Patterns of distribution, growth and survival of saplings of main species were studied in a riparian forest dominated by Pterocarya rhoifolia along the Nebusa Branch of the Ishizaki River in southern Hokkaido, Japan. Densities of saplings were higher on young stands of lower flood-plain deposits characterized by high relative illumination (RI) and immature soil than on the forest floor of closed stands on higher flood-plain deposits characterized by low RI and mature soil. P. rhoifolia and Alnus hirsuta were the most abundant species on the lower flood-plain deposits, while Acer mono and Ulmus laciniata were the most abundant species on the forest floor on higher flood-plain deposits. In the closed stand on higher flood-plain deposits, saplings of P. rhoifolia were distributed contiguously around a gap of the canopy and grew more slowly than U. laciniata, while those of U. laciniata were distributed randomly on the forest floor. On lower flood-plain deposits, the growth rate of A. hirsuta was higher than that of P. rhoifolia in the upper layer of the stand ; however the survival rate of A. hirsuta tended to be lower than P. rhoifolia in the lower layer. Therefore, it was concluded that P. rhoifolia is the intermediate species between the pioneer, like A. hirsuta, and the nonpioneer, like U.laciniata. I hypothesized that flooding disturbances and the site, like the narrow valley bottom with low light resources, favored the regeneration of P. rhoifolia.
The distribution of lucidophyllous forest dominated by Persea thunbergii (Machilus thunbergii) trees, which exhibited 4 or 5 on the Braun-blanquet's cover-abundance scale in the canopy layer, were studied in relation to ecological factors. In Japan, P. thunbergii forest was distributed in 224 localities from Kyushu to the Tohoku district. This forest was in a wide range from 1℃ to 11℃ of the mean temperature of the coldest month and was mostly within 300 m from the nearest coastline. In the Setouchi region, this forest was rarely found due to the small precipitation. At the northern limit of the lucidophyllous forest, this forest was developed. Especially, in the Hokuriku district, this forest was dominant in the coastal areas where evegreen oak species (Cyclobalanopsis spp. and Castanopsis cuspidata var. sieboldii) could not grow due to the severe northwestern monsoon condition. In the region along the Pacific ocean, this forest was developed on small islands and peninsulas which were often struck by typhoons. This forest was more closely affected by the northwestern winter monsoon or typhoons with salt-spray than the edaphic factors. It appeared that this forest was a preclimax in the narrow coastal areas affected by sea wind, or the seral stage in the inland areas.
The temporal changes of home ranges of three individual colonies of the ant Formica (Serviformica) japonica in a grassland were studied with the group-marking method. Individual colonies occupied a certain space as their home ranges. The home ranges were segregated between neighboring colonies, and this segregation pattern was more or less maintained during one day and for a few days, but changed seasonally. When an experimental barrier was established between two neighboring colonies to limit the home range of one colony for two days, the other colony did not expand its home range. When nestmates of one colony ceased to emerge on the ground surface for a few months, the neighboring colonies extended their home ranges toward the space once occupied by the former colony. These facts suggest that the home ranges of individual colonies of F. japonica were not influenced by the changes in the home ranges of neighboring colonies for a short period, but were for a long period.
Bark stripped from tree trunks and butts by Sika deer, Cervus nippon TEMMINCK, was surveyed in twelve 20×20m2 plots within 3 forest types on Mt. Odaigahara, Nara Prefecture, Japan. About 90% of Picea jezoensis (SIEB. et ZUCC.) CARRIERE var. hondoensis (MAYR) REHDER and 57% of Abies homolepis SIEB. et ZUCC. trees were barked while deciduous broad-leaved trees such as Fagus crenata BLUME and Quercus mongolica FISCHER ex TURCZ. var. grosseserrata (Bl.) REHDER et WILSON were not barked. The percentages of barked trees in 5 Picea jezoensis var. hondoensis-Sasa nipponica MAKINO et SHIBATA plots on the eastern part of the mountain (1550-1600 m in alt.) were 57% whereas they were 49% in 3 Fagus crenata-Sasa nipponica plots (1450-1550 m) and 17% in 4 Fagus crenata-Sasamorpha borealis (HACK.) NAKAI plots (1300-1450 m) on the western part of the mountain. These percentages appeard to be closely correlated with the intensity of the habitat utilization by Sika deer, assessed by the grazing intensity on Sasa and Sasamorpha leaves and fecal pellet density.
Synopsis Since soil pore formation depends on the subterranean part of plant communities, the study on the pore structure may lead to an understanding of the mutual interactions between vegetation and soil. However, it has not been widely recognized that the pore structure resulted from these mutual interactions. One of the reasons for this insufficient recognition may be due to the lack of an appropriate method for investigating the pore structure. An X-ray stereoradiographical method on soil pore structure has been developed and is characterized by the use of the new contrast medium (low viscous liquid). Owing to these characteristics, the detailed three dimensional features of soil pore, such as continuity, can be easily observed. The X-ray radiograph was applied to Andisols, that originated from Towada ashes, in order to evaluate the possibility whether the radiograph would be expected to be appropriate as the method for obtaining information on vegetation. The radiographs obtained showed the configuration of subterranean parts ; and, as a result, some plant species could be identified using those radiographs. Furthermore, the results of the opal phytolith analysis supported their identifications.
Life histories and population dysamics of two aquatic pyrarid moths, Elophila interruptalis (Pryer) and Neoshoenobia decoloralis Hampson, were surveyed in 1980 at Midorogaike Pond, Kyoto, where these two species coexisted. E. interruptalis was trivoltine, feeding on various kinds of water plants, Nupar subintegerrimum, Brasenia schreberi, Trapa bispinosa var. iimurae, etc. From the first to mid instar, the larvae lived on the undersides of leaves, spun between two leaves, or made portable cases of host leaf flagments ; and the mature ones usually spun the leaves or made the cases in order to feed and move. Pupation took place between two leaves or in the cases, attached to the hosts. The adults laid eggs in masses. Egg density was not very fluctuated among generations (within 2 times), and severe consumption of the host was not seen in any quadrat. N. decoloralis was bivoltine, and the life cycle was completed only on the N. subintegerrimum. From the first to mid instar, the larvae mined the leaves, later the larvae became petiole borers directly from the leaves or indirectly from the other leaves by moving on the surface of the water. Pupation took place in the petiole near the root. The adults laid eggs in masses and egg density increased in the second (overwintered) generation, 30-40 times that of the first one. In some quadrats a very high mortality during the younger larval stage was observed because of the defoliation of the leaves. Considering these results, E. interruptalis seems to be an ecologically generalist and N. decoloralis to be a specialist. They seem to coexist, even when they depend on the same host, by feeding on different portions of the host.