• Korean Journal of Agricultural and Forest Meteorology
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• v.7 no.1
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• pp.35-44
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• 2005

Microclimate of Gwangneung forest watershed is characterized by analyzing wind, radiation, profiles of air temperature and humidity, soil and bole temperature, precipitation and soil water content measured at and around the flux tower from April 2000 to September 2003. Mountain-valley wind was prevalent due to the topographic effect with dominant wind from east during daytime and relatively weak wind from west during nighttime. Air temperature reaches its peak in July-August whereas monthly-averaged incoming shortwave radiation shows its peak in May due to summer monsoon. Albedo ranges from 0.12 to 0.16 during the growing season. Monthly-averaged bole temperature is in phase with monthly- averaged air temperature which is consistently higher. Monthly-averaged soil temperature lags behind air temperature and becomes higher with leaf fall. With the emergence of leafage in April, maximum temperature level during midday shifts from the ground surface to the crown level of 15-20m in May. Profiles of water vapor pressure show a similar shift in May but the ground surface remains as the major source of water. Vapor pressure deficit is highest in spring and lowest in winter. Monthly averaged surface soil temperatures range from 0 to 20℃ with a maximum in August. Monthly averaged trunk temperatures of the dominant tree species range from -5.8 to 21.6℃ with their seasonal variation and the magnitudes similar to those of air temperature. Annual precipitation amount varies significantly from year to year, of which >60% is from July and August. Vertical profiles of soil moisture show different characteristics that may suggest an important role of lateral movement of soil water associated with rainfall events.

• Korean Journal of Agricultural and Forest Meteorology
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• v.2 no.3
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• pp.87-94
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• 2000

To recommend adequate covering materials and shapes of rice nursery bed for mechanical transplanting rice seedling, measuring of microclimate inside the rice nursery protected by polyethylene tunnel type, polyester tunnel type, and polyester flat type was compared to that outside the nursery. The vapor pressure deficit inside the polyester tunnel and polyethylene tunnel was higher than that outside the tunnel during daytime on a sunny day. During daytime on cloudy with rain day, the vapor pressure deficit inside polyester tunnel was higher than that in polyethylene tunnel or outside the nursery tunnel. The heat fluxes in the rice nursery tunnel during daytime flowed more to the soil than to the outside tunnel. Amounts of soil heat fluxes in polyethylene tunnel were higher than in polyester flat and polyester tunnel. The vertical profile of air temperature inside the nursery tunnel came to inversion during daytime and was lapse during nighttime regardless weather condition. The maximum temperature inside the nursery tunnel were 47.2$^{\circ}C$ in polyethylene tunnel and 37.$0^{\circ}C$ in polyester tunnel which was 21.1$^{\circ}C$ and 10.9$^{\circ}C$ higher than outside the tunnels respectively on sunny day. On cloudy with rain day, the temperature inside nursery tunnel was higher 8.4$^{\circ}C$ and 4.$0^{\circ}C$ polyethylene and polyester tunnel respectively then outside. Daily temperature changes became larger in the polyethylene tunnel, polyester tunnel, and outside the nursery tunnel in order. The rice seedling growth in polyester tunnel was better than the other nursery beds.

• Journal of Bio-Environment Control
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• v.26 no.4
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• pp.411-417
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• 2017

Environmental and growth factors such as light intensity, vapor pressure deficit, and leaf area index are important variables that can change the transpiration rate of plants. The objective of this study was to compare the transpiration rates estimated by modified Penman-Monteith model and artificial neural network. The transpiration rate of paprika (Capsicum annuum L. cv. Fiesta) was obtained by using the change in substrate weight measured by load cells. Radiation, temperature, relative humidity, and substrate weight were collected every min for 2 months. Since the transpiration rate cannot be accurately estimated with linear equations, a modified Penman-Monteith equation using compensated radiation (Shin et al., 2014) was used. On the other hand, ANN was applied to estimating the transpiration rate. For this purpose, an ANN composed of an input layer using radiation, temperature, relative humidity, leaf area index, and time as input factors and five hidden layers was constructed. The number of perceptons in each hidden layer was 512, which showed the highest accuracy. As a result of validation, $R^2$ values of the modified model and ANN were 0.82 and 0.94, respectively. Therefore, it is concluded that the ANN can estimate the transpiration rate more accurately than the modified model and can be applied to the efficient irrigation strategy in soilless cultures.

