The author previously made an attempt to clarify the humus characteristics (humus con-tent, composition, etc.) of volcanic ash soils which have developed over the Pleistocene upland from the eastern foot area of Nantai Volcano to the area along the Daiya and Kinu Rivers (Figure 1), and to presume the environment factors of soil formation (Watanabe, 1985). This report deals with the vertical and horizontal changes of the humus characteristics in the soil profiles in the same area as in previous study. The result is summarized as follows. 1. The vertical distribution of humus characteristics (carbon content, value (brightness) of soil colour and humus composition) was classified into three types, A, B and C (Figure 4). Type C, which may have received soil erosion, is regarded as a modification of type B. Though vertical distribution of humus characteristics in each soil profile reflects the changes of soil forming environment such as vegetation and climate, the main factor which regulates the classification mentioned above is inferred to be the frequency of volcanic ash fall deposit. As regards the samples located relatively far from Nantai Volcano, for example Nos. 13, 14 and 15 (Table 2) which are classified into type B, or type C, the degree of humus accumulation, darkness of the soil colour and degree of humification all tend to increase in the intermediated layers (30 to 50cm under the surface) in the humus profile. This is inferred to have been caused by the change of vegetation related with the thickness and rate of volcanic ash fall deposit. 2. The humic horizon was divided into three horizons from the viewpoint of soil mor-phology and tephrochronology supported by the 14C determinations (Figure 5). Horizon I is the layer which continues to accept humus supply and humification under soil forming environment in the present. Horizon II corresponds to the surface layer formed under the condition of warm climate, about 3, 000 to 5, 000 years ago. Horizon III is regarded to be the humus layer formed sequently to the decline of volcanic ash fall, about 10, 000 years ago. 3. The horizontal distribution patterns of humus characteristics such as carbon content, soil colour values (brightness) and the PQ values of humus in each horizon show clear locations (Figure 6). The areas where humus and humic acid accumulation are dominant in horizon II and III tend to move in the direction of west northwest. The changes of these locations mean the environment changes in each horizon. That is, the suitable climate for humus and humic acid accumulation in the period of horizon. II and III were formed, which is inferred to be corresponding to rain factor of each sampling site from 140 to 240, existed in higher location than present. 4. When the standard deviations of humus characteristics are determined for these three horizons, the values are found to be arranged in the following order: horizon I > horizon II _??_ horizon III. The lower layers have smaller variance and can be regarded as stable horizons. In this study, the influence of climate variation was recognized in the investigated area by examining the horizontal distribution of humus characteristics in each horizon. From this viewpoint, it will be possible to presume the past environment of soil formation such as climate variation. In future, it is desirable to investigate the vertical and horizontal changes of humus characteristics in buried humus horizons derived from Holocene tephras.
Coleman (1982) devised the “Scape and Fringe Map” method which delineate townscape, farmscape, wildscape, rurban fringe and marginal fringe on the maps of the Second Land Use Survey of Britain. The method, however, can not immediately applied in the analysis of Japanese land-use maps at 1:25, 000. Himiyama (1984, 1985) improved a method of delineating an ‘urban area’ in order to use the Japanese land-use maps. His method is applicable to the digital data and is easily operated with the aid of a computer. The purpose of this paper is to improve Himiyama's method and to show an alternative scape and fringe map classified into five land-use types such as townscape, farmscape, wildscape, rurban fringe and marginal fringe by using the Japanese land-use maps at 1:25, 000. The land-use data used here is the same one as Himiyama (1984, 1985), prepared by the method of systematic point sampling at 1cm interval on each map sheet. Sample field is Hiroshima City (four map-sheets named Gion, Nakafukawa, Hiroshima and Kaita). The process consists of the following four steps; Step 1. Forming of the basic category; Thirty-three types of land-use are classified into seven basic categories (Urban land use, Transport, Vacant land, Agricultural land, Un-vegetated land, Woodland and water). Step 2. The conversioning of an isolated point; If a point is simultaneously surrounded by four points which are classified into the same basic category, this point is newly assigned the basic category similar to surrounding points. Step 3. Extractioning of four primary scapes (waterscape, townscape, farmscape and wildscape); Each primary scape is measured by the attribute and the minimum number of a point group. If a point group is fulfilled with above measure, the point group is identified to each primary scape. Step 4. The resting point groups which were not identified to primary scapes at Step 3, are decided into fringes or scapes. If the number of group is more than five, it is recog, nized as rurban fringe or marginal fringe, or the rest is recognized as the adjoining scape (except waterscape). The Scape and Fringe Map made by the above 4 steps was highly fit for the real land-use pattern of sample field. The accumulation of the maps in various regions enables us to make a comparative study of land use in and around built-up areas of Japanese cities; and to assess the land-use planning better.