VARIATION OF SHOOT MORPHOLOGY AND BIFURCATION RATIO IN SUGAR MAPLE (ACER SACCHARUM) SAPLINGS

Open-grown sugar maple saplings differ qualitatively in their gross morphology when compared with saplings growing in shaded forest understories. Forest-grown saplings have their leaves distributed in a few planar layers, while open-grown saplings exhibit fuller crowns and more profuse branching. In order to quantify these observed differences in branching patterns, ordering methods were applied to twenty saplings each from forest and open sites. Bifurcation ratio, an index of branching previously assumed to be species constant, differed significantly between forest-grown and open-grown saplings. Bifurcation ratios for forest-grown saplings were low, with a mean of 3.19. Values for open-grown saplings were generally higher, with a mean of 7.05. This variation of bifurcation ratio between forest-grown and open-grown sugar maple saplings is the first such variation within any species to be reported. In addition, open-grown saplings were characterized by more extension growth of terminal shoots than forest-grown saplings. These results suggest that sugar maple has a range of branching and light interception characteristics that suit it well in different microenvironments.