Atmospheric ethylene (C_2H_4) levels were examined in a tropical rain forest situated at the equator, Amazonas Prefecture, Colombia, during 1982,During the rainy and dry seasons, the forest atmosphere showed scarcely vertical changes in C_2H_4 concentration for night and day determinations. The concentrations diurnally varied in the range of 1.1 to 1.9 and 0.9 to 1.3 ppb in the rainy and dry seasons, respectively. An air sampler was developed to collect atmosphere without contaminations due to pump and stopcock usage.
Experiments to see the relationship between the community responses to organic loading and successional age of the community were performed in aquatic microcosms consisting of bacteria, Chlorella, blue-green alga, ciliate protozoa, rotifer and aquatic oligochaete. Invertebrates in the microcosm declined to extinction when organic loading was added at a young stage, while invertebrates in the mature stage hardly became extinct after loading. Algae in the sediment, which increased as succession proceeded, contributed to the stabilization of invertebrate populations. Invertebrates in the microcosms loaded at a young stage were found to be extinct by a temporary rise of the un-ionized ammonia concentration, which was caused by the accumulation of total ammonia (due to the small amount of algae in the sediment) and by high pH. On the other hand, the mature microcosm showed high stability because a large amount of algae and low pH inhibited the increase of un-ionized ammonia subsequent to loading.
Core samples of sediments obtained from Tokoro along the Okhotsk Sea were studied to clarify the Holocene history of paleoenvironments based upon diatom assemblages. The Holocene history of Tokoro is inferred to be as follows. The sampling site in Tokoro was formed by the influence of flowing waters before 9,000 y.B.P. The initiation of transgression began from about 9,000 y.B.P. The transgression reached a peak about 6,000 y.B.P., and Tokoro was covered with sea water at this period. After that, relative regression, including depositional regression, occurred, and reached its maximum about 4,000 y.B.P. After 4,000 y.B.P., the transgression occurred again. Oceanic sea water flowed into TOKORO-1 site, and in TOKORO-2 site, a saline lagoon was developed. The saline lagoon lost its salinity about 3,000 y.B.P. Finally, relative regression occurred, and these sites became characterized by freshwater conditions including flowing waters.
The subalpine forest of Mt. Halla, Cheju Island, Korea, was investigated by the ZM school method. A new association, Saso-Abietetum koreanae, was recognized there, and it was further subdivided into two subassociations : symplocetosum and typicum. Each community was described in terms of floristic, structural and environmental features. The degree of human interferences, altitude and topographic characteristics appear to be the dominant environmental factors determining the distribution of these communities. Species diversity and species number appeared to decrease with increasing altitude. Thus, community diversity is lower in subass. typicum than in symplocetosum. Lastly, the altitudinal zonation of the subalpine zone of Mt. Halla was discussed from the phytosociological viewpoint.
Reserve materials in roots were measured in the young trees of Quercus variabilis BLUME. The method of "the cut-off experiment"was successful in estimating the presence of reserve materials ; newly unfolded shoots before lignification were repeatedly cut off to enable them to consume reserve materials. Allometric relationships between two parts of the dry weight of roots, aerial nonphotosynthetic parts, newly unfolded shoots in spring and leaf-number of individuals were compared before and after the cut-off experiments. The results showed that the percentage-content of reserve materials in roots of one-to five-year-old Q. variabilis was about 46 to 35% in root dry weight. The percentagecontent of reserve materials in roots tended to decrease with the increase in the size of the plant. The results suggested that a reasonable amount of the reserve materials consumed to make shoots may be retained in the aerial nonphotosynthetic parts in older trees.
In order to examine the pattern of forest response to gap formation, the species diversity and the floristic composition were compared in gaps and closed stands in a climax beech forest at Mt. Kurikoma, Miyagi Prefecture, northeastern Japan. Results showed that the vegetation in closed stands had the same values of species diversity as those in gaps, viewed from not only the species richness, but also from its equitability. Furthermore, the floristic composition was quite similar between gaps and closed stands. The above results strongly suggest that the regeneration process in gaps of a climax beech forest is a "reorganization" process of the vegetation established prior to gap formations. Thus, canopy gaps created in a beech forest hardly contribute to the persistence of pioneer species in a forest, but instead are indispensable for the regeneration of tree and subtree species which have pre-established juveniles in the forest floor of closed stands.
