Seasonal growth patterns of seedlings in open and shaded conditions were recorded for 31 deciduous broad-leaved tree species. Heavy seed species had a shorter growth period than light seed species to attain their maximum height. Early attainment of maximum height is advantageous to heavy seed species ; establishment in the forest understory, and in small gaps where there is sufficient light, can then occur before the leaf expansion in the canopy layer. Hypocotyl length or height of first leaf of heavy seed species were higher than those of light seed species. With long growth periods, light seed species could attain maximum heights comparable to those of heavy seed species. In shaded conditions, the growth period of light seed species became shorter, and height was lower than that of heavy seed species. Light seed species were assumed to be adapted to growth in open sites where light conditions are more favorable throughout the growing season than in the forest understory.
The fall of nuts and cupules and the survival of seedlings was studied in a natural beech forest in the Chichibu Mountains of Central Japan for three years (1984-1986) to clarify the regeneration dynamics of Fagus japonica MAXIM. The density of nut fall varied greatly from 310±99.64 nuts/m^2 in 1984 (a good mast year) to 0.08±0.16 nuts/m^2 in 1985 (a lean year). In 1984,the nut fall of F. japonica was not concurrent with that of the F. crenata in the same stand, and the ratio of sound nuts (31.9%) was nearly half of the sum of the percentages of empty husks and nuts damaged by insects, mammals and birds (39.8%, 15.5%, and 12.9%, respectively). Only 1.05% of the fallen sound nuts germinated, resulting in a density of 1.04 seedlings per 1.0m^2 in the following spring. A large number of the seedlings (about 98.6%) were infested by aphids (Phyllaphis fagi L.) and died by the end of June. The large variation in frequency and quantity of nut fall and the high mortality of seedlings suggest that the maintenance of seedling banks under the F. japonica canopy is tenuous. The successful regeneration of F. japonica forests is discussed, noting the relationships between seedling production, canopy gap formation, and sprouting.
Literature on the recent changes in the coastal biota of Hatakejima Island (33°41′N, 135°22′E) was reviewed and possible causes of the changes were explored. Six hundred and twenty one species of animals and plants have been recorded on this island's seashore. Three quarters of them are invertebrates. The coastal biota has prominently changed in the last three decades ; 64 species (>10% of all) increased or decreased conspicuonsly. The number of decreasing species was 5 times greater than that of the increasing ones. The decline in number of species was more obvious in molluscs and echinoderms than crustaceans. Water pollution seems to be an important cause of the observed changes. Oligotrophic species decreased and eutrophic species increased. Several species have disappeared only from the bay-head side of the island where pollution has been serious. Some circumstantial evidence suggests that the changes are also due to low temperatures in winter and harvesting of edible species by local people.
Ecological variation in Aconogonon weyrichii was studied at 3 sites. Comparisons of morphological characteristics were done at an open highland site, an open lowland site and an alder-forest site, Biomass and resource allocation comparisons were done at the open lowland site and the alder-forest site. Both open sites had oligotrophic mineral soil with low vegetation cover, whereas the forest site had eutrophic organic soil with high vegetation cover. Morphological characters were relatively similar at both open sites, and A. weyrichii populations had the same life-cycles. At the forest site, A. weyrichii was much larger in size and biomass than that at the lowland open site. The open site type had very deep vertical rhizomes which produced aerial shoots at the same locations every year. The forest site type had very dense and dynamic horizontal rhizomes which had many dormant buds, and actively produced large, dense ramets. The open site type allocated much resource expenditure to flower production, whereas the forest site type allocated much resource expenditure to aerial stems. High resource allocation to aerial stems and rhizome differentiation (vertical vs. horizontal) relative to forest type are adaptations which enable A. weyrichii, originally growing at unstable open sites, to grow in the alder-forest.
Age structures were surveyed in four plots of temperate coniferous forest dominated by Cryptomeria japonica, Abies firma, and Tsuga sieboldii in western Yakushima, southern Kyushu. The oldest stump in the plots was of Cryptomeria japonica, and more than 945 years old. Many trees of this species were between 100 and 300 years old. Their main regeneration periods had occurred later in upper river plots than in the lower plots. This might be the result of the harvesting locations of C. japonica from 300 to 100 years ago. Most Abies firma and Tsuga sieboldii were older than 250 years although their potential life spans were shorter than C. japonica. Only C. japonica trees were cut selectively. One of the A. firma stumps was 624 years old, the oldest known for this species in Japan.
An investigation on the altitudinal distribution of forest birds was conducted on Yaku-shima Island, south-western Japan, in May and June, 1983. Four assemblages of dominant bird species were recognized in the varying plant communities ranging from the coast to the mountains ; Parus varius, Ficedula narcissina, Zosterops japonica, Cettia squameiceps and Hypsipetes amaurotis were observed in evergreen broad-leaved forest (40-900 m), P. ater, P. varius, F. narcissina and Troglodytes troglodytes in Cryptomeria forest with evergreen broad-leaved trees (900-1200m), C. diphone, P. ater, T. troglodytes and Erithacus akahige in Cryptomeria forest with deciduous trees (1200-1555m), and C. diphone in Pseudosasa scrub (1555-1935m). Garrulus glandarius, H. amaurotis, F. narcissina and C. squameiceps resided in habitats different from those of conspecific populations on the Japanese mainland. The low-diversity bird communities of Yaku-shima Island are comprised of a small number of species. In both the Cryptomeria and evergreen broad-leaved forest, the richness of insectivorous species foraging in the lower forest layer and insect/frugivorous species was greater than that of the bird communities of the same forests on the mainland.
Studies on the effects of deer on plants and plant communities were reviewed. Many studies describe the floral and quantitative changes of community composition, but analytical studies based on autecology of each plant species are quite limited. Studies focusing on species diversity of plant communities are few. Grazing and browsing effects of deer and other herbivorous mammals are different from mechanical cutting in that animals eat plants selectively according to preference. Understanding of variables associated with this preference is essential for this kind of study. Anti-herbivory strategies of plants are divided into "exposing" strategy and defensive strategy. The former is adopted by graminoids, particularly by short grasses. The latter strategy is further divided into chemical defense and physical (mechanical) defense. Chemical defense is found in many forbs and shrubs but in few monocots or tree species, suggesting that this strategy is developed in particular taxonomic groups. Physical defense, typically shown by thorns, is found in many shrubs and several forbs. Discussion on interrelations between grasses and grazers would be more fruitful if they are focused on the meaning of grazing for plant communities rather than for plant species. Characteristic cervid behavior such as fraying and wallowing should be reconsidered in light of the effects on vegetation.