Most of the submergent vegetation in Lake Kasumigaura, Japan, has disappeared due to eutrophication, the construction of concrete embankments, and the artificial control of water levels. However, some propagule banks remain and include several species of submergent macrophytes. We investigated whether submergent macrophytes could be regenerated from propagule banks if they were protected from fish. Four fish-free enclosures were installed in the littoral zone of Takahamairi Bay, Lake Kasumigaura, in July 2002. Two weeks later, the density of crustacean zooplankton had increased to >500 individuals l^<-1> , chlorophyll a concentrations had decreased, and transparency had increased. By one and a half months after installation, however, both the density of crustacean zooplankton and the transparency had decreased. The macrophytes Potamogeton malaianus, Hydrilla verticillata, Elodea nuttallii, Egeria densa, and Trapa japonica emerged in all enclosures. Therefore, we suggest that fish-free enclosures may be useful for restoring submergent macrophytes in the littoral zone of Lake Kasumigaura.

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The species composition of submergent plants in propagule banks found in the sediments of Lake Kasumigaura, Japan, was investigated. Soil was dredged from the lake and spread over a 23,000m^2 area of the littoral zone, which sloped gradually from 0 to 100 cm in water depth. Nine submergent plant species grew from the dredged soil, including three endangered or vulnerable species, Chara braunii, Nitella hyalina, and Potamogeton pectinatus. These results suggest that distributing soil in the littoral zone is an effective approach for revegetation with submergent plants in Lake Kasumigaura.

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The largest seagrass bed along the coast of Okinawa Island, southwestern Japan, is located offshore from Henoko and covers 173 ha; the second largest is offshore from Awase and covers 112 ha. Both of these seagrass beds are threatened by the proposed construction of a U.S. military airport and by reclamation. To ensure that the environmental impact assessment compiled before development is fair and correct, an independent scientific survey conducted by citizens should be effective to monitor the development. Given these facts, the Nature Conservation Society of Japan decided to launch a community-based Seagrass-Watch monitoring program called "Okinawa Jangusa-Watch". In this program, volunteers were first trained to identify seagrasses and in the survey method; then, they measured the coverage of each seagrass species by snorkeling at two sites (Kayo and Henoko). After calibrating each observer's error, the distribution and abundance of seagrass were analyzed for each site. Each seagrass species had a specific distribution pattern, based on the distance from the shore. At Henoko, the seagrass coverage determined from the analysis of aerial photos was underestimated, as compared to the coverage measured in the ground survey. A mitigation plan that considers the variation in species composition and seagrass coverage obtained using the ground survey is needed to assess the effects of relocating the U S. military airport. Wide-range, long-term monitoring of seagrass beds by citizens should be effective with regard to monitoring the impact of red soil erosion and global environment change on seagrass beds, and in monitoring specific development projects.

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Kushiro Mire, a marsh located near the mouth of the Kushiro River, is suffering from the cumulative effects of pollution caused by land-use development in the watershed. A high wash load is of particular concern and accounts for approximately 95% of the total suspended sediment load that flows into the marsh. Research has found that turbid water floods the margins of the marsh; this is due to riverbed aggregation in a channelized stream reach that provides agricultural drainage. An analysis of Cs-137 concentrations determined that the rate of fine sediment deposition was approximately three to eight times higher in the channelized reach than in a reach of the natural river. This rapid sediment deposition has lowered groundwater levels and enriched the nutrient content of the marsh soil. Consequently, woody species are rapidly invading the margins of the marsh, causing concern about a vegetation shift from reed-dominated marsh to woodland To address the physical and biological changes that are taking place in Kushiro Mire, various restoration projects have been planned and are being implemented under the Kushiro Mire Conservation Plan. Two examples of projects in the Kushiro Mire Conservation Plan are a forest restoration near Takkobu Lake and a wetland restoration of a crane habitat. Fine sediments and nutrients have been accumulating in Takkobu Lake because of agricultural development and soil erosion in the uplands. The number of aquatic species in the lake has also been decreasing. An environmental assessment was undertaken in collaboration with "Trust Sarun", a non-profit organization, and sites were selected for conservation and restoration work. A larch forest was purchased to prevent it from being clear-cut and thus increasing sediment loading in the lake. The forest will be restored to its natural state. In addition, the Ministry of Environment in the Hirosato District acquired a wetland restoration site that was originally designated as an "ordinary area," i.e., the least regulated area of a national park. The restoration site is an abandoned agricultural field with an old drainage system developed in the 1960 s; it is an important breeding habitat for red-crowned cranes (Grus japonesis) Based on a preliminary investigation, and under careful supervision to avoid disturbing the cranes, soil excavation and seeding experiments have been undertaken.

