• Journal of The Korean Society of Grassland and Forage Science
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• v.11 no.4
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• pp.244-251
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• 1991

This study was undertaken to assess the effectiveness of magnesium-and boron-enriched complex fertilizer(CF, N-P$_2$O$_{5}$-K$_2$O-MgO-B$_2$O$_3$: 14-10-12-3-0.2) on the maintenance and management of hilly pasture. The effectiveness of CF was compared to those of some straight fertilizers (SF). This first part of the study was concerned with the soil chemical properties and the mutural balances of mineral nutrients in the soils of a mixed grass-clover and a pure grass swards. The results of a two-year field experiment are summarized as follows: 1. The Mg contents in the soils of the CF plots were higher than those of the SF plots. On the other hand, the Ca contents were higher in the SF plots than in the CF plots. The contents of Mg and Ca, and CEC, except K, in both the CF and SF plots were considerably below the optimum levels. At the normal application rate of NPK, the contents of available P$_2$O$_{5}$ were close to the optimum level in both the CF and SF plots. 2. The contents of exchangeable Mg were lower than the K contents in soils of all the plots. At the normal application rate of NPK, the Mg contents in the CF plots, but not in the SF plots, were close to the critical level for general crops (0.29me Mg/100g soil). The Mg contents in soils of all the plots, however, were considerably below the critical level for pasture forages and grazing cows (0.41me/100g). 3. Considering the desirable base saturation level of soil, the saturation levels of Ca and Mg were insufficient in both the CF and SF plots. The saturation levels of Mg in the CF plots, however, were relatively good compared with the SF plots. The equivalent ratios or Mg/K, Ca/Mg. Ca:Mg:K, and %Mg of CEC in soils were generally unfavorable in all the plots. These ratios of the CF plots, however, were relatively better than those of the SF plots. 4. Considering the contents of exchangeable Ca and Mg in soils, it is suggested that the application of slaked magnesium lime as a soil amelioration might be desirable for the fundamental increment of those contents at pasture establishment.

• Journal of The Korean Society of Grassland and Forage Science
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• v.38 no.4
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• pp.266-272
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• 2018

In this study, we created grassland establishment(paddock No.39), grassland improvement(Paddock No.44), and tall fescue seeding(paddock No.64), and the rate botanical composition, DM yield, nutritive value were examined through 2016 to 2017. The rate of botanical composition was 81% in 2016, 75% in 2017, up to 21% higher than No.39 67%, 60%, No.44 58% and 54%. The annual average DM yield was the highest at 13,234kg/ha in the district, followed by No.39, No.44, followed by 10,636kg/ha and 10,235kg/ha, respectively. The crude protein content was the highest at No.39 12.16%, with No.44 and No.64 showing 10.7%, respectively. NDF content (average for two years) was 55.90% in No.44 and No.39, slightly lower than 58.42% and 57.00%, respectively. The two-year ADF average content was 31.07% for the same trend as the NDF capacity in the No.44, below 31.71% and 32.65%, respectively. To sum up the results, Although there was a high level of incentive sowing plot(No.39) in nutritive value, considering the botanical composition and productivity of the pasture, it is also deemed desirable to have a tall fescue plot(No.64).

• Journal of The Korean Society of Grassland and Forage Science
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• v.19 no.1
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• pp.1-10
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• 1999

To find out the way to be able to prolong the grazing years of mixed pasture under Cheju summer-hot weather, an experiment designed with split plot (main plot : 3 cutting-plant height such as 15cm, 30cm and 45cm and sub plot : 4 white clover varieties such as Regal, Tahora, Brown and SRVR) was carried out at Cheju Agricultural Experiment Station during the period from Sept. 1994 to Oct. 1996 Dry matter yield in 15cm plant height in cutting dates has shown significantly lower increase than those in 30 and 45cm(P<0.05). There was highiy significant increase in dry matter yield of Brown plot when compared with other varieties of white clover in 2nd year(P<0.01). There was no difference on botanical composition of mixed sward as affected by plant height in cuttings dates in 2nd year. The percentage of white clover tends to lower in white clover varieties Brown and SRVR when compared with Regal and Tahora. The rate of weed was not affected by plant height in cutting dates and white clover variety in mixed pasture at last cutting time of 2nd year. In 15cm plant height, concentration of ADE and NDF was the lowest one while P contents was the highest one(P<0.01). Potassium contents was the lowest one in 30cm plant cutting height(P<0.05), and nitrogen showed statistically interaction between plant cutting height and white clover variety(P<0.01). White clover variety was no effective on concentration of constituents in mixed pastures. In conclusion, white clover variety SRVR harvested at 15cm plant height is effective on nutrient value of pasture and balance of grass and white clover in botanical composition.

