Twenty-two differential species of the floodplain plant communities along the lower reaches of the Sagami River, western Kanto, Japan, were examined for germination under controlled water conditions. The experimental conditions were prepared as follows: 1) wet, moist and dry conditions during seed storage, and 2) wet to dry conditions of germination beds, and 3) shallow and deep water flood conditions of them. Among the twenty-two species examined, seven species characterizing the communities with dry habitats germinated well on germination beds with moist and wet soil conditions, but germination rate was clearly suppressed by flooding. Germination of nine wet habitat species were inhibited by dry conditions, but could germinate under flood conditions. The remaining six moderate habitat species displayed intermediate germination characteristics. Thus, the suitable germination conditions of the species examined in the present study corresponded to the habitats of the plant communities to which they belonged. However, a common suitable habitat for seed storage could not be found.

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To study natural revegetation in the Tennyogahara Mire, a vegetation survey and mapping by GIS raster method with one meter mesh size was conducted in August 2001. The 127 quadrats obtained in 2001, together with 131 quadrats in 1981 and 1988, were grouped into 12 community types using TWINSPAN analyses in term of coverage of the total 104 presented species. They belonged to pool and hollow (2 types), lawn (6 types, among which three were disturbed and recovering types), and shrub and forest (4 types) vegetation, respectively. According to the new actual vegetation map (7820m^2), the largest community is Carex omiana-Hosta atropurpurea/Hosta rectifolia community (30.1% of the mire area) had decreased since 1988 (it was 33.8% in area). The disturbed and recovering area is 19.5%, which had decreased since 1988 (22.4%, based on a polygon vegetation map of 1988), due to the construction of a boardwalk. In the mire, 73.4% of the total area remains unchanged, 20.1% changed progressively, whereas 6.5% changed retrogressively. 68.1% of the changes occurred in the disturbed area. Rhynchospora yasudana-Cladopodiella fluitans community increased mostly, whereas shrub and forest types did slightly but progressively. The boardwalk has been a great help in preventing the vegetation from being damaged by human treading, thus hastening the natural recovery of the mire vegetation.

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Influences of cushion plants, lichen and moss, on vegetation development were studied in the alpine wind-blown ground on Mt. Koizumidake, in the northern part of the Daisetsu Mountains, northern Japan. In the study area, plant cover is low due to severe environmental conditions, and vegetation occurs mostly as isolated patches. Matted cover of cushion plants, lichen and moss dominate in some patches. 118 patches were recorded within the study plot (20m×20m). These patches are almost all classified as three types: DL type (patch dominated by cushion plants, Diapensia lapponica), matted cover, LM type (patch dominated by lichen and moss), matted cover, CS type (patch dominated by Carex stenantha). The number of species increases with the extension of patch size (p<0.01). The number of species per unit area is not significantly different in the three patch types (p>0.05). However, the patch size and the number of species in DL type and LM type were larger than those in CS type (p<0.01), and the number of seedlings per unit area in these patch types was more than in the CS type. Although cushion plants, lichen and moss do not contribute to species richness, they are considered to facilitate the invasion and establishment of vascular plants. Soil temperature, soil moisture, C/N ratio and nitrogen content were also measured in the three patch types. The annual accumulated effective temperature (standard temperature is daily mean soil temperatures of >5℃) in DL type and LM type were higher than that of the CS type, and bare ground about 30-60℃. The C/N ratio in DL type was highest among both of the patch types and bare ground (p<0.01). It is suggested that the matted covers of cushion plants, lichen and moss contribute to the growth of vascular plants due to the increase of soil temperature or organic supply. In severe alpine environmental conditions, cushion plants, lichen and moss can extend more than the cover of the vascular plants. Therefore, it is considered that these matted covers provide plant recruitment sites.

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Changes in the Kushiro Mire have recently attracted attention: These include vegetation changes and human impacts such as river channelization, agricultural development in drainage areas and the inflow of turbid water. I examined herbaceous vegetation and investigated the heights, breast-height diameters and annual ring growths of alder and ash trees in the mire at stands along the Onnenai River and the Kuchoro River. The former is an unimproved river, while the latter was improved by channelization between 1966 and 1980. At the Onnenai site, all of the tree stands were alder. The farther downstream the stand was, the lower the tree density and the higher the percentage of coppice stem clumps became. At the Kuchoro site, upstream stands were predominantly alder and ash. The farther downstream the stand was, the lower the tree density and the lower the percentage of coppice stem clumps exceeding breast height (130cm) became. At both sites, the farther downstream the stand was, the lower the stem volume became. At the Onnenai site, the farther downstream the stand was, the lower the tree height and the smaller the height increase became. At the Kuchoro site, the stand the farthest upstream was tall, while the stand farthest downstream evidenced growth hindrance having occurred at some stage. Also at the Kuchoro site, the stand farthest upstream had trees with annual rings revealing that the rate of growth for alder was very good between 1971 and 1975, inclusive, and that for ash rose dramatically from 1975 onward. This growth pattern was not found in control ash trees located outside of the mire. It is possible to attribute the pattern to conservation work along the Kuchoro River.

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We here report the floristic composition and stand structure of Distylium racemosum mixed forests established in Miyajima Island, Hiroshima Prefecture, SW Japan. Our recent vegetation survey throughout the island recognized that the Distylium racemosum mixed forests were partially established in a valley of the south-facing slope of the island. The forests were considered to be remnants, whose persistence could possibly be attributed to the island's cultural history in which nature conservancy was a part of the worship and reverence for the island practiced by its inhabitants since ancient times.

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