Autumn coloring, photosynthetic performance and leaf development of deciduous broad-leaved trees in relation to forest succession.

Autumn coloring of deciduous broad-leaved trees in northern Japan was found to develop either from the inner part of the crown outward (inner-type), or from the outer part of the crown inward (outer-type). Inner-type trees had early-successional characteristics, whereas outer-type trees had late-successional characteristics. Although alders (Alnus hirsuta (Spach) Rupr. and A. japonica (Thunb.) Steud.) did not change color in the fall, these early-successional species were also studied. Both chlorophyll content and chlorophyll a/b ratio increased then decreased with increasing leaf age. In early fall, however, chlorophyll content of leaves on the same branch decreased from older to younger leaves only in the inner-type species. Net photosynthetic rates at light saturation of individual leaves increased then decreased at a greater rate in inner-type species than in outer-type species. Leaf dry weight per unit area decreased more before leaf fall in outer-type species than in inner-type species. Inner-type species have younger leaves at the outer surface of crowns, whereas in outer-type species, leaf age is similar throughout the crown. Leaf senescence of outer-type species began in the outer surface of crowns. The pattern of leaf senescence and the development of fall colorations may be related to the growth strategy of the species.