There is a small mire consisting mainly of a bog and a pond system, of about 0.3ha in area, in the Hakkoda Botanical Laboratory of Tohoku University located near Sukayu Spa at about 900m a. s. l. in the Hakkoda Mountains, Northeastern Japan (Fig. 1). To conserve the bog environment, the laboratory attempted to maintain the water table at a constant level by dredging a drainage channel from the pond every summer. As a result, bare ground occurred at the eastern part of the pond. That operation was stopped in the late 1970s, and the bare ground has been gradually submerged by shallow water. Consequently, a type of hydrarch succession has progressed there. The process of invasion and establishment of Sphagnum recurvum var. brevifolium community in this hydrarch succession was examined for five years, from 1990 to 1994.
In the first stage, probably it commencing around 1980 when the bare ground dried up during the summer season, Juncus yokoscensis appeared. This was followed by invasion of Drepanocladus fluitans. Except during the summer drought, the habitat was continuously submerged in this stage. During these stages, the litter originating from these plants was thinly deposited on the bare ground. Around 1987, Sph. recurvum invaded the site and grew annually at a certain rate until 1991. It was thought that this process was as follows: many small pieces of Sph. recurvum shoots were torn off at the margin of the original bog (Fig. 3) and floated to the pond. These small pieces of shoots caught on the layer of litter and grew into the present shoots in situ. Judging from the growth rate of shoots examined for five years, it is assumed that the first invasion of pieces of shoots occurred in 1987. The growth of shoots decreased in 1992, and the lower part of these shoots became fibrous and separated from the upper part. This indicates that formation of sphagna peat began five years after the first invasion (Fig. 6)
To clarify the hydrological conditions supporting the invasion and formation of Sph. recurvum community, water levels of the pond were measured for two years, 1993 and 1994. The lowest water level, recorded on August 10 during the extraordinarily dry summer of 1994, was 10cm lower than the highest level. Under that condition, although the habitat of Sph. recurvum was exposed, the plants did not wither. The usual downward displacement of water level from the highest level in summer season was 6cm, and even under such conditions, most of the habitat was covered with less than 1cm of shallow water (Fig. 4 and Fig. 7). The most desirable environment for establishment of Sph. recurvum community on bare ground was a shallow pool with a water depth of less than 4cm (Fig. 4).
Based on the results of observations and measurements of the invasion process of Sph. recurvum mentioned above, the following questions are briefly discussed.
Some sphagna bogs have been destroyed by the trampling of hikers, and great efforts has been made to reestablish the injured bog vegetation. The results obtained here indicates that self-recovery is possible if a shallow water pool is artificially or naturally induced at destroyed sites. At such sites, the initial invaders, such as Juncus yokoscensis and some mosses, appear immediately and this stage progresses to the sphagna stage after a short duration.
Peat cores from many mires are frequently intercalated by layers of volcanic ash. Boundaries between peat and volcanic ash layers are mostly very sharp. This indicates that mire vegetation recovers immediately on a bare volcanic ash surface. Such vegetational recovery in the past is supported by the successional process of Sph. recurvum community examined here.

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Before about 1930, Michitoshi ODAUCHI (1875-1954) strove to study the human geography from an independent standpoint, and systematize the organization of geographical study from the standpoint of the non-main current school in opposition. He studied on the regional geography what attached importance to the inhabitants' occupation and life, and he wrote Teito to Kinko (The Capital and its Suburbs, 1918), Shuraku to Chini (Settlement and Geography, 1927) and others. On the other hand, he established Société de Géographie Humaine au Japon (The Human Geographical Society of Japan) at 1926, in rivalry with Chikyu Gakudan (The Geological Institute, Kyoto Imperial University; 1924-1937) and Nippon Chirigakkai (The Association of Japanese Geographers, Tokyo Imperial University; 1925-), and he intended to diffuse the human geographical thoughts.
ODAUCHI, from 1930 to 1940, endeavored to push forward the home geographical education in the situation of a non-regular staff member of the Education Ministry of Japan. His thoughts of homeland, homeland education and homeland study changed in quality with the change of the social conditions. However, he kept his subjectivity as much as possible, and tried to bring up the study of regional geography in the school education and the social education. Moreover, he tried to take part in both the land planning of Manchuria from 1940 to 1942, and the plan of the mountain village in the Oku-Aizu district from 1946 to 1949. These facts show that ODAUCHI's study made special features of practice and application.
On the other hand, ODAUCHI was one of the organizers of Kyodo Kyoiku Renmei (The league of homeland education) at 1930, and he tried to push forward the study of the synthetic regional geography by keeping step with the movement of the homeland education. There seemed to be his antagonism against the study of the regional geography with Keiji TANAKA (1885-1975) as the central figure in the bottom-current of ODAUCHI's speech and behavior. Moreover, he assumed a critical attitude toward Taro TSUJIMURA (1890-1983; successor to Naomasa YAMASAKI, 1870-1929)'s academic feature, especially toward his view of landscape study. Thus ODAUCHI took the independent position that he did take little part in the main current of the learned circle of geography in Japan.
What is the root cause why ODAUCHI made the academic features of his own, and took the position of the non-main current school? It is considered that the cause is his serious consideration of the historical and social scientific view point in his geographical study. This feature of his methodology appeared in his study of the satellite town in the west suburbs of Tokyo. Furthermore, he wished that the geographical study accepted his methodology after World War II in Japan.
ODAUCHI did not participate in training geographers as a full-time teacher at the university. In this sense, there was not a direct successor to him. However, it is considered that his advanced academic features had a great influence on many geographers, including Koji IIZUKA (1906-1970), specially after World War II in Japan. IIZUKA, who played an important role in the prosperity of social scientific geographical study after World War II, he seemed to have the fundamental ideas such as both the historical view of the advancement of geography and the methodology of geography that were somewhat similar to ODAUCHI's ideas. In addition, the learned circles of geography and social studies held the discussion meetings with ODAUCHI as the central figure at that time. These facts greatly estimate that ODAUCHI's achievements and academic features were very significant for the development of the geography and the social studies, hence it is inferred that he, directly or indirectly, had a far-reaching influence.

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Linear depressions are the graben-like landform on the crest slopes with multiple ridges or up-hill facing scarps. Deep-seated gravitational slope deformation (sagging) has been considered as the main cause of such depressions. The relation between formation of linear depressions and landslide occurrences are investigated with respect to the development of channel systems.
Drainage density of channelways and abandoned channelways are compared in two cases of the slopes with and without linear depressions, Here abandoned channelways are the shallow dry valleys covered with detritus transported from lateral slopes after past stream erosion. Though the drainage density of channelways is lower on the former slopes than on the latter, that of abandoned channelways indicates to the contrary.
Groundwater conductivity on the upper part of mountain slopes is thought to become high in the tension zones caused by deep-seated gravitational slope deformation. Consequently increased share of groundwater flow in total discharge in the tension zones prevents the development of channelways and promote that of abandoned channelways. Because groundwater infiltration is the main cause of landslides, linear depresions are considered to be a sign of landslide occurrences on the flank slopes.

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