The consequences of nutrient loss (oligotrophication) and attendant low productivity on biodiversity and productivity in the ecosystem has recently invoked the interest of researchers, as result of loss of wild anadromous fish by acceleration of urbanization and deterioration of natural riparian ecosystem such as dam construction, habitat destruction, and artificial hatchery program. In Japan, chum salmon (Oncorhynchus keta) have been mass-produced by hatchery program, while numerous wild Pacific salmon have been almost extinguished by a combination of the urbanization and the deterioration of riparian ecosystem. This review focuses on effects of anadromous fish on biodiversity and productivity in the riparian ecosystem with relation to dynamics of nutrient, biofilm, aquatic insects, salmonids, terrestrial animals, and human activity, and isotopic evidence for enrichment of salmon-derived nutrients. Anadromous fish are key species for sustaining production and biodiversity in the riparian ecosystem. For sustainable conservation management of riparian ecosystem, the rehabilitations of wild salmon population, system of material cycle, and natural rivers are critical important issues in Japan.
The geology of Mt. Apoi (42°6'20" N and 143°1'40" E ; 810.6 m above sea level) consists of peridotite, on which an ultrabasicosaxicolous flora has developed. On September 7, 1939, 300 hectares of an area with this ultrabasicosaxicolous flora was designated as a natural monument of Japan with the title Mt. Apoi Alpine Vegetation, and on March 29, 1952, was further designated as a special natural monument. The most characteristic features of the flora of Mt. Apoi are that the proportions of endemic species, endemic varieties, and endemic forms are probably the highest in the world due to the effect of the bedrock, despite the relatively low altitude and the small size of the mountain mass, and that succession of vegetation to forest has not occurred over the last 10,000 postglacial years. We therefore compared the flora of Mt. Apoi with other ultrabasicosaxicolous floras such as that of Mt. Yubari, distinguished neoendemic species and paleoendemic species among the endemic species of the ultrabasicosaxicolous flora and, selecting genealogically close ecological equivalent species in the ultrabasicosaxicolous floras of various regions, analyzed the percentages of modified species. It was found that (1) many of the plants endemic to Mt. Apoi were neoendemic species, which were newly developed ultrabasic modified elements, (2) many of the species distributed to two or more ultrabasic rock areas were paleoendemic, being ultrabasic relic elements existing from older times, and (3) the percentage of species modified in the ultrabasic rock areas was higher on Mt. Apoi than in other ultrabasic rock areas. In addition, (4) the finding that none of the ultrabasic plants that constituted the peridotite flora located in the northern part of the Hidaka Range were restricted to that region highlighted the characteristically high proportion of endemic species on Mt. Apoi, which is a similar peridotite area.
The vegetational changes on sites of ultrabasic rock on both Mt. Apoi and Mt. Horoman, Hokkaido, Japan, were studied using the quasi-permanent quadrat method. As to the vegetation on Mt. Apoi, as shown in the synthesis table, past conditions in 1983 and 1994 and the present condition in 2001 were compared, including the changes in the endangered species Callianthemum miyabeanum. As a result, in the Hypocoerio-Caricetum tenuiformis including the above species, the total number of species, number of species per quadrat, and vegetational cover of the community were clearly decreased. The number of quadrats including flowering plants and dominance of Callianthemum miyabeanum in the community also showed clear decreases, although the constancy of the species showed an increase owing to settlement of the quadrats. On the other hand, with regard to the vegetation on Mt. Horoman, past conditions in 1994 and the present conditions in 2001 were compared in the same way as those for Mt. Apoi. As a result, in the Allium schoenoprasum var. yezomonticola-Viola brevistipulata var. hidakana community and the Hypocoerio-Caricetum tenuiformis, both including Callianthemum miyabeanum, vegetational cover of the community and the number of quadrats including flowering plants of Callianthemum miyabeanum showed clear decreases. The above differences in vegetational changes between Mt. Apoi and Mt. Horoman were considered to correspond to the differences in time length of the activities of illegal flower-pickers. Furthermore, the results obtained by the quasi-permanent quadrat method were compared with those for a limestone plant community including Callianthemum sachalinense subsp. kirigishiense from Mt. Kirigishi, Hokkaido. The quasi-permanent quadrat method is considered to be useful for showing vegetational changes from the viewpoint of conservational biology, although it requires further refinements.
