Quantitative phenological measurements were taken on Ligustrum obtusifolium, a winter semi-deciduous shrub, growing under natural conditions at the edge and understory sites of a dense grove stand of Quercus actissima trees in a suburb of Mito, and of shrubs maintained under experimental conditions of 100%, 20% and 7% day light. Survivorship of the overwintering leaves was confirmed at every shaded study site, whereas at open sites all leaves had fallen before winter. This phenomenon seems related to the unfolding of large numbers of summer leaves during secondary shoot elongation, which increased markedly with increasing ambient environmental irradiance. This possibility was evaluated during the autumn to early winter period, through comparative examination of dormancy in buds and frost tolerance in leaves from each research site. Results suggest that, in the northern boundary regions of the warm temperate zone, the semideciduous habit of this shrub species results in it being well-adapted to a variety of habitat conditions, especially to various levels of irradiance.
To obtain characteristics of ski ground vegetation and predict its successional sere, surveys were undertaken on three ski grounds in Hokkaido : Play Bankei (constructed in 1968), Teine Olympia (1971) and Makomanai (1980), whose land surface were modified by heavy human impact, i.e., land cutting, sowing of herbs, and regular bush cutting. Analysis of species composition and clustering revealed vegetation of sites surveyed to be mainly divisible into four vegetation groups as follows : al) grassland of sowed herbs ; a2) Artemisia montana grassland ; b) low-cover grassland ; c) Miscanthus sinensis grassland. Many native plants were unable to colonize and/or establish themselves in the artificial vegetation, but were able to establish themselves at sites where coverage of sowed herbs was reduced. Woody plants, such as Salix hultenii var. angustifolia, gradually established themselves at sites where sowed herbs had decreased and/or M. sinensis was well-established. Examination of the degree of succession supported these findings. The regeneration process of ski ground vegetation in lowland Hokkaido is discussed in relation to these results.
Acorns of three species of Quersus distributed in the Nara Basin, Cyclobalanopsis-Quercus glauca, Q. myrsinaefolia and Q. gilva were sown in the laboratory in the springs of 1985,1986 and 1987. Following the sowing, seed germination, and the height and growth of seedings were monitored for a year. Although the three species are closely related, the condition of germination and the growth character of Q. gilva seed and seedling stages differed from those of Q. glauca and Q.myrsinaefolia. Q. gilva seeds required higher temperatures and moisture levels than the other species to germinate ; a feature which correlates with the distribution of Q. gilva forests in Japan. The shoot growth of Q. gilva was slow and its rate of leaf emergence was lower than that of the other species, suggesting the seeding of Q. gilva to be shade tolerant. These results also suggest that Q. gilva is better able to occupy stable habitats than Q. glauca and Q. myrsinaefolia. During the course of the experiment a high percentage of Q. gilva individuals failed to achieve leaf emergence, and most of these individuals perished prematurely.
The cone production of Pinus pumila scrub was studied in relation to the height and the mean annual stem elongation of the scrub at Mt. Kiso-ontake, central Japan. The cone density (number of cones/m2) of the scrub showed no clear correlation to scrub height, suggesting the latter factor alone to never strongly affect cone production. Maximum cone density (25.3/m2) was at tained at ca. 60cm height. The cone production of an individual stem increased with stem diameter. This trend differs from that at the scrub level : individual stems in the shorter scrubs produced only a small number of cones despite the high density of stems in the scrub. Conversely, taller scrubs had a low stem density, but individual stems carried a large number of cones. The mean annual stem elongation of the scrub showed no clear correlation with the cone density in general, although a clear relationship between these factors was evident in shorter scrubs (<50cm in height).
Vegetational data of Fagus crenata forest in the Japan Sea region of the Chubu district, central Japan, were examined by TWINSPAN classification and DCA ordination. Stands were divided and the hierarchy of each was displayed as a dendrogram, using the sequences of divisions as integral levels, Species classification was also produced. Data were ordinated by DCA. The sample sequences along first and second DCA axes effectively reflected temperature and moisture status, respectively. Vegetational structure revealed by TWINSPAN was recognized by comparing the species arranged on the DCA axes with the species characterizing the division of the same vegetation type analyzed by TWINSPAN.
Two hundred and six stands of submerged macrophytes were surveyed in Lake Biwa by SCUBA diving. Among the 20 species recorded throughout the survey, Hydrilla verticillata, Potamogeton maackianus and Elodea nuttallii were most-abundant species. Applying priucipal component analysis, all the species could be reasonably ordinated by the first (PC1) and second (PC2) principal components. Considering the horizontal and vertical distribution of respective species, PC1 and PC2 were respectively interpreted to represent hypothetical species able to grow in a windless habitat or to have a tolerance for wave force. Results suggested wind force to be the most important factor influencing the distribution of submerged macrophytes in Lake Biwa. Changes of submerged macrophyte flora, due to either water quality degradation or invasion of exotic species in the lake in recent years, are also described.
The efficiency of pitfall-trapping was compared with that of hand-sorting, based on the sampling data of Blattella nipponica ASAHINA in different vegetation types. The sampling efficiency of pitfall-trapping was related to the activity of B. nipponica, being higher in summer, when insects were more active, than in sutumn. During the autumn, however, positive correlations were evident between the two sampling methods : r=0.761 in the mean number of individuals captured and r=0.858 in the frequency of capture.
The photosynthesis of Antarctic mosses and lichens have been measured since the 1960's. Most of the measurements were performed with the objective of elucidating the relationships between photosynthetic rate and environmental factors, especially irradiation intensity and temperature. In the 1970's, live samples were transported to domestic laboratories and their activities were measured under controlled conditions. Recently, information obtained from further field measurements have enabled the modelling of the relationships between photosynthesis and environmental factors using with multiple regression analysis.