• Journal of Bio-Environment Control
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• v.7 no.1
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• pp.9-14
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• 1998

Air current speeds were controlled of 0.3, 0.5, 0.7 and 0.9 m.s$^{-1}$ to investigate the effects of air current speeds on the growth of eggplant plug seedlings (Solanum melongena L.) in a wind tunnel under artificial lighting. Growth of plug seedlings was influenced by the magnitude of air current speed and the traveling distance of regulated air flow. Stem length. ratio of length to diameter in stem, plant height .and number of leaves of plug seedlings decreased with the increasing air current speed and were significantly different at 5% level. Net photosynthetic rates of plug stand increased with the increasing air current speed and took a maximum value at the air current speed of 0.7~09 m.s$^{-1}$ . Stem diameter decreased and leaf area increased with the traveling distance of regulated air flow. Fresh weight and T/R ratio of dried weight were not influenced by the air current speed. Optimum control for microclimates inside the plug stand is needed to produce the uniform growth and high quality of plug seedlings in a semi-closed plant Production system under artificial lighting.

• Korean Journal of Agricultural and Forest Meteorology
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• v.11 no.3
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• pp.87-99
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• 2009

We evaluated modified Soil-Plant-Atmosphere model's performance to simulate the seasonal variation of net ecosystem exchange (NEE) of carbon and examined the critical controlling mechanism on carbon exchange using the model over a deciduous forest at Gwangnung in 2006. The modified Soil-Plant-Atmosphere (mSPA) model was calibrated to capture the mean NEE during the daytime (1000-1400 LST) and used to simulate gross primary productivity (GPP). Ecosystem respiration ($R_e$) has been estimated using an empirical formula developed at this site. The simulation results indicated that the daytime mean stomatal conductance was highly correlated with daily insolation in the summer. Low stomatal conductance in high insolation occurred on the days with low temperature rather than with high vapor pressure deficit. It suggests that the forest rarely experienced water stress in the summer of 2006. The model captured the observed bimodal seasonal variation with a mid-season depression of carbon uptake. The model estimates of annual GPP, $R_e$ and NEE were $964\;gC\;m^{-2}\;yr^{-1}$, $733\;gC\;m^{-2}\;yr^{-1}$, and $-231\;gCm\;^{-2}\;yr^{-1}$, respectively. Compared to the observed annual NEE, the modeled estimates showed more carbon uptake by about $140\;gC\;m^{-2}\;yr^{-1}$. The uncertainty of the estimate of annual NEE in a complex terrain is discussed.

• Korean Journal of Agricultural and Forest Meteorology
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• v.11 no.4
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• pp.233-246
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• 2009

The partitioning of evapotranspiration (ET) into evaporation (E) and transpiration (T) is critical in understanding the water cycle and the couplings between the cycles of energy, water, and carbon. In forests, the total ET measured above the canopy consists of T from both overstory and understory vegetation, and E from soil and the intercepted precipitation. To quantify their relative contributions, we have measured ET from the floors of deciduous and coniferous forests in Gwangneung using eddy covariance technique from 1 June 2008 to 31 May 2009. Due to smaller eddies that contribute to turbulent transfer near the ground, we performed a spectrum analysis and found that the errors associated with sensor separation were <10%. The annual sum of the understory ET was 59 mm (16% of total ET) in the deciduous forest and 43 mm (~7%) in the coniferous forest. Overall, the understory ET was not negligible except during the summer season when the plant area index was near its maximum. In both forest canopies, the decoupling factor ($\Omega$) was about ~0.15, indicating that the understory ET was controlled mainly by vapor pressure deficit and soil moisture content. The differences in the understory ET between the two forest canopies were due to different environmental conditions within the canopies, particularly the contrasting air humidity and soil water content. The non-negligible understory ET in the Gwangneung forests suggests that the dual source or multi-level models are required for the interpretation and modeling of surface exchange of mass and energy in these forests.

