To estimate potential loss of thermal habitat for Dolly Varden (Salvelinus malma) due to global warming, the relationship of population density and growth of Dolly Varden to stream temperatures was studied during summer in a cold spring-fed stream at southern margin of their range in southern Hokkaido, Japan. A simple regression equation was obtained for the longitudinal gradient of the stream temperature, logarithmically increasing downstream. Summer habitat of Dolly Varden was delimited by a thermal barrier of about 16℃, located approximately 10km downstream from the headspring, with fish density decreasing downstream. During mid summer, the specific growth rate of Dolly Varden decreased near the thermal barrier (probably due to too-high stream temperature), but not in the upper reaches of the stream where the temperature was lower. The upstream movement of the thermal barrier as a result of global warming was estimated from the elevation of groundwater temperatures and regression analysis of the longitudinal gradient of the stream temperature. For increases of 1.0-4.0℃ mean annual air temperature, the summer thermal habitat for Dolly Varden would be reduced by 25.0-74.0%.
The distribution pattern of a native population of Elatostema densiflorum, designated as a vulnerable plant species in Japan, was surveyed in Fuchu, Tokyo, in 1993 using the quadrat method. This population included a Houttuynia cordata community. The number of individual E. densiflorum plants was negatively correlated with the coverage of tree litter. The size of the plants was greater in areas excluding litter and other plants. The distribution of the plants was contiguous in the quadrats containing litter and other plant species, while it was random in quadrats without them.
Bird communities in a deciduous forest in Tama Hill, a suburb of Tokyo, were compared between 1968/69 and 1994. There was no obvious difference between the two periods in number of bird species recorded in all observations (S^+). However, the number of species recorded in the census area (S), the diversity (H') and the total number of birds were higher in 1994 than in 1968/69. Some resident species such as Siberian Meadow Bunting (Emberiza cioides), Bull-headed Shrike (Lanius bucephalus), and Tree Sparrow (Passer montanus) decreased in number, and 9 seasonal species disappeared altogether. Other resident species such as Brown-eared Bulbul (Hypsipetes amaurotis), Great Tit (Parus major), and Japanese Pygmy Woodpecker (Dendrocopos kizuki) increased in number, and 14 new seasonal species appeared. The dominant species changed drastically from Siberian Meadow Bunting and Rustic Bunting (Emberiza rustica) in 1968/69 to Great Tit and Brown-eared Bulbul in 1994. These changes were probably related to environmental changes such as fragmentation of habitat, and growth and succession of forests in and surrounding the study area.
The depth-of-subcutaneous-fat index (SFI), the weight-of-omentum-fat index (OFI), Riney's kidney-fat index (KFI), and relative body weights (RBW) were measured in 32 adults (20 females, 12 males) Japanese monkeys (Macaca fuscata) collected in Nikko, central Japan during 1983-90. Most indices of fat were significantly interrelated (P<0.05). The SFI was useful as an indicator of relatively good condition, the OFI and KFI were useful indicators of relatively poor condition, while the RBW had no value as an indicator of physical condition. The OFI of adult males and adult females increased in early summer and summer, respectively, and declined over winter in both sexes.
A new understanding resulting from recent studies on the mechanism of marine algal succession has enabled a means to control its process. Crustose coralline red algae occur as climax communities, called coralline flats, due to biological and hydrographical factors in the process of sublittoral cyclic succession. Coralline flats enlarge its area when other climatic phases of large perennial brown algae, marine forest, are reduced by combined hydrographical factors. High temperatures and/or low nutrients result in decreased marine forest. Destructive grazing by dense populations of herbivors maintain the coralline flats. Since the secondary metabolite of crustose corallines, dibromomethane, induces normal metamorphosis of sea urchin larvae, this algal-origin chemical enforces the interaction between herbivors and coralline flats. Marine afforestation in coralline flats contributes towards reduction of grazing pressure due to the growth of large annuals at the primary stage. This relative decrease in grazing pressure drives algal succession towards the marine forest phase. An increased survival of large perennials establishes the marine forest in the final stage. Sustained coralline flats called "Isoyake", which have wrought considerable damages to the fisheries industry, could be restored ecologically with this technology.
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