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Volume 63, Issue 3
Displaying 1-4 of 4 articles from this issue
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Daisuke YASUTAKE, Tetsuo KOBAYASHI, Daichi IKEGAMI, Risa IWANAGA, Weiz ...2007 Volume 63 Issue 3 Pages 115-124
Published: 2007
Released on J-STAGE: January 11, 2008
JOURNAL FREE ACCESSCrop coefficients and water balance in an irrigated cornfield during the 2004 growing period (Apr. 27 to Oct. 12) in the upper Yellow River basin in Inner Mongolia, China, were analyzed using the dual crop coefficient approach recommended by the FAO, in which crop transpiration and soil evaporation were evaluated based on the crop coefficients and the reference evapotranspiration determined from meteorological conditions. During the initial stage when ground cover by corn plants was approximately less than 10%, the mean crop coefficient was 0.50 and soil evaporation accounted for 84% of evapotranspiration. In the crop development, mid-season and late season stages when most of the ground surface was covered with corn plants, the mean crop coefficients were 0.63, 1.18 and 0.99, respectively, and soil evaporation accounted for only 10-20% of evapotranspiration. During the entire growing period, cumulative crop transpiration and soil evaporation were 389.1 mm and 126.0 mm, respectively, and corresponded to 75.5% and 24.5% of the cumulative evapotranspiration estimated by this approach (515.1 mm), which almost equated with the measurement made by the Bowen ratio method (512.3 mm). Cumulative precipitation was 294.6 mm and about 150 mm of water was irrigated at the end of the crop development stage. These results suggest that approximately 30% of the rainwater and the irrigation water was lost by soil evaporation and about 70 mm of water was supplied to the root zone by capillary rise from the shallow water table (-1 m to -2 m).View full abstractDownload PDF (1070K)
Full Papers (in Japanese)
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Masayoshi MANO, Akira MIYATA, Yukio YASUDA, Hideyuki NAGAI, Tomoyasu Y ...2007 Volume 63 Issue 3 Pages 125-138
Published: 2007
Released on J-STAGE: January 11, 2008
JOURNAL FREE ACCESSAs the number of monitoring sites of carbon dioxide (CO2) and water vapor fluxes is increasing and long-term measurements of these fluxes are popularized, guidelines for practical procedures of quality control of measured flux data are needed to produce reliable datasets which are suitable for data analysis.
Several quality control tests for eddy covariance data have been proposed. To examine whether such tests are suitable for practical use, we applied three types of quality control tests to a two-year dataset obtained by the open-path eddy covariance method at a rice field. Raw data quality control tests detected time series inappropriate for flux calculations such as runs with rainfall or instrumental failure. Steady state tests detected two kinds of non-steady state runs. Monotonic trends were detected by the instationarity test, while intermediate changes of turbulence structure were detected by the nonstationarity test. Integral turbulence characteristic tests based on flux-variance similarity were useful for confirming whether turbulence was well developed or not. Results of these quality control tests, together with additional information on the length of recording time, wind direction relative to the sonic anemometer, and precipitation records were categorized into nine classes and combined for evaluation of the final data quality of the covariances. The final data quality was then evaluated as either discard, high quality, low quality, or normal quality. By visual inspection of the daily courses of CO2 fluxes, we confirmed that anomalies and unexpected covariances had been rightly judged to be discarded in the final data quality classification. Energy imbalance ratios also supported the evaluation of the final data quality as the average of the half-hourly energy imbalance ratios decreased with the increase of final data quality. We concluded that the quality control tests examined and the final data quality evaluation proposed in the present study provide a suitable guide to data quality and can be a useful tool for flux studies.View full abstractDownload PDF (2246K) -
Keisuke ONO, Ryuichi HIRATA, Masayoshi MANO, Akira MIYATA, Nobuko SAIG ...2007 Volume 63 Issue 3 Pages 139-155
Published: 2007
Released on J-STAGE: January 11, 2008
JOURNAL FREE ACCESSSince both open- and closed-path eddy covariance techniques have been used in ecosystem observation networks such as AsiaFlux, estimating the random and systematic differences in CO2 fluxes observed by the two techniques is important. In the present study, CO2 fluxes measured by open- and closed-path eddy covariance systems were compared using year-round data obtained in a single-cropping rice paddy and in a larch forest. The two sites were similar in eddy covariance instrumentation and data processing, but dissimilar in canopy height and structure, phenology, and climate. For both sites, differences in half-hourly CO2 fluxes measured by the open- and closed-path systems followed a Laplace distribution, but were significantly biased, resulting in the open-path system measuring lower values than the closed-path system and in a larger carbon sequestration by vegetation being estimated with the open-path system. The systematic difference between the two systems mainly arose from an inconsistency between the open-path CO2 flux and the WPL correction for the effect of air density fluctuations, and increased with the magnitude of the WPL correction. During the growing season, the systematic difference at the paddy site was consistently smaller than that at the larch site because of the much low Bowen ratio and the resulting small WPL correction term caused by standing water in the paddy field. The WPL correction term was large and thus, the systematic difference became apparent in late winter because of the high Bowen ratios at the paddy and larch site, each covered with dried soil and snowpack, respectively. The year-round, half-hourly data accumulated after quality control tests showed that, between the two systems, relative differences existed of 9.9% (N=6074) for the paddy site and 15.8% (N=4591) for the larch site.View full abstractDownload PDF (1321K) -
Teruhiko SUGIMURA, Masaru WAKISAKA, Junichi IMAGAWA2007 Volume 63 Issue 3 Pages 157-164
Published: 2007
Released on J-STAGE: January 11, 2008
JOURNAL FREE ACCESSThis study investigated forcing conditions for promoting bud bursting in the forced culture of the ‘Tonewase’ persimmon. Bud burst occurred earlier with the advance of the forcing starts when cuttings, with the Development Index (DVI) for endodormancy breaking of ‘Tonewase’ persimmon greater than 0.60, were forced at 18°C or 24°C. Furthermore, bud burst occurred earlier with the advance of forcing starts when cuttings, with the DVI were greater than 0.91, were forced at 11°C or 15°C. Pre-heating to 5°C or 8°C, most effective temperatures for endodormancy breaking before forcing at 15°C, similarly promoted bud burst of cuttings. The bud burst rate of cuttings was examined using pre-heating at 8°C for 9-40 days before 15°C forcing between 13 December and 12 January from 2003 to 2005. Pre-heating at 8°C for 20 days before 15°C forcing, to render the DVI as greater than 1, promoted bud burst of cuttings five days earlier compared with no pre-heating. Pre-heating of ‘Tonewase’ persimmon trees in the air temperature range between 6-8°C and 10-15°C in a greenhouse for 17-29 days induced the bud burst stage two to five days earlier compared with no pre-heating. These results suggest that, in the forcing culture of the ‘Tonewase’ persimmon, the forcing start date and set temperature can be determined according to the degree of endodormancy completion based on the DVR model, and that bud break can be further advanced by pre-heating at temperatures effective for endodormancy completion before forcing.View full abstractDownload PDF (927K)
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