Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MAIK NAUKA/INTERPERIODICA/SPRINGER  

Soil physical properties and hydrological processes were analyzed in two experimental catchments with different forest types: one catchment is covered mostly with conifer type trees and the other catchment is covered with conifer and broad leaf trees. To analyze the effects of forest type on soil physical properties, we applied an hourly time step lumped conceptual model, which includes a physically-based infiltration sub-model and an evapotranspiration sub-model, to simulate long term discharge. The estimated model parameters and some measured soil characteristics were compared for the two catchments to reveal the differences in soil physical properties. The differences in hydrological processes were compared through observed hydrological factors (rainfall, discharge and meteorological data) between the two catchments.

DOI： 10.1134/S0097807816120034

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER WIEN  

The determination of evaporation and transpiration separately is very important in improving water use efficiency and developing exact irrigation scheduling. Hourly crop evapotranspiration (ET (c)) and soil evaporation (E (g)) beneath the buckwheat canopy were measured using Bowen ratio energy balance method and micro-lysimeters, respectively. The total ET (c) and E (g) in the whole growth season of buckwheat were 187.4 and 72.1 mm, respectively. Crop coefficient of buckwheat plant was simulated by days after sowing (DAS) and leaf area index (LAI), the average values for four growth stages were 0.58, 0.59, 1.10, and 0.74; and soil evaporation coefficient (the ratio of soil evaporation to reference evapotranspiration) was modeled by soil water content at 5-cm depth by dividing the LAI into two stages. The relationship between the ratio of soil evaporation to actual evapotranspiration (E (g)/ET (c)) and LAI was decided. It was found that E (g)/ET (c) decreased from 1 to 0.3 with the increase in LAI.

DOI： 10.1007/s00704-014-1325-6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER WIEN  

This study presents models for predicting hourly canopy resistance (r (c)) and evapotranspiration (ETc) based on Penman-Monteith approach. The micrometeorological data and ET (c) were observed during maize and buckwheat growing seasons in 2006 and 2009 in China and Japan, respectively. The proposed models of r (c) were developed by a climatic resistance (r (*)) that depends on climatic variables. Non-linear relationships between r (c) and r (*) were applied. The measured ETc using Bowen ratio energy balance method was applied for model validation. The statistical analysis showed that there were no significant differences between predicted ETc by proposed models and measured ETc for both maize and buckwheat crops. The model for predicting ETc at maize field showed better performance than predicting ETc at buckwheat field, the coefficients of determination were 0.92 and 0.84, respectively. The study provided an easy way for the application of Penman-Monteith equation with only general available meteorological database.

DOI： 10.1007/s00703-015-0369-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOC AGRICULTURAL METEOROLOGY JAPAN  

This paper evaluated the applicability of four AAR (areal average rainfall) estimation methods in the mountainous Kamo River watershed by using measured monthly rainfall at nine stations within and near this watershed between 1998 and 2010. The four methods were (i) the arithmetic mean, (ii) the Thiessen polygon, (iii) the elevation regression and (iv) the combination of (ii) and (iii). Method (iv) was newly developed in this study. For methods (iii) and (iv), linear monthly relationship between elevation and monthly rainfall was applied and it was evaluated as useful for predicting rainfall even at a high elevation.
Firstly, the applicability of the four AAR methods was evaluated by relationships between annual AAR (=P) and annual evapotranspiration ratio (Et/Ep). Annual evapotranspiration (Et) was obtained using the water balance equation by incorporating each AAR and measured discharge, and Ep was calculated using Penman equation. The low Et/Ep by methods (i) and (ii) was caused by the underestimation of AAR, which resulted in the underestimation of Et, mainly because these methods did not include the effect of larger rainfall in the higher elevation area. Methods (iii) and (iv) produced Et/Ep reasonably and demonstrated closer relationship to that in another mountainous watershed.
Secondly, the applicability was evaluated by examining relationships between annual Ep/P and annual Et/P with a rational method of Fu (1981), where the watershed parameter w was optimized for each method. Methods (i) and (ii) produced relatively low w as a value of a mountainous watershed, which would be caused by the underestimation of annual AAR. Method (iii) produced relatively high w as a value of a mountainous watershed and R-2 was relatively low. As a result, the newly presented combination method (iv) was determined to be most applicable for AAR method in this mountainous watershed.

