• ALGAE
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• v.28 no.3
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• pp.281-288
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• 2013

Photosynthetic carbon fixation regulates air-sea $CO_2$ fluxes in the waters of coral reefs. However, little has been documented on the effects of solar UV radiation (UVR, 280-400 nm) upon photosynthetic behaviors of phytoplankton dwelling in these ecosystems. In order to evaluate the aforesaid, surface dwelling tropical coral reef phytoplankton assemblages collected from the South China Sea were exposed to solar radiation (i.e., photosynthetically active radiation [PAR] + UV radiation A [UVA] + UV radiation B [UVB], 280-700 nm; PAR + UVA, 320-700 nm; and PAR, 400-700 nm) under static or simulated-mixing conditions. Under the static condition, UVA and UVB significantly reduced the carbon fixation with the maximum of 22.4 and 15.3%, respectively; while lower UVR-related photosynthetic inhibition was observed in case of phytoplankton samples being subjected to mixing. At a moderate level of mixing (i.e., circulation time 80 min), the UVA and UVB caused inhibition were lowered by 52.1 and 79.6%, respectively. Based on this it could be stated that vertical mixing induced by winds and/or tides in the natural environments could reduce the inhibitory effect of solar UVR on phytoplankton productivity in the coral reefs water.

• ALGAE
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• v.29 no.1
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• pp.27-34
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• 2014

Availability of nutrients is known to influence marine primary production; and it is of general interest to see how nutrient limitation mediates phytoplankton responses to solar ultraviolet radiation (UVR, 280-400 nm). The red tide diatom Skeletonema costatum was cultured under nitrate (N)-limited and N-replete conditions and exposed to different solar irradiation treatments with or without UV-A (315-400 nm) and UV-B (280-315 nm) radiation. Its photochemical quantum yield decreased by 13.6% in N-limited cells as compared to that in N-replete ones under photosynthetically active radiation (PAR)-alone treatment, and the presence of UV-A or UV-B decreased the yield further by 2.8 and 3.1%, respectively. The non-photochemical quenching (NPQ), when the cells were exposed to stressful light condition, was higher in N-limited than in N-replete grown cells by 180% under PAR alone, by 204% under PAR + UV-A and by 76% under PAR + UV-A + UV-B treatments. Our results indicate that the N limitation exacerbates the UVR effects on the S. costatum photosynthetic performance and stimulate its NPQ.

• Korean Journal of Agricultural and Forest Meteorology
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• v.21 no.4
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• pp.358-365
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• 2019

An agrivoltaic systems (AVS) is mixed systems associating photovoltaic panels (PVPs) and crop cultivation at the same time on the given land area. It is receiving attention to improve rural economy. However, it is likely that, the crop yield should be decreased due to the reduced absorption of solar radiation by leaves. Thus, before popularizing the AVS, it is necessary to comprehend the degree of shading by PVPs in AVS. In this study, the change of radiation condition under AVS mimic shading net was investigated. The minimum and maximum of difference of photosynthetically active radiation (PAR) between under and outside shading net were 3.03 mol/㎡/day on a cloudy day and 17.08 mol/㎡/day on a sunny day. This difference decreased when the ratio of diffuse irradiance to global irradiance increased. Such a shading effect resulted in the increase of rice height and decrease of rice tillering.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.207-209
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• 2003

Quantifying crop production is one of the most important applications of remote sensing in which the temporal and up-to-date data can play very important role in avoiding any immediate insufficiency in agricultural production. A combination of climatic data and biophysical parameters derived from Landsat7 ETM+ was used to develop a mathematical model for wheat yield forecast in different geographically wide Wheat growing districts in Egypt. Leaf Area Index (LAI) and fraction of Absorbed Photosynthetically Active Radiation (fAPAR) with temperature were used in the modeling. The model includes three sub-models representing the correlation between the reported yield and each individual variable. Simulation results using district statistics showed high accuracy of the derived correlations to estimate wheat production with a percentage standard error (%S.E.) of 1.5% in El- Qualyobia district and average (%S.E.) of 7% for the whole wheat areas.