• Proceedings of The Korean Society of Agricultural and Forest Meteorology Conference
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• 2013.11a
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• pp.26-27
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• 2013

산림생태계의 에너지, 물질, 정보의 교환 과정과 그 변화를 이해하려면 먼저 생태계의 구조와 기능이 어떻게 상호작용하는지를 이해해야 한다. 생태계의 기능은 한, 두 가지의 특징에 의해서만 이루어지는 것이 아니다. 그렇기 때문에 그 기능을 파악하고 적절히 이용하거나 대응하기 위해서는 한 생태계와 주변 환경 전체를 바라볼 수 있는 시스템 사고가 필요하다. 이에 우리는 생태계의 '구조'를 파악함으로써 생태계의 '상태'를 이해하고자 한다. 본 연구에서는 Ruddell and Kumar (2009)의 접근법을 따라, 어떻게 한 생태계의 상태를 파악할 수 있는가라는 질문을 광릉활엽수림에 적용하여 답하고자 한다. 즉, 우리는 산림생태계가 열린 복잡계라고 가정하고, 생태계 내에서 다양한 프로세스들 간의 시시각각 변하는 네트워크의 구조가 각 시점의 시스템의 상태를 나타내는 지표가 될 수 있다고 가정하였다. 이 연구에서는 그 구조적 특징을 정량화하여 나타내는데 초점을 맞추었다. 각각의 프로세스를 대표하는 상태 변수들 간의 정보 흐름의 양과 방향, 시간 규모를 계산해냄으로써 네트워크 구조를 파악하고자 하였다. 온대 산악지형 활엽수림인 GDK의 2008년 순생태계교환량(NEE), 총일차생산량(GPP), 생태계호흡량(RE), 현열플럭스(H), 잠열플럭스(LE), 하향단파복사(Rg), 강수량(Precipitation), 기압(Pressure), 기온(T), 포차(VPD)의 시계열 자료를 월별로 나누어 최장 18 시간 규모의 정보 흐름을 계산하였다. 정보 흐름의 구조를 파악하기 위하여 변수들 간의 전이엔트로피(Transfer entropy)와 상호정보(Mutual Information)를 계산하는 방법을 사용하였다. 또한 시계열 자료를 이용함으로써 변수들 간에 정보가 전달되는 시간 규모의 특성을 파악할 수 있었다. 최종적으로, 계산한 정보 흐름을 시각화하여 프로세스 네트워크 구조를 나타내었다. 결과는 월별로 생태계의 정보 흐름의 종류, 방향과 시간 규모, 그에 따른 프로세스 간 상호 작용의 특징 등을 보여준다. 이를 통해 계절적 환경 변화에 따라 시스템의 네트워크 구조와 상태가 어떻게 변화하는지 이해할 수 있을 것이다. 이 연구는 추후 우리 연구실에서 생산한 8 년 자료에 적용함으로써 다양한 날씨 및 기후변화와 환경 변화에 따라 생태계의 구조와 상태가 어떻게 변화하는지 연구하는 시작점이 될 것이다. 이 접근법은 단위나 차원에 무관하게 다양한 종류의 자료에 적용할 수 있는 반면에, 일관성 있게 정의된 시스템의 상태 및 그 상태를 구성하는 주요 하부 시스템들의 네트워크 상태를 이해하는데 이용될 수 있다. 본 연구는 비평형 열역학과 복잡계의 관점에서 바라 본 시스템 사고를 적용하려 하는 여러 연구 분야에 새로운 도전을 촉발할 좋은 선행연구가 될 것이라 기대된다.

• Korean Journal of Remote Sensing
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• v.33 no.5_2
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• pp.721-732
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• 2017

