• The Korean Journal of Zoology
• /
• v.9 no.1
• /
• pp.1-6
• /
• 1966

Frequently , large masses of the young short necked clam, Tapes japonica , die at their tidal flats in summer and this phenomenon has not been explained clearly. The purpose of the present investigation is to study the thermal condition and the chlorinity level of tidal flats in which the young clam appears to be injured. A study is also mad efor the burrowing organism in the lower layer of the esturay over which the fresh water flow during the low tide. Observation are made at five places of the tidal flat near Ikawazu Fixheries Laboratory of Tokyo University during the ebb and flow tide period of the spring tide. The diurnal and monthly changes of tidal temperatures and chlorinities are measured. Results of the study are ; 1. The surface temperature of the tidal flat increases with the ebb tide, reaches the highest between 12-14PM, and gradually decreases thereafter. The temperatures of tidal flat below 5 and 10 cm increase gradually until the flow tide reaches the surface. 2. At the spring tide in summer , the diurnal change of surface of the tidal flat temperature is very extensive ; it reaches 37-39$^{\circ}C$ in August. At the depths of 5 and 10 cm the temperature remains at 33 $^{\circ}C$ and 31$^{\circ}C$ , respectively. 3. The chlorinity of the tidal flat is higher during May through June and lower July through August, and this seems to be related to the amount of rainfall. 4. The chlorinity of the surface of tidal flat increases slightly during the ebb and flow tide periods. The observed higher chlorinity of surface of the tidal flat was 18.82% Cl. 5. At near the esturay, the fresh water that overflows the tidal flat affects the chlorinity of the surface but no such influence to the depth of the flat. 6. From above observations, it is assumed that the young short necked clam in the tidal flat could be exposed to the severe change of environmental conditions. The high temperature of the tidal flat in summer and the low chlorinity of it at flood period may be considered as the change in environment.

• Radiation Oncology Journal
• /
• v.3 no.2
• /
• pp.169-174
• /
• 1985

The mouse is one of the most popular experimental animal which has wide variation of strains, diet, environment, breeding technique, and diurnal cycle. Total 731 mice (male 372, female 359) were used for the standard data of our laboratory. Proper age for experiment were $30\pm3$days, body weight were $25\pm2gm (male)$, $23\pm1gm$. (female), minimal diurnal variation showed from 9A.M. to 12P.M.

• Journal of Korean Society on Water Environment
• /
• v.25 no.5
• /
• pp.713-719
• /
• 2009

A natural wetland in the Nakdong River basin which effectively removes non-point source pollutants was investigated for 2 years to understand wetland topography, vegetation types, and water quality characteristics. The water depth of the natural wetland was in the range of 0.5~1.9 m which is suitable for the growth of non-emergent hydrophytes. The wetland has a high length to width ratio (3.3:1) and a relatively large wetland to watershed area ratio (0.057). A broad-crested weir at the outlet increases the retention time of the wetland whose hydrology is mainly dependent on storm events. The concentrations of dissolved oxygen in the growing season and the winter season showed anoxic and oxic conditions, respectively. Diurnal variations of DO and pH in the growing season were also observed due to weather change and submerged plants. COD and TP concentrations were low in the winter season due to low inflow rate and increased retention time. Increased TP concentrations in the spring season were caused by degradation of dead wetland plants. Nitrogen in the wetland was mostly in organic nitrogen form (>75%). During the growing season, ammonium concentration was high but nitrate nitrogen concentration was low, possibly due to anoxic and low pH conditions which are adverse conditions for ammonificaiton and nitrification. The results of this study can be used as preliminary data for design, operation, monitoring and management of a constructed wetland which is designed to treat diffuse pollutants in the Nakdong river watershed.

