The Ogasawara Islands are located in latitude 27°N belong to the subtropical region. In these islands, tomatoes are usually sown late summer and seedlings are transplanted at fall in the field. However, the early yield is low remarkably by the poor fruit set of lower clusters. To find the relation between low fruit set percentages and meteorological factors, experiments were carried out.
1. In the field, the fruit set percentages on each flowering date were observed. The result of investigation on the relation between fruit set percentages and environmental factors, showed that the high amounts of solar radiation were effective, on the other hand, daily maximum temperatures were ineffective for poor fruit set. It was suggested, also, that high Water Suturation Deficit (W.S.D.) in leaves caused by high solar radiation decreased fruit set percentages strongly.
2. Twenty-four plants were grown in Wagner's pots. Half of them were irrigated every day, however, the remainder did not water one day during the experiment, to be suffered water stress.
The ratio of fruit set percentage on each flowering day was indicated as latter to former. Consequently, this ratio on the non-watered day dropped remarkably, and also dropped on the previous day. However, the ratio rose on the next day conversely.
3. Fifty-four plants grown in the field were divided between two plots. One was shade-treated plot: the plants belong in the plot were shaded a couple of days two times. The other was untreated plot: the plants belong to the plot were not shaded. Over 11 days, the daily W.S.D. at 13:00, and the fruit set percentages on each flowering day were observed. Consequently, the daily W.S.D. ratios of shade-treated plot to un-treated plot, and the daily fruit set percentage ratios of shade-treated plot to un-treated plot, were inversely related.
4. Photosynthetic rate, solar radiation, and W.S.D. at 13:00 were daily correlated in direct proportion to each other. Accordingly, reduction of photosynthetic rate was not observed at the water stressed day.
5. Thus, fruit set percentages on each flowering day dropped according to the increase in daily plant water stress. However, the physiological causes were not shown in the lack of photosynthetic rates, it should be studied as the subjects of hormones or matter translation.

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黒岩 (1966) の物質生産理論式で求められる剰余生産力が, この式に含まれる各種のパラメータの変化に対してどのような振る舞をするかという問題が, コンピュータ・シミュレーションによって検討された。
この黒岩式から得られる剰余生産力を, 群落の葉面積指数 (A) と吸光係数 (K) の関数として表わしたときに, 一つの極大値が存在することが, 最近報告されている (及川, 1985)。このことは最適吸光係数 (K_opt) と, それに応じた最高剰余生産力 (P_{s, top}) とがあることを意味している。そこで本論文では, 剰余生産 (P_s) に対する単葉の光飽和したときの光合成速度 (p₀) と暗呼吸速度 (r_A) の影響が, 新たに開発された等高線・三次元表示法に基づいて, 重点的に調べられた。
その結果, p₀とr_Aの変化に対するK_optとP_{s, top}への影響が系統的に明らかにされた。ここで特に注目される点は, p₀とr_Aの値が変われば, K_optやA_optの値は変化するが, r_A/p₀比が一定である限り, P_{s, top}の値は常に一定である, という関係が成り立っていたことである。引き続き, 植物の葉の生理特性に基づいて, このP_{s, top}値の一定であることの, 物質生産における意義が論じられた。

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At many agricultural meteorological stations, soil temperatures are observed once a day at 9:00 A.M. In the upper soil layers, however, the temperature fluctuates widely during the course of a day, and the vertical profile taken at a time of day is not sufficient for an understanding of the soil temperature regime. Thus, it is desired to evolve a method for utilizing the observations made at 9:00 A.M. as fully as possible.
We constructed a simple numerical method for the purpose of estimating the monthly mean maximum and minimum temperatures in the upper soil layers from the monthly mean profile taken at 9:00 A.M., and examined the accuracy of the estimation, using the data obtained in the bare observation fields of Shimane University (clay) and Sand Dune Research Institute, Tottori University (sand).
In the present method, monthly mean curves of diurnal temperature variations at all depths are approximated by pure sinusoidal functions of time around a mean which is constant throughout the layers. The approximation becomes better with increasing depth. The function has four parameters, that is, the daily mean, the amplitude at the surface, the damping depth and the instant at which the surface temperature is at its mean and increasing. The last one averaged over a month can be estimated within half an hour from the time of sunrise; the instant comes about 2 hours and 15 minutes after sunrise in bare clay fields and 15 to 30 minutes further behind it in bare sand fields. The other three parameters are estimated numerically from the instant and the monthly mean temperatures observed at three depths at 9:00 A.M.; then the maximum and minimum temperatures are calculated by using the estimates of the parameters.
Results obtained by the analyses of the two sets of data above are similar in trend. The estimated values of monthly mean maximum and minimum temperatures at a depth of 5cm are about 1 to 3°C lower than the observed ones in the spring and summer months, but are in fair agreement with the observations in the autumn months. The accuracy of the estimated values at 20cm depth is about ±1°C for the maximum and about ±0.3°C for the minimum. The accuracy is quite satisfactory in view of the approximated character of the present method and the fact that only the time of sunrise and the soil temperature profile taken at 9:00 A.M. are needed to utilize the method.

