Betula ermanii, a Dominant Subalpine and Subarctic Treeline Tree Species in Japan: Ecological Traits of Deciduous Tree Life in Winter

Abstract

Betula ermanii (Japanese mountain birch), a dominant tree species of the subalpine and subarctic treeline ecotones in East Asia, was investigated with respect to frost hardiness, bud phenology, and woody-tissue respiration above and below snow at the treeline on Mt. Fuji, Japan. On the Pacific-facing south slope, the minimum air temperature regime at 2450 m altitude is not harmful to the viability of previous year's shoots and emerging leaves. Betula ermanii will approach its upper distribution limit where the risk of spring frost damage in immature tissues interferes with the need for a minimum length of the growing season. In the cold Pacific winter climate of Japan, susceptibility of bursting buds and dehardened shoots to frost down to -7°C late in May is a major determinant for the species' altitudinal distribution limit at 2800 m altitude. It is concluded that two periods of minimum temperature affect the upper distribution of a deciduous broad-leaved tree species in temperate climates: (1) periods of subzero temperature which determine the occurrence of spring frost damage and affect the beginning of the growing season and (2) cool periods during the growing season that affect development and ripening of overwintering plant compartments.