Mt. Apoi (810 m above sea level, N 42°07', E 143°02') is located in the southern part of the Hidaka mountain range. Many alpine plants are distributed along the ridge, despite its relatively low altitude. From a botanical viewpoint, this mountain has a number of special and interesting features due to the abundance of endemic plants. The following factors may contribute to the growth of alpine, endemic and relic plants at low altitude : (1) Reduction of solar radiation as well as air temperature by fog in the summer. (2) The bedrock of Mt. Apoi is ultrabasic rock (olivine). The physical and chemical characteristics of this soil and rock environment are unfavorable for plant growth, and are the cause of the abundance of endemic plants on Mt. Apoi (Watanabe 1970, 1971). The alpine meadow plant community of this area has been altering as a result of invasion of woody plants over the last 40-50 years (Watanabe 2001). In the present study, we investigated the process of invasion of Pinus pumila and Pinus parviflora var. pentaphylla (a pioneer woody plant) in this alpine meadow by measurement of tree age. The special soil environment (ultrabasic rock) in the investigated area has helped to maintain the special alpine meadow on Mt. Apoi. The delicate relationship between the soil environment and alpine plant growth will be affected by global warming and/or acid rain, resulting in a rapid decline in the distribution area of the alpine meadow.
Mt. Apoi in Hokkaido is a massif in which olivine is the bedrock. There are many endemic plant species on this mountain, and alpine plants grow at a comparatively low altitude of 810 m. For these reasons, the characteristic soil environment is of considerable interest. In this study, metal ion exchange in the soil environment and plant distribution were investigated. The results showed that the environment has a high nickel and magnesium concentration and a low calcium concentration in areas where characteristic plant species are distributed, alpine plants growing mainly in olivine soil.
Callianthemum miyabeanum is a rare and endemic species growing on Mt. Apoi in Hokkaido, northern Japan. Size structures of Callianthemum miyabeanum were compared in five populations, and size-class transition based on basal-leaf number and flowering behavior of individual plants was monitored in a population during a four-year period to estimate the population dynamics. The proportion of juvenile plants having one or two leaves was about 90% in four of the populations, and the number of flowering plants was very small in every population. New recruitment was only 5% of all individuals, including revival individuals after one or two year's dormancy. About 60% of juvenile individuals remained at the same class in the following year, and 18% showed a decrease in size class. Plants that bloomed once within the monitored plots did not bloom again during the monitoring period. These results suggest that growth of this species is restricted by resources. Survival rate was high (88% on average) and increased with size class. Populations of this species were considered to be maintained by low mortality, despite the low recruitment.
On Mt. Apoi, an ultrabasicosaxicolous flora with probably the greatest proportion of endemic species in the world has developed. Moreover, the flora has not been subject to succession to forest over the last 10,000 postglacial years. In the past 50 years, however, the flora of Mt. Apoi has experienced rapid deterioration and decline, mainly because of human activity-namely the illegal gathering of plant specimens-and succession to Pinus pentaphylla forest, with dramatic encroachment on beds of alpine flora. The former phenomenon has been conspicuous in Japan since 1970, when popular enthusiasm for mountain herbs began to grow. Organized illegal gathering as an occupation subsequently became pronounced, and Callianthemum miyabeanum, and other populations have declined sharply. The succession has predominantly involved invasion of ultrabasicosaxicolous flower beds on the southern slopes, primarily by Arundinella hirta, Calamagrostis sachalinensis, and Miscanthus sinensis. These have paced the continued existence of these flower beds in extreme jeopardy, and have acted as a precursor to the succession to Pinus forest. Nucifraga caryocatactes japonica bury Pinus seeds in these flower beds, facilitating sprouting. Pinus individuals reach heights of about 2.5 m within 15 years, during which time invasion by Lespedeza bicolor var. nana and Sasa apoiensis accelerates succession to forest. Global warming is certainly hastening the pace of this change. The disappearance of the flower beds is no doubt causing the loss of plants such as the endemic Hypochoeris crepidioides, which is found only on Mt. Apoi. It can be concluded that the ultrabasic area has already entered the final stages of forest succession.