Patterns of Architectural Variation in Thuja occidentalis L. (Eastern White Cedar) from Upland and Lowland Sites

The distribution of Thuja occidentalis L. (eastern white cedar) within its range in northeastern North America is bimodal, as it occurs both on cliffs (dry uplands) and in swamps (wet lowlands). A comparison of the gross architecture of individual trees was made in situ, in order to characterize the architecture of this species and to examine the pattern of architectural variation among sites of the same habitat type and between habitat types. Architectural measurements were made on randomly selected trees growing in three cliff and three swamp sites in southern Ontario. Height, maximum crown diameter, basal stem diameter, angle of initial stem orientation, angle of present growth, number of reiterated axes, number of points of contact with the substrate, and age were determined for each tree. Architectural variation was small among sites of the same habitat type and between cliff and swamp habitats as well. These results confirm other findings that the trees studied were part of a larger rather homogeneous population. Our investigation lends no support to the existence of well-developed upland and lowland architectural forms of T. occidentalis in southern Ontario.