DOI： 10.2480/agrmet.D-14-00055

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Language：Chinese   Publishing type：Research paper (scientific journal)   Publisher：Chinese Society of Agricultural Engineering  

Soil evaporation consumes a large part of evapotranspiration during the crop growth season, especially during the seedling or sparse crop growth stage. It has been reported that soil evaporation makes little contribution to crop yield, and thus it has been seen as invalid water consumption. Separate determination of soil evaporation and transpiration is required in many irrigation management programs or yield analysis models. However, it is quite difficult to directly measure soil evaporation and transpiration separately. To achieve this purpose, a soil evaporation model was developed using a new defined soil moisture function based on the actual measurement of meteorological data (air temperature, relative humidity, and wind speed), soil surface moisture and soil evaporation data. The model combined two processes of water vapor transfer: one is the vapor transport in air while the other is molecular diffusion of vapor in the surface soil pore with the vapor being carried from the interior soil pore to the land surface. For the field observation, air temperature and relative humidity were measured in three different heights above the buckwheat canopy in order to determine the actual evapotranspiration with Bowen ratio energy balance method. Leaf area index and plant height was measured regularly, with the maximum values of 2.25 and 62.7 cm, respectively. The variation of surface soil water content (5 cm) was from 11.2% to 30.9%. An important parameter, surface moisture availability, in the proposed model was decided by surface soil moisture and wind speed. It was shown that surface soil water content was the main factor affecting surface moisture availability, and wind speed had slight influence on it. The modeled surface moisture availability with soil content and constant wind speed was compared to calculated value with varied wind speed. By assuming surface moisture availability to be 1 in the model, another important parameter, bulk transfer coefficient, could be calculated. It has been reported that the bulk transfer coefficient for bare field is mainly influenced by soil texture and atmospheric stability. In this study, average value of bulk transfer coefficient was applied for three different leaf area stages based on the analysis of its actual variation. Actual evapotranspiration and soil evaporation beneath the buckwheat canopy respectively measured by Bowen ratio energy balance method and micro-lysimeter were compared and the soil evaporation measured by micro-lysimeter was applied to validate the accuracy of the model. It was shown that the soil evaporation beneath the buckwheat canopy during seedling stage was quite close to actual evapotranspiration measured by Bowen ratio energy balance. The average hourly soil evaporation measured by Bowen ratio energy balance and micro-lysimeter were 0.16 and 0.17 mm, respectively
while the average relative error between two methods was 12%, root mean square error was 0.077, and correlation coefficient was 0.89. It was also shown that the soil evaporation beneath the buckwheat canopy could be reproduced using the constructed surface moisture availability model with average relative error of 13.5%, root mean square error of 0.249, and correlation coefficient of 0.95. The study is very important in separately estimating soil surface evaporation beneath the canopy and crop transpiration, and in decreasing invalid water consumption through soil surface beneath the canopy.

DOI： 10.3969/j.issn.1002-6819.2015.02.015

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Penerbit UTM Press  

Several studies have suggested the spikelet fertility would be significantly damaged if the air temperature (Ta) was high at heading and flowering stage. In this study, we evaluated the effect of water ponding in two paddy fields to decrease leaf temperature (Tl) and panicle temperature (Tp) during the 2014 growing season. Within the first conventionally water managed paddy field (cultivar Akitakomachi), we set 1 m × 1 m experiment plot (Plot A1) from July 8th to August 24th, and water was put in 15 cm depth in the morning at 8:30. For expecting larger difference of leaf and panicle temperature between in and outside the plot, the plot was expended to 2 m × 2 m (Plot A2) from August 25th to September 8th, 2014, and water was put in 15 cm depth at noon. This method was also used in the plot B (2 m ×2 m) which was installed in another conventionally water managed field (cultivar Nikomaru) from September 9th to 30th, 2014. Tl and Tp were measured every two or three hours during daytime in every 10 cm canopy layer in and outside plots. In the first experimental paddy field, at largest, Tl and Tp in the plot were 4.3 °c, 5.5 °c lower than Tl and Tp outside the plot, respectively. Tp was 6.6 °c lower than Ta under low relative humidity condition. In the second experimental paddy field, Tl and Tp in the plot were 3.6 °c, 3.4 °c lower than Tl and Tp outside the plot, respectively. It revealed water ponding was a useful method to decrease leaf and panicle temperature under larger solar radiation, higher air temperature and lower relative humidity conditions at heading and flowering stage.

