• Korean Journal of Ecology and Environment
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• v.34 no.1 s.93
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• pp.45-53
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• 2001

Transport of cyanobacterial toxins (microcystin-LR, -RR, -YR) were assessed from a eutrophic lake, Lake Suwa, through the outflowing river, the Tenryu River, and its irrigation channel branch. Temporal variation of phytoplankton species composition in the river coincided with those of the lake; Microcystis ichthyoblabe dominated from June to July, and M. viridis dominated from August to September. When cyanobacterial bloom occurred, microcystins were continuously detected at the concentration of $0.3{\sim}3.2\;{\mu}g/l$ even at 32 km downstream. The change of the content of three microcystin variants were related both with the total cell density of Microcystis and with the change of Microcystis species composition. When Microcystis ichthyoblabe dominated during July, only microcystin-RR (MC-RR) and -LR (MC-LR) were detected, while when Microcystis viridis dominated between August and October, microcystin-RR,-YR (MC -YR) and -LR were detected. Along 29 km flowing distance (flow time 11 hours) between site 2 and site 5 in the Tenryu River, cyanobacterial density and microcystin concentration were reduced by 73% and 72%, respectively, which is mostly contributed by the dilution effect of tributary waters (61% and 57%, respectively) . In the artificial irrigation channel microcystins and cyanobacterial cells were decreased less than in the natural river. The results indicate that cyanobacterial toxins can be transported far downstream without much removal and give hazards to water usage in downstream of eutrophic lakes with cyanobacterial blooms.

• Korean Journal of Ecology and Environment
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• v.36 no.4 s.105
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• pp.391-402
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• 2003

Last 20 years have witnessed many studies dealing with effects of elevated $CO_2$ on terrestrial ecosystems. However, fewer efforts have been made to elucidate effects on wetland ecosystems, although they play a key role in global biogeochemical cycles. This review synthesizes published data to reveal effects of elevated $CO_2$ on wetland plants. In particular, we focused on the changes in primary production, community structures, evapotranspiration, and nutrients in plants. Many studies have reported increases in primary production in individual plants, but we could not conclude that this will lead to increases in carbon sequestration in wetland ecosystems. The reasons include transport of photosynthates into belowground parts, speciesspecific responses, interaction among different species, and limitation of other nutrients. However, elevated $CO_2$ increased transpiration rates in many wetland plants, suggesting substantial influences on water budgets of wetlands. In addition, similar to terrestrial ecosystems, elevated $CO_2$ increased C/N ratio of many plants, which may impede organic matter decomposition in the long term. However, further information on dynamics of belowground carbon supplied from wetland plants is warranted to assess effects of elevated $CO_2$ on wetland carbon cycle accurately.

• Asia pacific journal of information systems
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• v.23 no.1
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• pp.45-63
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• 2013

The purpose of this research is on the identification of the effects of perceived interactivity formed by the electronic collaborative referral system on the organizational loyalty. Two channels through which the effects proceeded were investigated. One is the "system channel" which consists of "interactivity of the inter-organizational system ${\rightarrow}$ intention of using the system ${\rightarrow}$ organization loyalty" (hypothesis 1, 2), that is the channel which anticipates that a better understanding on the interactivity of the inter-organizational system makes the intention of the using the system strong, and this strong intention results the higher organization loyalty. The other is "organization channel" which consists of "interactivity of the inter-organizational system ${\rightarrow}$ perceived interactivity on the counterpart ${\rightarrow}$ perceived relation benefits with the counterpart ${\rightarrow}$ organization loyalty" (hypothesis 3, 4, 5). The channel means that as the perceived interactivity of users on the inter-organizational system becomes greater, the perceived interactivity with the counterpart is increasing. And this makes the users feel that more benefits can be obtained by the relationship with system providing organization, and finally makes the organization loyalty that is the intention to maintain the relationship greater. The corroborative evidence data confirm the two channels are obtained by questing on the electronic referral system of Samsung Medical Center to the doctors of the first and second collaborated hospitals or clinics, and by analyzing statistically. The verification result for the "system channel" showed that as the perception on the interactivity of inter-organizational system was increasing, the intention for consistent using increased(support hypothesis 1), and then the organization loyalty that is the relationship maintaining indication by using the referral system also increased(support hypothesis 2). And the confirmation result for the "organization channel" indicated that the perceptive interactivity on the counterpart increased as the understanding on the interactivity of inter-organizational system increased(support hypothesis 3), consecutively, with the intuitive relation benefits increase with the counterpart(support hypothesis 4) the organization loyalty means the intention to maintain the relationship was confirmed to increase(support hypothesis 5). These results demonstrate that when the perceived interactivity in using many systems at the collaboration between organizations is increasing, the positive image on the systems creates the consistent system using intention, and the positive image increases the wants for preserving the relationship with counter organization. In addition, the perceived interactivity of inter-organizational system users affects directly on the perceived interactivity of the counter organization, so the important role of inter-organizational system in promoting the interactivity between cooperative counterparts was recognized. And the perceived interactivity on the counter organization become greater, the influence on the perceived benefits from cooperation is positive. Therefore, the perceived interactivity by using inter-organizational system was confirmed as a prerequisite for the continuous relationship.