• Journal of Ecology and Environment
• /
• v.44 no.2
• /
• pp.106-114
• /
• 2020

Background: Determining patterns of habitat use is key to understanding of animal ecology. Approximately 1% of bird species use brood parasitism for their breeding strategy, in which they exploit other species' (hosts) parental care by laying eggs in their nests. Brood parasitism may complicate the habitat requirement of brood parasites because they need habitats that support both their host and their own conditions for breeding. Brood parasitism, through changes in reproductive roles of sex or individual, may further diversify habitat use patterns among individuals. However, patterns of habitat use in avian brood parasites have rarely been characterized. In this study, we categorized the habitat preference of a population of brood parasitic lesser cuckoos (Cuculus poliocephalus) breeding on Jeju Island, Korea. By using compositional analyses together with radio-tracking and land cover data, we determined patterns of habitat use and their sexual and diurnal differences. Results: We found that the lesser cuckoo had a relatively large home range and its overall habitat composition (the second-order selection) was similar to those of the study area; open areas such as the field and grassland habitats accounted for 80% of the home range. Nonetheless, their habitat, comprised of 2.54 different habitats per hectare, could be characterized as a mosaic. We also found sexual differences in habitat composition and selection in the core-use area of home ranges (third-order selection). In particular, the forest habitat was preferentially utilized by females, while underutilized by males. However, there was no diurnal change in the pattern of habitat use. Both sexes preferred field habitats at the second-order selection. At the third-order selection, males preferred field habitats followed by grasslands and females preferred grasslands followed by forest habitats. Conclusions: We suggest that the field and grassland habitats represent the two most important areas for the lesser cuckoo on Jeju Island. Nevertheless, this study shows that habitat preference may differ between sexes, likely due to differences in sex roles, sex-based energy demands, and potential sexual conflict.

• Journal of Ecology and Environment
• /
• v.34 no.4
• /
• pp.411-423
• /
• 2011

This study was conducted to quantify soil $CO_2$ efflux using the continuous measurement method and to examine the applicability of an automatic continuous measurement system in a Korean deciduous broad-leaved forest. Soil respiration rate (Rs) was assessed through continuous measurements during the 2004-2005 full growing seasons using an automatic opening/closing chamber system in sections of a Gwangneung temperate deciduous forest, Korea. The study site was an old-growth natural mixed deciduous forest approximately 80 years old. For each full growth season, the annual Rs, which had a gap that was filled with data using an exponential function derived from soil temperature (Ts) at 5-cm depth, and Rs values collected in each season were 2,738.1 g $CO_2$ $m^{-2}y^{-1}$ in 2004 and 3,355.1 g $CO_2$ $m^{-2}y^{-1}$ in 2005. However, the diurnal variation in Rs showed stronger correlations with Ts (r = 0.91, P < 0.001 in 2004, r = 0.87, P < 0.001 in 2005) and air temperature (Ta) (r = 0.84, P < 0.001 in 2004, r = 0.79, P < 0.001 in 2005) than with deep Ts during the spring season. However, the temperature functions derived from the Ts at various depths of 0, -2, -5, -10, and -20 cm revealed that the correlation coefficient decreased with increasing soil depth in the spring season, whereas it increased in the summer. Rs showed a weak correlation with precipitation (r = 0.25, P < 0.01) and soil water content (r = 0.28, P < 0.05). Additionally, the diurnal change in Rs revealed a higher correlation with Ta than that of Ts. The $Q_{10}$ values from spring to winter were calculated from each season's dataset and were 3.2, 1.5, 7.4, and 2.7 in 2004 and 6.0, 3.1, 3.0, and 2.6 in 2005; thus, showing high fluctuation within each season. The applicability of an automatic continuous system was demonstrated for collecting a high resolution soil $CO_2$ efflux dataset under various environmental conditions.

• Journal of Korean Society for Atmospheric Environment
• /
• v.33 no.2
• /
• pp.174-183
• /
• 2017

The background level and timely variation characteristics of atmospheric $^{222}Rn$ concentrations have been evaluated by the real time monitoring at Gosan site of Jeju Island, Korea, during 2008~2015. The average concentration of atmospheric radon was $2,480mBq\;m^{-3}$ for the study period. The cyclic seasonality of radon was characterized such as winter maximum and summer minimum, consistent with the reduction in terrestrial fetch going to summer. On monthly variations of radon, the mean concentration in October was the highest as $3,041mBq\;m^{-3}$, almost twice as that in July ($1,481mBq\;m^{-3}$). The diurnal radon concentrations increased throughout the nighttime approaching to the maximum ($2,819mBq\;m^{-3}$) at around 7 a.m., and then gradually decreased throughout the daytime by the minimum ($2,069mBq\;m^{-3}$) at around 3 p.m. The diurnal radon cycle in winter showed comparatively small amplitude due to little variability in atmospheric mixing depth, conversely, large amplitude was observed in summer due to relatively a big change in atmospheric mixing depth. The cluster back-trajectories of air masses showed that the high radon events occurred by the predominant continental fetch over through Asia continent, and the radon concentrations from China continent were about 1.9 times higher on the whole than those from the North Pacific Ocean. The concentrations of $PM_{10}$ also increased in proportion to the high radon concentrations, showing a good linear correlation between $PM_{10}$ and radon concentrations.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.6 no.1
• /
• pp.60-64
• /
• 1986

