Acorns (nuts and cupules) of 88 Quercus serrata Thunb. individuals in central Japan were collected in 2000 and 2001, and the relationships between twelve acorn traits and several environmental factors, such as altitude, warmth index (WI), annual mean temperature and precipitation were examined. All nut traits, three cupule traits and a peduncle trait were correlated negatively with altitude and precipitation during the acorn growing season, and positively with WI and annual mean temperature. These results indicated that the higher the precipitation was and the lower the WI, the smaller were the size and volume of nuts and cupules. This suggests that the differences in the length of the acorn growing season among the sampling sites may be responsible for the trends in acorn size and volume. The acorn size traits of Q. serrata were negatively correlated with precipitation during the acorn growing season, especially within the latter part of the growing season. Thus, we conclude that acorn size of Q. serrata had some strong relationship to less precipitation in the latter part of the acorn growing season. However, it was difficult to separate the effects of precipitation from those of temperature on acorn traits in our analysis. Moreover, Q. serrata nut length was more dependent on thermal conditions than was nut width. This difference may be caused by the different developmental patterns between these two dimensions, especially after August when the width stopped increasing but the length did not.

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The traits of seed germination, seedling establishment, and seedling growth of three Ulmaceae trees, Ulmus parvifolia, Celtis sinensis var. japonica, and Aphananthe aspera, which occur frequently in riparian zones of the warm-temperate regions in Japan, were investigated for the purpose of elucidating the reason why only U. parvifolia can expand rapidly on high and dry habitats of gravelly bars. As the result of a field survey in the Monobe River, Shikoku, southern Japan, many seedlings and saplings of U. parvifolia were recognized to establish on bare land and grassland on gravelly bars. In contrast, those of C. sinensis var. japonica and A. aspera, which produce sap fruit dispersed by birds, occurred mostly beneath the sap fruit trees. Seeds of U. parvifolia and A. aspera do not have primary dormancy and were able to germinate after 6 months' preservation in dry conditions. However, seeds of C. sinensis var. japonica germinated only after preservation in wet conditions. As the result of the germination and establishment experiment, we found that the seedlings of U. parvifolia can establish on high and dry conditions, whereas those of C. sinensis var. japonica can not. In addition, thin and flat pericarp of U. parvifolia was considered through detailed observation to help the radicle elongate safely into soil. These results suggest that U. parvifolia, which makes anemochorous seeds, can disperse and establish easily to bare land or sparsely covered grassland. Although the survival rates of the seedlings of all species under high and dry conditions were low, the surviving seedlings, particularly of U. parvifolia, grew vigorously. These ecological characteristics of U. parvifolia enable the seedlings to establish on high and dry habitats, and hence are thought to be more adaptable in high, dry and stable habitats on gravelly bars than those of the other two species.

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We studied species composition and size structure of Abies homolepis-Prunus ssiori forest (hereafter AP forest) established on the montane-subalpine transitional zones in the headwaters of the Kinugawa River, central Japan, in comparison with adjacent forest types; i.e., Fagus crenata-Aesculus turbinata (FA forest), Picea jezoensis var. hondoensis-Tsuga diversifolia (PT forest) and T. diversifolia-Thuja standishii forest (TT forest). Relative basal area of A. homolepis, P. jezoensis var. hondoensis, T. diversifolia, T. standishii, P. ssiori, Tilla japonica, F. crenata and A. turbinata were 10% or more in either of four forests. A. homolepis appeared in four forests, and reached maximal values of relative basal area in AP forest. In AP and PT forests, canopy height reached to 35-40m, and the maximum height of conifer trees was greater than that of deciduous broad-leaved trees. DBH class distributions of A. homolepis in AP forest and P. jezoensis var. hondoensis in PT forest were discontinuous. Thus we thought that the regeneration of A. homolepis in AP forest depended on some large catastrophic disturbances such as typhoons. AP and PT forest had similar species composition of conifer/broad-leaved mixed forest in Yastugatake and Kamikochi region, and contained many indicator species of the upper-temperate forest zone. We concluded the AP forest and PT forest belong to the upper-temperate forest.

