The course of sporophyte development in Dryopteris amurensis and Dryopteris austriaca was followed by observations of the frequency distribution of populations and sporophyte structure, as represented by the leaf arrangement, ontogenetic changes in leaf-shape and fertility. The developmental age was measured quantitatively by the number of midrib branches of the leaf (NV, number of venation). When measured in this way, the maximum developmental age of leaves of D. amurensis was 41,and that of D. austriaca was 62,in the populations around Sapporo. The initiation of fertility was measured as a percentage of the smallest NV of fertile leaves to the maximum NV (RDA, relative developmental age) ; it was 78% for D. amurensis and 60% for D. austriaca. The ratio of the number of fertile leaves to the number of total leaves was 0.109 in D. amurensis and 0.489 in D. austriaca. Leafshape was quantified by the presence of costa branches (NV of pinnae) and was similar for both species up to a NV of 40. A greater values of NV, the leaf-shape changed from pentagonal-oval into ellipticaloval, and the leaf number in a sporophyte increased in the mature sporophyte of D. austriaca. When analysed in these ways, it appeared that D. austriaca has a greater degree of sporophyte development than D. amurensis in northern Japan.
The dynamics of current seedlings, mainly Cryptomeria japonica, were studied under different canopy tree densities in a cool-temperate forest at Ashu, Kyoto in 1979 and 1980. Most seedlings germinated early in the growing season. Germination was mostly dependent on the amount of rainfall, and most mortality was caused by predation and drought. The survival rate of Cryptomeria japonica seedlings was similar in 1979 and 1980. A larger number of seedlings germinating meant a larger number seedlings established. The probability of death for seedlings was higher in the early growing stages, and dead seedlings reaching to later growing stages were very few. These results reveal that germination of Cryptomeria japonica in this stand is greatly enhenced by rainfall, rather than temperature and current seedlings growing quickly lead to their higher survival rates.
The distributions of the introduced and native dandelions were surveyed in the Tokyo metropolitan area of Japan. In the centre of the Tokyo metropolitan area, the introduced dandelions had superiority in abundance to the native ones, being frequently distributed without the native ones, though the relative population sizes were small. In the outskirts of Tokyo, the native dandelions were not always inferior in abundance to the introduced ones and were distributed widely, though the relative population sizes were not large. Urbanization seemed to have two effects on the dandelions, one was to destroy the populations of the native dandelions, and the other was to reduce the population sizes of the introduced ones. The hypothesis that the introduced dandelions expelled the native ones through direct competition was discussed critically, and the importance of land use as a means to allow dandelions to settle and maintain their populations was discussed.
For all the examined fresh soils taken from four different vegetations, degradation rates of ethylene (C2H4) under aerobic conditions showed logarithmic increases with the increase in atmospheric C2H4 concentration up to approximately 100 ppm. The degradation rates of the same soils air-dried were generally one-tenth lower than those of the fresh soils. At the atmospheric concentration of 30 ppmC2H4,the rates of the fresh soils of the Fagus crenata, Cryptomeria japonica and Thujopsis dolabrata forests and the paddy field examined were 150,130,60 and 5 nl/g d.w./day, respectively. Highly regular correlations were observed between theC2H4 degradation rates of the fresh soils and the amount of both the organic carbon and nitrogen in the soils. The rates determined under soil moisture ranging from 50 to 100% were approximately two times higher than those under the range from 150 to 200%. The decrease in atmospheric C2H4 concentration close to the soil surface was examined in the Cryptomeria japonica plantation by placing the vessel close to the soil surface. The decrease rates increased almost linearly with the increase of atmosphericC2H4 concentrations. The rate determined under atomosphericC2H4 concentrations of 10 ppm was 1.2×103 nl/cm2 soil surface/hr.
A total of 1182 adult beetles belonging to twelve species of the family Silphidae were caught with meat-baited pitfall traps from May to October, 1983,on the Ishikari Coast, northern Japan. Spatiotemporal distributions of five dominant species, which were comprised of two silphines and three nicrophorines, were determined. There was a significant difference in resource use among all but one pairwise combinations of the dominant species in either habitat or season dimensions, or a combination of both. This finding was discussed in relation to the food types and food habits of the silphid beetles.
In 1984 a survey of ants was conducted around Mt. Usu, the top area of which had been deforested by eruptions in 1977 and 1978. The mountaintop area was still deforested but already inhabited by 13 species, most of which were dominant, common or subterranean on the foot of the mountain. Based on ITO and SHIMIZU (1980), who presumed the vegetational state before the eruptions, SAKAGAMI et al. (1980), who surveyed the myrmecofauna in 1977-78,and the results of the present census, the original myrmecofauna inhabiting the mountaintop area before the eruptions was estimated to be 22 species.
The divergence of feeding habit in relation to fish size and the food animals' environment was studied for stream resident Japanese charr. It is suggested that the enormous amounts of nocturnal drift represents an unavailable food resource, because most charr are diurnal feeders. In the daytime drift, fallen animals exceeded benthic ones. Benthophagus area seems to be calm area where the benthos was not abundant and in this condition, larger charr tends to feed on fallen animals.
The ecology of loggerhead sea turtles was studies along the coast of Miyazaki Prefecture, in southeast Kyushu, for 9 years (1976-1984). The number of turtles coming ashore fluctuated from 79 to 532 (χ^^-=278) in number per year along a seashore 15.9 km in length. Intra-seasonal fluctuation in the number of turtles landing and nesting shows a weak two to three week periodicity. This interval was similar to that of the renesting of individual turtles. Turtles tagged from 1977 to 1983 were recaptured mainly in the East China Sea, but two turtles remigrated to Miyazaki after 2-year absence. These data suggest that turtles nesting in Miyazaki migrate to the East China Sea after the breeding season and some of them come back in a few years.
Zonation of sand beach vegetation was investigated in Ishigaki Island, southern Ryukyu Archipelago, the subtropical island. Transects were placed at thirteen points of seven beach localities. The field survey was carried out in Aug. 1983,Oct. 1983 (just after a typhoon struck) and July 1984 on four beaches, and the latter two times, on three beaches. The survey also included profiling of the beach and coastal dunes, and observing the sea conditions. The wave action influencing the beach is usually weak because the island is surrounded by a coral reef. Nevertheless, the strand vegetation was easily destroyed by storm waves caused by a typhoon, but it immediately recovered. The recovery is due to the elongation of new shoots from remaining rhizomes and seedlings from drift seeds. The zonal distribution patterns of the communities are different at the beaches. On the beach with a narrow backshore, the herbaceous zone is not developed and coastal forests grow right down to the back of the beach. The dunes are stable and covered with coastal scrubs and forests. A Spinifex littoreus community forms the platform dune only on the wide beach. There is a close relation between the zonation of coastal vegetation and shore processes and coastal depositional topography. These are based on the geographical environment and also on the regional characteristics.
Breeding season of the Japanese toad, Bufo japonicus japonicus, in Kanazawa prefecture was about 10 days at the end of March or the beginning of April. In 2 ponds (H and Y) most breeding behavior was observed to begin just after the temperature increased several degrees simultaneously with the falling of rain, but in one pond (M), 2 breedings out of 3 were initiated without rain, almost all breeding behavior was interrupted when the minimum temperature decreased to 0℃ or more. It seems probable that the breeding activity of this species is influenced not only by cimatic factors such as temperature and rain, but also by other factors such as mating or the releasing call of the first arriving male.