• Korean journal of applied entomology
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• v.15 no.3 s.28
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• pp.111-126
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• 1976

Regional differences in economic importance of the four species of rice leafhoppers, viz., Laodelphax striatellus, Nephotettix cincticeps, Nilaparvata Iugens and Sogatella furcifera, were analyzed and discussed based on population surveys conducted in Suweon and in southern and south-western coastal areas. The economic importance of L. striatellus and N. cincticeps, which are found throughout the year in Korea, seems to be less in middle regions. This is believed due to effective natural control through severe winter climate, cultural practices in rice and barley growing, and natural enemies such as spiders. However, the economic importance of these two species is significantly greater in southern regions with a less severe winter climate, and where cultural practices in rice and barley favour synchronization between the life cycles of insects and the seasonal succession of host plants. with regard to N. lugens and S. furcifera, which cannot overwinter in Korea, initial populations are the result of long distance migration across the East China Sea. Weather elements related to their migration result in more abundant immigrants of these two species in southern than in middle regions. Thus, different policies are needed for the integrated control of rice leafhoppers in middle and southern Korea.

• Journal of Korean Society of Forest Science
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• v.90 no.2
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• pp.217-226
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• 2001

This study estimated the impacts of the building permit area change on the forest products import quantities in Korea. The first objective of this dissertation is to analyze whether there is any causal relationship between change in the building permit area and changes in the import quantities of forest products in Korea. Assuming that there is any causal relationship, the second objective is to evaluate the dynamics of the impacts of the building permit area change on the forest products import quantities in Korea. The relationship between the building permit area and the import quantity was represented by bivariate vector autoregressive or vector error correction model. Whether there is any causal relationship between change in the building permit area and changes in the import quantities of forest products was analyzed by the causality test of Granger. And the dynamics of the impacts of the building permit area change on the forest products import quantities were evaluated by variance decomposition analysis and impulse response analysis. The import quantity of forest products can be explained by the lagged building permit area variables and the lagged import quantity variables in Korea. Change in the building permit area causes change in the high-density fiberboard import quantity in Korea. In the bivariate model of the high-density fiberboard import quantity, after six months, the building permit area change accounts for about ten percent of variation in the import quantity, and its own change accounts for about ninety percent of variation in the import quantity. On the other hand, the impact of a shock to the building permit area is significant for about six months on the import quantity of high-density fiberboard in Korea. That is, if the building permit area change indeed had an impact on the import quantity of high-density fiberboard in Korea, it was only of a short-term nature.

• Journal of Korean Society of Forest Science
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• v.81 no.4
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• pp.325-336
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• 1992

The successional status and potential natural vegetation were examined in a mixed broadleaved-Abies forest located at Mt, Odae National Park. The examination was based on the subsequent process of generation replacement by understory saplings for the dominant canopy trees within 88 $5m{\times}50m$ belt transects. The transition matrix model, which was modified from mathematical theory of Markov chain, was employed to analyze the successional status of the study forest. The model suggests that the study forest is still seral, and it is considered to be more than 700 years away from the steady state or climax in terms of species composition. The simulations predict a remarkable decrease in the proportion of species composition of the present dominant Quercus mongolica and Tilia amurensi.s from current 28% and 13% to less than 3% and 5%, respectively, at the steady state. On the contrary, the proportions of Abies holophylla, Acer pseudo-sieboldianum, Carpinus cordata, and Pinus koraiensis will increase at the steady state. The ratio of mixture between deciduous and coniferous trees will be gradually changed from current 6.5 : 3.5 to 5.0 : 5.0 at equilibrium. Discussion for the problems of Quercus mongolica in successional status noted that the species behaved as a mid-successional dominant, not a climax species in the study forest. The hypothesis and sensitivity of the transition matrix model were also discussed to evaluate the applicability to the real situation. The overall results indicated that the present dynamics of the forest must reflect the seral state due to previous disturbance mainly by hyman related interference.

