A palynological study was made on the Holocene sedments of Matsuzaki-cho, Shizuoka Prefecture, Japan. The pollen diagram enabled the core sediment structure to be divided into three local fossil pollen assemblage zones, IZM-I, IZM-II and IZM-III, respectively characterized by the high frequencies of Abies and Cryptomeria, by the rapid increase of Castanopsis and the high frequencies of Abies and Cryptomeria, and by the appearance of Quercus (Cyclobalanopsis) and the high frequencies of Castanopsis and Cryptomeria. The stratigraphical sequence of pollen in the core sediments revealed the vegetation to be composed of a warm-temperate coniferous forest stage and a lucidophyllous forest stage. Coniferous forest, mainly composed of Abies, changed into lucidophillous forest 8700 years ago. The lucidophyllous forest of Castanopsis together with Illicium and Daphniphyllum flourished for about 6000 years. The Crytpomeria forest thereafter continued to flourish throughout the Holocene. This may be explained by the location of the survey area in the southwestern part of the Izu Peninsula, the vegetation of this area having been greatly influenced by the ambient warm and rainy oceanic climate during the early Holocene.
To clarify the feeding patterns of the pomacentrid fish Abudefduf vaigiensis, habitat, defined by distance from shoreline, feeding behaviour, diet, abundance of food resources, and home range were studied through three size classes (small, <5cm ; medium, 5-13cm ; and large, > 13 cm total length) at Kuchinoerabu Island, one of the Osumi Islands of southern Japan. Small fish switched from particulate-feeding on zooplankton exhibiting large short-term fluctuations in density to browsing on benthic algae when zooplankton density waslow. Large fish, except territorial males, tended exclusively to particulate-feed on zooplankton. The difference in feeding patterns between small and large fish was considered due to the differences in copepod density in the water column of the respective habitats and home range sizes. The ecological significance of feeding on benthic algae as an alternative diet is discussed in relation to copepod density, fish size class, and parental care behaviour.
A study was made of the applicability of ion exchange resin (IER) in measuring the movement of various elements, especially cations, by water within forest soil. The size of the bag needed and the method for preparing the IER and extracting ions adsorbed on the IER were established by laboratory testing. IER was prepared and then buried for six months under soil in sugi (Cryptomeria japonica) and hinoki (Chamaecyparis obtusa) forests at depths of 5,20,and 50cm. The amounts of Ca2+, Mg2+, K+, and Inorg-N absorbed at 5cm were several times greater than at 20 or 50cm. At 50cm, the amounts per unit area of all the elements except Na^+ were nearly equal to those in the stream discharge. Further study is needed of the interaction of soil water with the IER bag and surrounding soil, the effect that drying of soil has on the IER ability to adsorb ions, and the effects that root elongation and microbe activity within the IER bag have on the elements adsorbed on the IER.
During October 1986,excessive sap uptake by jumping plant lice (Heteropsylla cubana) caused severe damage to the canopy foliage of the Leucaena leucocephala scrub at a site in central Okinawa Island. From December 1986 to June 1988 a study was made of the vegetational succession on the floor beneath the damaged canopy. By the December 1986,two types of herbaceous undergrowth, zebra grass (Miscanthus sinensis) and the climber Ipomoea acuminata, had begun to grow. Investigations revealed about 4,000 seeds/m^2 to be burried in the topsoil, 35% of which were lost during half of the 1987 growing season. Seedling number gradually decreased due to both coverage by the herbaceous species and to the repeated attacks by jumping plant lice. The seedlings of broadleaved tree species were suptessed by zebra grass, and gradually decreased in number, whereas in stands of the climbing plant, they were able to maintain their numbers. The damage to Leucaena trees by jumping plant lice is so severe that reforestation by making coppices from remnant trees and the growth of seedlings on the stand floor does not feasible. Following the likely the stand floor destraction of the Leucaena scrub, succession may depend on the result of the competition between zebra grass and the seedlings of broad-leaved tree species.
The fruits of Zelkova serrata show no modification for dispersal and usually fall in autumn still attached to the fruiting shoot with several brown leaves. Observations on the fruit distribution on the ground beneath mature Z. serrata trees revealed over 65 percent of fruits to be still attached to the fruiting shoot and that almost all fruits lay at some distance from the mature trees. The fall velocities of fruits with and without shoot were measured at 1.51m・sec-1 and 5.36m・sec-1, respectively. From these observations and data, it is concluded that the fruiting shoot acts as a winddispersed diaspore, assisting the fruit dispersal of Z. serrata. The detachment of the fruiting shoot is not incidental but is related to the abscission of Z. serrta.