We investigated the invasion of Robinia pseudoacacia and subsequently affected riparian vegetation of the Saigawa and Azusagawa Rivers, which are upper tributaries of the Shinano River, the longest river in Japan.　Habitats that had been affected by river water disturbance in recent years were located at a height relatively near the river surface and were composed of coarse gravel with numerous annual plants.　We found subtrees and shrubs of R. pseudoacacia under willow canopies, but small willow individuals did not occur under the R. pseudoacacia canopies.　Furthermore, forest floors in willow communities hosted more wetland and riverside species, including herb species, than those beneath R. pseudoacacia canopies.　Mature R. pseudoacacia stands reduced the distribution of wetland and riverside species.　Furthermore, the species composition at these sites was not riparian, instead consisting of various forest species.　The resulting forest landscape is unlike the natural riparian zone in this area.

Habitat assessment plays a critical role in rare plant conservation.　In environmental impact assessments, developers often need to evaluate importance of vegetation types as rare plant habitats to mitigate the impacts of development projects.　However, information on rare plants is often difficult to obtain owing to rarity or non-disclosure.　A practical approach to link species occurrences and vegetation types therefore is needed for estimating distribution of plants within their habitats.　This study aimed to classify multiple plant habitats and associate them with the phytosociological classification system.　A total of 1129 relevés were classified into 129 plant communities based on a tabular comparison and 29 habitat types based on the occurrence of sixty-nine near-threatened species.　These habitat types clearly correspond to upper units of the phytosociological system and roughly correspond to keywords from literature descriptions of species ecology.　Habitat classification based on phytosociological plant communities is considered effective for plant conservation and impact mitigation.

Dicentra peregrina is a pioneer plant growing on the alpine periglacial debris fields or in the unstable volcanic desert in northern and central Japan.　In Yatsugatake volcanic Range, this plant is widely distributed around the gentle col between Mt. Ioudake and Mt. Yokodake.　To clarify the cause of extensive distribution of this plant, the authors examined volcanic geology and natural history of the areas where D. peregrina grows.　The authors found that the distribution of D. peregrina coincides with the distribution of fresh-looking scoria.　Therefore, the authors guessed that the scoria fields were made by small eruptions in recent geological age.　But this guess was not correct.　After the re-investigation, it was found that a small part of the scoria fields had been formed by the recent small eruptions in truth.　However, most scoria fields had been originated in old volcanic deposits, went back more than one hundred thousand years before.　Old welded scoria layers or tuff breccia had been disclosed after a long time of denudation of upper lava layers, and they had been decomposed by the severe frost action in winter season.　Along the col between Mt. Ioudake and Mt. Yokodake, old welded scoria layers or tuff breccia were distributed widely, and after decomposition of scoria layers and tuff breccias, suitable scoria fields for the growth of D. peregrina were formed extensively.　But in the case of thick tuff breccia strata exist on debris slope, they make small cliffs with no vegetation and under the cliffs small taluses come into existence.　On these taluses many kinds of alpine plants grow and D. peregrina is rather few.　In the case of thin lava layers existing on slopes, they were also destroyed by severe frost action and made into the rocky debris field.　There, D. peregrina are able to grow, although in low density.

This study performs to survey present marsh vegetation in Yonaguni island, Okinawa, Japan.　Over 38 years, the change of the vegetation has been reported.　In this study, twelve types of plant communities are identified, however, five of them were not reported in previous studies.　Also, most of survey plots, which are classified as newly found five communities, appears in abandoned paddy fields or reclaimed meadows from paddy fields.　Regarding exotic species, nine species are reported.　Out of nine, two species, Urochloa mutica and Symphyotrichum subulatum var. subulatum, are the first to appear in this study, and other two, Paspalum distichum and Alternanthera sessilis, shows the increase number of appearance compared to the previous studies.　Additionally, the land use maps reveal that the total area of the paddy fields have decreased by 68% from 1976 to 2014.　Some of the former paddy fields have marsh vegetation.　Large part of marshes in this island are composed of these secondary marshes.　This indicated that the former paddy fields could be important habitats for both native and exotic marsh species.

To evaluate the thalassochory potential of the coastal dune plant Linaria japonica Miq., the buoyancy and viability of seeds exposed to salt water （3.45% sodium chloride solution） were examined.　The results showed that most seeds continued to float on salt water for more than one month.　In laboratory germination tests under controlled conditions, the final germination rate was significantly lower in seeds exposed to salt water for one month than in control seeds without exposure to salt water.　However, more than 40% of the former seeds germinated.　In sowing tests using pots under outdoor conditions, there was not a significant difference in the final emergence rate between seeds exposed to salt water for two months and control seeds.　These results suggest that L. japonica has thalassochory potential, and its viable seeds can be successfully dispersed over a long distance via sea currents.