Altitudinal distributions of vegetation were studied on Mt. Hachijo-Fuji (854m ; a Holocene volcano) and Mt. Mihara (701m ; a Pleistocene volcano) in Hachijo-jima Island, part of the Izu Islands group, and were compared with those on Mt. Kaimon-dake (922m ; a Holocene volcano) and Kuro-shima Island (622m ; a Pleistocene volcano) situated in southern Kyushu. Kaimon-dake and Kuro-shima have similar climatic and geological conditions to Hachijo-jima. In Hachijo-jima, a Persea thunbergii zone (below 650m) and Eurya japonica zone (above 650m) on Hachijo-Fuji, and a Castanopsis cuspidata var. sieboldii zone (below 600m) and P. thunbergii zone (600-700m) on Mihara were recognized. In southern Kyushu, a Quercus glauca zone (below 300m), P. thunbergii zone (300-500m) , Quercus acuta zone (500-650m) and E. japonica zone (above 650m) on Kaimon-dake, and a C. cuspidata zone (below 550m) and Q. acuta zone (above 550m) on Kuro-shima were recognized. The dominance of P. thunbergii on the Holocene volcanos (Hachijo-Fuji and Kaimon-dake) and of C. cuspidata on the Pleistocene volcanos (Mihara and Kuro-shima) seems to arise from succession from P. thunbergii forest to C. cuspidata forest. On the other hand C. cuspidata, P. thunbergii and E. japonica had wider dominant areas in Hachijo-jima along altitudinal gradients than on Kaimon-dake and Kuro-shima. This fact suggests niche expansions of these species in Hachijo-jima, due to the lack of evergreen Quercus species. In life form, evergreen nothophyll trees were dominant up to the top of the mountains of Mihara and Kuro-shima, below 600m on Hachijo-Fuji and below 650m on Kaimon-dake. Evergreen microphyll trees were dominant above the areas where evergreen nothophyll trees were dominant on the latter two Holocene volcanos. The altitudinal distributions of life forms were similar between the two Holocene volcanos, and between the two Pleistocene volcanos.

View full abstract

We studied the floristic composition and environmental factors of the beech forests in the Kyusyu District to clarify details of their compositional differentiation, compared with that of adjacent communities such as fir forests, hemlock forests, oak forests, elm forests, wingnut forests, ash forests, pine forests, and shrub communities. Phytosociological classification using the Braun-Blanquet method indicated that the beech forests had a relationship with the adjacent communities in terms of floristic composition ; in particular the closest relationship was with the ravine forests. Using the DCA ordination technique, the score of AXIS 1 correlated most closely with temperature and altitude, while the score of AXIS 2 correlated most closely with topographical gradient which determined the soil water condition. The pattern of coordinate distribution of sample stands on AXIS 1 and AXIS 2 varied in relation to geology of mountains (Paleozoic system, Tertiary system, and Quaternary system). Generally speaking, in the Quaternary system there was the least community differentiation, while in the Paleozoic system there was the greatest community differentiation. In the Tertiary system the community differentiation was intermediate between that of the Quaternary and that of the Paleozoic. Our study also showed that changes in compositional differentiation corresponded to the variation in site conditions. In the Paleozoic system, which is geologically the oldest system, the compositional differentiation along topographical gradient was most remarkable. This was mainly due to the presence of the "Sohayaki" element plants in the ravine forests.

View full abstract

We measured the growth of a Quercus mongolica ssp. crispula population in the cool temperate region of Central Japan. Measurements were made of trunk diameter and height of trees in a 20m×20m permanent quadrat and of planted saplings over the period 1983-1995. Saplings planted on the floor of the Quercus mongolica ssp. crispula coppice died during the course of the experiment, but those planted in an adjacent open area grew well. Mean tree diameter at breast height increased from 11.5 cm in 1983 to 14.0 cm in 1995, an average growth rate of 2.1 mm yr^<-1> ; growth during this period was approximated by the following equation : d (t) = 27/ [1+1.32 exp (-0.027t)] where d (t) is tree diameter in year t and t is years since 1983 when 1983 is 0. During this period, trunk density decreased from 84 to 73 per 20m×20m (0.9 yr^<-1>). The distribution of DBH approached a normal distribution in 1986, but subsequently diverged from normality. The relationship between tree density (N, the number of trees 400m^<-2>) and mean diameter at breast height d was described as : N (d) = 157.3 exp (-0.05d). Mean tree height increased from 8.4m in 1983 to 9.4m in 1995 (8.4cm yr^<-1>). The mean diameter at stem base of the saplings increased from 1.1cm in 1983 to 5.8cm in 1995. Sapling height increased from a mean of 0.53m in 1983 to 2.21m in 1993 (16.8 cm yr^<-1>). The relative growth rate (RGR) of the product of height and diameter of sapling varied annually from 0.17 to 0.45. Multiple regression was used to examine the factors that affected RGR including monthly air temperature and precipitation at the experimental site. The results suggest that RGR was influenced negatively by precipitation in May, the time when new leaves develop on Q. mongolica ssp. crispula.

View full abstract

Vegetation on Mt. Kurino-dake, Kirishima Volcano Complex, South Kyushu was studied and classified into 3 types of forest ; Machilus thunbergii forest around 600 m a. s. 1., Distylium racemosum forest around 700 m and Abies firma forest above 800m to the summit area including such subseres as Prunus grayana and Illicium anisatum stands which is due to canopy damage given by repeated typhoons every year. Seedlings on the forest floor were observed for three years from April 1992 to April 1995 or four years from August 1991 to April 1995. In the Kurino-dake forests seedlings co-existed with their mother trees in the plot, but a few species of them did not. While in the Minamata IBP Research Area a large number of disseminules came from outside of the plot, and a few were supplied in the plot. This relationship shows that Minamata forest was in the process of diversification and in the process of maturation for Kurino-dake forests. In the M. thunbergii forest a number of Idesia polycarpa seedlings were produced under the damaged canopy by a typhoon, but they were almost extinct in one year after their bursting into germination. While seedlings of M. thunbergii, a canopy species, died quickly, too, a few numbers of them survived until next mast year. A mass production of seedlings was not observed in canopy species other than M. thunbergii. In the forest on the top of the mountain there were a number of seedlings of secondary species, and it is hard to find any signs that this forest will develop into a climax Abies firma forest so far as our short term observation shows.

View full abstract