• Journal of the Korean Society for Marine Environment & Energy
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• v.9 no.2
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• pp.109-119
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• 2006

This study investigated the effect of artificially enhanced mesozooplankton on the phytoplankton dynamics during fall blooming period using a mesocosm in Jangmok bay located in the Southern Sea of Korea in 2001. The four bags with 2,500 liter seawater containment were directly filled with the ambient water. And then, abundances of mesozooplankton in two experimental bags were treated 6 times higher than those in control bags by towing with net($300{\mu}m$) through the ambient water. Phytoplankton community between control and experimental bags were not significantly different in terms of chlorophyll-a(chl-a) concentration and standing crop (one-way ANOVA, p>0.05) during the study period. Initial high standing crop and chl-a concentration of phytoplankton drastically decreased and remained low until the end of the experiment in all bags. Diatoms, accounting for most of the phytoplankton community, consisted of Skeletonema costatum, Pseudo-nitzschia seriata, Chaetoceros curvisetus, Ch. debilis, Cerataulina pelagica, Thalassiosira pacifica, Cylindrotheca closterium, and Leptocylindrus danicus. Noctiluca scintillans dominated the temporal variation of mesozooplankton abundances, which peaked on Day 10 in the control and experimental bags, while the next dominant copepods showed their peak on Day 7. Shortly after mesozooplankton addition, copepod abundance in the experimental bags was obviously higher than that in the control bags on Day 1, however, it became similar to that in the control bags during the remnant period. It was supported by the higher abundance and length of both ctenophores and hydromedusae in experimental bags relative to the control bags. However, the cascading trophic effect, commonly leading to re-increase of phytoplankton abundance, was not found in the experimental bags, indicating that copepods were not able to control the phytoplankton in the bags based on the low grazing rate of Acartia erythraea. Besides that, rapidly sunken diatoms in the absence of natural turbulence as well as N-limited condition likely contributed the no occurrence of re-increased phytoplankton in the experimental bags.

• Journal of Wetlands Research
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• v.7 no.2
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• pp.105-120
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• 2005

This study was carried out at Reed Marsh of Sihwa Lake from July 2003 to June 2004. We observed total(sum of maximum population) 5,752 individuals of 70 species including 12 species of ducks, 10 species of egrets, 6 species of wagtails and buntings, 4 species of eagles. The most dominant species was Spotbill Duck(Anas poecilorhyncha - 3,518 individuals, 61.16%), and other species were Mallard(Anas platyrhynchos - 540 individuals, 9.39%), Great Reed-Warbler(Acrocephalus arundinaceus - 217 individuals, 3.77%). Reed Marsh of Sihwa Lake were observed many kinds of protected species such as Great Bittern(Botaurus stellaris), Mandarin Duck(Aix galericulata), Chinese Sparrow Hawk (Accipiter soloensis), Eurasian Sparrow Hawk(Accipiter nisus), Japanese Buzzard(Buteo buteo), Hen Harrier(Circus cyaneus), Eurasian Hobby(Falco subbuteo), and Common Kestrel(Falco tinnunculus). Since the Reed Marsh of Sihwa Lake arrived many individuals of waterbird, crop damage by the waterbird occurred in the surrounding rice fields. It was an area adjacent to the reed marsh of sihwa lake such as Yoopori and Samhwari Bibongmyoun, Yamokri Maesongmyoun Hwaseong City. Bird of crop damage was ducks openly. The most species was Spot-billed Duck. Crop damage types by the Spot-billed Duck were grazing, used the grain up or lower in quality with step on the rice. Crop damage size was about 560bags of rice during the one month on August 2002. In 2003, After carrying out the various crop damage reduction countermeasures, which measured crop damage size in 2002's crop damage area. It happened about 152bags of rice during the two months from on August to September 2003. Migration routes of Spot-billed Duck were that it was migrated from up the sihwa lake to reed marsh. It took a rest at reed marsh and migrated the surrounding rice fields for the feeding action. In 2002, it was migrated direct from up the sihwa lake to in surrounding rice fields. But as environment of reed marsh was improved better than 2002, it was migrated to reed marsh because of reducing the energy attrition rate. Crop damage reduction countermeasures are get on ears to use explosion machine, searchlight, start-gun and patrol at regular intervals. Which was an effect short term. Indirect method is to make a feeding area of substitution at up the sihwa lake and reed marsh of sihwa lake.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.19 no.3
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• pp.265-273
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• 1986

