The influence of neighbours on the growth of trees II. The fate of buds on long and short shoots in Betula pendula

Abstract

In Betula pendula buds are produced on long and on short shoots. The long shoots bear many daughter buds on elongated internodes and they contribute overwhelmingly to the increase in the size of the tree and to its architecture. Short shoots normally bear only one bud and at best only replace themselves each year in the shoot population. Individual trees were grown close together in groups of three so that each experienced interference from neighbours on one side and not on the other. A lower proportion of buds in the high-interference zone developed into long shoots in the second and third years of the three-year experiment and a lower proportion survived to the end of the growing season in year 2. The overall proportion of buds that died was greater in the high-interference zone. The influence of neighbours became more marked as branches aged and were overtopped in the canopy. This led to asymmetry in the form of the trees. The different sides of a single tree in this study may approach the form of an open-grown individual on one side and that of a forest tree on the other.