• Journal of Ecology and Environment
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• v.43 no.2
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• pp.246-253
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• 2019

Background: Water use efficiency (WUE) is an indicator of the trade-off between carbon uptake and water loss to the atmosphere at the plant or ecosystem level. Understanding temporal dynamics and the response of WUE to climatic variability is an essential part of land degradation assessments in water-limited dryland regions. Alternative definitions of and/or alternative methodologies used to measure WUE, however, have hampered intercomparisons among previous studies of different biomes and regions. The present study aims to clarify semantic differences among WUE parameters applied in previous studies and summarize these parameters in terms of their definition and methodology. Additionally, the consistency of the responses of alternative WUE parameters to interannual changes in moisture levels in Northeast Asia dryland regions (NADRs) was tested. Results: The literature review identified more than five different WUE parameters defined at leaf and ecosystem levels and indicates that major conclusions regarding the WUE response to climatic variability were partly inconsistent depending on the parameters used. Our demonstration of WUE in NADR again confirmed regional inconsistencies and further showed that inconsistencies were more distinct in hyper- and semi-arid climates than in arid climates, which might reflect the different relative roles of physical and biological processes in the coupled carbon-water process. Conclusions: The responses of alternative WUE parameters to drying and wetting may be different in different regions, and regionally different response seems to be related to aridity, which determines vegetation coverage.

• Korean Journal of Remote Sensing
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• v.34 no.3
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• pp.553-564
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• 2018

Water use efficiency (WUE) is the amount of carbon uptake per unit of water use, which is a key measure of the functions of terrestrial ecosystems, as it is related to both the hydrologic and carbon cycles. Furthermore, it can vary with many factors, such as climate conditions and land cover characteristics, in different regions. In this study, we aim to understand the spatial and temporal variations in WUE on the Korean Peninsula as well as the associated response to drought. The Moderate Resolution Imaging Spectroradiometer (MODIS)-derived gross primary productivity (GPP) and evapotranspiration (ET) datasets and climate data were used to derive a drought index. Based on the monthly WUE, we found that WUE decreased during the monsoon summer in all regions and for all vegetation types. Furthermore, the annual WUE was negatively correlated with the drought index, with increasing correlation coefficients from the northern region to the southern region of the Korean Peninsula.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.45 no.1
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• pp.6-13
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• 2000

Water deficit is the primary constraint of soybean [Glycine max (L.) Merr.] yield, and a physiological understanding of processes affected by water deficit is a key step in identifying and improving drought tolerance in soybean. The objectives of this research were to evaluate biomass and nitrogen accumulation patterns and water use efficiency (WUE) as possible mechanisms associated with the drought tolerance of Jackson. Biomass accumulation of Jackson was contrasted with the PI416937, which also has demonstrated tolerance to drought. For water-deficit treatment, total biomass accumulation was negligible for PI416937, but biomass accumulation continued at approximately 64 % of the well-watered treatment of Jackson. Transpirational losses for Jackson and PI416937 were approximately the same for the water-deficit treatment, indicating that Jackson had superior WUE. Isotopic discrimination of $^{13}$ C relative to $^{12}$ C also indicated that Jackson had higher WUE. Results indicated that increased WUE for Jackson under water deficit showed it was tolerant to drought rather than had an avoidance mechanism.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.140-140
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• 2016

수분 이용효율(Water Use Efficiency, WUE)은 식생이 흡수한 수분 중 증발산에 이용한 비율로, 육상생태계의 수문학적 순환 및 탄소 순환의 기능을 측정할 수 있는 중요한 지표이다. 또한 이는 특정 지역의 기후 조건이나 토지 피복과 같은 다양한 요인에 따라 변할 수 있다. 본 연구에서는 한반도에서 2010년부터 2014년까지의 기후 요인(강수, 기온)과 토지 피복에 따른 WUE의 변화를 살펴본다. MODerate resolution Imaging Spectroradiometer (MODIS) 기반 총일차생산성(Gross Primary Productivity, GPP), 증발산량(Evapotranspiration, ET), 잎면적지수(Leaf Area Index, LAI)와 Willmot의 기상자료 등 대상지역에 대한 격자 자료를 사용한다. 구체적으로 숲, 초원, 농지와 같이 다양한 토지 피복 조건에 대한 월간 및 연간 WUE(=GPP/ET)를 산정하고, 이의 LAI나 기후 조건(강수, 기온)과의 관계를 분석하고자 상관성 및 요인 분석을 진행한다. 기후 조건 및 토지 피복 조건을 고려한 15년간 한반도에서의 WUE의 변화에 대한 분석은 앞으로의 수자원 관리 및 산림 정책에 활용할 수 있을 것으로 판단된다.