DOI： 10.11113/jt.v76.5965

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Understanding the effects of land use change on the hydrological cycle is very important for development of sustainable water resource in an upland field catchment. In this study, soil and hydrological properties in an upland field catchment, which was reclaimed partially from a forest catchment, were compared with another forest catchment. The soil properties of surface and subsurface layers were investigated in the two catchments. The soil was compacted and waterholding capacity of soil in the upland field catchment became smaller after the reclamation from forest to upland field, which decreased infiltration rate and water storage in the soil layers.We found that peak discharge and direct runoff in the upland field catchment increased compared with the forest catchment. Annual evapotranspiration from the upland field catchment tended to be lower due to the change in vegetation type and soil properties. Furthermore, a semi-distributed hydrological model was applied in the upland field catchment to understand the integrated effects of reclamation on the hydrological cycle. The model parameters, which were determined using a nonlinear optimization technique-the Shuffled Complex Evolution method (SCE), were compared between the two catchments. The Nash and Sutcliffe coefficient was used to evaluate the model performance. The simulated results indicated that evapotranspiration was decreased and change in discharge was more obvious in the surface layer. We considered that declined infiltration and water storage and increased peak discharge and direct runoff have a negative impact on water resources in the upland field catchment. This study will provide information for forest managers in planning and making decisions for land and water resource management. © Higher Education Press and Springer-Verlag Berlin Heidelberg 2013.

DOI： 10.1007/s11709-013-0218-6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER WIEN  

In this paper, three methods for estimating soil evaporation in a bare field were evaluated: evaporation ratio method (k ratio), complementary relationship and bulk equation. Micro-lysimeters were used to measure the actual evaporation for validation of the three methods. For the k ratio method, pan evaporation was used as the reference evaporation instead of the value obtained from the Penman-Monteith equation. This result is important for areas where meteorological data are unavailable. The results showed that, for daytime evaporation, the k ratio and bulk equation produced a good fit with the observation data, while the complementary relationship generated a larger deviation from the measured data. We recommend that the k ratio method and bulk equation could be used to calculate daytime soil evaporation with high accuracy when soil water content and pan evaporation data or meteorological data are available, while the complementary relationship could be used for a rough estimation when pan evaporation is available. All the methods could be applied to calculate cumulative evaporation.

DOI： 10.1007/s00703-012-0213-9

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

The energy flux on the ground surface depends not only on climatological and biophysical controls in the vegetative canopy, but also on the available energy and energy partitioning beneath the canopy. Quantifying the evaporation and energy partitioning beneath the canopy is very important for improving water and energy utilization, especially in arid areas. In this study, we measured meteorological data, the net radiation and latent heat flux beneath the rice canopy, and then applied the radiation and energy balance equations to get the water surface temperature beneath the rice canopy. To apply the equations, we constructed shortwave and longwave radiation beneath the canopy sub-models and a bulk transfer coefficient sub-model. A plant inclination factor was parameterized with plant area index for the shortwave and longwave radiation sub-models. Bulk transfer coefficient was parameterized by plant area index and soil heat flux was predicted by the force restore model. With calculated water surface temperature and constructed sub-models, we reproduced net radiation and latent heat flux beneath the rice canopy. As a result, the reproduced water surface temperature, net radiation, and latent heat flux beneath the rice canopy were very close to the measured values and no significant differences were found according to 2-tail t test statistical analysis. Therefore, we conclude that these constructed sub-models could successfully represent water surface temperature, net radiation, and latent heat flux beneath the rice canopy.

DOI： 10.1007/s10333-011-0273-3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Stomatal ozone flux and flux response relationships were derived for winter wheat (Triticum aestivum L.) grown under fully open-air ozone fumigation. A stomatal conductance (g(sto)) model developed for wheat in Europe was re-parameterized. Compared to European model parameterizations, the main changes were that the VPD and radiation response functions were made less and more restrictive, respectively, and that the temperature function was omitted. The re-parameterized g(sto) model performed well with an r(2) value of 0.76. The slope and intercept of the regression between observed and predicted g(sto) were not significantly different from 1 to 0, respectively. An ozone uptake threshold of 12 nmol m(-2) s(-1) was judged most reasonable for the wheat flux-response relationship in subtropical China. Judging from both flux- and concentration-based relationships, the cultivars investigated seem to be more sensitive to ozone than European cultivars. The new flux-response relationship can be applied to ozone risk assessment in subtropical regions. (C) 2012 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.envpol.2012.01.014

