Patterns of branching and extension growth of vigorous saplings of Japanese Acer species in relation to their regeneration strategies

Abstract

The patterns of branching and extension growth of vigorous saplings of eight Japanese Acer species were studied in relation to gap sizes where they regenerate in late-successional forests. Three types were recognized: sympodial-spread type, elongate type, and monopodial-spread type. In the sympodial-spread type, long and short shoots do not occur, and the amount of extension growth is small. These characteristics are more adapted to producing an efficient photosynthetic surface area than height growth. Extension growth is determinate. Determinate species flush leaves simultaneously at budbreak, which ensures a long duration of photosynthesis in a year. This type regenerates in small gaps with its shade-tolerant growth mode. In the elongate type, long and short shoots occur, and the amount of extension growth is large. These characteristics are more adapted to height growth than producing an efficient photosynthetic surface area. Extension growth is indeterminate. Indeterminate species start rapid height growth earlier than determinate species. This type responds to the occurrence of gaps and regenerates in large gaps with this competitive growth mode. In the monopodial-spread type, long and short shoots do not occur, the amount of extension growth is large, and extension growth is indeterminate. This type regenerates in middle-sized gaps with a growth mode intermediate between the previous two types.