カンレンボク小型林分の葉令に関する2,3の考察

抄録

The leaf longevity of five-year-old seedings of Camptotheca acuminata (Nyssaceae) was investigated in a sample stand at the Forest Experimental Nursery of the Kyoto University in Kyoto. The annual height growth was vigorous, being more than 1m/yr. In spring a great number of leaves emerged(70% of the total number in a year), but the leaf size was small. As time passed, the number of leaves decreased and conversely the area of the individual leaf increased until it reached 130cm^2 in September. The individual leaf longevity was rather short ; the leaves which appeared in spring lasted only one or two months. Those which came out in summer continued to stay on the seedlings for two to three months. None of the leaves which emerged in spring or summer could last to the end of the vegetative season in late autumn, when the major leaf-fall occurs, when about 25 percent of the annual leaf mass was shed. The leaf-fall was observed through the growing season and the seasonal variation of the amount of fallen leaves seems to have a close relation to the height growth of the seedlings. From these observations, it can be concluded that Camptotheca seedlings have a relatively shorter leaf longevity than those of deciduous species indigenous to Japan. Further comparative studies are necessary to explain the shortness of the leaf longevity of the Camptotheca species ; to ascertain whether it is inherent to the species or due to rapid self-thinning owing to the rapid height growth.