マテバシイ

Coastal coppices dominated by Pasaniu edulis Makino are found along the Genkai Sea in northern Kyushu. In this paper these forests were studied from the view points of floristic composition, growing environments, and biomass production for the purpose to provide fundamental data which are important in managing these forests as environmental or commercial forests. The results may be summarized as follows: A. Floristic composition and environmental factors. (1) Pasania forests have been recognized as coppices in the past, and characteristics of floristic composition have not been clarified due to the lack of character species. (2) According to cluster analysis of floristic compositions, Pasania forests were separated from other communities with only the domination of Pasania edulis, and with no specific follower plants. (3) There was a slight tendency that Pasania forests developed even on more poor sites in available water. (4) Principal component analysis was used for the purpose to know the effect of each environmental factors in the general adaptability. Analysis showed that Pasania forests developed on slightly xeric sites in all communities analized. But no effective factor which restricts distribution of communities was found. According to these results, it was considered that distribution and expansion of Pasania forests depend on man-made factors rather than natural environment. B. Biomass production. (1) Aboveground biomass of 34-year-old coppice dominated by Pasania edulis were 214 ton/ha, and leaf biomass occupied 9.7 ton/ha. These values were larger than those of coppice in same tree height dominated by Castanopsis cupidata var. Sieboldii. (2) The forest canopy of sampled stand was thin, but showed very high density. Relative light intensity declined abruptly around the top of the forest canopy, and was restricted at the low level of 1.6 or 2.0% on forest floor. (3) By stem analysis, stem volume of stand sampled was estimated as 320 m^3/ha. And remarkable elongation was observed in 1 or 2 years after clearcut. This seemed to indicate a possibility of vigorous sprouting. (4) Two different patterns of stem volume development were observed. Sample trees which had DBH less than 10 cm increased their stem volume gradually. On the other hand, samples with DBH more than 10 cm showed a peak in 23 or 25 years old. (5) Ages of stems gained from the same stump were different. It was, therefore, considered that earlier sprouts can not always remain. (6) L. A. I. was 4.8 ha/ha, which was smaller than those of Castanopsis forests. The value of light extinction coefficient (K) was very large as 0.82. But, strict linearity between log (Relative light intensity) and cumulative L. A. I. were not observed. At the upper part of the forest canopy the value of K was 0.21. They were considered to have resulted from change of leaf angles through the leaf development of Pasania edulis. (7) A tendency that vegetation of forest floor become poorer with the development of tree layer, was recognized. It was expected that this tendency continues until1 light condition under the forest canopy will be improved by the self-thinning through the competition between individuals forming the forest canopy.