Regeneration Dynamics and Genetic Variability of Sugar Maple (Acer Saccharum [Marsh.]) Seedlings at the Species' Northern Growth Limit, Lake Superior Provincial Park, Canada

Abstract

The transition from deciduous to boreal forest is abrupt regionally and topographically in Lake Superior Provincial Park, Ontario, Canada. The northern range limit of Acer saccharum is coincident with the forest transition to boreal forest. The goal of our study was to characterize the distribution of A. saccharum seedlings at the transition zone to determine variability in seedling demographics and genetics with topographic position and along a short north-south gradient. Seedling density, size, age, and growth were evaluated in permanent plots across the regional transition zone, and at the south-facing, ridge top and north-facing limits across the topographic transition. Growth over 5 yrs. was determined by measuring the distance between terminal bud scars, and compared with regional climate data. Genetic material was collected and analyzed from two of these sites. No significant differences were detected in density or growth of Acer saccharum across the regional transition but mean age increased and height decreased as the limit was approached. Across the topographic transition, ridge top seeding densities were greater than the south-facing or north-facing limits. Genetic variability is great with no cohort preference for topographic position detected.