The marine algal communities of Yonhwa-do at the southern coast of Korea were investigated in aspects to quantitative analysis of their structure and dynamics. As a result, 114 species, including 2 blue-green, 69 red, 25 brown and 18 green algae, were identified. The R/P value(2.8) is higher than that of other regions of the southern coast of Korea. Sheet and filamentous groups of the functional groups of algae showed higher composition rate in spring and summer than in autumn and winter, but coarsely branched and thick leathery groups showed an opposite tendency. Cluster analysis based on species presence suggested the existence of 5 distinct groups in spring, but 3 groups in the other seasons. The species exhibiting important value above 20 were as follows: Porphyra suborbiculata, Corallina pilulifera, Hizikia fusiforme, Sargassum thunbergii, Undaria pinnatifida, Ishige okamurai, Chondria crassicaulis, and crustose coralline algae. The coverage of algal communities composed only of crustose coralline algal complex was higher than that of other algal complex, but occurrence frequency of these two communities was indifferent. It is suggested that the occurrence in high quantity of crustose coralline algae from this area is related to grazing by herbivorous animals.

• Korean Journal of Ecology and Environment
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• v.41 no.2
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• pp.237-246
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• 2008

Filtration rates and fecal production of freshwater bivalve, Unio douglasiae on two kinds of hibernal diatom communities were measured simultaneously in a laboratory. One community is the Han River (HAN), which dominated by Asterionella Formosa. Stephanodiscus hantzschii (ca. 98% of total phytoplankton). The other community is the Ilgam Lake (IL), which dominated by Synedra ulna, Scenedesmus sp. Microcystis aeruginosa (ca. 82%). The HAN water has higher concentrations of nutrient (TN and TP) and chlorophyll $\alpha$ (Chl-$\alpha$), lower turbidity and conductivity than the IL water. Water sampling for the feeding experiment was conducted in the same day (Jan 15, 2008) and similar time (AM 10:00 for HAN, AM 11:00 for IL). Mussels with the similar size ($0.0{\pm}0.5\;cm$) were collected from the Gunsan and Okgu district (Jeonbuk), and starved in a laboratory for 2 days before the experiment. The experiment comprised CON (no addition of mussel), LOW (addition of mussel at 0.3 indiv. $L^{-1}$), MID (1.0 indiv. $L^{-1}$) and HIGH (2.0 indiv. $L^{-1}$), respectively. With the increment of mussel density and time, the concentration of Chl-$\alpha$ in two diatom communities were clearly decreased; Chl-$\alpha$ of HAN gradually decreased after 1 hour of mussel treatment, while that of IL decreased as soon as mussel introduction. In 7 hours of treatment, the former was removed finally up to about 90% of control, while the later was remained as about 50%. Under the presence of mussel, total phytoplankton density was shifted as the similar patterns to that of Chl-$\alpha$ (r=0.705, P<0.0001), however, there showed the drastic differences following a species. Based on the concentration of Chl-$\alpha$, filtration rate of U. douglasiae averaged 0.266 $L\;g^{-1}\;h^{-1}$ (0.115 to 0.442) on HAN and $0.577\;L\;g^{-1}\;h^{-1}$ (0.146 to 1.428) on IL water, respectively. There were no differences in feces production among the mussel density in the HAH water (ANOVA, P>0.5), while in IL water, including lots of seston, the HIGH mussel produced the higher fecal materials, over one hundred times of LOW. These results suggest that freshwater bivalve Unio douglasiae have the alternative potential, as a filter-feeder of seston in turbid lake, and a biological controller of diatom bloom in cold stream.