Effects of light intensity and temperature on the growth of six submerged macrophytes growing in Lake Biwa, Japan, were examined using an experimental growth system. Light intensity and temperature were controlled at five (100, 50, 25, 13 and 1 %) and four (11, 17, 23 and 29°C) levels, respectively, and shoot length, dry weight, and total leaf area were measured at 10 day intervals for 60 days. Potamogeton malaianus died in 20 days at a water temperature 23°C and light intensity of 1 μmol/m²/s. The exotic species Elodea nuttallii died in 30 days at a water temperature 29°C and light intensity of 1 μmol/m²/s. However, Potamogeton maackianus and Hydrilla verticillata survived in all temperature and light conditions. Light compensation points were 12 μmol/m²/s for P. malaianus and Vallisneria asiatica var. biwaensis, and 1-6 μmol/m²/s for P. maackianus, H. verticillata, Egeria densa and E. nuttallii. Comparison of the Relative Growth Rate of each species showed that V. asiatica, H. verticillata and E. nuttallii had high values at a water temperature of 29°C, and P. maackianus and E. densa had high values at a water temperature of 23°C. Egeria densa, H. verticillata, E. nuttalli and P. malaianus showed faster shoot elongation, P. maackianus and V. asiatica slower. When shoots were near the water surface, the elongation speed of E. nuttallii, E. densa and H. verticillata decreased, and active branch extension was noted. However, P. malaianus shoots elongated. We confirmed that each species of submerged macrophyte showed specific responses to minor changes in water temperature and light intensity at around the compensation point, and responses specific to each species to seasonal fluctuations of the water level can be predicted.

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This study investigates the species distribution of willow forests at 23 rivers in Japan. These rivers were categorized into four groups (G1 to G4) by flooding histories and Salix species. G1 and G2 groups are located in Hokkaido and Tohoku/Hokuriku districts, respectively, which are characterized by snowmelt floods in April to June and predominance of northern species fitted to low temperature. G3 group is rivers in Kinki/Chugoku districts, where snow melt floods occur in January to March and moderate temperature species are dominant. Rivers in Kanto/Chubu/Kinki/Shikoku/Kyushu districts, categorized by no snowmelt floods and warm species, are selected into G4 group. The comparison was conducted for the ratio of the willow forests (WF ratio) and the total forests (TF ratio) with respect to the surveyed length (TF) in gently sloped river channels (=1/5000-1/500). The WF ratio was greatest for G1 (72%), followed by G2 (45%), G3 (25%) and G4 (4%). The ratio did not differ significantly between G2 and G3. The TF ratio was greatest for G1, followed by G2, G3 and G4, although there are only slight differences between G1 and G2 and between G2 and G3. The influence of flow regimes on WF ratio was also investigated, indicating that although the number of days of snow melt floods are positively correlated to WF ratio, summer flood days had a negative correlation. These findings indicates that Salix species compositions fall into three regional groups, or four if flood types are considered. The WF ratio differed among those four groups. Thus, the regional factors are important for riparian forest management.

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We examined effects of fine sediment on embryo survival rate and on redd environments of an endangered species, Sakhalin taimen (Hucho perryi). Sediment accumulation, permeability, water quality and embryo survival were quantified at the redds in mountain streams in northern Hokkaido, Japan, and their correlations were assessed. The results indicated that the survival rate was negatively correlated with dissolved oxygen concentration. However, the direct effects of fine sediment on the embryo were not clarified because the accumulations were low in those streams. Moreover, results clarified that accumulations lower the interchange ability of redd water and conduction of heat, despite the low accumulation level. Further research must investigate the fine sediment effects associated with heat flux.

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We examined the influence of forest fragmentation on species composition of non-flying mammals. We classified the study sites into three isolation gradients (mountain forest, continuous forest, and isolated forest), depending on the degree of isolation of each forest type, and chose three study sites from each isolation gradient. We located remote cameras along animal trails from April to October in 2005 and 2006, and recorded species composition and Relative Abundance Index (RAI) of non-flying mammals. Analysis of species presence or absence was done using non-metric Multi-dimensional scaling (nMDS) and Hierarchical Cluster Analysis (HCA) techniques. Non-flying mammals in the habitats were classified into four types: (1) mountainous species inhabiting mountain forest at high frequency; (2) hill species inhabiting mountain forest and continuous forest; (3) widely distributed species inhabiting mountain forest, continuous forest, and isolated forest; and (4) Locality species locally inhabiting mountain and continuous forest. Species richness decreased as isolation increased. Therefore, we conclude that mountain forests are species sources, and isolation forests are important habitats for generalist species. In the ecological network planning, mountain forests may function as core areas, and isolation forests may function as base and center for generalist species.

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Although most of the natural coasts in the temperate regions of Japan are composed of rocky reefs along the shore, there have been only a few reports on the relationships between fish communities and rocky reef structures. In this study, researches on relationships between several reef structures and fish communities were conducted based on long-term observations in the shallow sea areas in northern Kyushu, Japan. These survey areas were divided into 4 environmental clusters by using multivariate statistical techniques based on reef structural data. Further, each environmental cluster that provided the intended meaning was retained. In analyzing fish community data, these survey areas were also classified into four clusters (fish community cluster), and we were able to associate each fish community cluster with its corresponding environmental cluster. In addition, several structural factors were positively or negatively correlated with several fish community data. The diversity index of reef structure correlated positively with the diversity index of fishes and the number of fish species; the proportion of rocky bottom areas and the frequency of sea algal correlated positively with the number of individuals. A negative correlation was observed between average depth and the number of immature individuals. These results suggest that diversity of fish communities require reef structures such as a diversity bottom and abundant algal cover. In addition, immature fish require shallow areas for habitation.

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[in Japanese]

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In Lake Kasumigaura, the second largest lake in Japan, lakeshore conservation projects started in 1988 and more than 140 projects were completed by 2002. Yet little appraisal of these projects has been conducted. We carried out an evaluation of lakeshore conservation in light of the physical environment, i.e. change in the lakeshore area and the ratio of vegetation to sandy beach. We concluded that most conserved sites successfully increased the lakeshore area; however, the extent of sandy beach, working as the other important component at lakeshore, is diminishing at the conserved sites because of vegetation encroachment under stable condition. To keep the sandy beach in balance, the introduction of wave disturbance, e.g. appropriate opening in the breakwater, is found to be useful.

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Based on data for riparian revegetation for Phragmites japonica and Carex dispalata, a situation was surveyed in which ecotones ware formed. In place with riparian revegetation, the planted species were dominant and spreaded in the water area, which contributed to creation of a diverse riparian environment, for instance by decreasing the flow velocity in the riparian area. Phragmites japonica grew runners and spreaded throughout the growth area. It readily creates riparian ecotones, even in rapids. However, in some cases, the plant grows as high as 2m, which obstructs view and undesirable from a landscape point of view. In the cases in Carex dispalata, which does not obstruct view, was used, vegetated bank protection was formed in the stream. The growth area of Carex dispalata is smaller when the roots are in the water and stems of the plants are above the water. However, it is expected to function as a riparian ecotone. When using a coconut fiber roll, vegetation bank protection must form before the coconut fiber deteriorates. It is important that planted plants advances to a water side, especially to diversify the waterside environment. For the reason, Phragmites japonica and Carex dispalata, a perennial plant which can advance to a water areas, must be planted.

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[in Japanese]

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