A new association of deciduous broad-leaved riparian forests, namely, Kerrio japonicae-Quercetum serratae is described on the Pacific Ocean side in central Honshu, Japan. This association is dominated by Quercus serrata and is accompanied with Zelkova serrata, Castanea crenata, Prunus spp., Acer spp., and Carpinus spp. in the tree layer. Comparing with the other associations of Quercus serrata, Kerrio japonicae-Quercetum serratae is characterized by the elements of Fraxino-Ulmetalia Suz.-Tok. 1967, such as Kerria japonica, Rhamnus japonica var. decipiens, Ostrya japonica, Acer mono var. ambiguum, and Lilium cordatum. The distribution of this association is inland area of central Honshu of the intermediate temperate zone between warm temperate zone and cool temperate zone. The habitats of this association are riverside stable terraces in the middle reaches with surface deposits consisting of cobbles, gravels, and coarse sands. This association can be classified into the following upper unit: Carpino-Quercion serratae Miyawaki et al. 1971, Quercetalia serrato-grosseserratae Miyawaki et al. 1971, Querco serrato-Pinetea densiflorae Nakanishi, Takeda et Hattori 1977. The Kerrio japonicae-Quercetum serratae can be regarded as one of the edaphic climax of alluvial plain.

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Flower and fruit morphologies of Hibiscus hamabo Siebold et Zucc. were investigated in nine populations, five on the Omura Bay side and four on the ocean side of the Nishisonogi Peninsula in Nagasaki Prefecture, southwestern Japan, and were compared among populations. The morphological characters investigated were petal length, petal width, style length, anther-stigma distance, anther-anther distance, number of stamens, fruit length, fruit diameter and potential number of seeds per fruit. Observed variations were mainly among populations, and each population had specific characters in flower and fruit morphologies. Population diversity is important for conservation and restoration in Hibiscus hamabo communities. Petal length, petal width, anther-anther distance, number of stamens, fruit length, fruit diameter and number of seeds in populations on the Omura Bay side were significantly smaller than each of those characters on the ocean side, but anther-stigma distance was longer. These characters may indicate that the populations on the bay side had evolved in the pollinator-rich environment and become to avoid self-pollination.

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Altitudinal changes in vegetation of tree species (>1.3m tall) and understory herb and fern species were studied at 13 sites between 800m and 3000m a.s.l. on Mount Norikura, central Japan. Based on the result of cluster analysis, altitudinal vegetation pattern was roughly classified by tree species into a montane deciduous broad-leaved forest type between 800m and 1600m a.s.l., a subalpine coniferous forest type between 1600m and 2500m a.s.l. and an alpine dwarf pine Pinus pumila scrub type between 2500m and 3000m a.s.l. Understory herb and fern species also changed with altitude, but the altitudinal change of vegetation of the understory species did not correspond with that of tree species. Especially, understory species formed a large cluster between 1400m and 2800m a.s.l., although a subcluster was definitely recognized between 1400m and 2000m a.s.l. because of the dominance of the dwarf bamboo Sasa senanensis. The number of tree species decreased with increasing altitude, but the number of understory herb and fern species did not decrease. Species diversity, expressed as the Shannon-Wiener H' index and Simpson's index (1-D), of tree and herb species tended to decrease between 1400m and 2000m a.s.l. because S. senanensis excluded the other plants. Therefore, this study suggests that altitudinal changes in vegetation differed between taxonomic groups, such as tree species and understory herb and fern species, and the species diversity is determined not only by altitude, but also by S. senanensis.

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Coppice forests with various covers of evergreen species were studied to clarify the effect of increasing cover of evergreen species on species diversity and species composition in Hokusetsu area, Hyogo, western Japan. We investigated three communities: Quercus acutissima community which has been maintained by traditional management, Quercus serrata community which was already abandoned and is under progressive succession toward evergreen broadleaved forest, and Quercus glauca community which is dominated by evergreen species in the tree layer. Cumulative cover of evergreen species was significantly correlated negatively with the number of all species in all layers, number of summergreen species in all layers and those in the herb layer. Cumulative cover of evergreen species was significantly correlated with the first axis of Detrended Correspondence Analysis performed for the study plots, which represent differentiation of species composition of the three communities. Species richness per 100m^2 was 50.8 in Q. acutissima community, 41.2 in Q. serrata community and 19.3 in Q. glauca community, showing a difference between communities. Summergreen species counted 33 in 38 indicator species for Q. acutissima community, 11 in 15 for Q. serrata community and 2 in 11 for Q. glauca community, respectively. It is considered that degradation of light conditions, originating from the increase of evergreen species, inhibits the growth of shade-intolerant species, resulting in decrease of species richness and changes in species composition.

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We investigated the ecological distribution of seven evergreen Quercus species in southern and eastern Kyushu, Japan by analyzing previously reported vegetation data. Analysis along an elevation gradient, together with cluster analysis of species correlations, revealed two major species groups with distinct distributions: a high-elevation group comprised of Quercus acuta, Q. salicina, Q. myrsinaefolia, and Q. sessilifolia and a low-elevation group consisting of Q. gilva, Q. glauca and Q. hondae. The distribution of Q. acuta had the highest elevation range, Q. hondae the lowest, of the seven species. Q. acuta also showed a preference for upper slope topographic positions. In contrast, the occurrence of Q. sessilifolia, Q. gilva and Q. hondae was biased towards lower slopes. The occurrence of Q. sessilifolia was particularly restricted to lower slopes at lower elevation (<400m), suggesting that it is a characteristic component of riparian lowland areas. Q. salicina had the highest frequency and least pronounced site preference with respect to both elevation and topography, indicating that it is a typical generalist species. Q. glauca had no topographic preference and was grouped with pioneer and/or deciduous species in cluster analysis, suggesting that it is an early-seral or disturbance-dependent species.

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[in Japanese]

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