• Korean Journal of Agricultural and Forest Meteorology
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• v.18 no.4
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• pp.366-377
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• 2016

Water use efficiency (WUE) is considered as an important ecological indicator which may provide information on the process-structure relationships associated with energy-matter-information flows in ecosystem. The WUE at ecosystem-level can be defined as the ratio of gross primary productivity (GPP) to evapotranspiration (ET). In this study, KoFlux's long-term (2007-2015) eddy covariance measurements of $CO_2$ and water vapor fluxes were used to examine the WUE of needle fir plantation in Korea National Arboretum. Our objective is to ascertain the seasonality and inter-annual variability in WUE of this needle fir plantation so that the results may be assimilated into the development of a holistic ecological indicator for resilience assessment. Our results show that the WUE of needle fir plantation is characterized by a concave seasonal pattern with a minimum ($1.8-3.3g\;C{\cdot}(kg\;H_2O)^{-1}$) in August and a maximum ($5.1-11.4g\;C{\cdot}(kg\;H_2O)^{-1}$) in February. During the growing season (April to October), WUE was on average $3.5{\pm}0.3g\;C\;(kg\;H_2O)^{-1}$. During the dormant seasons (November to March), WUE showed more variations with a mean of $7.4{\pm}1.0g\;C{\cdot}(kg\;H_2O)^{-1}$. These values are in the upper ranges of WUE reported in the literature for coniferous forests in temperate zone. Although the growing season was defined as the period from April to October, the actual length of the growing season (GSL) varied each year and its variation explained 62% of the inter-annual variability of the growing season WUE. This is the first study to quantify long-term changes in ecosystem-level WUE in Korea and the results can be used to test models, remote-sensing algorithms and resilience of forest ecosystem.

• Journal of Bio-Environment Control
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• v.18 no.4
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• pp.408-412
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• 2009

Daily last time of irrigation in perlite bag culture was investigated to get high water use efficiency (WUE) and fertilizer use efficiency (FUE) and also sustain high productivity for tomato. The water content in the substrate was higher as the last time of irrigation was later from 4 to 1hour before sunset. The growth were not significantly different in all treatments. The marketable yield was the highest in treatments of 1 or 2hours before sunset and the lowest in treatment of 4hours. In the result to investigate for 128days WUE and FUE were the lowest in treatment of 1hour before sunset but the highest in treatment of 3hours before sunset. In the conclusion, it looks best to end irrigation 2~3hours before sunset in the aspects of plant growth, yield, WUE, and FUE.

• Proceedings of The Korean Society of Agricultural and Forest Meteorology Conference
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• 2015.08a
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• pp.18-28
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• 2015

Apple is cultivated under various climatic conditions in many parts of the world. Better understanding of how climate, genotype, soil, and management factors interact to determine crop productivity will improve our ability to optimize crop selection, management strategies, and resource use efficiencies. We developed and applied a physiology-based apple canopy model to evaluate how climatic factors and crop phenotypes interact to determine biomass accumulation, radiation use efficiency (RUE), and water use efficiency (WUE) at multiple production sites between western and eastern states of the US including WA, CA, NY, WV, and PA. Our results indicate that solar radiation is a dominant factor limiting biomass production in the eastern states while VPD is the primary factor governing crop water use across eastern and western states during the peak growing season. Crop RUE and WUE were strongly correlated in the western states but not in the eastern states while VPD showed highly negative correlation with both RUE and WUE across all locations. The RUE improved with increasing fraction of diffuse radiation ($f_{df}$) and the $RUE-f_{df}$ relationships revealed distinctive responses between western and eastern states. Overall, the eastern locations exhibited slightly higher RUE and WUE than the western locations. However, overall productivity and total water use were greater in the western states. A clear decline of productivity with increasing temperature and afternoon VPD past an optimum was predicted in the western locations but this pattern was less clear in the eastern locations. We also discuss potential phenotypes with specific physiological and morphological traits that are differentially suitable for western and eastern locations. Our results provide plausible, spatially explicit explanations and insights to disentangle the complex relationships between crop productivity, resource use efficiencies, phenotype, and climate drivers in apple grown in the US.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.362-365
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• 2011