To determine the effects of soil moisture on diurnal changes of photosynthesis, transpiration and stomatal resistance, sorghum and soghum-sudangrass hybrid were grown at large concrete pots maintained at 100, 80, 60 and 40% of field moisture capacity. Photosynthesis were measured from a.m. 6 to p.m. 6 on a fine day. 1. Photosynthesis and transpiration reacted similarly to water stress and environmental factors, and they reached at their maximum points from noon to 2 p.m. and decreased sharply after 4 p.m. 2. Photosynthesis and transpiration of sorghum were higher at 60% field moisture capacity than those of the other field moisture capacities. In sorghum-sudangrass hybrid, photosynthesis was in the order of 60>80>40>100% and transpiration was in the order of 60>80>100>40%. 3. Stomatal resistance did not show clear diurnal change and was the lowest at 60% among four field moisture capacities.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.42 no.5
• /
• pp.556-563
• /
• 1997

The endogenous gibberellin(GA) levels of sorghum grown under different photoperiodic conditions were measured by GC-MS-SIM. The effect of photoperiods on the diurnal GA levels of the 13-hydroxylation pathway was investigated by sampling every 6 h for 1 day. Levels of $GA_12$, $GA_53$, $GA_19$, $GA_20$, $GA_1$ and $GA_8$ were not constant throughout sampling times but rather rhythmic in productions. Wild-type seedlings grown under short photoperiod contained more $GA_20$ and $GA_1$ than those of long photoperiod. Although plant height of phyB-l(phytochrome B mutant) was taller than wild-type under all photoperiods tested, $GA_1$ concentration of wild-type grown under 10 h photoperiod was higher than that of phyB-l grown under the same photoperiod. These results are compatible with the idea that phytochrome B changed seedling responsiveness to GAs.

• Korean Journal of Soil Science and Fertilizer
• /
• v.48 no.6
• /
• pp.593-601
• /
• 2015

The NDVI (Normalized difference vegetation index) is used as indicators of crop growth situation in remote sensing. To measure or validate the NDVI, reliable NDVI sensors have been needed. We tested new fixed-field NDVI sensor, "SRS (Spectral Reflectance Sensor)" developed by Decagon Devices, during Kimchi cabbage growing season at the cultivation area located in Gochang, Gangneung and Taebaek in Korea from 2014 to 2015. The diurnal variation of NDVI measured by SRS (SRS NDVI) showed a slight ${\cap}$-profile shape and was affected by water on the sensor surface. This means that SRS NDVI around noontime is resonable, except rainy day. Comparisons were made between the SRS NDVI and NDVI of used widely mobile sensor (Cropcircle NDVI). The comparisons indicate that SRS NDVI are close to Cropcircle NDVI (R=0.99). SRS NDVI time series displayed change of the plant height and leaf width of Kimchi cabbage. An obvious exponential relationship is found between SRS NDVI and the plant height ($R^2{\geq}0.92$) and leaf width ($R^2{\geq}0.92$) of Kimchi cabbage. Thus, SRS NDVI will be used as indicator of crop growth situation and a very powerful tool for evaluation of remote sensing NDVI estimates and associated corrections.

• Journal of the Korean Solar Energy Society
• /
• v.29 no.6
• /
• pp.94-101
• /
• 2009

This study which is the fundamental work to investigate the property of urban climate compared the property of thermal environment in the downtown location and the outskirt site based on the field observation in the summer. We analysed thermal environment in the downtown location mainly by distributional characteristics during day and night with changes and correlation analysis of the air temperature, the globe temperature and the surface temperature through the simultaneous observation of the property of thermal environment at two places in real time. The summary of finding in this study is as follows. (1)It is observed on the day chosen by sample that diurnal air temperature range in the downtown location is $22.3{\sim}34.9^{\circ}C$, and diurnal air temperature range in the Outskirt site is $20.0{\sim}34.3^{\circ}C$, so, we found that the diurnal air temperature range in the outskirt site is $1.7^{\circ}C$ higher than in the downtown location. (2)In comparison of the globe temperature after sunset, we found the change of more sudden temperature drops in the outskirt site than in the downtown location. (3)It is observed on the days chosen by sample that the average of globe temperature range is $1.1^{\circ}C$, the average of surface temperature range is $1.0^{\circ}C$, and air temperature range is $2.0^{\circ}C$, thus, the we found that the average of air temperature is $1.0^{\circ}C$ higher than globe temperature and the surface temperature. (4)After the consideration of air temperature and globe temperature distribution, the highest temperature reaching time of globe temperature is one hour earlier than air temperature in the downtown location, on the other hand, although the highest temperature reaching time of globe temperature in the outskirt sites is one hour later than in the downtown location, the timelag found in the downtown location was not found in the outskirt site.