• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.153-153
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• 2019

Evapotranspiration (ET) is an important component of hydrological processes. Accurate estimates of ET variation are of vital importance for natural hazard adaptation and water resource management. This study first developed a soil water index (SWI)-based Priestley-Taylor algorithm (SWI-PT) based on the enhanced vegetation index (EVI), SWI, net radiation, and temperature. The algorithm was then compared with a modified satellite-based Priestley-Taylor ET model (MS-PT). After examining the performance of the two models at 10 flux tower sites in different land cover types over East Asia and Australia, the daily estimates from the SWI-PT model were closer to observations than those of the MS-PT model in each land cover type. The average correlation coefficient of the SWI-PT model was 0.81, compared with 0.66 in the original MS-PT model. The average value of the root mean square error decreased from $36.46W/m^2$ to $23.37W/m^2$ in the SWI-PT model, which used different variables of soil moisture and vegetation indices to capture soil evaporation and vegetative transpiration, respectively. By using the EVI and SWI, uncertainties involved in optimizing vegetation and water constraints were reduced. The estimated ET from the MS-PT model was most sensitive (to the normalized difference vegetation index (NDVI) in forests) to net radiation ($R_n$) in grassland and cropland. The estimated ET from the SWI-PT model was most sensitive to $R_n$, followed by SWI, air temperature ($T_a$), and the EVI in each land cover type. Overall, the results showed that the MS-PT model estimates of ET in forest and cropland were weak. By replacing the fraction of soil moisture ($f_{sm}$) with the SWI and the NDVI with the EVI, the newly developed SWI-PT model captured soil evaporation and vegetation transpiration more accurately than the MS-PT model.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.5
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• pp.679-687
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• 2011

The water management of crop is different according to the area as well as climate condition and growth stage, however it is the most important and difficult problems for the farmers. The optimum irrigation manual those irrigation interval and amount of irrigation as water saving, are developed based on the lysimeter experiments carried out by the RDA for 11 years about PET (Potential Evapo-Transpiration), crop coefficient (Kc). The average PET (Potential Evapo-Transpiration) during 30 years of 45 regions for the autumn chinese cabbage cultivation was a $2.17mm\;day^{-1}$.

• The Journal of the Convergence on Culture Technology
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• v.7 no.1
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• pp.49-57
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• 2021

This study is to find ways to self-produce energy even in buildings through the system of trees that grow by themselves focused on literatures and case studies. It is divided into the structure, circulation and reaction system of tree. 1) In the structural system, the tree is divided into the shoot and root system, and maintains rigidity with the cell membranes. The wind resistance caused by the trunk and crown can be applied to the seismic structure principle of building, and the role of platelike buttresses of lateral roots can be applied to the horizontal truss and suspension bridge. 2) In the circulation system, the transpiration action through the fine stomata of the leaves can be a very effective cooling means because a large amount of heat is released and this method can be directly introduced into the cooling of buildings. 3) In the responsive system, the response system according to environmental changes that can be read from the leaves and flowers of trees can be applied to the roof and exterior design of buildings through the use of new sensing technologies and materials.

• Journal of Bio-Environment Control
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• v.6 no.4
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• pp.250-257
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• 1997

Stem diameter and shoot fresh weight of tomato grown in greenhouse were measured non-destructively at 10 minutes interval from 1 to 16 July, 1996 with displacement detector using strain gauges and with suspension-type load cell, respectively, and simultaneously were measured soil water potential, transpiration and solar radiation. Ample water was irrigated before experiment, and thereafter, irrigations were made on the next morning when visual symptoms of wilting appeared. Shoot fresh weight and stem diameter showed very similar patterns in diurnal changes which are characterized by predawn maximum and afternoon minimum and in long- term evolutions, suggesting that stem diameter shrinkage and expansion are closely related to plant water content and growth, respectively, Shoot weight and stem diameter reached minimum values a little later than the time on which transpiration showed maximum. The daily net gains of fresh weight(DG) and stem diameter(DI) showed significantly Positive correlations with solar radiation in those days on which plants were not water-stressed. However, Dl and DG on those days of water stress showed much lower values than expected from the relationships between solar radiation and them. Transpiration was much lower than the expected potential transpiration on 10 July, implying that plants were water-stressed. In this case water stress was not detected from visual symptom of wilting and/or soil water potential, but was able to be identified by the lower DI and DG than the expected. The maximum contraction of stem diameter(MC) and the maximum loss of fresh weight(ML) during daytime showed significantly positive correlations with solar radiation in those days on which plants were not water-stressed and were observed greater than expected from the relationships on severely water-stressed days. But mild water stress could not be discernable by ML and MC. It would be concluded that the daily net gains of fresh weight and/or stem diameter could be used as criteria for diagnosing the water status of tomato and for triggoring the onset of irrigation in automatic system.

