| 著者 |
小原, 洋
大倉, 利明
高田, 裕介
神山, 和則
前島, 勇治
浜崎, 忠雄
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内容記述 |
Soil classification in Japan has developed in line with the public work projects, soils in Japan have tended to be classified independently for different land use, such as cultivated area(paddy field, upland field), forest, and so forth. As a result, there is no available soil map drawn with a single framework of soil classification in practical map scale. This causes a barrier to advancement of environmental studies such as watershed-level nutrient cycling, carbon sequestration and so on. To find a way out of this situation, The Japanese Society of Pedology developed a new soil classification system, and published the Unified Soil Classification System of Japan‐2nd Approximation(2002). However, since this classification system lacked lower categories for attribution such as soil texture and the presence or absence of gravel layers, it was insufficient to provide practical soil mapping units. To address this issue, we propose the Comprehensive Soil Classification System of Japan‐First 1st Approximation, a more practical system that enables the nationwide classification of soils. We applied the following four basic policies in drafting this proposed classification system:(1) integrating the Classification of Cultivated Soils in Japan‐Third Approximation with the Unified Soil Classification System of Japan‐2nd Approximation(2002);(2) retaining as much correspondence as possible to the Classification of Cultivated Soils in Japan ‐Third Approximation to enable continued use of existing data and knowledge;(3) keeping less laboratory analysis to obtain criteria for classification so as to enable easy classification for users;(4) validating the system using available data, and do not introduce new taxonomic units and differentiating criteria that are not absolutely necessary. In this proposed system, we defined the following categories: soil great group, soil group, soil subgroup, and soil series group, determined by dichotomous keys that defined in Chapter 6. The keys consist of diagnostic horizons, diagnostic properties, and diagnostic materials, which defined as objectively and quantitatively as possible. Identifying a soil is to determine the presence or absence the diagnostic horizons or characteristics in the soil profile, and the position in which they appear in the profile. The soil great group has 10 great groups: Man-made soils, Organic soils, Podzols, Andosols, Dark Red soils, Lowland soils, Red-Yellow soils, Stagnic soils, Brown Forest soils, and Regosols. Each soil great group is further subdivided into 1‒6 soil groups according to moisture regime, parent materials, and other soil formation factors. Soil subgroups are lower categories, ranging from soils with properties intermediate to the different soil groups to those that are typical of a particular soil group. Soil subgroups are further divided into soil series groups according to differences in soil texture, presence or absence of a gravel layer, and other characteristics. Consequently, this proposed system contains 27 soil groups, 116 soil subgroups and 381 soil series groups. Setting these 4 category levels enables the system to be used for both general outlines and detailed description, and for the creation of soil maps and soil information of various scales. Since development of this proposed system required consideration of the regional distribution of soils, land use diversity and other purposes, we received strong cooperation of university and independent administrative research institutions experts joined as outside members of a committee, which National Institute for Agro-Environmental Sciences personnel were involved in soil classification. |
niaes_report_No29p1-73p.pdf (1.1 MB)
