<資料・研究ノート>東北タイの"丘陵上の水田" : 特に,その"産米林"の存在について

Abstract

Northeast Thailand has two types of rice lands, one on an upland plain and the other on upland hills. The former has an extensive distribution between the Chi and the Mun rivers, whereas the latter forms rice land patches of much smaller scale in the marginal zones of Northeast Thailand, as shown in Fig. 1. This paper concerns the latter type of rice lands. Each rice land in upland hill regions has twofold structure, which comprises rice fields on valley bottom and those on valley slopes as illustrated in Figs 2 and 3. Rice fields on valley bottom are flat and open, and usually treeless. These are long-established, well irrigated, fertile (average yields is ca 30 tang/rai) and stable fields. Rice fields on valley slope, on the other hand, are gradient, wooded and of very recent opening, non-irrigated, less-fertile (average yield is 10-20 tang/rai) and unstable. A very rapid expansion and invasion of rice-growing plots into forest areas has resulted in unregistered rice fields on valley slopes, in these some ten years. An example is shown in Photo 1, which shows a notice board reading "forest reservation" in a plot where rice is grown. Regarding this fact, "rice-growing plots in upland hills regions" could be categorized into three; i.e. irrigated rice fields on valley bottom, and rain-fed rice fields and "rice producing forests" both on valley slope, in which the acreage of the last seems to be too great to be neglected. The structural pattern of rice land mentioned above is not particular characteristic to the upland hills of Northeast Thailand, but it is applicable to the most of the marginal zones of the Central Plain of Thailand as well. If this is the case, 40% of total rice land of Thailand should be accompanied with the "rice producing forest" and this disguised rice fields should constitute enormous addition to the explicit figures of rice field appeared on statistics.