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To establish a method for measuring CO₂ flux from soil surface, the relation between CO₂ flux and the ventilation rate of a chamber was studied for the four different soils such as Andosol, Brown Lowland soil, Gray Lowland soil and Sand. The CO₂ concentration in the air at the inlet and the outlet of the chamber was determined with an infrared gas analyzer (see Fig. 1). CO₂ flux from soil surface was calculated from the CO₂ difference between the inlet and outlet of the chamber and the air flow rate.
1. It was found that the CO₂ flux for the soils increases gradually with increasing the ventilation rate, approximating to respective constant levels at the higher ventilation rate. The critical ventilation rates at which the respective CO₂ flux are assumed to approach to constant levels were about 13 times/hr for the Andosol and about 9-13 times/hr for the other tested soils.
2. One dimensional CO₂ balance equations for soil layer and a chamber were solved to derive the relationship between CO₂ flux and the ventilation rate, and to obtain CO₂ profile in the soil layer. The derived relationship indicates that CO₂ flux is affected with effective CO₂ gas diffusivity in a soil layer and ventilation rate (see Fig. 4). The theoretical results agreed well with the experimental results presented in Figs. 2 and 3.
3. The experimental results obtained using the CO₂ chamber system and Eqs. (5) and (6) were used to calculate the average effective CO₂ gas diffusivity over the soil layer with 15cm depth and the CO₂ concentration at the bottom of soil layer and results obtained are shown in Table 1. Under flooded conditions, the effective CO₂ gas diffusivity for the tested soils was over a range from 0.035 to 0.042cm²s^-1. These values were lower than molecular diffusivity of CO₂ in the air.
4. The chamber method was applied to measurements of the CO₂ flux at the soil surface of three rice plant fields. CO₂ flux measurement was made together with measurements of microclimatic elements during the period of rice cultivation in 1984 and 1985. The results are shown in Fig. 5. The daily CO₂ flux was higher for a rice field with the application of organic manure than without that. It was found that CO₂ flux at the rice field decreases gradually with lowering of soil temperature.

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The purposes of this study are to examine how to utilize efficiently the daily soil temperature observed at 9:00 A.M. and to estimate monthly mean maximum and minimum soil temperatures from this daily observation. Since soil temperatures fluctuate widely during the course of the day in the surface layer, the vertical soil temperature profile observed at 9:00 A.M. is not a sufficient element to understand the general soil temperature conditions. As a result, it was proposed that two methods would be suitable to estimate the monthly mean maximum and minimum temperatures in the soil surface layer by using the monthly mean soil temperature profile observed at 9:00 A.M. The first was a simple numerical method, of which the characteristics of utilization and application were discussed in the previous report. The second method using the factor of sunshine duration is described in this report.
This method was derived using three kinds of empirical coefficients calculated from the following factors which were measured in the experimental fields: (1) the difference between the soil temperature observed at 9:00 A.M. and the minimum soil temperature, (2) the average of the daily soil temperature range profiles and (3) the proportional relationship between the daily range of the soil surface temperature and the sunshine duration.
Based on this method, the monthly mean maximum and minimum soil temperatures were estimated using only the two factors of the soil temperature observed at 9:00 A.M. and the sunshine duration observed on that day. In applying this method to the routinely collected meteorological data observed in the Sand Dune Research Institute, the estimated results from this method were found to agree closely with the data stored. The estimated monthly mean daily minimum soil temperature agreed with the stored data within a margin of ±0.5°C, except in the case of the drought months. Also, the estimated monthly mean daily maximum soil temperature agreed within a margin of ±1.0°C, except in the case of drought months. From these results, this method may be considered to be more effective in estimating accurate monthly mean maximum and minimum soil temperatures under usual meteorological conditions.