• Korean Journal of Environmental Agriculture
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• v.6 no.2
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• pp.39-45
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• 1987

A water culture experiment was conducted to investigate the effect of As content in a culture solution on the water status and growth of rice plants. Rice (Oryza sativa L. Line. Iri 316) seeds were germinated in bentonite and cultivated there for 30 days. Rice seedlings were transplanted into 3.5l pots containing the culture solution on May 1, 1985 and allowed to grow without As treatment for one month. Afterwards, they were grown in a culture solution maintaining the final concentration of As, 0, 1, 5, 10 and 15mg/1 renewing in the solution dissolved sodium arsenate at intervals of 3 to 7 days. Plants were cultivated in the green house during the growing period and harvested 60 days after As treatment. The results obtained were as follows: Transpiration of rice plants was decreased with the increase of the As level in the culture solution. Stomatal diffusive resistance and leaf temperature increased with increase of As levels though the humidity and the air flow rate in leaf decreased. Air flow rate, transpiration and stomatal diffusive resistance showed a highly significant correlation with As contents in shoots and roots of rice plants: Espally The air flow rate and transpiration revealed a significantly higher correlation with As contents in the root than that in the shoot, but diffusive resistance showed adverse tendency. High levels of As in the culture solution depressed plant height, no. of tillers, leaf width and dry weight of plant remarkably. Typical symptoms of As toxicity were root discoloration, and necrosis of leaf tips and margins, and leaf rolling during the sunny daytime were also another symptoms.

• Journal of Korean Society of Forest Science
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• v.82 no.2
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• pp.152-165
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• 1993

This is the basic study in order to know the amount of transpirational water loss in a Larix leptorepis stand by a heat pulse method. Especially this study has been measured and discussed the diurnal and seasonal trends of heat pulse velocity by changes of radiation, temperature and humidity, differences of heat pulse velocity by direction and depth in stem, differences of heat pulse velocity by dominant, codominant and suppressed trees, diurnal change of heat pulse velocity by change of leaf water potential, sap flow path way in sapwood by dye penetration and amount of daily and annual transpiration in a tree and stand. The results obtained as follows : 1. Relation between heat pulse velocity(V) and sap flow rate(SFR) was established as a equation of SFR=1.37V($r=0.96^{**}$). 2. The sap flow rate presented in the order of dominant, codominant and suppressed tree, respectively. The daily heat pulse velocity was changed by radiation, temperature and vapor pressure deficit. 3. The heat pulse velocity in individual trees did not differ in early morning and in late night, but had some differed from 12 to 16 hours when radiation was relatively high. 4. The heat pulse velocity and leaf water potential showed similar diurnal variation. 5. The seasonal variation of heat pulse velocity was highest in August, but lowest in October and similar value of heat pulse velocity in the other months. 6. The heat pulse velocity in stem by direction was highest in eastern, but lowest in southern and similar velocity in western and northern. 7. The difference of heat pulse velocity in according to depths was highest in 2.0cm depth, medium in 1.0cm depth, and lowest in 3.0cm depth from surface of stem. 8. The sap flow path way in stem showed spiral ascent turning right pattern in five sample trees, especially showed little spiral ascent turning right in lower part than 3m hight above ground, but very speedy in higher than 3m hight. 9. The amount of sap flow(SF) was presented as a equation of SF=1.37AV and especially SF in dominant tree was larger than in codominant or suppressed tree. 10. The amount of daily transpiration was 30.8ton/ha/day and its composition ratio was 83% at day and 17% at night. 11. The amount of stand transpiration per month was largest in August(1,194ton/ha/month), lowest in May (386ton/ha/month). The amount of stand transpiration per year was 3,983ton/ha/year.

• Magazine of the Korean Society of Agricultural Engineers
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• v.11 no.1
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• pp.1561-1579
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• 1969

