Leaf Survivals of Tree Species in Deciduous Broad‐Leaved Forests1)

Abstract Leaf survival patterns of tall trees, small trees and shrubs were surveyed in temperate deciduous broad-leaved forests in northern Japan. Leaves of tall trees which constitute the crown layer of the forest emerge simultaneously in spring as a flush and also fall simultaneously in autumn. This was considered to be a “competitive type” of leaf survival strategy. Species which invade open sites near rivers show a “succeeding type” of leaf-emergence and leaf-fall. Their leaf longevities are short. They are pioneer strategists and are assumed to use abundant resources luxuriously by shedding older low-efficient leaves and producing new, high-efficient leaves. Intermediate between the two is a type considered to be adapted to light gaps in forests. Leaf longevities of species in forest understorys where shade stress prevails were long. To prolong leaf longevity is the method to utilize limited resource efficiently. Three strategies based on the two axes of stress and disturbance were applied to the leaf survival patterns of trees. Environmental conditions around a tree change with height growth of the tree. Leaf survival patterns also change with the development of trees. A three-dimensional graph model which expresses such changes as a function of tree-height is presented. Mean longevities of leaves compared between 1-year-old seedlings and adults revealed that differences between the two were larger in “intermediate type” species than for succeeding or flush type species.