The growth of Skeletonema costatum and Chaetoceros didymus was measured in bialgal cultures with Prorocentrum micans and in Prorocentrum-conditioned media, and it has been found that P. micans excretes a diatom-inhibitory substance which may play an important role in maturing of Prorocentrum-blooms. This substance was considered to have a high molecular weight because it was non-dialyzable by a cellulose tube and its inhibitory effect disappeared on autoclaving.
A study was made of the effects of temperature and photoperiod on developmental patterns of Hestina japonica in Fukuoka city. This species was sensitive to day length in the 3rd and 4th instars and diapaused in the 4th or 5th instar under short photoperiodic conditions. The critical photoperiods for inducing larval diapause in the 4th and 5th instars were estimated as 12 hr 40min and 14 hr 10 min, respectively. The heat units required for completion of the overwintering generation (from termination of diapause to emergence) and the non-diapausing generation were 355 degree-days and 898 degree-days above 8℃, respectively. These data were superimposed on the photothermograph of Fukuoka in order to predict the seasonal life cycle. The predicted life cycle corresponded well with the field observations and records of adults collected. In this locality, this species was basically bivoltine but some larvae of the 2nd generation did not diapause. Using these data and observations in several places of its distribution, the geographical variation in voltinism is discussed.
Some characteristics of the seed-phase of Quercus variabilis including the seed fall-and seedlingstage were studied physiologically and ecologically. The germination-rate and the rate of rootelongation of Q. variabilis were determined at various temperatures under the wet conditions of a Petri dish. Under wet conditions the germination reached 100% at 24.5℃ much faster than the other temperatures. Dry conditions disturbed germination-rate and delayed its onset. The growthrate of the roots was maximum at 25℃, and the time necessary for unfolding of the shoot after germination varied with temperature. From these experimental results and by making use of meteorological records for the Nagoya district, it was expected that, if the supply of water was sufficient, the germination-rate of seeds of Q. variabllis during the mast-year would be high in Nagoya and its vicinity, and that the root would elongate until the next spring without unfolding of shoot. The results of field observations confirmed those expectations with the logical exception of a little delay in seed-germination in the dry area. Discussions were directed to the possibility of elucidating the distribution of Q. variabilis by these characteristic features of its seed-phase.
The long-armed freshwater prawn genus Macrobrachium is represented in the Shimanto River system, Shikoku, by three species, i.e. M. nipponense, M. formosense and M. japonicum. M. nipponense occurs mainly in the tributaries that join the mainstreams near the estuary, such as the Nakasuji and Takeshima Rivers. In the main stream of the Shimanto M. nipponense is not distributed upstream further than Gudo. M. formosense occurs from the river mouth to Ekawazaki, and M. japonicum from Fuwa to Taisho-cho. Their ranges overlap in the area between Fuwa and Ekawazaki. The daytime habitats of these species serve as retiring places and shelters. While M. formosense prefers pools and other slow-flowing or stagnant water, M. japonicum inhabits the riffles zone. At night, the active period of the prawns, M. formosense was found in the riffles zone together with M. japonicum.
A recently proposed criterion for determining climax in intertidal algal vegetation is confirmed by the comparison of an additional 25 adequately old algal vegetations which are considered as being at the climax stage. As a modification of the previous conclusion that more than 3-4 years were required, now it appears that 7 years are sufficient to attain the climax stage. Climax vegetation bearing one of the annuals, viz. Ulva pertusa, as a dominant, is common in the southern Hokkaido area, especially in sheltered conditions such as where protected by breakwaters. Thus, it appears the current concept of a climax vegetation as "one in which perennials dominate" should be transformed into "vegetation in which certain algae, having the ability to contimuously occupy the habitat, dominate". Frequent reproduction of Ulva pertusa in the temperate areas in Japan and of some species of the Cyanophyceae in tropical and subtropical areas, is considered to support their position as dominants in such climax vegetations. Finally, stability in intertidal climax vegetation is discussed and it is suggested that there is some ability to reduce algal invasion not only from within the same belt-like vegetation but from the belt above as well.
The algal vegetation of the Laminaria-bed was grouped into 4 communities, viz. Laminaria religlosa community, Ulva pertusa community, Laurencia sp. community, and Pachymeniopsis yendoi community. Each representative species of these 4 communities had high indicator values and Z^3 values. In the standing crop of all the algae of each community, surveyed in mid-June, the maximum (3403 g/m^2) appeared in the L. religiosa community and the minimum (403 g/m^2) appeared in the P. yendoi community. Although the mean standing crop of L. religiosa was 1195 g/m^2 in the area surveyed, it was 2926 g/m^2 in the L. religiosa community, about 300 g/m^2 in the U. pertusa and the Laurencia sp. community, and 87 g/m^2 in the P. yendoi community. The mean density of L. religiosa in the area surveyed was 48/m^2,and it was 108/m^2 in the L. religlosa community. The other communities had lower densities of less than 20/m^2. The mean blade length of L. religiosa was 44.2 cm in the area surveyed, and the maximum blade was 240 cm in the L. religlosa community in which mean blade length was 74.5 cm. In the other communities, the mean blade length was less than half of that in the L. religiosa community.
The dynamics of big wood litter (diameter>10 cm)was studied at Pasoh Forest, a lowland rain forest reserve in West Malaysia. The mean accumulation and mean fall rate of big wood litter amounted to 49 t ha^<-1>and 9.3 t ha^<-1>y^<-1>. The rate of decomposition of wood litter was estimated from the rate of CO_2 evolution and the dry weight/CO_3 conversion factor (0.56) obtained by determining the carbon content of the dead wood. The CO_2 evolution rate was linearly correlated with the bulk density of the wood, showing that the loss of weight of wood litter followed a logistic curve. The estimated half-time of weight loss in wood samples of two tree species was 1.4-2.5 years, being nearly ten times as long as that of fine litter. Based on the above formulations, the mean loss of organic matter due to the decomposition of big wood litter was calculated at 16.1 t ha^<-1>y^<-1>, though to a certain extent this might be overestimated.
The vertical distribution of estuarine decapod crustaceans was investigated in the estuary of the Yuhi river, Okinawa. The zonation including land crab was classified in relation to the tide level into six main zones : 1) a cardisomine zone, 2) a sesarmine zone, 3) an ocypodine zone, 4) a macrophthalmine zone, 5) a mixed zone, 6) a Scylla zone. Factors governing these zonal arrangements are classified into two groups : the major factors related to the physiological tolerance of crabs and the factors related to the habitat preference of species. These arrangements and factors are compared with results from the mangrove swamps of Java and the Brisbane river, and discussed.