In Korea, the duty of water in paddy fields was measured at the Agricultural Experimental Station in Suwon about 60 years ago. After that time some testing has been made in several places, but the key points in its experiment were the water depth of evapo-transpiration. Improved breeds, progress in cultivation and management techniques as well as development of measuring apparatus in recent years have necessitated the review of the duty of water in paddy fields. The necessity of reviewing the conventional methods has become even more important, as no source of information has been made available through survey of water utilization on a soil use basis which requires data on peculiar features of the water depth of evapo-transpiration. For example, the duty of water in paddy field is largely affected by the water depth of evapo-transpiration in connection with the wetted paddy field, whereas in connection with the normal paddy fields without this characteristic the vertical percolation become the predominant factor in measuring the decreasing depth of water. Therefore, it becomes important. that not only the water depth of evapotranspiration but also the vertical percolation process should also be observed in order to arrive at a realistic conclusion. As the vertical percolation has aclose relationship to the height of the underground water, the change of the latter can be measured. As the conclusion of this experiment, the following subjects are indicated. 1. In order to determine the economic duty of water in paddy fields on a basis of varying soil features, the varying soil features in the benifited area should be investigated thoroughly. The water depths of evapo-transpiration(ET) ratio to evaporation in the evaporator(V) on a basis of the varying soil features are as follows: clay loam ET/V = 1.11, loam ET/V = 1.64, sandy loam ET.V = 1.63 2. The decreasing depth of water consists of the water depth of evapotranspiration, the vertical per colation and the percolation of foot path. Among these three, the percolation of foot path can be utilized again. 3. As the result of this experiment, it shows the decreasing depth of water as follows. clay loam 9.3 mm/day, loam 13.5mm/daty, sandy loam 15.3mm/day 4. On a basis of the varying soil features and the height of the underground water, the vertical percolation varies. 5. The change of the vertical percolation on a basis of the varying soil features shows as follows: clay loam $1{\sim}2$ mm/day, loam $2{\sim}3$mm/day, sandy loam $3{\sim}4$mm/day 6. The level of the underground water changes sensibly by priority of clay loam, loam, sandy loam. When it rains, the level of the underground water rises fast and falls down slowly. 7. The level of the underground water changes within the scope of 25cm 8. The transpiration ratio is given in table 8 and their value are as follows: clay loam 168.8, loam 255.6, sandy loam 272.5

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.04a
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• pp.311-314
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• 2002

국내에서 자생하는 포플러중 현사시, 양황철, 이태리포플러를 대상으로 제초제인 atrazine의 제거특성을 조사하였다 Atrazine이 포플러에 미치는 독성을 평가하고, 식물체에 의한 atrazine 제거효율 및 제거속도를 조사하였다. 또한 식물체의 체내로의 흡수에 의해 atrazine이 제거되므로 식물체로 흡수된 후의 생물학적 변환 과정에 대해서도 조사하였다. 현사시, 양황철, 이태리포플러 모두 실험이 진행된 전범위의 농도에서 황백화현상, 낙엽증가, 생체량 감소와 같은 식물독성을 나타냈으며, 현사시인 경우 양황청 및 이태리 포플러에 비해 상대적으로 민감한 반응을 나타내었다. Atrazine 독성여부 평가의 하나로 초기 atrazine 농도가 증가할수록 현사시, 양황철, 이태리포플러의 증산량은 상대적으로 감소함을 관찰하였다. 포플러에 의한 atrazine 생물학적 변환실험에서는 atrazine이 중간생성물질인 HA, DEA, I)IA를 거쳐 ammeline을 포함한 HDAP로 전환되는 것을 확인하였다. 이 결과의 중요성은 atrazine 부산물은 상대적으로 독성이 적고, 미생물에 의해 어렵지 않게 완전 무기화할 수 있기 때문이다. 즉, 식물체내에서도 HBAP 이후 과정을 통한 분해가 이루어질 수 있는 가능성이 있다고 추측할 수 있다.

• Water Engineering Research
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• v.5 no.1
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• pp.1-16
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• 2004

The purpose of this study is to understand the characteristics of hourly PET(Potential Evapo Transpiration) variation estimated using Penman ET model. The estimated PET using Penman model was compared with measured ET. For this study, two subwatersheds were selected, and fluxes, meteorological data and soil moisture data were measured during the summer and winter days. During the winter days, the aerodynamic term of Penman ET is much greater than that of energy term of Penman ET for dry soil condition. The opposite phenomena appeared fer wet soil condition. During the summer days, energy term is much more important factor for ET estimation compared with aerodynamic term regardless of soil moisture condition. Penman ET, measured ET, and energy term show the similar hourly variation pattern mainly because the influence of net radiation on the estimation of Penman ET is much more significant compared with other variables. Even though there are much more soil moisture in the soil during the wet days, the estimated hourly ET from Penman model and measured hourly ET have smaller values compared with those of dry days, indicating the effect of cloudy weather condition.

• The Korean Journal of Ecology
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• v.20 no.4
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• pp.239-244
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• 1997

Hybrid poplar (Populus trichocarpa $\times$ P. deltoides) clones were fumigated with ozone. Fumigation was applied for 6 to 8 hours each day for approximately 3 months at ozone concentrations of 0.090 to 0.115 ppm using by open-top chambers. Growth and biomass of hybrid poplar seedlings were reduced by ozone exposure. Mean percentage of falling leaves in ozone-treated plant was 6 times higher than that of charcoal-filtered plant. Among physiological responses, rate of photosynthesis, stomatal conductance, transpiration and initial Rubisco activity were significantly lower in seedlings grown in ozone environment compared seedlings grown in charcoal-filtered air. All these physiological results supported that biochemical process to be a key feature to understand reduction in photosynthesis.