Leaf survival of woody plants in deciduous broad-leaved forests. 1. Tall trees

Seasonal changes in mean numbers of leaves per shoot were shown for 41 tall-tree species in deciduous broad-leaved forests in Hokkaido, northern Japan. Three types of leaf-emergence pattern were recognized; namely (1) succeeding type, (2) intermediate type, and (3) flush type. The two species showing the succeeding type emergence pattern have homonomous winter buds characterized by one-lamina and two-stipules sets. The species of intermediate- or flush-type emergence pattern usually have heteronomous winter buds with several bud scales. A negative correlation was found between leaf-emergence duration and number of bud scales. Species having a long leaf-emergence duration were open land or gap invaders. Among them, those having long leaf-fall duration were found in riverside forests. On the other hand, species showing flush-type leaf emergence with short duration and almost simultaneous leaf fall with also short duration were mainly found in mixed-forest stands. The longevities of leaves at the basal part of the shoot were short in the species whose bud scales have not entirely differentiated from foliage leaves. The main evolutionary trend in the shoots was suggested to be from homonomous to heteronomous structure and towards the clear distinction between foliage leaves and bud scales.