• ALGAE
• /
• v.20 no.1
• /
• pp.43-52
• /
• 2005

A study on the seasonal changes in the phytoplankton community was carried out in four aquaculture ponds of Bangladesh over a period of 16 months from August 2000 to November 2001. Out of 45 phytoplankton species identified, 30 belong to Cyanophyceae, 7 to Chlorophyceae, 5 to Bacillariophyceae and 3 to Euglenophyceae. The highest phytoplankton abundance was observed in spring followed by early autumn, summer, and the lowest was in winter. The annual succession of Cyanophyceae was characterized by spring and early autumn period dominated by Microcystis sp. Anabaena sp. and Planktolymbya sp. with Microcystis sp. as the main blue-green algae represented. Chlorophyceae was characterized by rainy season domination of Chlorella vulgaris, Pediastrum sp. and Scenedesmus denticulatus with maximum abundance of Chlorella vulgaris. Whereas Bacillariophyceae was dominant during the winter period. Navicula angusta and Cyclotella meneghiniana were the most frequently occurring species of Bacillariophyceae throughout the study period. Euglenophyceae was dominant in late autumn and Euglena sp. was the dominant species. The effect of various physicochemical water quality parameters on the seasonal distribution and succession of the above mentioned phytoplankton population as well as the interaction and eutrophication are discussed.

• Korean Journal of Ichthyology
• /
• v.30 no.1
• /
• pp.9-17
• /
• 2018

This study investigated how the larvae of three winter-spawning fishes are adapted in a cold water environment by examining the morphology, digestive system, and swimming ability of larvae from three winter-spawning species (Gadus macrocephalus, Liparis tanakae, Hexagrammos agrammus). Data were collected at hatching and first feeding. The results were compared with repored data on several non-winter-spawning species. Mean total lengths at hatching (${\pm}SD$) were $4.35{\pm}0.11mm$, $5.26{\pm}0.08mm$, and $7.48{\pm}0.35mm$ for G. macrocephalus, L. tanakae, and H. agrammus, respectively. Three winter-spawning fishes had well-developed digestive tracts after hatching than those of non-winter-spawning fish larvae. Yolks were intact until 5 days post-hatching in all three species, indicating that they had longer mixed-feeding periods compared with fishes spawned during other seasons. G. macrocephalus, L. tanakae, and H. agrammus larvae had superior cruise and burst speeds (measures of swimming ability) than non-winter-spawning larvae. We conclude that the unique characteristics of these three winter-spawning species are naturally selected adaptations under lower water temperature in winter.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.32 no.1
• /
• pp.78-85
• /
• 1987

In order for Paldanghomil (winter rye) to be investigated if its grain yield is able to be produced after clipping just before winter season for forage utilization this experiment was carried out under the four sowing dates of four locations in Korea (Chunchon, Suwon, Hwasung and Chungju). In rye clipping plot earlier sowing showed taller plant height, more number of tillers/㎡ and higher forage yield before winter season, indicating the highest forage yield (1803 kg/10a) in Chunchon by sowing of September II. Forage yield of rye before winter season was mainly influenced by plant height and number of tillers/㎡, showing more effect of plant height. Rye plants were more or less affected on winter damages, late heading and short culm by clipping before winter season. Analysis of variance indicated that only number of spikes/㎡ among grain yield components showed the high significance according to the clipping method, and that there showed little variation for other yield components due to the sowing date and clipping method. There showed more grain yield in non-clipping rather than that of clipping plot, indicating the difference of 46kg/10a. This was resulted from short culm and severe winter damages caused by clipping before winter season. Of the grain yield components, number of spikes/㎡ was greatly influenced for grain yield by analysis of stepwise regression. Therefore, grain yield of rye was able to produce after forage utilization before winter season due to the appropriate crop and soil managements, by resulting from the little variation in grain yield between clipping or non-clipping plots and from the higher grain yield by the early sowing.