• Ocean and Polar Research
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• v.40 no.4
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• pp.281-288
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• 2018

The transmission of solar light according to the distribution of chromophoric dissolved organic matter (CDOM) was measured in the Pacific Arctic Ocean. The Research Vessel Araon visited the ice-covered East Siberian and Chukchi Seas in August 2016. In the Arctic, solar [ultraviolet-A (UV-A), ultraviolet-B (UV-B), and photosynthetically active radiation (PAR)] radiation reaching the surface of the ocean is primarily protected by the distribution of sea ice. The transmission of solar light in the ocean is controlled by sea ice and dissolved organic matter, such as CDOM. The concentration of CDOM is the major factor controlling the penetration depth of UV radiation into the ocean. The relative CDOM concentration of surface sea water was higher in the East Siberian Sea than in the Chukchi Sea. Due to the distribution of CDOM, the penetration depth of solar light in the East Siberian Sea (UV-B, $9{\pm}2m$; UV-A, $13{\pm}2m$; PAR, $36{\pm}4m$) was lower than in the Chukchi Sea (UV-B, $15{\pm}3m$; UV-A, $22{\pm}3m$; PAR, $49{\pm}3m$). Accelerated global warming and the rapid decrease of sea ice in the Arctic have resulted in marine organisms being exposed to increased harmful UV radiation. With changes in sea ice covered areas and concentrations of dissolved organic matter in the Arctic Ocean, marine ecosystems that consist of a variety of species from primary producers to high-trophic-level organisms will be directly or indirectly affected by solar UV radiation.

• Korean Journal of Ecology and Environment
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• v.36 no.4 s.105
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• pp.403-412
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• 2003

Temporal and spatial variations of size-structured phytoplankton (chlorophyll a) were investigated over an annual cycle (February-October, 2003) to elucidate phytoplankton dynamics in the Juam Reservoir, Chonnam. Physical properties were also measured to investigate the relationship between the properties and temporal and spatial variations of size structured phytoplankton using simple linear regression. Phytoplankton (chlorophyll a) were grouped into three size classes: micro-size(> 20 ${\mu}m$), nano-size (3-20 ${\mu}m$) and pico-size (< 3 ${\mu}m$) in this study. Physical properties included water temperature, light attenuation coefficients, PAR (photosynthetically active radiation) and turbidity. Maximum chlorophyll a was observed in April, 2003 in the lower region whereas a peak of chlorophyll a developed in October, 2003 in the upper region. Large cell-sized phytoplankton (micro-size class)were dominant in the events of the chlorophyll a peaks. Potential mechanisms in the physical properties affecting the size-structured phytoplankton dynamics in the Juam Reservoir were discussed.

• Journal of Korean Society of Forest Science
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• v.96 no.5
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• pp.520-527
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• 2007

Biomass and species diversity of understory vegetation after fertilization were studied for 28-year-old Quercus acutissima plantation (MQA), 29-year-old Pinus densiflora plantation (MPD), 8-year-old Betula platyphylla var. japonica plantation after coal reclamation (YBP), and 4-year-old Pinus densiflora plantation after forest fire (YPD) in central Korea. Nitrogen + phosphorus + potassium (6:4:1) fertilizer was applied for 3 years from 2004. Thereafter photosynthetically active radiation (PAR) and understory species richness and diversity were measured in late July-early August 2006. PAR (${\mu}mol\;m^{-2}S^{-1}$) was higher at the fertilization treatment (100.9) than at the control (67.0) for MQA while was lower at the fertilization treatment (156.5) than at the control (268.7) for MPD. Total understory biomass (t $ha^{-1}$) was lower at the fertilization plot (1.8) than at the control plot (3.0) for YPD, however, there were no differences in biomass between fertilization and control plots for MQA, MPD and YBP. Total species number of understory vegetation was higher for fertilization than for control at MPD (47 vs. 45) and YPD (21 vs. 13), and was higher for mature plantations (33 vs. 37 for MQA and 47 vs. 45 for MPD) than for young plantations (16 vs. 16 for YBP and 21 vs. 13 for YPD). Species richness and diversity were higher at the fertilization treatment than at the control for MQA, YBP, and YPD while were lower at the fertilization treatment than at the control for MPD, however, the differences were not statistically significant. Our results indicate that there were no consistent patterns in light conditions, biomass and species richness and diversity of understory vegetation following fertilization. More detailed long-term studies with different fertilizer applications would be necessary to conclude the influence of fertilization on understory vegetation in the region.

