The regeneration process of Castanopsis cuspidata var. sieboldii Nakai and Persea thunbergii Kosterm. was studied in an evergreen broad-leaved climax forest on Miyake-jima, Izu Islands. In this forest, C. cuspidata var. sieboldii was a dominant tree species, especially in patches of mature-phase forest. However, in patches of young-phase forest, P. thunbergii and C. cuspidata var. sieboldii were co-dominants. There were more saplings (<0.5m in height) of P. thunbergii than those of C. cuspidata var. sieboldii. The latter's canopy trees had large crown areas and many sprouts reaching the canopy layer. The repair process in two small gaps involved canopy expansion of C. cuspidata var. sieboldii and a few other species. It seems that sprouting and canopy expansion are advantageous to the survival of C. cuspidata var. sieboldii in the canopy layer, and that this may compensate for the low regeneration ability from saplings. On the other hand, P. thunbergii seems to regenerate from saplings more frequently than C. cuspidata var. sieboldii, but may not survive as long as the latter in the canopy layer. Consequently, P. thunbergii seems to be able to dominate only in patches of young-phase forest in the regeneration complex of the climax forest.
Species composition, spatial structure and biomass of reef fish communities, and the spatial structures of reefs, were studied by diving observations at six stations in Onagawa Bay and Sendai Bay, Miyagi Prefecture. From Simpson's index of diversity of reef structure, these stations were divided into two groups : highly structured reefs (2) and less structured reefs (4). Reef fish communities at the stations consisted of six to 13 species, and the number of fish species corresponded to the diversity of the habitat structure. Shallow parts of the reefs were occupied by a greater number of small fish, and bottom parts by a smaller number of large fish. Among the stations, the number of fish differed by up to 2.2-fold and the biomass index by up to 7.5-fold. Fish biomass was correlated with the cross-sectional area of reefs, which differed by up to 5-fold among the stations.
The present study focused on the mechanisms and the ecological significance of sprouting of Magnolia obovata Thumb, Tilia maximowicziana Shirasawa and Fraxinus lanuginosa Murata, in a mixed forest in Shiretoko National Park, northern Japan. We defined M. obovata and T. maximowicziana as belonging to the upper canopy, and F. lanuginosa to the lower canopy as the upper-canopy and lower-canopy sprout species, respectively. We investigated the size structure and gap dependence of sprout stems for both the upper-canopy sprout and lower-canopy sprout species. The upper-canopy sprout species were well sprouted and the production of sprout stems was dependent on the parent DBH size, irrespective of gap formation. The sprouting of lower-canopy sprout species was not so vigorous, and the production of sprout stems was governed by gap formation improving the light environment at the level of individual tree size. Therefore, it was suggested that sprouting of the upper-canopy sprout species was associated with individual growth dynamics (i.e. parent tree growth), playing an important role in stabilizing the population dynamics. In contrast, it was expected that the stem sprouting of the lower-canopy sprout species was associated with expansion of productive structures, playing an important role in persistence of the population in the lower canopy layer.
Range expansion of the bamboo, Phyllostachys pubescens, over a 30-year period was studied using topographic maps, land-use maps and aerialphotographs in the Nishiyama, Ohyamazaki, Tanabe and Yamashiro areas of Kyoto Prefecture, Central Japan. The former two areas, being close to Kyoto City, were densely populated, and the appearance of the bamboo was balanced by its disappearance due to development projects for housing construction, the total bamboo area showing little change. In the latter two areas, the bamboo stands had expanded several times. Plantation and natural expansion of bamboo were considered to be the causes of the range expansion. Until the mid 1970s, both plantation and natural expansion were responsible for the range expansion, but thereafter the bamboo stands expanded without much plantation. Considering the soil conditions in this region and the ecological competition between Phyllostachys pubescens and trees, it seems that bamboo stands will not be replaced by other types of forest, and that range expansion will continue in the future.
Over the last two decades, a number of studies have provided evidence that bryophytes play an important role in the function of many terrestrial ecosystems. This is largely due to the ecophysiological attributes of bryophytes, which are different from those of many vascular plants, i.e. 1) poikilohydric water relation and 2) direct uptake of water and nutrients from the shoot surface. These attributes allow the plants to grow in habitats where most vascular plants cannot colonize, depending on transient water and nutrient supply. These habitats include exposed rock surfaces, tree trunks and cold deserts. On the other hand, bryophytes are generally small and susceptible to soil mobility. In boreal forests and humid mossy forests, bryophytes not only contribute the primary production but also play a major role in nutrient cycling. This is largely due to their effective nutrient uptake and slow nutrient release. Because of their large waterholding capacity, bryophytes may also affect the water balance in some forests. Furthermore, they affect the colonization of tree seedlings. Bryophytes are important first colonizers of volcanic lava fields, whereas they are usually scarce in mobile ash and scoria fields. Pioneer bryophytes have several adaptations for colonizing dry, nutrient-poor habitats. Their contribution to humus formation and nutrient accumulation seems to be significant. However, there is little direct evidence that bryophytes promote the colonization of vascular plants in volcanic deserts. The role of bryophytes in ecological succession is still only scarcely defined.