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To predict the yield losses in winter wheat due to the elevated ozone concentration in eastern China, we tested the ozone dose response functions (O3 DRF), i.e. the relationship between the accumulated stomatal ozone flux above a threshold of 6 nmol m-2 s-1 (AFst6) and the relative grain yield (RY), via observations of three cultivars of winter wheat in a FACE-Ozone (free-air concentration enrichment with ozone) experiment. We also presented a new O3 DRF based on the new ozone dose using the FACE-Ozone results. The AFst6 was calculated by applying the flag leaf stomatal conductance model of each cultivar developed in this study. The observed RY fell below the linear O3 DRF: ‘RY (%)=100-4.8 AFst6’, which has been derived in Europe and widely used (Pleijel et al, 2000
2007), at higher AFst6. This deviation was due to the synergetic effect of the accelerated drop in photosynthesis and the decelerated increase of AFst6 caused by the stomatal closure at a higher ozone dose. We therefore presented a curvilinear O3 DRF: ‘RY (%)=100-k (AFst6)l’ for the wheat cultivars in the FACE-Ozone experiment. We also explored the applicability of the relative net primary productivity (NPP) of the flag leaf canopy (RNPPc) as a better ozone dose than AFst6. The NPP of the flag leaf was calculated by applying the flag leaf photosynthesis model developed in this study for each cultivar. The relationship between RNPPc and RY of the three cultivars showed good correlation, suggesting that RNPPc could be used as O3 DRF to predict RY or the yield loss due to the increased ozone concentration. © 2011, The Society of Agricultural Meteorology of Japan. All rights reserved.

DOI： 10.2480/agrmet.67.1.2

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In order to quantify evaportranspiration and separate it into evaporation and transpiration, the two-layer model was applied. The aerodynamic and rice canopy resistance were estimated based on the two-layer model with measured meteorological data, water surface evaporation beneath the rice canopy and transpiration from the canopy measured by lysimeters. The aerodynamic resistances included aerodynamic resistance between the rice canopy and the air (rac), aerodynamic resistance between the water surface beneath the rice canopy and the air (rag), and the total aerodynamic resistance (ra). It was found that the aerodynamic resistances decreased with the increase in wind speed, while they increased with the increase in plant height. The relationships between these aerodynamic resistances and the wind speed above the canopy were individually parameterized by plant height. The rice canopy resistance (rc) was mainly influenced by the global solar radiation (SR) and the vapor pressure deficit of the air (VPD). The rcdecreased with the increase in SR, while it increased with the increase in the VPD. The rcmodel was developed by a hyperbolic function with SR for the three growing stages and the model parameter was decided by the VPD. By incorporating these resistance sub-models into the two-layer model, evaporation from the water surface beneath the canopy and transpiration by the rice canopy were reproduced successfully. © 2011, The Society of Agricultural Meteorology of Japan. All rights reserved.

DOI： 10.2480/agrmet.67.3.1

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In aims to estimate stomatal O3 flux and predict the yield loss of wheat in eastern China, the focus was on developing a stomatal conductance (gs) model and a photosynthesis (P) model of a wheat flag leaf. To date, relationships between the relative yield of European spring wheat and the stomatal O3 flux of the wheat flag leaf have been presented by Pleijel et al. (2000), UNECE (2004) and many researchers with high correlations on the basis of the open-top chamber experiments. The gs and P of flag leaves and other winter wheat leaves were measured, both in the ambient field and FACE (Free Air Concentration Enrichment) field, whereby the O3 concentration ([O3]) was artificially elevated, on 6 days from before heading to before harvest, 2008. The gs model was developed by a multiplicative approach with a maximum value of gs (gsmax) multiplied by modifications of photo-synthetically active radiation incident on the leaf (PARi), accumulated exposure of O3 over a threshold concentration of 40 ppb for daylight hours (AOT40) at the canopy top, phenology, VPD and the time of day. A relationship between gs/gsmax and P/Pmax (Pmax is the maximum value of P) of a flag leaf measured in PARi=2000μmol m-2 s-1 was represented by a linear regression line with a slope of 1.0 and intercept of 0.0. Therefore, the P model was developed by the multiplicative approach with Pmax multiplied by modifications of PARi for P and the same other parameters as the gs model. The models reproduced the gs and P of a flag leaf and even those of the other leaves successfully. For the practical use of these models, [O3]at the canopy top ([O3]canopy) and PARi were also modeled. By applying the logarithmic profile of [O3] above the canopy, and modeling the roughness length for [O3] (Z0O3) with the wind speed, the [O3]canopy was reproduced successfully. To model PARi, the inclination factor of a leaf (Fi) was decided so that the modeled vertical profile of shortwave radiation within the canopy could fit the measurements using the vertical two streams shortwave radiation model (e.g. Oue, 2003a
2003b). Fi at z=0.6-0.8 m, where most flag leaves exist, was found to be from 0.4 to 0.6 for a wheat canopy of LAI= 5. © 2009, The Society of Agricultural Meteorology of Japan. All rights reserved.