• Korean Journal of Soil Science and Fertilizer
• /
• v.45 no.2
• /
• pp.185-191
• /
• 2012

This study was performed to screen fallow crops during winter period for improvement of soil quality and utilizing as mulching material in watermelon cropping system during winter period. Five fallow crops, mainly, hairy vetch, barley, rye, oat and wheat, were sown in early November. They were mowed for covering the soil surface instead of polyethylene (PE) film before watermelon planting in early April the following year. The highest absorbed nutrients and dry matter yield were found in rye. Bulk density in plots with fallow crop was lower than control plot. There was observed no significant differences among the fallow crops. However, porosity was the lowest in control plot. Soil EC reduced to 12%, 13%, 14%, 16% and 22%, respectively, by cultivation of hairy vetch, oat, wheat, barley and rye. Microbial biomass carbon and dehydrogenase activities were higher in soil treated with gramineous crops, such as barley, rye and oat. The growth of watermelon was more affected by regeneration of fallow crop than the occurrence of weed, especially in plots treated with rye or oat. Also, the fruit damage by aphid was found severe in these treatment plots. The fruit yield in plots treated with hairy vetch and barley was increased 5.7% and 2.6%, respectively, compared to that of PE films. The present experiment findings implied that these fallow crops had significant beneficial effects on improvement of soil qualities and could be utilized for mulching materials in watermelon cropping system.

• Journal of Environmental Science International
• /
• v.14 no.11
• /
• pp.1063-1069
• /
• 2005

In order to investigate the distribution of suspended particulate matter of the surface water in the South Sea of Korea in early winter, the cruise results during 2 to 8 December 2004 were analyzed in relation to the hydrography. The front was formed along the line connecting between Tsushima and Cheju Islands, which divided the water into two water masses; the coastal water with for temperature and for salinity, and the Tsushima Warm Current Water with high temperature and high salinity. In the coastal water the suspended particulte matter was 5.0-6.5 mg/l, while in the oceanic water suspended particulate matter was 4.5-5.0 mg/l. The coastal water showed higher mixing effects, compared to the oceanic area where vertical stratification was clearly formed. These indicate that the distribution of suspended particulate matter was affected by the stratification or mixing of the water column. Also it is suggested that the mixing effects of sea surface cooling and rind play an important role on the distribution of suspended particulate matter in the South Sea of Korea in winter time.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.8 no.1
• /
• pp.14-19
• /
• 1988

This experiment was conducted to investigate the effects of the different cutting height on the changes of nonstructural carbohydrate contents, winter survival, spring yields of Italian ryegrass, tall fescue and pernennial ryegrass swards. It was carried out on the experimental field of Livestock Experiment Station, in Suweon, from Sept. 1986 to May 1987. The results obtained are summarized as follows: 1. The changes in soil surface temperature of plots were slightly appeared among grasses. But not appeared with cutting heights. 2. Nonstructural carbohydrate contents of three grasses until wintering showed much more in line with unclipped, 15 cm cutting and 6 cm cutting height. Among three grasses, Italian ryegrass was highest and tall fescue was lowest. Otherwise, wintering survival was not show the difference among grasses and cutting heights. 3. The green yields was much more producted in line with Iralian ryegrass, perennial ryegrass and tall fescue. But in dry matter yields, it was not significantly different among grasses and cutting heights.

• Journal of Preventive Medicine and Public Health
• /
• v.49 no.2
• /
• pp.134-138
• /
• 2016

Objectives: Season of birth, an exogenous indicator of early life environment, has been related to higher risk of adverse psychiatric outcomes but the findings for Alzheimer's disease (AD) have been inconsistent. We investigated whether the month or season of birth are associated with AD. Methods: A nationwide nested case-control study including all community-dwellers with clinically verified AD diagnosed in 2005 to 2012 (n=70 719) and up to four age- sex- and region of residence-matched controls (n=282 862) residing in Finland. Associations between month and season of birth and AD were studied with conditional logistic regression. Results: Month of birth was not associated with AD (p=0.09). No strong associations were observed with season (p=0.13), although in comparison to winter births (December-February) summer births (June-August) were associated with higher odds of AD (odds ratio, 1.03; 95% confidence interval, 1.00 to 1.05). However, the absolute difference in prevalence in winter births was only 0.5% (prevalence of those born in winter were 31.7% and 32.2% for cases and controls, respectively). Conclusions: Although our findings do not support the hypothesis that season of birth is related to AD/dementia risk, they do not invalidate the developmental origins of health and disease hypothesis in late-life cognition. It is possible that season does not adequately capture the early life circumstances, or that other (postnatal) risk factors such as lifestyle or socioeconomic factors overrule the impact of prenatal and perinatal factors.

