DISTRIBUTION OF PADDYLANDS AT HIGH ELEVATIONS AND IN COOLER CLIMATES IN JAPAN: POTENTIAL ALTITUDINAL LIMITS BASED ON AIR TEMPERATURE

Abstract

Several studies on the vertical distribution of paddyland have been conclu ded; the results may be summarized as follows: 1. The existing vertical distribution of paddyland has been ascertained; the highest fields are located in the Central Highlands at about 1300 meters elevation while in southwestern Japan, elevations average about 900 meters (Figure 1). The upper limit of paddyland in each district is shown in Table 1. 2. The differences in altitude between the uppermost paddylands on nor thern and southern slopes have been calculated and are shown in Table 2 and Figure 3. In general, there is less than 100 meters difference between the two slopes with the paddylands reaching higher elevations on the southern slope. In each unit area, too, the average altitude of the southern slope paddys exceeds that of the northern slope fields. However, in the Saku District of Nagano Prefecture and in the Hachinoe District of Aomori Prefecture, the higher fields are generally found on the northern slopes and. the average paddy altitudes within a unit area are similarly higher on the northern slopes. This anomaly may be.explained by the effect of the afternoon sun on valleys ouinted toward the northeast or northwest. 3. An attempt was made to clearly establish the potential altitudinal limits of paddy culture in Japan. It was assumed that an average August temperature of 19°c (18. 7°) approximates the temperature of the highest paddylands in the Central Highlands and, as such, represents the minimum temperature required for. successful paddy culture in other areas of Japan (Figures 2 and 4). Thus, it appears that in many areas of Honshu, Kyushu, and Shikgku, paddy culture has not yet reached its altitudinal. limits. Cap Tohoku's Pacific slopes and in Hokkaido's inland basins, the altitudinal potential is unexpectedly high. 4. The relationship between altitude of the land the potential altitudinal limits of paddyland as established above were examined (Figures 4). On the Pacific slopes, it was determined that the potential paddyland limit based on air temperature is generally below the height of the land itself; on the other hand, on the Japan Sea slopes and in the Central Highlands, as well as in each district of Kyushu, Shikoku, Chugoku, and Kinchi, it was found that the climatic limits exceed the height of the land.