JAPANESE JOURNAL OF ECOLOGY

Communities and populations of forest plants in urban areas may be modified by human activities. The vegetation at 50 study sites in fragmented urban forests in Kamakura, Japan, was studied in 1988 and 1998. Changes in the plant community during a decade were analyzed by principal component analysis. In normal succession, vegetation usually shifts from deciduous forest to evergreen forest. However, the forest communities did not show such a shift to evergreen forest. Therefore, normal succession was not dominant in these fragmented urban forests. Some evergreen plants, pioneer trees, and forest-edge plants significantly increased in frequency during the ten-year period. No significant decrease of forest plants was observed. This change in species composition was related to the distance of the study site from the nearest road, residential area and forest edge, and to the number of zoochoric species. Invasion of zoochoric species from roads, residential areas and forest edges may have an important influence on community change. Such an edge effect on population levels should be considered in community conservation planning, in addition to the physiological edge effect caused by sunlight and wind. The effect of roads decreased with distance inside the forest.

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Many missing sinks still remain in the global carbon cycling system. It is important to find the missing sinks in temperate-forest ecosystems as well as arctic-tundra ecosystems, since these forests cover a large part of the global ground surface. In general, a forest consists of several stories of plants, but few studies have focused on the forest floor vegetation. We have noticed the importance of understory plants in the carbon budget of a forest ecosystem. Therefore, we studied the carbon balance of forest floor vegetation composed of a Sasa senanensis community in a cool-temperate forest, in central Japan. The Sasa senanensis community showed seasonal and annual changes in the component organic matter with different age variations. All the leaves were viable for 3 years after spreading out and almost all of the culms were viable for about 5 years after sprouting. The annual averages of above-ground biomass were about 6.8 t d.w. h^-1 in 1993 and 6.6 t d.w. ha^-1 in 1994. The annual averages of underground biomass were about 5.9 t d.w. ha^-1 and 3.9 t d.w. ha^-1, respectively. The rate of monthly net production of the Sasa community was high in spring and autumn when the deciduous canopy trees were leafless. On the other hand, net production was minus during summer because of the shortage of solar radiation penetrating to the forest floor. The rate was also minus during the snowbound season. Net production and gross production were estimated to be 1.1〜1.2t C ha^-1 yr^-1 and 5.2〜6.3t C ha^-1 yr^-1, respectively. The annual respiration of the Sasa community was about 4.1〜5.1 t C ha^-1 yr^-1. We evaluated that this deciduous forest absorbed carbon dioxide in spring before greening of the deciduous trees, and in autumn after leaf shedding. This suggests that the active carbon assimilation of the floor vegetation contributes to the total carbon absorption of the whole forest during the leafless season.

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We conducted fecal analysis of the common bat, Pipistrellus abramus, foraging above rice fields in Kyotanabe City, Kyoto, Japan. Two classes and eight orders of arthropods were identified. Most of the prey arthropods were flying insects such as Diptera, Hemiptera, and Hymenoptera. The diet composition varied seasonally, and the principal prey taxon changed from Diptera in June to Hemiptera in September.

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Genes move between plants through reproduction, in a process known as gene flow. There are various statistical methods for quantifying current spatial genetic structures of populations, and the recent development of highly polymorphic markers has made it possible to identify gene flow between individuals with high accuracy. Nonetheless, none of the previous methods provides satisfactory visual imaging of the continuously changing spatial genetic structure resulting from gene flow and reproduction. In this study, we developed visualization techniques for illustrating spatial genetic structures on commonly used spreadsheet files, for one specific case study. When combined with basic gene flow models over two generations, we can quantitatively assess the effects of ecological factors in reproduction on spatial genetic structures of offspring, together with visual illustrations. Consequently, for the specific population, we can easily recognize how spatial genetic structure is affected by the density of parents and distance distributions of pollen and seed dispersal, and that if the ratio of maternal adults succeeding in reproduction is small, then extensive pollen flow will be necessary in order to preserve the current genetic diversity.

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