We investigated the diversity and spatial distribution patterns of coastal plants in relation to coastal microtopography and size of 16 sandy beaches restored by offshore breakwaters and seven natural sandy beaches in Yumigahama, Tottori Prefecture, western Japan. We also used 5×5 m quadrats to survey representative areas of three beaches with offshore breakwaters and one natural beach. The total number of coastal plant species for beaches with offshore breakwaters was 24, and that for natural beaches 20. The incidence of six coastal plants, Ischaemum anthephoroides, Arabis stelleri var. japonica, Zoysia macrostachya, Viola mandshurica var. crassa, Salsola komarovii, and Tetragonia tetragonoides, showed a significant difference between beaches with offshore breakwaters and natural beaches. Logistic regression analysis revealed that five species, Carex pumila, Glehnia littoralis, Sedum oryzifolium, Vitex rotundifolia, and Linaria japonica, all declined in number as the size of the beaches with offshore breakwaters decreased. These results show that the differences in the microtopographic characteristics and disturbance due to uprush waves both affect floral diversity. Thus, while beaches with offshore breakwaters could be important habitats for coastal plants, any conservation measures focusing on these beaches need to be implemented over as wide an area as possible to ensure that a wide variety of microtopographies are available for colonization by coastal plants.

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We investigated the effects of caprock on vegetation in areas underlain by granite on the lower slopes of dissected lava plateaus on Teshima Island in western Japan. Caprock is a geological term that refers to a harder or more resistant rock type overlying a weaker or less resistant rock type. Teshima Island was divided into eastern and western regions based on the distribution of sanukitic andesite caprock; the east of the island has extensive areas of andesite caprock overlaying granite, while the west of the island has no andesite caprock overlaying the granite areas. Catchment area indexes calculated using a digital elevation model showed that the catchments were larger on the eastern side of the island. Grain size analysis revealed that the andesitic surface soils were mainly composed of fine particles, with the surface soils in eastern areas of granite with caprock tending to be more affected by andesite on the upper slopes. We compared differences in vegetation distribution between the eastern and western areas by superimposing a vegetation map based on a phytosociological survey conducted in 2002 onto a vegetation map published in 1982. The results showed that by 2002, broad-leaved deciduous forests dominated by Quercus serrata and Q. variabilis had expanded considerably eastward, displacing the pine forests (mainly Pinus densiflora) that dominated the area in 1982. Indeed, 19% and 6% of the forests in the eastern and western areas, respectively, were broad-leaved deciduous forests. These findings showed that pine forests have been more resilient in the western areas in the 20-year period between surveys. In addition, it appears that the andesite caprock, which promotes soil water retention and is resistant to weathering and erosion, was associated with the larger catchments, and conducive to the development of pine forests in areas overlain by granite on the lower slopes of the island.

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This research aimed to understand the impact of the large-scale flood caused by the Typhoon 0709 in September 2007 on the vegetation in the flood plain of middle Tama River, central Japan. After the flood, new natural bare gravel grounds appeared along the river channel, and annual herb and Phragmites japonica communities occurred extensively. However, the vegetation change was limited to the vicinity of the river channel before and after the flood, and little change occurred in the high-water channel. Our results suggest that a large-scale flood has limited impacts on the vegetation of the whole riverbed and that the formation of herb communities peculiar to flood plains is not expected under the current condition of Tama River.