With the increasing socio-economic importance of rice as a global staple food, several models have been developed for rice yield estimation by combining remote sensing data with carbon cycle modelling. In this study, we aimed to estimate rice yield in Korea using such an integrative model using satellite remote sensing data in combination with a biophysical crop growth model. Specifically, daily meteorological inputs derived from MODIS (Moderate Resolution imaging Spectroradiometer) and radar satellite products were used to run a light use efficiency based crop growth model, which is based on the MODIS gross primary production (GPP) algorithm. The modelled biomass was converted to rice yield using a harvest index model. We estimated rice yield from 2003 to 2014 at the county level and evaluated the modelled yield using the official rice yield and rice straw biomass statistics of Statistics Korea (KOSTAT). The estimated rice biomass, yield, and harvest index and their spatial distributions were investigated. Annual mean rice yield at the national level showed a good agreement with the yield statistics with the yield statistics, a mean error (ME) of +0.56% and a mean absolute error (MAE) of 5.73%. The estimated county level yield resulted in small ME (+0.10~+2.00%) and MAE (2.10~11.62%),respectively. Compared to the county-level yield statistics, the rice yield was over estimated in the counties in Gangwon province and under estimated in the urban and coastal counties in the south of Chungcheong province. Compared to the rice straw statistics, the estimated rice biomass showed similar error patterns with the yield estimates. The subpixel heterogeneity of the 1 km MODIS FPAR(Fraction of absorbed Photosynthetically Active Radiation) may have attributed to these errors. In addition, the growth and harvest index models can be further developed to take account of annually varying growth conditions and growth timings.

• Journal of Bio-Environment Control
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• v.18 no.4
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• pp.385-392
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• 2009

This study was performed to evaluate the influence of temperature, relative humidity, and light conditions during healing and acclimatization on the graft-take and growth of grafted peppers (Capsicum annuum L.), in order to propose optimum environmental conditions for the healing and acclimatization of grafted peppers. The healing and acclimatization period was for six days and was divided into three stages (Stage I, II and III), of which each period was two days. Grafted peppers were healed under the condition of 30 and 95% relative humidity (RH) during Stage I. During Stage II and III, grafted peppers were healed and acclimatized under different temperatures ($20^{\circ}C$, $25^{\circ}C$, or $30^{\circ}C$) and RH conditions (75%, 85% or 95%). The growth of grafted peppers was greater under lower temperature and lower relative humidity conditions. The graft-take just after the end of healing and acclimatization was greater grafted peppers under high RH condition. However, the graft-take of peppers which were healed and acclimatized under $30^{\circ}C$ and RH 95%, dropped by about 10 percent on day seven after healing and acclimatization. And also, grafted peppers were healed and acclimatized under the different temperatures ($25^{\circ}C$ or $30^{\circ}C$), RH conditions (65%, 75% or 85%), and light condition (dark or light). Lower RH (to 65%) and light condition at $25^{\circ}C$ during healing and acclimatization promoted the graft-take and growth of grafted peppers.

• Korean Journal of Agricultural and Forest Meteorology
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• v.11 no.1
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• pp.39-47
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• 2009

The importance of securing water resources and their efficient management has attracted more attention recently due to water deficit. In water budget analysis, however, evapotranspiration(${\lambda}E$) has been approximated as the residual in the water balance equation or estimated from empirical equations and assumptions. To minimize the uncertainties in these estimates, it is necessary to directly measure ${\lambda}E$. In this study, using the eddy covariance technique, we have measured ${\lambda}E$ in a mixed forest in the Seolmacheon catchment in Korea from September 2007 to December 2008. During the growing season(May-July), ${\lambda}E$ in this mixed forest averaged about $2.2\;mm\;d^{-1}$, whereas it was on average $0.5\;mm\;d^{-1}$ during the non-growing season in winter. The annual total ${\lambda}E$ in 2008 was $581\;mm\;y^{-1}$, which is about 1/3 of the annual precipitation of 1997 mm. Despite the differences in the amount and frequency of precipitation, the accumulated ${\lambda}E$ during the overlapping period(i.e., September to December) for 2007 and 2008 was both ${\sim}110$ mm, showing virtually no difference. The omega factor, which is a measure of decoupling between forest and the atmosphere, was on average 0.5, indicating that the contributions of equilibrium ${\lambda}E$ and imposed ${\lambda}E$ to the total ${\lambda}E$ were about the same. The results suggest that ${\lambda}E$ in this mixed forest was controlled by various factors such as net radiation, vapor pressure deficit, and canopy conductance. In this study, based on the direct measurements of ${\lambda}E$, we have quantified the relative contribution of ${\lambda}E$ in the water balance of a mixed forest in the Seolmacheon catchment. In combination with runoff data, the information on ${\lambda}E$ would greatly enhance the reliability of water budget analysis in this catchment.