DOI： 10.2480/agrmet.65.3.7

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The Penman-Monteith (PM) equation for evapotranspiration (ET) estimation has been applied in the world. Its weak point is the estimation of the canopy resistance. This paper proposed a simple canopy resistance model for estimating ET on an hourly basis. A non-linear functional relationship between canopy resistance, aerodynamic resistance, and climatic resistance was proposed. For model validation, data was collected in an irrigated wheat field in the Hetao Irrigation District, which is the largest one along the Yellow River. Surface energy balance and near-surface weather variables were measured during the growth cycle of wheat. Measured hourly ET values were obtained by the Bowen ratio energy balance method. Regression of predicted versus measured ET data resulted in r2=0.97 with slope of 0.98 and intercept of 0.01 which are not different from 1 and 0 at 99% confidence. This study provided a simple way to estimate ET with a general available meteorological database which can be further applied in hydrologic models considering effects of variable canopy resistance. © 2009, The Society of Agricultural Meteorology of Japan. All rights reserved.

DOI： 10.2480/agrmet.65.1.10

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The stomatal conductance (gs) of rice leaves in vertical canopy layers was measured in both the ambient and FACE fields, where the concentration of ozone ([O3]) was elevated artificially, during the heading and flowering stages, 2007. The gs sub-model of rice was developed by a multiplicative approach with modifications of PAR, VPD, AOT40 and [O3], while the multi-layer model of the O3 uptake process in the rice canopy was developed by incorporating the gs sub-model. By the proposed model, vertical profiles of O3 fluxes on a single leaf (FO3) and in each canopy layer were calculated in the conditions 46.0, 40.2 and 43.6 ppb of [O3] at z=280 cm at 1030, 1200 and 1530 h on August 30. O3 uptake by a single leaf (-FO3) in the upper canopy layer peaked at 1530 h and was smallest at 1200 h. The smallest -FO3 at 1200 h was caused not only by the lowest [O3] but also smaller gs, while the smaller gs at 1200 h was caused by smaller PAR on the flag leaf, even under the largest global solar radiation (SR) condition, because the leaf stands erect. The estimated O3 uptakes in the paddy field were 14.9, 13.7 and 12.1 (nmol m-2 s-1) at 1030, 1200 and 1530 h, respectively. The predicted FO3 under different [O3] conditions by the model revealed that FO3 would exceed the threshold of -6 nmol m-2 s-1 in more than 60 ppb [O3] at 1030 and 1200 h and in more than 50 ppb at 1530 h. The predicted FO3 under different SR conditions with fixed [O3] of 80 ppb revealed that FO3 would reach the threshold in more than 400 W m-2 of SR at 1030 and 1200 h and more than 200 W m-2 at 1530 h under this relatively high [O3] condition. © 2008, The Society of Agricultural Meteorology of Japan. All rights reserved.

DOI： 10.2480/agrmet.64.4.8

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DOI： 10.3178/jjshwr.20.8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Changes in crop water use due to elevated CO, concentration ([CO2]) must be evaluated for predicting agricultural productivity and water resource availability. We quantified the effects of elevated [CO2] on the energy balance and canopy evapotranspiration (ET) in rice paddies. Rice (Oryza sativa L.) was grown under both ambient [CO2] (A-CO2) and elevated [CO2] (E-CO2) imposed by free-air CO2 enrichment (FACE) in northern Japan. Observations were made of micrometeorology and plant characteristics, including stomatal conductance and leaf area index (LAI). We estimated energy balances using a double-source model with heat transfers from the vegetation canopy and the water surface to avoid errors due to uncertainty in the measured radiative infrared (IR) temperatures. E-CO, reduced stomatal conductance by 13% in upper leaves and by 40% in lower leaves at the particle initiation stage, but the reduction rates subsequently decreased. Stomata closed more in the E-CO, plot as vapour pressure deficit increased. Daily mean temperature of the vegetation canopy increased by 0.2-1 degrees C in response to stomatal closure under E-CO2, whereas water surface temperature decreased by 1 degrees C before rice heading because of increased shading from the larger leaves in E-CO2. The radiative IR temperature decreased by up to 1 degrees C in E-CO, before June, and increased by up to 0.6 degrees C thereafter. Latent heat flux decreased in E-CO,, which was balanced by increased sensible heat flux and upward long-wave radiation. The decrease was greatest under dry and windy conditions. Total water use by plants throughout the growing season was 268.7 mm in A-CO2 and 246.8 rum in E-CO2, giving a saving of 22 mm of water in E-CO2. Reduced transpiration (by 8.2%), combined with increased total biomass (by 9.1%), increased water use efficiency in E-CO2 by 19%. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.agrformet.2005.09.010

