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Volume 60, Issue 1
March
Displaying 1-7 of 7 articles from this issue
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Full Papers
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Atsushi MARUYAMA, Kazuhiko OHBA, Yoshitaka KUROSE, Teruhito MIYAMOTO2004 Volume 60 Issue 1 Pages 1-15
Published: 2004
Released on J-STAGE: January 13, 2006
JOURNAL FREE ACCESSEvapotranspiration from mat rush (Juncus effusus L.) was observed using the Bowen ratio method based on heat balance in a commercial paddy field located on the Yatsushiro Plain (32° 33.9′N, 130° 38.4′E, 1 m above sea level). Observations were conducted from transplanting (December) to harvest (July) in 1999/2000 (2000 season) and 2000/2001 (2001 season). Seasonal variation of evapotranspiration (E) showed an increasing trend with air temperature and solar radiation. Average and total values of E during the entire growth period in the 2000 and 2001 seasons were 2.02, 2.16 mm day-1 and 491, 499 mm, respectively. Daily mean values of E were compared with the reference crop evapotranspiration (E0) and potential evaporation (EP). Seasonal variations of E/E0 showed an increasing trend from 0.46 to 1.00 during the growth of mat rush. Similarly, E/EP showed an increasing trend from 0.42 to 0.84 during the growth of mat rush. E/E0 and E/EP of mat rush could be expressed as a function of plant area index (PAI). Root mean square error (RMSE) of estimating E using the function was 0.5 mm day-1 on a 1-day scale, 0.2 mm day-1 on a 5-day scale and 0.1 mm day-1 on a 10-day scale. Variations in E/E0 and E/EP were conjectured to be also influenced by soil moisture, wind speed and saturation deficit as the result of change in transpiration from mat rush. However, it was difficult to explain the difference in E/E0 and E/EP that was found between 2000 and 2001 seasons, based only on the difference in environmental factors described above. It was suggested that the difference in the physiological activity of the mat rush, which was indicated by differences in stem color between 2000 and 2001 seasons, affected the E/E0 and E/EP.View full abstractDownload PDF (954K)
Short Papers
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Yuping LEI, Hidenori TAKAHASHI, Weiqiang LI2004 Volume 60 Issue 1 Pages 17-23
Published: 2004
Released on J-STAGE: January 13, 2006
JOURNAL FREE ACCESSAlthough concrete mulch hasn't been used widely for agriculture, it is advantageous for conserving soil water because concrete forms a surface without gaps and can limit evaporation and retain water. A jujube (Ziziphus jujube Mill.) field experiment and a lysimeter-plot experiment were carried out in this study to evaluate the hydrothermal properties of concrete mulch by comparing the differences in surface energy balance, surface temperature and soil moisture and temperature between the mulched and bare soils. The rate of evaporation from the mulched lysimeter-plot was about 0.04 mm per day, whereas it was 1.74 mm from the bare lysimeter-plot in September. During the freezing/thawing period (December to February), the soil moisture in the surface 10 cm layer increased by 0.030 g g-1 in the mulched jujube plot, whereas it decreased by 0.032 g g-1 in the bare jujube plot. Daytime net radiation at the concrete surface was lower than that at the bare soil surface; however, the heat flux into mulch layer was higher than into bare soil when bare soil moisture was rather high. The surface temperature of concrete mulch rose as high as 57°C and was about 10°C higher than that of bare soil in summer, but it was moderate under a tree canopy. The mulched soil temperatures at 5 and 10 cm depth were higher by about 2°C than those for bare soil during the night in summer and winter.View full abstractDownload PDF (621K)
Full Papers (in Japanese)
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Masahito UEYAMA, Ryuichi TOSA, Tatsuki DOKE, Ken HAMOTANI, Nobutaka MO ...2004 Volume 60 Issue 1 Pages 25-32
Published: 2004
Released on J-STAGE: January 13, 2006
JOURNAL FREE ACCESSSimilarity law is tested over a forest in a complex terrain. For the wind from the valley zero-plane displacement showed reasonable value, about 0.7 of the canopy height. However, for the wind from the ridge, it sometimes became negative. The non-dimensional profiles of wind speed and temperature for the wind from the valley indicated a similar shape as observed over flat terrains; however, for the wind from the ridge it did not obey the law.
