Relationships between bacteria and predators, especially protozoa, were analysed using a laboratory model of an epibenthic microbial community and partial sterilization techniques. Heating at 45°to 65℃ brought about an increase in the number of bacteria in the microbial community. The elimination of the predatory activity of protozoa was thought to be the cause of this phenomenon. In addition, an increase in the amount of dissolved nutrients occuring incidentally due to heating, also influences the increase of bacteria. Treatment with the surface active agent, Aerosol-OT, was also effective in eliminating protozoa, and brought about an in crease in the number of bacteria in the treated sample. The results of these experiments indicate that predation by protozoa may be one of the important factors regulating the bacterial population of such a microbial community.
The growth of sunflower plants in experimental stands was analyzed in terms of the growth of every internodal segment consisting of a leaf and a piece of stem. The growth of a single leaf and an internodal stem length were both successfully approximated by the simple logistic curves having the same coefficient of growth in common. Daily rates of gross photosynthesis, surplus production and weight increase of each leaf were calculated with Kuroiwa's formula based on the logistic growth of leaf area and stem length in combination with the known light-photosynthesis curve and other properties of sunflower plants. The growth in weight of each stem segment was also calculated on the assumption that the daily surplus production in all leaves was distributed to all internodal stem segments in proportion to their current length. Results of the calculation agreed fairly well with the actually observed patterns of stem growth and their change with plant density.
Studies have been made on the mixing effect of two kinds of leaf-litter on their decomposition rates, which were measured by the litter bag method in the field and by CO_2 evolution in the laboratory. The addition of hardwood leaves, conifer needles with higher nitrogen, or nitrogen fertilizer hardly accerate the decomposition of conifer needles with lower nitrogen. That is to say, the chemical properties of the added leaves and nitrogen fertilizer may be nothing but to temporarily encourage any biotic activity and promote rapid decomposition of the leaves. However, the mixture of two kinds of leaf-litter in natural condition may show results different from this study, because of the detail change of the circumstance of the A_0 layer.
The distribution of three kinds of thermal indices, KIRA's warmth index (WI) and coldness index (CI) and Thornthwaite's potential evapotranspiration (PE), over the Korean Peninsula was examined based on the temperature observation records at 148 stations. The continentality of climate was evaluated in terms of the sum of WI and-CI. The value of PE was found to be almost linearly correlated with that of WI, and hence the two indices were not much different in their indicator value. Detailed distribution maps of WI and CI were prepared, and their close correspondence with the vegetation map was suggested.
The structure of the mangrove forest distributed from Tanegashima to Okinawa Island (Kandelia candel dominant area) is described. Investigated mangrove forests were composed of two species, Kandelia candel and Bruguiera conjugata. The 7 forest types were observed ; 1) K. candel (I) forest. 2) K. candel (II) forest. 3) K. candel (III) forest. 4) K. candel・ (B. conjugata) forest. 5) K. candel・B. conjugata forest 6) B. conjugata・ (K. candel) forest. 7) B. conjugata forest. Two different regeneration systems weres observed, one occured inside of tidal zone (quadrat 5 type), another outside of tidal zone (quardrat 1 type). Regeneration and development of the mangrove forest are as follows : i) K. candel forest : quadrat 1 type→K. candel (II) forest→K. candel (III) forest. quadrat 5 type→K. candel (I)-a forest→K. candel (I)-b forest or K.candel (III) forest. ii) K. candel and B. conjugata forest : K. candel (I) forest→K. candel・B. conjugata forest→K. candel・ (B. conjugata) forest→B. conjugata・ (K. candel) forest.
Dormant one-year-old twigs collected from mature trees growing under different climates during mid-winter were artificially hardened at sub-freezing temperatures to overcome the differences of the sites of collection and to induce maximum freezing resistance. Evergreen broad leaf trees which range from the tropics in East Asia to the warm Pacific sea coasts can survive freezing to-5--7℃. Hardy evergreen broad-leaf trees and less hardy deciduous trees which have their northern limits of natural ranges in the northern Kanto District resistered freezing from -10 to -15℃. In these trees, the winter minimal temperatures appear to be the principal factor limiting the northern limits of their natural ranges. Most of the hardy deciduous trees which have their northern limits of natural ranges in northern Honshu and southern Hokkaido resisted freezing to only about -30℃. In these genera, the winter minimal temperatures appear to be the principal factor governing their geographical distribution in severe cold climates. In most of the more widely distributed deciduous species which extend to inland Hokkaido, Sakhalin and East Manchuria, the buds and cortical tissues of the twigs resisted freezing to -70℃.