巻号一覧
69 巻 (2013)
- 4 号 p. 229-
- 3 号 p. 101-
- 2 号 p. 47-
- 1 号 p. 1-
69 巻, 4 号
選択された号の論文の5件中1～5を表示しています
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Full Paper
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Kentaro HAYASHI, Masayoshi MANO, Keisuke ONO, Takahiro TAKIMOTO, Akira ...2013 年 69 巻 4 号 p. 229-241
発行日: 2013/03/10
公開日: 2013/12/15
[早期公開] 公開日: 2013/10/07ジャーナル フリーThe aim of this study was to clarify the atmosphere-paddy exchange of ammonia (NH3) at a single-crop rice paddy field in central Japan. Measurements of NH3 air concentrations were carried out using passive samplers at two heights above the ground surface (4.0 and 1.5 m) on a weekly basis over a four-year period. The mean NH3 air concentrations ± standard deviations at 4.0 m were 2.5 ± 0.8 and 3.0 ± 1.0 (20°C, 1013 hPa) in the cropping and fallow seasons, respectively. Sharp increases in the NH3 concentrations coincided with the application of poultry manure and post-harvest field-burning activities; those values exceeded the 95% range of the weekly mean concentrations. The NH3 exchange fluxes were calculated using a gradient method in which the flux was expressed as the product of the difference in air concentrations multiplied by the diffusion velocity between the two heights. The mean NH3 exchange fluxes ± standard deviations were 0.016 ± 0.022 and 0.019 ± 0.115 μg N m-2 s-1 of deposition in the cropping and fallow seasons, respectively; where the weekly mean flux was assumed to be zero if the difference in the air concentrations between the two heights was not significant (p < 0.05). In general, the paddy field acted as a net sink of atmospheric NH3, with an annual net deposition of 7-9 kg N ha-1 yr-1. However, the application of poultry manure in February 2008 induced a strong NH3 emission of approximately 10 kg N ha-1 during three weeks, which nearly counterbalanced the annual deposition for an entire year. Passive samplers are a convenient option for long-term monitoring, although the weekly mean exchange fluxes of NH3 had a systematic error; a case study showed a 66% overestimation for the weekly mean exchange flux.抄録全体を表示PDF形式でダウンロード (936K) -
Toshichika IIZUMI, Gen SAKURAI, Masayuki YOKOZAWA2013 年 69 巻 4 号 p. 243-254
発行日: 2013/03/10
公開日: 2013/12/15
ジャーナル フリーThe grid interval of a global climate model (GCM) is generally hundreds of kilometers in latitude and longitude. The spatial heterogeneity of crop condition (e.g., phenology and yields) at that scale could be substantial. Because the atmosphere-cropland exchanges of energy, water, and materials are sensitive to crop condition, this issue poses a question: How can we simulate the condition of a crop of interest on a GCM grid scale while taking into account the spatial heterogeneity of crop condition at a sub-grid scale? We therefore proposed an ensemble approach that uses stochastic parameter values to represent the spatial variation in the phenological and biophysical characteristics of a crop within a given GCM grid box, and tested its feasibility with simulation experiments. The combination of the Soil and Water Assessment Tool (SWAT) applied to maize in the Central Great Plains, United States, and coarse-resolution (2.5°×2.5°) reanalysis data was taken as the example. The ensemble simulations successfully captured the spatial variation in the phenology and yield. Our conclusion is that the ensemble approach is feasible and expected to benefit large-area crop modeling when extending those models to include more information on the spatial heterogeneity of crop condition than ever.抄録全体を表示PDF形式でダウンロード (1230K) -
Daitaro ISHIKAWA, Gerrit HOOGENBOOM, Yukihiro OZAKI, Etsuji ISHIGURO2013 年 69 巻 4 号 p. 255-263
発行日: 2013/03/10
公開日: 2013/12/15
ジャーナル フリーIn this study, the visible spectra and Chlorophyll (Chl) bands of tea leaves were investigated by using a handheld spectrometer during their growing period. The original absorbance spectra and their second derivative spectra in the 400-1100 nm were obtained, and bands at around 485, 558 and 680 nm were assigned to Chl absorption. Because the absorption around 485 nm is sensitive to the instrument's detector, and the 558 nm is weaker than the 680 nm band, the absorption band at around 680 nm was used for our detailed analysis. It was found that the growing stage of Japanese tea can be separated into three stages, the first, second, and final stage based on day of year (DOY): 74-91, 91-112, and 112-116, respectively, by the inflection point's changing of the band around 680 nm. That inflection points were located at different positions for the first and final stages. This result suggests that the old and new leaves have a peak at different wavelengths. On the other hand, the band linearly shifted to a shorter wavelength between DOY: 91-105 (second stage). However, with respect to combination of the old and new leaves in the simulation, it was confirmed by the ratio of old and new leaves in the field of view (FOV) that this type of the behavior may occur during this period. The intensity change in the band was also separated into three stages; in the second stage, especially, the intensity of the band also increased linearly. It is very likely that the intensity change in the second stage depends mainly on the growth of new leaves. Therefore, the results obtained suggest that it is possible to evaluate the growth of tea leaves by using the band around 680 nm because of the function of Chl.抄録全体を表示PDF形式でダウンロード (909K)
Short Paper
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Yasuyuki WAKIYAMA, Ryoji SAMESHIMA, Takahiro HAMASAKI, Manabu NEMOTO, ...2013 年 69 巻 4 号 p. 265-276
発行日: 2013/03/10
公開日: 2013/12/15
ジャーナル フリーWe conducted a study to determine the threshold intensity of twilight illumination for photoperiodism in rice (Oryza sativa L.) based on solar altitude in an open-field, day-length-extension experiment and utilization of a crop model. Light supplementation was provided by incandescent lamps and controlled based on solar altitude using four japonica rice cultivars: Hitomebore, Koshihikari, Nipponbare, and Nikomaru. First, pot experiments were conducted individually with supplementary light treatment in the morning and in the evening. By comparing the difference in heading time between rice with and without supplementary light, we determined the threshold intensity of twilight illumination. The threshold was between a solar altitude of 0° and -2° in the morning and evening civil twilight. Second, a field experiment was conducted with light supplementation in the morning and evening civil twilight. Based on the results, we concluded that the threshold intensity of illumination would be around a solar altitude between -1° and -2° in the morning and the evening civil twilight.抄録全体を表示PDF形式でダウンロード (893K)
Research Notes
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Seiichiro YONEMURA, Seiichi NISHIMURA, Shigeto KAWASHIMA2013 年 69 巻 4 号 p. 277-287
発行日: 2013/03/10
公開日: 2013/12/15
ジャーナル フリーWe systematically and explicitly derived equations to estimate trace-gas uptake by soil using closed-chamber and flow-through-chamber techniques. We began from fundamental equations and reasonable assumptions, such as first-order kinetics and constant gas concentration in chambers for surface fluxes and laboratory bulk-soil experiments (emission and uptake). The important variables are deposition velocity, uptake rate in volume per unit mass of soil, and (relative) uptake rate in volume per unit of soil volume. Units of the uptake rate in volume per unit mass of soil and the (relative) uptake rate in volume per unit of soil volume are m3 kg-1 s-1 and s-1 in MKS, respectively. We discuss the concept of deposition velocity with those of destruction velocity and uptake velocity. We also mention the relatively well-conserved mass balance of surface-soil chamber measurements of trace gas uptake.抄録全体を表示PDF形式でダウンロード (609K)
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