• Journal of Veterinary Clinics
• /
• v.26 no.3
• /
• pp.306-310
• /
• 2009

Mass mortality was occurred in adult koi carp(Cyprinus carpio) at a private pond near Samchunpo city in the early November, 2007. Its water temperature was $11^{\circ}C$ and turbidity was very high. The fishes diseased were shown widely distributed hemorrhages, deep ulcerations on the whole body surface and severe erosions in the all fins. In necropsy, excess ascitic fluid was observed and spleen and kidney affected were enlarged. In microscopic observation, it was examined widely distributed severe dermal ulceration, multifocal gill lamella hyperplasia, severe fibrinous pericarditis, multifocal nephritis and hepatitis. The bacteria suspected were isolated using tryptone soya agar and identified as motile Aeromonas hydrophila as results of biochemical tests using API 20E and 20NE. According to previous reports, A. hydrophila infection were mainly occurred in fingerling at high temperature. However, this case exhibited that A. hydrophila infection can develop on adult koi carp even in the winter season.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.42 no.3
• /
• pp.169-175
• /
• 2022

This study aimed to examine the changes in dry matter yield and growth characteristics of alfalfa (Medicago sativa L.) in response to variations in sowing dates during the autumn season of 2021-22 in a dry paddy field of Chilbo-myeon, Jeongeup-si, Jeollabuk-do. Treatments comprised four sowing dates at 10-day intervals, i.e., October 8, October 18, October 28, and November 8, 2021. The winter survival rate of alfalfa showed a significant difference between different treatments but was at a satisfactory level for all (p<0.05). The winter survival rate for the fourth sowing date, a month later than the first sowing date, was approximately 11.7% lower than that for the first sowing date. The plant height ranged between 82.3-93.1 cm and 60.5-63.7 cm at the first and second harvest, respectively, smaller at the second harvest than at the first harvest. The total dry matter yield of alfalfa was the highest at 13,316 kg/ha for the first sowing date, and the later the sowing date, the lower the dry matter yield. The protein content of alfalfa ranged between 13.6-17.3% in the first harvest, lower than the standard alfalfa protein content of 20% or more. In relative feed value, the first sowing (Oct. 8) was the most significantly higher in the first harvest (p<0.05). These results suggest that the early and mid-October sowing dates are optimum for sowing alfalfa during autumn and result in improved plant growth, dry matter yield, protein content, and winter survival compared to those at later sowing dates. Therefore, dry paddy fields can be safely employed for alfalfa cultivation with sowing dates in early and mid-October during autumn.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.24 no.4
• /
• pp.309-316
• /
• 2004

This experiment was carried out to assess the growth and development of five rye(Secale cereale L.) cultivars based on the Feekes scale in relation to sowing date at the Experimental Livestock Farm, Seoul National University(SNU), Suwon from 30 September 2001 to 4 May 2002. The experiment was conducted in split plot design with three replications. The main plots consisted of two sowing date such as early(30 September) and late(15 October). The subplots consisted of rye cultivars of five different maturity groups such as 'Kodiak', 'Koolgrazer', 'Danko', 'Homil22' and 'Olhomil'. The plant height of early sowing rye cultivars was higher than that of late one. Among the rye cultivars tested, plant heights of early maturing cultivars were higher than those of the other cultivars. The tiller number at early sowing(48.0) was higher than that of late(24.3), however, late maturing cultivars were higher than those of the other cultivars among the rye cultivars tested. Growth and development in the early sowing were generally three days earlier than those of late sowing cultivars. Growth and development in 'Olhomil' rye cultivars was earlier than 'Danko' rye cultivars when sown in early, but 'Olhomil' and 'Koolgrazer' rye cultivars showed an early maturity than 'Danko' rye when sown in late. Therefore, the developmental stages of winter rye cultivars could be categorised the following maturity; 'Olhomil' and 'Koolgrazer' are early in maturity, 'Homil22' is medium, and 'Kodiak' and 'Danko' are late in maturity.