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JOHN WILEY & SONS LTD  

Observations made in a paddy field were analysed to show the influences of meteorological and vegetational factors on the crop's energy budget. Energy budget in the paddy field was characterized by the major partitioning to latent heat flux LE and by the negative Bowen ratio B mostly in the afternoon. Canopy resistance r(c), estimated with the Penman-Monteith equation, was related to the influences of solar radiation SR, vapour pressure deficit VPD and plant height. The results demonstrated that r(c) could not directly account for B but that critical canopy resistance r(cc), defined as the canopy resistance when B = 0, could be used to standardize r(c), and that r(c) - r(c), proved to be a good parameter to account for B. Influences of bulk stomatal response on energy partitioning were assessed as follows: the Bowen ratio dropped below zero, while the bulk stomatal aperture dwindled with the increase of VPD. In addition, stomata of a big leaf acted to promote the partitioning to LE against the rise of SR in the condition of higher VPD. Copyright (c) 2005 John Wiley & Sons, Ltd.

DOI： 10.1002/hyp.5589

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：FERDINAND BERGER SOEHNE  

The elevated CO2 concentration in the atmosphere could induce global warming and physiological changes in plants, e.g. stomatal closure. Through FACE (Free Air CO2 Enrichment) experiments in a paddy field, it has been confirmed that CO2-induced stomatal closure decreases transpiration, which causes a rise of leaf temperature (T-l). Thus, with elevated CO2, the probability of heat-induced spikelet sterility (HISS) of rice could increase. The objectives of this study were as follows: (1) Measure differences in stomatal conductance (g(s)), particle transpiration conductance (g(p)), T-l, and particle temperature (T-p) of rice plants between FACE plots (E-CO2) and ambient plots (A-CO2) at Wuxi, China (31 degrees 37' N, 120 degrees 28' E) at heading and flowering stages. (2) Model the heat balance on a panicle surface. (3) Simulate T-p and clarify the impacts of FACE on T-p using the model. Panicles emerged and flowered about 4 days earlier in E-CO2 than in A-CO2. The measured T-p was 1 - 2 degrees C higher in E-CO2 than in A-CO2, which was equivalent to or even higher than the difference in T-l between in the two plots. The g(p) decreased with panicle age after heading, while g(s) increased asymptotically with the increase of photosynthetically active radiation. But, under both CO2 conditions, g(p), was not significantly different for the same days after heading. By modelling heat balance on a panicle surface and by simulating T-p, influences of elevated CO2 on T-p were quantified. First, lower g(p) due to older age after flowering. Second, higher air temperature (T-a) followed by higher T-l. Third, higher long wave radiation emitted from leaves (L-l). The effects of T-a and g(p) on T-p were significant but the effect of g(p) on T-p was not significant. On the same number of days after heading, the net effect of g(p) on T-p would be almost zero. Therefore, raised T-a would be a critical factor for the increase in T-p.

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DOI： 10.3178/jjshwr.17.274

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Language：Japanese   Publisher：THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES  

The multilayer micrometeorological model (Oue, 2001) is improved incorporating the stomatal conductance model and the single leaf photosynthesis model of rice developed in the previous paper (Oue, 2003) . One of the improvements is that energy balance of a plant body is solved for sunlit and shaded side. Simulation by the model can reproduce observed vertical profiles of transmissivity of solar radiation, horizontal wind speed, air temperature, vapor pressure and plant surface temperature successfully. Energy balance in the rice canopy is characterized by negative sensible heat flux from which additional latent heat flux originates in the afternoon. Simulation by the model demonstrates that sensible heat flux on the shaded leaf is negative in almost every case and thus the shaded leaf has an important role in energy balance in the paddy field. Water use efficiency in each canopy layer (WUE<SUB><I>c</I></SUB>) is lower in case that incident solar radiation on a leaf surface is large or small enough, which predicts that WUE<SUB><I>c</I></SUB> is lower in a canopy of small or large leaf area density and that an optimum leaf area density exists for maximum WUE<SUB><I>c</I></SUB>.

