The savanna stand where the present study was carried out was composed of herbaceous vegetation along with sparse distribution of only one shrub, Zizyphus jujuba. The calorific values of the aboveground parts of the herbaceous vegetation were rich during the rainy season, while those of the underground parts were during the winter season. In the shrubs, the calorific values of the leaves were maximum in June, while those of the twig were maximum in February. The stem, branch and underground parts showed an increase in energy values from June 1976 to February 1977. The annual net energy fixation was 5890.56 Kcal/m^2 with an energy conserving efficiency of 0.90 per cent. The aboveground parts retained 81.76 per cent of the total fixed energy, and the rest was retained by the underground parts. The litter component received only 27.4 per cent of the total energy fixed in the aboveground component. At each transfer, contribution of the herbaceous vegetation was much higher than that of the shrub. The system lost 39.63 per cent of the total net energy fixed by the community through litter and underground disappearances ; the remaining energy was sustained in the system.
New distribution density functions were proposed by using the finite difference method to express the frequency distribution of individual plant sizes in a stand. The finite differences were computed for plant weights arranged in descending order. The finite difference equation of the first order using constant coefficients resulted in distribution density functions of a uniform and reciprocal type. One type of Pearson's VIIth type distribution density function was obtained from a difference equation of the second order to simulate frequency distributions with a maximum frequency value. In addition, a more general function with wider applicability, which enabled the simulation of asymmetric (with respect to the mode of frequency) and even extremely skew distributions, was derived.
This report deals with the vegetation in a reclaimed land area developed from the sand pump dredging of marine sediment. In areas where precipitation exceeds evaporation, it is generally thought that desalting is completed after 4-5 years and no halophytic vegetation will glow. In this area, however, there was an unexpected growth of halophytic vegetation, although there was evidence of desalting in some places. The halophytic vegetation showed a sequence which roughly resembled a concave microrelief. Other factors besides the microrelief were also taken into consideration. At present it is no more than an assumption that the method of reclaimed land construction or the materials used could have been influential factors. Future studies are needed to elucidate the vegetation-soil microrelief relationship of this area. In this initial report we discuss the occurrence of vegetation in relation to its environment.
The regeneration of climax conifer forest dominated by T. sieboldii and Chamaecyparis obtusa was studied on Kubotani-yama, Shikoku, mainly by means of tree ring count, stem analysis, and dead tree and buried seed survey. An extensive destruction of canopy tree layer and a gap formation of smaller scale, which took place, respectively, about 260 and 50 years ago, were detected. Both resulted in the regenetation of conifer seedlings that continued for about 50 years after the canopy destruction. The present canopy was formed by the old tree group originating from the first regeneration, while the death of a few old trees some 50 years ago caused the gap formation to give rise to the younger tree group growing in and around the gap. The process of regeneration was, however, quite similar in both cases. The release of growth of pre-existing conifer seedlings by the canopy opening proved to play an important role in the re-establishment of forest. The survival rate of trees during the course of forest recovery was also estimated and discussed.
Forty-five secondary oak forests were studied phytosociologically in Tama district in the western suburb of Tokyo City to clarify the influences of urbanization on their herb-layer species composition. Principal component analysis was applied to the presence-absence data of 74 herb-layer species. The first principal component (PC1) differed little between the stands, and they could be reasonably ordinated by the second (PC2) and the third (PC3) principal components. PC2 was positively correlated with the percentage of residential area around a stand, while PC3 showed negative correlation with the abundance of phanerophytes in the herb-layer. These correlation analyses and the scores for PC2 and PC3 of respective species suggested that PC2 should be identified with the change due to urbanization and PC3 with the intensity of human disturbance. Some suggestions were made on the technical principle of forest conservation in suburban areas.
Leaf-fall pattern of six alder species (subgenus Gymnothyrsus : Alnus hirsuta, A. inokumae, A. glutinosa, A. japonica ; subgen. Alnaster : A. maximowiczii, A. pendula) was investigated from 1976 to 1979. A large quantity of leaves of the species belonging to the subgen. Gymnothyrsus fell in summer, which reached 30-50% of the yearly leaf fall. The first, second and/or the third leaves counted from the shoot base of these species almost fell in summer. These two or three leaves near the shoot base are small-sized, which indicates that these leaves are in course of reduction, and they fall early in summer after they have played a role as early leaves. In the subgen. Alnaster, the lamina of the first node is reduced and disappeared, and the remaining two stipules are connate in a bud scale which fall in late spring or early summer after it has played a role of the bud protection, while the leaves did not fall until autumn. Thus the extraordinary leaf fall in summer was not observed on the species of this group, and it was less than 10% of the total fall.