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The criteria or indices based on the climatic and land conditions were obtained for vegetable cultivation. The indices were used to evaluate the culture type fit to a sloping land or mountainous area in Shikoku districts.
The results were expressed on the classification maps with respect to the climatic and land conditions, i. e., (i) air temperature; the monthly and annual means of air temperature, cropping type of vegetables, marginal high temperature of monthly mean air temperature in August for vegetables, and high or semi-high altitude cool regions, (ii) precipitation; the monthly and annual means of precipitation and the amount of precipitation in August, and (iii) the inclination angle and soil properties of a concerned area.
The principal indices were represented on the 1/300000 scale classification map and an example with its explanatory noses was shown in Fig. 4.
The investigation reveals that the results are reasonable and these indices can be utilized as a criterion to determine cropping types of vegetables. It is possible to cultivate various vegetables rationally where the proper location and arrangement of vegetables are carried out according to these indices, i. e., a suitable selection of vegetable varieties and a cropping season or cropping type at a sloping land in Shikoku districts.

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A simple climatological method to estimate the global radiation incident on a slope surface was developed. The direct, the sky diffuse and the ground-reflected diffuse radiations under actual weather conditions were considered in this model.
The global radiation (R_s) incident on a slope surface may be expressed as follows;
R_s=R_b+R_d+R_r
where R_b, R_d and R_r are the direct, the sky diffuse (isotropically distributed diffuse component +circumsolar component) and the ground-reflected diffuse radiations incident on a slope surface, respectively.
Each component was formulated as follows;
R_b=[a+b(n/N)] [a′+b′(n/N)]R_sdir
R_d=[a+b(n/N)] [R_sdif+{1-a′-b′(n/N)}R_sdir]
R_r=[a+b(n/N)] R_sref
where R_sdjr, R_sdif and R_sref are the apparent direct, the isotropical sky diffuse and the ground-reflected radiations incident on the slope under “standard clear sky conditions”, respectively. n is the number of hours of bright sunshine, N the number of daylight hours, a, b, a′ and b′ are the empirical constants.
R_sdir, R_sdif and R_sref are given as follows;
R_sdir=(r_o/r)²R_oP^m sinh′
R_sdif=R_sdir(0)(1+cosβ)/2
R_sref=ρ[R_sdir(0)+R_sdif (0)](1-cosβ)/2
where r and r₀ are the earth-sun distance and its mean, R₀ the solar constant (=1382Wm^-2); P the transmission coefficient, m the relative optical airmass, h′ the altitude of the sun for a slope surface, β the slope angle of the surface, ρ the mean albedo of the ground surface, R_sdir (0) the R_sdir for a horizontal surface and R_sdif (0) the sky diffuse radiation incident on a horizontal surface which was given by Berlage (1928).
The values of empirical constants a, b, a′ and b′ are determined for several stations in Japan. Monthly mean values of these constants for the Pacific coastal zone in Japan, a=0.298, b=0.727, a′=0.119 and b′=1.116 were obtained (Table 2 and Table 3).
The results obtained by this model are shown to compare favorably well with the observation data measured by Uchijima et al. (1981).
The dependencies of R_s, R_d and R_b on the slope angles with each different slope orientation were evaluated. The results show that the values of R_s on the slope surface vary widely with the slope angle and with the orientation in winter season than that in summer as shown in Fig. 6.
The annual changes of monthly mean values R_s/R_s, H; R_b/R_{b, H} and R_d/R_{d, H} are shown in Fig. 7 (A, B, C), where the suffix H indicates the radiation on a horizontal surface, respectively. The maximum annual variation of R_s/R_{s, H} is seen in the south-facing vertical slope (β=90°) surface with the values from 0.2 to 1.8. The change of direct radiation component (R_b) greatly contributes to the change of the total short-wave radiation (R_s) especially in winter. On the contrary, the diffuse radiation component (R_d) play an important role in summer season because the weather condition is generally abound with cloudy.
The effect of the albedo on incoming shortwave radiation on the steep angle slope surface is greater than that on the gentle angle.

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