The purpose of this study was to elucidate the restoration process of the flora at an artificial beach formed by sedimentation of drifted sand through the use of artificial structures, such as breakwaters. The Kasai Marine Park was built in 1976 near the Tokyo urban area to conserve the natural ecosystem. In particular, the East Beach area was constructed inside the park as a sanctuary for marine species, including coastal plants. The investigation of flora was conducted and vegetation maps were created in 1986, 1996, and 2001. We referred to these reports and investigated the coastal vegetation in 2008. We simultaneously collected the 7 documents in which the records of the coastal plants of the Tokyo Bay area (except for the Kasai Marine Park) had been published. These records were used for the analysis of our field investigation data. Results showed that in the Kasai Marine Park, the area of vegetation had spread and the number of plant communities and species had increased over time. From the detailed analysis of the Kasai Marine Park flora, we showed that both the coastal grassland plants and the sea cliff plants had increased over time, contributing to the return of native beach flora to the Kasai Marine Park. Because U-shaped (open toward the offing) breakwaters often catches the sand drifts, resulting in the formation of various microtopographies in this area. These have enabled the immigration of more coastal plants over time. In this study, we identified the basic species of coastal vegetation in Tokyo Bay. The number of species and areas of beaches were significantly correlated. These results enable the prediction of the number of species required in the creation or restoration of the coastal beaches in future. Our results provide useful information for the rehabilitation and restoration of the Tokyo Bay.

View full abstract

The influence of riparian landscape change on the fish richness and abundance was studied in a river flowing through the Satoyama area of the Noto Peninsula, Ishikawa, Japan. The fish collection survey, aerial photo interpretation and interview survey were performed to clarify the present and past status of fish fauna and its surrounding riparian environment in a small catchment located on the Noto Peninsula, Ishikawa Prefecture. In the upper reaches of the Kumaki River, masu salmon (Oncorhynchus masou masou), takahaya (Phoxinus oxycephalus jouyi), aburahaya (Phoxinus logowskii steindachneri) and bullhead (Cottus pollux) dominate the waters. In the middle and lower reaches of this river, Japanese dace (Tribolodon hakonensis) and Oyoshinobori (Rhinogobius sp.) dominate. In total, fifteen species of fish were caught during the field survey. We analyzed environmental factors to determine species richness and biomass using GLM (generalized linear models). Results of the analyses indicates that various sizes of riverbed substances were significant for fish biomass, and pools with covers and contain a higher gravel rate were important for fish richness. Results of aerial photos and survey interviews on the past riparian environments before rapid economic growth occurred, indicates that although channel morphology has not changed, riparian forests on river banks have decreased by one third since 1963, when the embankment was replaced with a concrete one, and was ten time longer than the 1963 one. Critical habitats such as deep pools were lost within the last 50 years, so that dominant fish species in the past such as ayu (Plecoglossus altivelis altivelis), catfish (Silurus asotus), eel (Anguilla japonica) remarkably declined. These results indicate that both pools with cover and a riverbed with abundant amounts of gravel are critical factors in order to maintain a rich fish fauna environment.

View full abstract

Over-abundance of deer population in forest landscapes are thought to have significant impacts on the abundance and diversity of birds by reducing shrub and ground vegetation layers. There is, however, little evidence of deer impacts on bird at species level because previous studies only provided deer impacts on avian guild level. Here, we assessed the impacts of sika deer on breeding site selection of ground-nesting bird, Asian stubtail in the forest landscape with over-abundant deer population, Nakajima Island of Lake Toya, Hokkaido. First, we recorded population trends of forest birds from April to June 2010 by using line-transect distance sampling. Secondary, we used automated sound recording survey for determining songs of Asian stubtail in 10 rectangular quadrats (20 x 20 m) between 5:00 - 5:30 a.m. from mid-April to late-July, 2011. Then, we collected understory vegetation coverage and height from 80 sub-quadrats (8 sub-quadrats in 1 x 1 m for each rectangular quadrat). A number of bird species at forest understory was low, and some major shrub-layer birds such as Japanese bush warbler were absent in this study area. On the other hand, we collected 525 hours of active bird songs with automated sound recording, and were able to detect 11,021 callings of Asian stubtail during breeding seasons. The forest understory was dominated by unpalatable plants for deer, Japanese pachysandra and Aleutian ragwort. Although the stubtails were present at all 10 quadrats during mating season, only 6 quadrats were used for natal and breeding sites. Based on limited numbers of calling observed consecutive breeding seasons, deer overabundance could affect breeding site selection of Asian stubtail; however, even if unpalatable plants cover exceeded 20 % of ground, and if height of ground vegetation exceeded 20 cm in height, we concluded the stubtail could breed successfully in the deer over-browsed forest landscapes.

View full abstract