Wind profiles inside the canopy showed a secondary peak near the forest floor for the wind from the ridge, but this peak was not clear when wind was from the valley. These characteristics including the variance of the turbulence are examined by using the 2nd-order turbulence closure model for the horizontally homogeneous field. The results indicate that the flow from the valley in this terrain is similar to that for homogenous flat forests.View full abstractDownload PDF (1132K) -
Eui-Nyun CHOI, Yoshio INOUE2004 Volume 60 Issue 1 Pages 33-41
Published: 2004
Released on J-STAGE: January 13, 2006
JOURNAL FREE ACCESSThis study investigated the potential of thermal remote sensing for estimating ecosystem surface CO2 flux. Ecosystem surface CO2 flux was measured by the eddy covariance method for more than three years, in conjunction with thermal and optical remote sensing measurements as well as micrometeorological, soil, and plant measurements. The soil was Andisol (Hydric Hapludands), a humic volcanic ash soil, which is the major cultivated soil for upland crops in Japan. The soil surface CO2 flux under bare soil conditions was best correlated with the remotely sensed surface temperature, while air temperature was less well correlated and soil temperature and soil water content were poorly correlated. The relationship was well expressed by an exponential Q10 function (r2=0.70, RMSE=0.095). The value of Q10 and the threshold temperature at which the CO2 flux approached zero were estimated to be 1.31 and 10.0°C, respectively. Results suggested that the soil surface temperature had the dominant effect on the microbial respiration as well as on the physical processes determining the CO2 gas transfer at the soil-atmosphere interface. Remotely sensed surface temperature will provide useful information for investigation of CO2 transfer processes near the soil surface, as well as for quantitative assessment of ecosystem surface CO2 flux.View full abstractDownload PDF (3394K) -
—A Simple Method for Remote Sensing of Canopy Transpiration—Eui-Nyun CHOI, Yoshio INOUE2004 Volume 60 Issue 1 Pages 43-53
Published: 2004
Released on J-STAGE: January 13, 2006
JOURNAL FREE ACCESSThe study investigated diurnal and seasonal dynamics of evapotranspiration (ET) and transpiration (Tr) in a soybean canopy, as well as the relationships among ET, Tr, solar radiation and remotely sensed spectral reflectance. The eddy covariance method (ECM) and stem heat balance method (SHBM) were used for independent measurement of ET and Tr, respectively. Micrometeorological, soil, and spectral reflectance data were acquired for the entire growing season. The in-stantaneous values of canopy-Tr estimated by SHBM and ET by ECM were well synchronized with each other, and both were strongly affected by the solar radiation. The daily values canopy-Tr increased rapidly with increasing leaf area index (LAI), and got closer to the ET even at a low value of LAI such as 1.5—2. The daily values of ET were moderately correlated with global solar radiation (Rs), and more closely with the potential evapotranspiration (ETp) estimated by the “radiation method.” This fact supported the effectiveness of the simple radiation method in estimation of evapotranspiration. The ratio of Tr/ET as well as the ratio of ground heat flux (G) to Rs (G/Rs) was closely related to LAI, and LAI was a key variable in determining the energy partitioning to soil and vegetation. It was clearly shown that a remotely sensed vegetation index such as SAVI (soil adjusted vegetation index) was effective for estimating LAI, and further useful for directly estimating energy partitioning to soil and vegetation. The G and Tr/ET were both well estimated by the vegetation index. It was concluded that the combination of a simple radiation method with remotely sensed information can provide useful information on energy partitioning and Tr/ET in vegetation canopies.View full abstractDownload PDF (2530K) -
—Determination of Parameters in the Three-Layered Soil Model and Experimental Result of Model Calculation—Reiji KIMURA, Naru TAKAYAMA, Makio KAMICHIKA, Nobuhiro MATSUOKA2004 Volume 60 Issue 1 Pages 55-65
Published: 2004
Released on J-STAGE: January 13, 2006
JOURNAL FREE ACCESSParameters used for a three-layered soil model are determined for the purpose of understanding the soil water content and heat balance on the Loess Plateau, China. The soil types on the Loess Plateau are divided into heavy loam, medium loam, light loam, sandy loam and sand. The soil water potential and the surface albedo are parameterized as the function of soil water content. The diffusion distance of water vapor that decides the evaporation efficiency can be simulated by using the saturated volumetric soil water content, field capacity of soil water content, wilting point and maximum value of the diffusion distance, even if the soil types are different.
The model calculation is verified by comparing the observed results. The calculated results of the soil water content and evaporation coincide with the values observed by gravimetric sampling and lysimeter. According to the results observed by the column experiment, the model calculation represents the qualitative difference of evaporation due to the soil texture.
Seasonal variation of the soil water content is simulated by using the actual meteorological data for the Loess Plateau. The soil on the Loess Plateau was generally superior from the viewpoint of the maintenance ability of moisture. It is found that the fractional extractable water calculated by the soil water content can be an index to classify the present state of vegetation cover such as forest, shrub, grassland or desert.View full abstractDownload PDF (1678K) -
Ryoji SAMESHIMA2004 Volume 60 Issue 1 Pages 67-75
Published: 2004
Released on J-STAGE: January 13, 2006
JOURNAL FREE ACCESSWater temperature (Tw) is known to have an effect on the developmental rate (DVR) of paddy rice. However, Tw is not employed as input data in most developmental models. Moreover, DVR is often modeled as a function of air temperature (Ta) alone for northern Japan. The purpose of this study is to determine the reason why accurate prediction using models without consideration of Tw is possible and to determine whether the models are valid even for cool years.
The results of the first experiment showed that soil temperature (Ts) affects DVR (Ts at a depth of 1 cm was measured instead of Tw in this study). In the second experiment, pot containers with equally raised rice seedlings were buried in nine paddy fields in the three prefectures of Aomori, Iwate and Miyagi. Rice growth, Ta and Ts in all of the fields were monitored. The following results were obtained.
(1) A correlation exists between Ta and Ts.
(2) Parameters for the five developmental models were determined. Accuracy of the simple EAAT-model, in which only air temperature is employed, is as good as that of other models. This is because the correlation between Ta and Ts is incorporated in the EAAT-model and Ts is implicitly estimated from Ta.
(3) The correlations between Ta and Ts in cool years with short periods of sunshine and in other years are not the same. This difference caused larger error in prediction in cool years such as 1993.
In conclusion, the EAAT-model can be used for northern Japan for years with normal weather conditions but not cool years with short periods of sunshine. Some method for adjusting the prediction by an existing model should be developed.View full abstractDownload PDF (1125K)
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