Stream in Seoul, Korea to investigate spatial and temporal changes in benthic macroinvertebrate communities in response to natural disturbances such as floods and droughts. We collected samples monthly or semimonthly with a Surber net ($30cm{\times}30cm$), and measured environmental factors, including stream temperature, discharge, width, conductivity, dissolved oxygen and pH at each sampling site. Benthic macro invertebrates were strongly affected by floods as well as droughts. In addition, benthic macroinvertebrate communities displayed different responses to the onset of the rainy season in summer 2006 and 2007, apparently due to differences in the intensity and amount of precipitation. Chironomids were particularly sensitive to heavy rain. Floods and droughts also affected the proportions of functional feeding groups during the survey period: the proportion of scrapers was high right after heavy rains, while the proportion of predators tended to increase in intermittent-type streams as the riffle zone decreased. Finally, although species richness and abundance were strongly influenced by heavy rain, they recovered to background levels for within one month, and varied consistently among stream types, indicating habitat stability.

• 한국해양학회지
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• v.13 no.2
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• pp.31-41
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• 1978

The planktonic algal communities of the Han River with a particular emphasis on water pollution was studied over a twelve month of period. Results of observing many algal communities from 7 stations of the Han River have shown that these communities are generally composed of many species, most of which have relatively small populations with a few exceptional dominant species. The distribution of the total standing crop of phytoplankton in the studid area is characteristic, summer in the polluted zone. Diversity indices of all samples were computed and have shown that the H values of 7 stations are relatively low. However, a detailed examination of these H values reveals that the seasonal fluctuations of the species diversity remarkably coincide with those fo phytoplankton standing crop.No reduction in the species diversity at stations 4, 5, 6, and 7 where the water is heavily polluted indicates that a great number of species capable of invading stations, 4, 5, and 6 from the various tributaries, and the station 7 from the contaminated with sea water are probably more important in the functional changes of the communities than the size of sampling area. It is evident that the diversity index in a lotic environment does not indicate water quality as far as phytoplankton communities are concerned.

• The Korean Journal of Ecology
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• v.11 no.4
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• pp.213-225
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• 1988

The plant communities of the eastern ridge in Mt. Cheonma, Central Korea, Quercus mongolica, Q mongolica-Acer pseudo-sieboldianum, and Q. mongolica-Rhododendron schlippenbachii communities in the northern slope and Q. variabilis and Q. cutissima communities in the southern slope were detected by Zurich-Montpellier method. The undergrowth of Q mongolica community in the northern slope was dominated by Ainsliaea acerifolia, Carex siderosticta, Astilbe chinensis var. davidii, Heloniopsis orientalis, Pseudostellaria palibiniana, ranging 3.3 to 2.2 in dominance-sociability, while the those of Q variabilis and Q acutissima in the southern slope were dominated by Spodiopogon cotulifer, Artemisia keiskeana, Carex humilis, Atractylodes japonica, Lysimachia clethroides and Disporum smilacinum with similar degree in dominance-sociability to that of Q mongolica community. The two communities were considered as regenerating forest after severe disturbance judging by their age structure. The relationship between Shannon's diversity index (H') and Simpson's dominance index (i) was in reciprocal proportion in both two communities. The Q. mongolica and Q. variabilis communities were showed 13 and 12 m respectively. Seasonal changes of undergrowth coverage in the two communities were seemed to be affected especially with soil moisture among environmental factors such as temperature, light intensity, relative humidity and organic matter.

• The Plant Pathology Journal
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• v.38 no.3
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• pp.203-211
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• 2022

Bacterial wilt, which is a major soil-borne disease with widespread occurrence, poses a severe danger in the field of tobacco production. However, there is very limited knowledge on bacterial wilt-induced microecological changes in the tobacco root system and on the interaction between Ralstonia solanacearum and fungal communities in the rhizosphere soil. Thus, in this study, changes in fungal communities in the rhizosphere soil of tobaccos with bacterial wilt were studied by 18S rRNA gene sequencing. The community composition of fungi in bacterial wilt-infected soil and healthy soil in two tobacco areas (Gengma and Boshang, Lincang City, Yunnan Province, China) was studied through the paired comparison method in July 2019. The results showed that there were significant differences in fungal community composition between the rhizosphere soil of diseased plants and healthy plants. The changes in the composition and diversity of fungal communities in the rhizosphere soil of tobaccos are vital characteristics of tobaccos with bacterial wilt, and the imbalance in the rhizosphere microecosystem of tobacco plants may further aggravate the disease.

• Journal of Plant Biology
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• v.26 no.2
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• pp.53-71
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• 1983

Physicochemical properties of soil, mineral cyclings, production of plants, and relationship between sodium(Na) content and progresses of plant communities were studied in a coastal salt marsh in Incheon. Contents of Na, available phosphorus(A-P) and value of electric conductivity of soil decreased in order of Salicornia herbacea, Limonium tetragonum, Phragmites communis and Zoysia sinica communities, but contents of organic matter, total nitrogen(T-N) and calcium(Ca) of soil were vice versa. Specise diversity index decreased with increase of Na content of soil with correlation coefficient of -0.82. The aboveground biomass of plant communities were 2,981 g.dw/$m^2$ in P. communis, 1,471 g.dw/$m^2$ in Z. sinica, 189g.dw/$m^2$ in S. herbacea and 71 g.dw/$m^2$ L. tetragonum, respectively. Seasonal changes of contents of inorganic nutrients per unit land area coincided with those of biomass of plant communities, however, the maximum contents of K occured earlier than the maximum biomass. Amounts of inorganic nutrients absorbed by plant were directly proportion to its biomass and it was true to reverse in restored amounts of them to soil. In turnover times of nutrients of the communities, it took the shortest time for P but the longest for Ca and P. communis community took the shortest but L. tetragonum the longest. For example, in P. communis turover time of P took one year and that of Na 1,440 years. Lack of P element, therefore, was expected in this study area.

• Journal of the Korean Society for Library and Information Science
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• v.23
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• pp.1-31
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• 1992

The present study aims at a systematic access to EC information. EC information is the outcome of the complex organizations, the continuous changes in functions and the subsequent changes in policies. An attempt for an effective approach to the information requires the examination of the organizational structures and changes, the processes involved in formulating and implmenting the information policies, and the infrastucture for information. Information activities of the major organizations of EC have been examined with a special reference to the Commission of European Communities. The Commission is the EC institution from which the majority of the EC's documentation originates. The information functions of the Commission have been studied in such categories as information production and distribution, authorizing services, and information services to the public.