• Journal of Bio-Environment Control
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• v.17 no.4
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• pp.283-287
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• 2008

To investigate the effects of different wavelengths of photosynthetically active radiation on the morphology and leaf color changes of a single tomato (Lycopersicon esculentum) seedling, we stored the seedling at $10{\pm}0.5^{\circ}C$ under eight different wavelengths (peak wavelengths; 405, 450, 505, 545, 600, 645, 680, and 700 nm) with a constant photosynthetic photon flux of $3{\mu}mol\;m^{-2}s^{-l}$ for 28 d. Under the 405, 450, and 505 nm wavelength conditions, the leaves of the seedlings showed vigorous shape with an upright morphology. Rachis elongation was suppressed and hence compact appearance was observed under the 450 and 505 urn conditions. Although the difference in leaf color between before storage and on 28 days after storage was observed under all wavelength conditions, the 405 and 700 um irradiations changed the leaf color to light green. Application of light-emitting diode (LED) light irradiated from around 450 to 545 nm can contribute to vigorous shape with an upright morphology of tomato seedlings during low light irradiation-low temperature storage.

• Journal of Practical Agriculture & Fisheries Research
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• v.25 no.4
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• pp.84-89
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• 2024

Light is an important component among which plays a crucial role in determining the production and quality of fruit trees. Since the disturbance of light directly leads to reduced photosynthetic efficiency, their damage can be increased especially in fruit trees such as Japanese apricots with a short growing time. In this study, we investigated how the effects of shading condition can affect the production and quality of Japanese apricots according to increased damages by light disturbance in the main orchard complex. The average photosynthetically active radiation (PAR) level in Japanese apricots was rapidly dropped as the shading time was increased compared to the control (304 μmol/m²/s) and the PAR level decreased to 142 μmol/m²/s after shaded for eight hours. The maximum photosynthetic efficiency, with a PAR value of 900 to 1,000 μmol/m²/s, corresponds to the time period without shading and the time period with 2 hours of shading, and these times range from 11 a.m. to 3 p.m. And the time period for shading for 4 hours was from 1:00 p.m. to 2:00 p.m., and under conditions of shading for 6 and 8 hours, the effect was a low amount of light. There was no difference in the weight of Japanese apricots during 2 hours shading time, however, it was significantly reduced as shading time were increased. The difference of the acid content and L/D ratio was not significant on shading time, but the SSC was decreased as times going on. In conclusion, our results indicate that the shading for more than 2 hours make negative effects to decrease the weight and SSC and the yield and affects directly to drop in fruit quality.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.18 no.4
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• pp.15-27
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• 2015

The objectives of this study are to analyze the quantitative ecological principal components of Korean Peninsula using the multivariate spatial environmental datasets and to compare the ecological difference between South and North Korea. Ecological maps with GIS(Geographical Information System) are constructed by PCA(Principal Component Analysis) based on seventeen raster(cell based) variables at 1km resolution. Ecological differences between South and North Korea are extracted by Factor Analysis using ecosystem maps masked from Korean ones. Spatial data include SRTM(Shuttle Radar Topography Mission), Temperature, Precipitation, SWC(Soil Water Content), fPAR(Fraction of Photosynthetically Active Radiation) representing for a productivity, and SR(Solar Radiation), which all cover Korean peninsula. When it performed PCA, the first three scores were assigned to red, green, and blue color. This color triplet indicates the relative mixture of the seventeen environmental conditions inside each ecological region. The first red one represents for 'physiographic conditions' worked by high elevation and solar radiation and low temperature. The second green one stands for 'seasonality' caused by seasonal variations of temperature, precipitation, and productivity. The third blue one means 'wetness condition' worked by high value such as precipitation and soil water contents. FA extraction shows that South Korea has relatively warm and humid ecosystem affected by high temperature, precipitation, and soil water contents whereas North Korea has relatively cold and dry ecosystem due to the high elevation, low temperature and precipitation. Results would be useful at environmental planning on inaccessible land of North Korea.