Leaf diversity in yellow birch (Betula alleghaniensis)

Abstract

Analysis of leaves from several crown positions of a single yellow birch (Betula alleghaniensis Britton) indicated that particular short-shoot leaves from the middle and lower inside crown were more uniform than those from other crown positions. The short-shoot leaves typically occur in pairs. Each pair consists of two distinctly different leaves, termed here the A and B leaves. The A leaf is consistently larger, with more veins and teeth and a more inequilateral base than the B leaf. Because of their relative uniformity, lower inside crown A leaves would be useful as "standard" leaves for among-tree and among-population comparisons. Late leaves, borne on long shoots in exposed portions of the upper crown, were smaller than the short-shoot leaves in all dimensions. Principal components and canonical variates of the short-shoot leaves from the lower and middle inside crown exhibited the most compact and least variable groupings of all of the leaf types. The first canonical variate separated the leaves of the lower and middle crown from those of the upper crown. The second canonical variate separated A and B leaves. Observations of emerging leaves indicated no systematic differences in position of the A and B leaf.