Sixty seven species of Pterophyta growing in the deciduous forest at low altitudes in Hokkaido are surveyed. As the result, the phenology is classified into thirteen different types, according to the periods of unfolding and decaying of the fertile and sterile leaves. One of the summer green types is predominant in the Pterophyta in Hokkaido, which unfolds the fertile and sterile leaves during late May to June and decays during October. It is observed that the summer green ferns increase their number of species with rising latitudes in the archipelagos of Japan. Moreover, some species such as Coniogramme intermedia and Stegnogramme pozoi subsp. mollissima retain evergreen in warm areas of Japan, although they become summer green in colder areas. Thus, it might be postulated that the summer green is the result of adaptation of Pterophyta to cold climates which cause the phenological restriction for the spore-dispersal period of ferns in Hokkaido. To understand more about the phenological adaptation of the life cycle of ferns with reference to the alternation of generation, autecological studies of ferns in different climates are required.
Litterfallrates in Chamaecyparis forest planted in 1929 on a gentle slope of Mt. Watamuki-yama was measured from 1966 to 1976. The peak of leaffall was found in autumn, but the fall of fresh and green leaves occurred irregularly in all seasons associated with storms or heavy snowfall. The death of older leaves occurred in October once a year, but the leaffall continued until the following early spring. The yellow coloring of leaves in autumn began after the daily minimum temperature had dropped under 7℃ and finished at -9 to -10℃・d of the accumulative temperature expressing the degree of coldness during the final period of growing season. It is possible to measure the death rate of leaf, the production rates of cone, seed and male flower, and the fall rates of green leaf, branch and bark, with catching the fall by litter traps. The standard deviations of the fall rates decreased with increase in the mean fall rate for all organs except for cone, For the cone it increased in proportion to the mean fall rate for the year of high production.
The rate of CO_2 evolution from soil, Y (mg C/kg dry soil/hr), was highly correlated with the amount of dissolved orgainc carbon in soil solution, X (mg C/kg dry soil), obtained by a centrifugalization. The rates Y of soils of a forest floor at 25℃ were almost invariably 1.5 in a wide range of the contents of soil water from 60 to 120% on an oven-dry weight basis, while those of soils of a paddy field were 0.9 in arange from 80 to 150%. The amounts X were also constant within these ranges, being about 3.7 in the soils of the forest floor and 2.6 in the soils of the paddy field. At the lower ranges of the contents of soil water, the rates Y decreased with the decrease of the amounts X. The equation Y=0.370X holded equally well both in the soils of the forest floor and in the soils of the paddy field except in the soils at extremely high contents of the soil water.
In 1978,faunal composition and population density of aquatic insects and tadpoles in irrigated paddy fields were studied by using the plastic pan water trap, by the direct observation, and by sweeping, in Kochi Prefecture. The aquatic insects trapped were dominated with Bidessus japonicus (Col.) and Microveria douglasi (Hem.) and the fauna was simple. Sympetrum frequence (Odo.), Gerris lacustris (Hem.) and Berosus vesticus (Col.) were collected in an earlier season, while Orthetrum albistylum specicum (Odo.), Pantala flavescens (Odo.) and Microveria douglast were abundant in a later season, Bidessus japonicus was abundant throughout the seasons. As rice plant grew taller with more tillerings, the total number of insects per m^2 increased, while egg colonizing species (Odonata and Ephemeroptera) and tadpoles disappeared, as a result the diversity of insect fauna decreased irrespective of the date of planting time. In a thinly planted field, even such egg colonizing species persist until late due to availability of water surface between rice canopy and the diversity remained constant. So it is condsidered that this change in the fields planted in ordinary density is due to the covering of water surface by the grown rice plant. The later the planting date was, the higher the initial density of insects was.