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Ohdaigahara has one of the largest natural forests in western Japan. The forest, however, is facing collapse because high densities of sika deer strip tree bark and browse on tree seedlings. The Ministry of the Environment has selected the forest in this area for restoration. In the Fagus crenata Blume-Abies homolepis Sieb. et Zucc.-Sasa nipponica Makino et Shibata community, one of the three main vegetation communities in Ohadaigahara, we conducted field experiments with manipulations of Sasa nipponica deer, mice and/or birds. The soil, plant and animal communities have been monitored since 1997. We also compared vegetation and bird communities among sites with different densities of deer. We found that the population of sika deer and the aboveground biomass of Sasa nipponica are currently in equilibrium, with a balance of supply and demand. In deer exclosures, however, the aboveground biomass of Sasa nipponica showed an eight-fold increase over a five-year period. A system dynamics model was constructed for deer-Sasa nipponica-soil interactions within the nitrogen cycle. In addition, the model included the effects of deer density and Sasa nipponica biomass on the number and diversity of tree seedlings, arthropods and birds. With the aim of promoting forest regeneration and an increase in ecosystem biodiversity, we determined the best management strategy for the deer population and Sasa nipponica biomass. We concluded that the aboveground biomass of Sasa nipponica must be reduced, along with a removal of deer, to prevent a rapid increase of Sasa nipponica biomass inhibiting the survival of tree seedlings. We also found that there is no optimal deer density or Sasa nipponica biomass, because they have different effects on different groups of organisms. Based on the model predictions, we present various proposals for restoring the Ohdaigahara forest.

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We describe the ecosystem management of habitats containing alien species, and discuss related problems in theory and practice. We introduce two examples and a mathematical model, which show that the control of one alien species can cause an increase in another alien, with consequent severe damage to the native species community. On Amami-oshima Island in southwestern Japan, the Japanese government has been controlling an alien Java mongoose (Herpestes javanicus) , where a large population of alien black rats (Rattus rattus) also inhabits. We fear that if the rat population is released from predation by the Java mongoose, it will then damage native animal populations. We also suggest that the yearly fluctuation in nut production by Castanopsis sieboldii Hatusima ex Yamazaki et Mashiba has a big impact on community dynamics, including alien species. We also discuss the practice of adaptive management and the role of scientists in forest-ecosystem conservation on Amami-oshima Island.

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Dendranthema indicum (tetraploid with 2n = 36, rarely with B chromosome(s)), a wild chrysanthemum, is distributed mainly in Japan, Korea, and China. A survey of plants on roadside slopes in Oda Town, Ehime Prefecture, found a wild chrysanthemum population identified as D. indicum sensu lato that differed from native Japanese populations in that it had adventitious roots on the middle/upper stems, which is characteristic of var. procumbens, a variety of D. indicum that is distributed in southeastern China. As the population was restricted to a recently built roadside slope that was seeded with shrubs, and no population of native D. indicum was found nearby, the chrysanthemum likely invaded from elsewhere, probably China. In addition, putative hybrids between D. occidentalijaponense (hexaploid with 2n = 54), a wild chrysanthemum endemic to Japan, and the invader D. indicum were found nearby. Cytological studies revealed that these hybrids included the first generation (2n = 45, pentaploid), further generations, and a heptaploid (2n = 63) thought to be derived from an unreduced D. indicum gamete (n = 36) and a normal D. occidentalijaponense gamete (n = 27). This genetic contamination of D. occidentalijaponense and genetic invasion by a foreign chrysanthemum is a cause for great concern.

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Flower visitations by both native and exotic bumblebee species were investigated at 21 monitoring sites in various regions of Japan in the spring and summer of 2002. The investigation was part of a long-term program that has been in progress since 1997 to monitor the invasion of an alien bumblebee, Bombus terrestris L. (Hymenoptera: Apidae). Flower visitation by B. terrestris was ascertained at two monitoring sites, one in Shizuoka and one in Hokkaido, where a large number of colonies of this species have been commercially introduced for agricultural pollination.

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