• Korean Journal of Environmental Biology
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• v.27 no.4
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• pp.425-432
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• 2009

Mesozooplankton dynamics were studied in Watan stream which flows into the Yellow Sea in Yeonggwang, Korea. Samples were collected at eight stations bimonthly during April 2006~February 2007. Mesozooplankton community was consisted of 45 taxa (8 cladocerans and 29 cope-pods). The abundance varied between the highest one ($31{\sim}127,587\;indiv.m^{-3}$) in October, and the lowest ($12{\sim}233\;indiv.m^-3$) in December. Diversity index showed to be the highest value in July (0.671) and the lowest one in August (0.368). A euryhaline species, Acartia hongi was dominant in brackish water stations (the highest abundance at $13.4^{\circ}C$ and 14.1 psu). In freshwater stations of the upstream, two cladoceran species of Polyphemus pediculus and Moina weismani occurred in high abundance in August. Dominant taxa of copepod were clustered to two or three groups mainly due to the difference of salinity gradients. Spatial distribution of mesozooplankton revealed to be determined by salinity gradients which were affected by opening and closing of the artificial dam in Watan stream.

• Information Systems Review
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• v.7 no.2
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• pp.101-115
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• 2005

IT companies make a lot of effort to share and utilize the experiences of their members and transform them into organizational knowledge as a competitive core. However they face a dilemma in that they have to spend time and financial resources to perform activities around knowledge management for the long-term gains, while carrying at field-work for making short-term profits. As an initial attempt to tackle this managerial problem, this paper tries to investigate the mechanism of knowledge management in a small IT company in Korea with a synthetic view-point using system dynamics simulation model. It depicts the dynamic behaviors of knowledge management and presents some findings of political leverage. Although this model has to be further replenished, the scheme for the dynamism of knowledge management and the findings presented in the paper could be useful for the decision makers, especially of knowledge-intensive organizations.

• Korean Journal of Environmental Agriculture
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• v.24 no.4
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• pp.358-363
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• 2005

A large amount of oyster-shell waste has been illegally disposed at oyster farm sites along the southern coast of Korea, which already created serious environmental problems. Therefore, the study was undertaken to increase the consumption of oyster shell meal as a soil amendment. The effects of oyster shell meal on dynamics of heavy metals and uptake of heavy metals by spring Chinese cabbage were evaluated in silt loam soil (in Gyeongsang National University, Jinju, Gyeongnam-do, Korea), where 0, 4, 8, 12 and 16 Mg $ha^{-1}$ oyster-shell meal fertilizer were added. Lime treatment (2 Mg $ha^{-1}$) was selected as a control. In the results of this study, cabbage yields were increased by increasing levels of oyster-shell meal fertilizer. With increasing levels of oyster-shell meal fertilizer, total heavy metals concentrations were not significant among treatments. However, 0.1N HCl extractable heavy metals concentration was significantly reduced due to increasing of soil pH. A lot of portion (ca. $80{\sim}90%$) heavy metals fraction of all fractions was residual phase in soil after harvesting. The contents of Cu, Mo, Zn in cabbage were slightly increased by increasing levels of oyster shell meal fertilizer. However, there were no toxic symptoms of heavy metals during cultivation. Conclusively, it was estimated that oyster shell fertilizer could be a good amendment to increase productivity of crop and reduce uptake of heavy metals by crop and mobility of heavy metals in soil.

• Korean Journal of Ecology and Environment
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• v.39 no.3 s.117
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• pp.402-412
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• 2006

The Shihwa constructed wetland was established to treat the severely polluted water from Banwoul, Donghwa and Samhwa streams. This study was focused on investigating the dynamics of epiphytic algal communities on reed (Phragmites communis) planting area at 5 stations from October 2001 to June 2002. The concentration of total nitrogen and phosphorus of inlet stations from the streams were decreased after flowing through the wetland. However, the TN : TP ratios at all stations were slightly over 16 indicating that the total phosphorus may play some role as a limitation factor. Epiphytic algae on the reed were total 329 taxa which were composed of 295 species, 13 varieties, 3 forma and 18 unidentified species. The species numbers were recorded in the order of Chlorophyceae-Bacillariophyceae-Cyanophyceae-Euglenophyceae-Chrysophyceae. The relative percentage showed a seasonal variation from Cyanophyceae to Bacillariophyceae and to Chlorophyceae. The biomass of epiphytic algae measured by chlorophyll-a concentration ranged from 0.6 to $36.4\;{\mu}g\;cm^{-2}$. Dominant species were 16 taxa which were Lyngbya angusta of Cyanophyceae in the early investigation, and were changed to Stigeoclonium lubricum of Chlorophyceae, and Nitzschia palea of Bacillariophyceae etc. in the late. Species number, standing crops and chlorophyll-a concentrations of epiphytic algae showed higher values at the inlet stations than the stations after flowing through the wetland.