Role of axis reversal from the short-shoot to long-shoot habit for crown maintenance in slow-growing Betula maximowicziana trees

PREMISE OF THE STUDY: Branch growth and its spatial arrangement determine tree crown architecture and leaf display, and thus the productivity of trees. Branch axes elongate by the sequential production of shoots with differing morphology and function, such as short shoots and long shoots. This study investigated ontogenetic changes in axis growth in Betula maximowicziana and quantified the role of axis reversal between the short-shoot and long-shoot habit, particularly reversal from the short-shoot to long-shoot habit. METHODS: From eight trees with varying levels of growth vigor, 716 branch axes forming the basic crown architecture were sampled. Past growth of the branch axes was reconstructed from leaf and bud scale scars, and compared between slow-growing and vigorously growing trees. KEY RESULTS: Branch axes reversed more frequently between the long- and short-shoot habits in slow-growing trees than in vigorously growing trees. Short-shoot-origin axes that reversed to the long-shoot...