단위면적당 증발산량 중 일부가 식생의 물질 생산에 이용될 수 있는지를 나타내는 지표인 수분 이용효율 (Water Use Efficiency, WUE)은 총 일차생산성(Gross Primary Productivity, GPP)과 단위면적당 증발산량(Evapotranspiration, ET)의 비로 산출된다. 이전 연구들에서의 수분 이용효율의 적용은 수분 스트레스에 대한 작물의 생산성 차이 분석과 같은 작물학과 농림학 분야의 연구들이 대부분이었지만. 기후 변화가 생태계 생산성 또는 에너지 수지에 영향을 미치는 등의 전 지구적 규모의 수문학적 연구에도 적용할 수 있다. 본 연구에서는, Moderate Resolution Imaging Spectroradiometer (MODIS) 영상자료에서 1km 해상도로 8일 단위의 총 일차생산성과 증발산량을 산정함으로써 수분 이용효율을 구하였다. 향후에는 산정된 이 지표를 남한지역에 적용하여 수분 이용효율에 대한 지도를 작성하고, 실측된 총 일차생산량과 증발산 값을 이용하여 검증한 후 알고리즘을 개선해 나갈 계획이다.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.302-304
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• 2019

탄소 순환과 수문 순환의 관계를 이해하기 위해서는 효율적인 물 사용과 실제 물 사용 간의 비율로 정의되는 용수효율(Water Use Efficiency; WUE)을 정량화 하는 것이 필요하다. 특히 용수효율을 평가하기 위해서는 탄소 순환의 주요 인자인 총 1차 생산량(Gross Primary Productivity; GPP)과 순 1차 생산량(Net Primary Productivity; NPP)을 산정하는 것이 중요하다. 본 연구에서는 전 세계적으로 가장 많이 활용되고 있는 지면 모형 중 하나인 Community Land Model(CLM)을 활용하여 동아시아 지역에서의 GPP와 NPP를 산정하였다. 모형을 통해서 산정된 광역의 GPP와 NPP는 Flux tower에서 관측된 지점 자료를 활용하여 검증할 예정이다. 또한 지면 모형에서 획득한 동아시아 지역의 GPP와 NPP에 대한 공간 분포를 분석하여 탄소 순환 인자들에 대한 시공간적인 변화에 대하여 확인하고자 한다.

• The Korean Journal of Quaternary Research
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• v.17 no.2
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• pp.123-128
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• 2003

This study was conducted to examine the water use efficiency (WUE) in five species of one-year-old seedlings grown in a field nursery in Mongolia. Larix sibirica and Pinus sylvestris are the most dominant coniferous species while Ulmus pumila is an important deciduous species known well-adapted in harsh conditions such as in semi-arid forests and Gobi desert regions. Caragana arborescens (Siberian pea shrub) and Hippophae rhamnoides are N-fixing shrubs in Mongolia. Thirty one-year-old seedlings were sampled from each of the five species (a total of 150 samples) and measured for net photosynthetic rate (Pn) and transpiration rate (E). The Pn and E were used to calculate and compare the WUE of each species. Pn differed significantly among the five species (p < 0.05). However, there was no significant difference in Pn between L. sibirica and H. rhamnoides (p > 0.05). C. arborescens showed the highest Pn whereas U. pumila did the poorest. E differed significantly among the five species (p < 0.05). L. sibirica and U. pumila showed considerably lower E than other species. Thus, WUE values of coniferous species such as L. sibirica and P. sylvestris were significantly greater than deciduous or shrub species such as U. pumila, C. arborescens and H. rhamnoides (p < 0.01). It may result that conifers showed relatively high water use efficiency than deciduous or shrub trees due to their lower transpiration rates, which resulted in morphological and physiological characteristics of their leaves. This may indicate that L. sibirica and P. sylvestris can be widely used for rehabilitation works in Mongolia attributed to their dominant distributions but also their high drought-resistance properties.