The frequency distribution of individual tree height in a forest stand was studied by applying Pearson's type VII distribution to the observed tree height data obtained from Chamaecyparis obtusa plantations in the Kanto region, Japan. The tree height data followed a model designated as the 1/2 power law of tree height. This model described the dependence of mean tree height on tree density in a stand. Limited by the model, all the coefficients of Pearson's type VII distribution were formulated by empirical equations of tree density. From these empirical equations, a mathematical model was developed for the frequency distribution of individual tree height in forest stands limited by the 1/2 power law of tree height. Furthermore, the dependence of individual tree height upon tree density was formulated by a function of tree density.
Marked individuals of the adult Japanese toad, Bufo japonicus japonicus, were generally observed to restrict themselves within an area of 30-35 m during 2 years, although their average movemest during 3 to 7 years was 45 m. On the other hand, 2.2% of them were observed to move over 100 m (maximum 188 m) during 2 years, and in the case of between 3 and 7 years, the rate of long distance moved individuals was increased 7-8%. Some of these toads moved between two habitats, but others did not return to their original places.
Both sexes of Cercion calamourum meet at, or near, a pond used for oviposition. Within a pond area, sexual encounters occur more frequently at the better oviposition sites, suggesting that more females arrive at the better oviposition sites. However, since females come from outside the study area, they are often seized while en route at the surrounding bushes by males searching there. The probability of such interception increases with the number of males searching at the surrounding bushes. C. calamourum males maintain the tandem position with their mates throughout an oviposition bout to prevent takeover of mates by other males. Consequently, once seized by a male, a female is not available to any other males. The evidence suggests that, at sites far from the shore, even if there are good oviposition sites, the number of females arriving decrease with an increase in distance from the shore because, to reach there, females pass through a wider male search zone and are thus more likely to be intercepted. Thus, site suitability for oviposition and the distance from the shore are important factors affecting the spatial distribution of receptive females within the reproductive area.
Larger males of the crab, Hemigrapsus penicillatus (DE HAAN), were frequently found hiding in the empty flip-top beverage cans scattered over the intertidal and upper subtidal zones at Hirakata Bay. The frequency with which cans were occupied either by single males or by both sexes showed a marked increase corresponding to the early and late periods of the reproductive season of March through September. The decrease in the frequency in the summer paralleled an increase in the number of reproductive gobies found in the cans, suggesting interspecific competition over possession of the cans. We suppose that the empty-can-possessing habit of the larger males (and also females) of this species is related with their mating activity, but direct evidence is still lacking.
Machilus thunbergii forests were studied in Kanmurijima Island, Kyoto Pref., to clarify the influence of disturbance by birds' nesting and streaking on the community structure of the forest. Density of nests was negatively correlated with the number of plant species and individuals, the skewness of frequency distribution of height and DBH, Shannon H' and the relative basal area of Aucuba japonica, respectively. Species composition, species diversity index, dominance-diversity curves, skewness of height distribution, crown projection diagrams and other ecological characteristics showed that the disturbance by birds resulted in poor vegetation and the development of simple stratification. The species diversity became slightly higher as the aboveground biomass increased. In these forests Mallotus japonicus very often filled up gaps of canopy trees, and seedlings and saplings of Machilus thunbergii were growing around patches of Carex matsumurae and some herbs as stable spots for germination on the forest floor.
Seasonal observations and culture experiments were made during a period from April 1977 to October 1979 in order to clarify the cause of the occurrence and growth of a filamentous green alga (Pitophora oedogonia) appearing in the surface water of four paddy fields subjected for a long period (52 years in 1979) to different fertilizer treatments (non-fertilizer, inorganic fertilizer, organic fertilizer and green manure). Before the midseason drainage done in summer, this alga appeared only in the organic fertilizer and green manure plots. In early autumn a fair amount of it appeared in the inorganic fertilizer plot. To investigate the effects of different levels of nutrient concentration on the algal growth, culture experiments were made twice with solutions simulated to the concentrations observed in the field plots under relative light intensities of 67,36,10,4 and 1%. The growth of this alga was generally optimum at a total nitrogen concentration of 50 μM, an average in the green manure plot in early summer, while it was independent of phosphate concentration. The difference of algal appearance and abundance in the four plots was explained mainly by the seasonal changes of the NH_4+ concentration in each paddy water. Some additive effects of light regime and competitive interference were discussed.
Pollen analytical studies were made on materials collected from thirteen moors developed on the Hachimantai Mountains in order to clarify the vegetational history in the subalpine zone of the mountain range. The Abies mariesii forest began increasing in the subalpine zone 3000-2500 years ago, and it markedly extended there during the last 1500 years. Before then, it was suggested that the region was covered by a deciduous scrub dominated by Quercus from 5000 to 3000-2500 years ago.