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Natural beech (Fagus crenata) forests in Japan have been rapidly fragmented because of human activities since the end of the Second World War. In order to examine the effects of forest fragmentation on the species richness and composition of such forests, we surveyed the species of forest interior flora and the habitat conditions of 20 natural beech forest patches of various areas (450-856300 m^2) on Mt. Ouginosen, Japan, and analyzed the relationship between species richness or species composition and patch area on a whole-patch scale. A high positive correlation between the number of species and patch area was observed for all species, tree species, shrub species, terrestrial herb species, terrestrial pteridophyte species, endangered species (ES), rare species (RS), and species showing a preference for habitats with moist soil conditions (MS). Analysis of the relationship between the distribution of each species and patch area showed that many species, particularly ES, RS, and MS, tended to be absent in smaller patches. In addition, the first-axis score of a detrended correspondence analysis ordination for the patches was highly correlated with patch area. These results indicate that forest fragmentation has a considerable negative impact on species richness and can simplify species composition to a considerable extent. The absence of ES, RS, and MS in smaller patches may be attributable to certain factors associated with the decrease in patch area, such as a decreased likelihood of occurrence, an increased risk of extinction due to the decrease in population size, and the lack of landforms with moist soil conditions.

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To characterize the changes in the flora of a suburban forest, we analyzed floristic changes over approximately 50 years using past flora lists and the current list for the Tama Forest Science Garden in the southwest Tama area, Tokyo. The numbers of taxa (species, subspecies and varieties) recorded in the past (1950-60s), recently (2000s), and both (1950-60s and 2000s) were 164, 141, and 626, respectively. Although 20% or less of past taxa was replaced by other taxa, the total number of taxa seen changed little. However, the taxa recorded in the past included rare species in a higher proportion than those observed recently. By contrast, taxa that exist today included a higher proportion of alien species, as compared to taxa that appeared in the past. These patterns indicate significant shifts in species composition in the suburban forest over the past 50 years.

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A vegetation recovery test was conducted in two communities, dominated by Moliniopsis japonica and Sasa palmata of the degraded bog, Shinoro Mire, northern Japan. Three treatments, including mowing, removal of the top 0-20 cm of decomposed peat, and removal of 0-30 cm of decomposed peat, were applied to the two communities in autumn 2000. Vegetation was recorded from 2001 to 2008. In the first year after the treatment, the mowed quadrats recovered its vegetation cover associated with several newly recruited species, however, the coverage of S. palmata decreased slightly. The peat removal quadrats had no S. palmata, and communities differing from the present vegetation emerged. The 0-20 cm peat removal treatment promoted the germination and growth of typical mire species such as Rhynchospora fauriei, Carex lasiocarpa subsp. occultans, and Carex michauxiana subsp. asiatica. In contrast, the 0-30 cm peat removal quadrats frequently experienced floods, and only a few species were present with low coverage during 2001-2003. In 2006, the coverage of C. lasiocarpa subsp. occultans started to increase in the 0-30 cm peat removal quadrat of M.japonica community. In the 0-30 cm peat removal quadrat of Sasa community, Utricularia japonica showed temporarily thick coverage during 2004-2005, and thereafter, Schoenoplectiella hotarui, Schoenoplectus tabernaemontani and Phragmites australis increased. These treatments promoted the occurrence of new species lacking in the present vegetation and/or this mire flora. It is speculated that most of them germinated from the soil seed bank. The 0-20 cm peat removal treatment was beneficially effective in forming a wetland community from the present vegetation. However the newly emerged species were limited, and thus, recovery of the bog vegetation using the surface soil removal might be difficult.

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Aquatic flora was surveyed and their distribution maps were drawn in 12 irrigation channel networks along the Tama River, Tokyo. Of the recorded 15 aquatic plants, nine species were threatened or near threatened species listed on the red list of Ministry of the Environment or Tokyo Metropolis. Our result showed that irrigation channels had an important role for aquatic plants as their persistent habitat in the urbanized alluvial fan area. Comparing with past studies conducted from 1980s to 1990s, however, aquatic flora of this area degraded in some of the channel networks. Each species showed different distribution patterns. Distribution range of each species was concerned with their vegetative propagation character, such as root formation from plant fragments, rhizome formation, and the type of turion. Dispersal limitation between channel networks was also considered as a cause of limited distribution of some species. In addition, location of spring water seemed to determine restrictive occurrences of evergreen species which prefer cool water.

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