DOI： 10.3178/jjshwr.16.389

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Language：Japanese   Publisher：THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES  

Through a series of the studies, targeting high water use efficiency from a viewpoint of effective use of water for crop production, optimum leaf area density obtaining the highest water use efficiency under given meteorological and soil water conditions will be discussed. In this paper, stomatal conductance (gs) model and single leaf photosynthesis (CER<SUB><I>l</I></SUB>) model of rice, which could be incorporated to a multilayer model (Oue, 2001), are developed by observed gs, CER<SUB><I>l</I></SUB>, crop growth and micrometeorological data within a rice canopy. Analysis of observed data reveal that other than photosynthetically active radiation on the leaf (PAR<SUB><I>l</I></SUB>), height of the leaf (<I>z</I>) and VPD at <I>z</I> are very important for parametrizing gs and that PAR<SUB><I>l</I></SUB> and gs of the leaf are very important for parametrizing CER<SUB><I>l</I></SUB>. Height and VPD are effective parameters for gs because they made a reverse impact on gs each other. The gs model developed is very suitable for incorporating to a multilayer model because it predicts gs of a leaf in every layer in response to micrometeorological condition in the layer. The CER<SUB><I>l</I></SUB> model is very suitable to reproduce the photosynthetic processes and water use efficiency in the multilayer model because it predicts CER<SUB><I>l</I></SUB> of a leaf in response to gs of the leaf and micrometeorological condition in the layer.

DOI： 10.3178/jjshwr.16.375

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DOI： 10.2151/jmsj.79.925

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Language：Japanese   Publisher：水資源・環境学会  

CiNii Books

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DOI： 10.3178/jjshwr.11.515

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Language：Japanese   Publisher：THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES  

An experimental study of estimating the bulk transfer coefficient and the surface moisture availability in the paddy field is presented. The results are as follows: (1) The bulk transfer coefficient of the paddy field as one layer that was estimated for every two or four hours fluctuated, while daily average value was close to that calculated by the multilayer model of Kondo & Watanabe. (2) The surface moisture availability of the paddy field as one layer was higher in the morning, lower in the afternoon and higher when it was cloudy or the humidity was higher, and inversely correlated to wind speed. The surface moisture availability of the rice canopy was lower than that of the one layer and the variational tendency was similar to that of the one layer. (3) The wet imitation leaf method was supposed to estimate well the ratio of the leaf transfer coefficient for latent heat and sensible heat because the leaf temperature was close to that of actual leaf. (4) The result of estimating the daily latent heat flux by one layer or two layers models showed no superiority because the surface moisture availabilities of both models changed hourly. For the application of each model, the variational tendency of the surface moisture availability should be studied further.

DOI： 10.3178/jjshwr.9.252

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DOI： 10.11408/jjsidre1965.64.10_1007

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DOI： 10.11408/jjsidre1965.63.2_143

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Language：Japanese   Publisher：愛媛大学農学部  

CiNii Books

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Publisher：THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES  

An experimental study of the microclimatic role of agricultural land use in the area of confused land use is presented. The observed results are as fallows: (1) Air temperature was lowest at the top of the densely vegetated rice canopy and the profile was reversed above the paddy in the afternoon on clear and relatively hot day. It was verified experimentally that the rice canopy acted as a sink of heat, which was effective about 140 cm above the canopy surface and more than 40 m downwind. (2) In the daytime on another clear day, the rice canopy acted not as a sink of heat but as a source of cool, affecting about 140 cm above the canopy surface and 10∼20 m downwind. (3) Advection effect was observed in the small agricultural lands.

DOI： 10.3178/jjshwr.7.2_130

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DOI： 10.11408/jjsidre1965.62.10_955

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DOI： 10.11408/jsidre1965.1993.164_97

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：INT ASSOC HYDROLOGICAL SCIENCES  

Web of Science

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DOI： 10.11408/jsidre1965.1992.161_45

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