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Species composition and distribution of evergreen conifer plantations dominated by Cryptomeria japonica, Chamaecyparis obtusa and/or Chamaecyparis pisifera was studied by phytosociological method in the eastern part of the Kanto region, central Japan. The vegetation was divided into four communities: Cryptomeria japonica-Microlepia marginata community (CM), Cryptomeria japonica-Houttuynia cordata community (CH), Cryptomeria japonica-Athyrium yokoscense community (CA) and Cryptomeria japonica-Fraxinus lanuginosa f. serrata community (CF). The distribution of each community was influenced by air temperature. Warmth index (WI) of the distribution area of CM was higher than 120℃・month. CH was distributed in the area where WI was lower than 120℃・month and mean temperature of the coldest month (MTCM) was higher than 2℃. CA was distributed in the area where WI was lower than 100℃・month and MTCM was lower than 2℃. CF was distributed in the area where WI was lower than 90℃・month. The distribution area of the community in this study nearly corresponded to the distribution area of association of natural forest in the Kanto region. Comparing the life form in each community, evergreen woody plants showed a high component ratio in CM and CH. On the other hand, the component ratio of deciduous woody plants had an increasing tendency in the following communities: CM, CH, CA and CF. Compared with the component ratio of character and differential species in the other vegetation units, the character and differential species in Camellietea japonicae and the lower units of the class showed a high component ratio in CM and CH. On the other hand, the character and differential species in Fagetea crenatae showed a high component ratio in CA and CF. Furthermore, component ratio of the character and differential species in Rosetea multiflorae and Artemisietea principis showed a 15-30% ratio in each community. Therefore, plantation vegetation involved species of mantle communities, and the establishment of these species may be influenced by forest management.

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Ecogeography of a forest community, which includes Siebold's beech (Fagus crenata Blume), in the Pacific side of eastern Japan (Yamizo Mts., Abukuma Mts. and Kitakami Mts.) was studied, based on data from 54 forest stand. Forest stands were classified into five groups, A to E, by TWINSPAN analysis. Four groups (A-D groups) were characterized by the species which are common to climax forests of the lower temperate zone in the Pacific side of eastern Japan, such as Fagus japonica forests and Abies firma forests. On the other hand, E group was characterized by the evergreen shrub species which were common to the climax Siebold's beech forests in the Japan Sea side region. Many species such as Quercus serrata, Carpinus laxiflora, F. japonica and A. firma, were co-dominant in A, B and C groups, without a single, major dominant species, but Siebold's beech was the major dominant in D and E groups. The climatic cline among stand groups was obvious; from A group to E group, the Kira's warmth index decreased, while the amount of winter precipitation and the maximum depth of snow increased. In terms of micro-topography, most forest stands were established on the ridge or on the upper side slopes. Population structure of Siebold's beech showed distinct differences, in accordance with the change of vegetation from A group to E group; the relative dominance and the density of Siebold's beech increased, and the size structure changed from the sporadic type to the continuous type. It is considered that Siebold's beech originally had an extensive distribution both horizontally and vertically, as a component of the various types of climax temperate forests in the area, forming dominant forests in the upper temperate zone, and forming scatterred metapopulations in the lower temperate zone.

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We modeled the distribution of the habitat of Lagerstroemia subcostata var. fauriei (LSF), a rare riparian species which is indigenous to Yakushima Island, southern Japan, by analysis of GIS-derived topographic factors. We measured the distribution of LSF at sample sites (ca 15 ha in total) located within two catchments (60 ha in total) on the western side of Yakushima Island. Based on this data, we modeled the distribution of tree density of LSF in 12.5m×12.5m grid cells covering the entire area of the two catchments (11280 cells in total) by using Poisson loglinear modeling of GIS-derived topographic factors. The modeling was performed by progressively adding four different levels of topographic factors as follows: Level-1, topographic attributes of the target cell, such as elevation or slope inclination; Level-2, cell position relative to the adjacent channel; Level-3, attributes of the adjacent channel; and Level-4, catchment-scale attributes. The AIC factor of the models obtained decreased with the addition of attribute data from the Level-1 to Level-4 factors. This indicated that the topographic attributes of the target cell (Level-1) alone are not sufficient to describe suitable habitat for LSF, and that channel characteristics (Level-2 and 3 factors) are also useful. Moreover, the models adopting Level-4 factors showed the best performance, indicating the importance of catchment characteristics, such as the existence of sediment sources or seed sources, in explaining the actual distribution of LSF.

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The early-stage vegetation on the shores of the crater lake formed by the 2000 eruption of Usu Volcano, Hokkaido Japan, was investigated in the summer of 2004. Invasion and establishment of vascular plants in the study area began in the spring of 2001. By the summer of 2004, 21 plant species, including emergent aquatic plants, had become established at the study site, and the vegetation exhibited changes with respect to differences in microtopography. Many of the plants were anemochorous or anthropochorous weeds. Emergent aquatic plants dominated the shores of the crater lake and other waterlogged sites. It is inferred that the most of seeds of these emergent aquatic species appear to have been dispersed by birds, and especially by waterfowl.

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