The effect of climate on seedling recruitment of sugar maple (Acer saccharum Marsh) at its northern range limit in western Quebec, Canada

By its strong competitiveness, sugar maple (Acer saccharum Marsh.) dominates the temperate forests in the south of Quebec, and its northern limit defines at the same time the limit between the temperate and the boreal biomes. Seedling establishment, especially at the range limit, is a critical step for the regeneration of plant species because of the commonly high mortality rates during this stage and because of the potential to alter the spatial and temporal patterns of recruitment. To understand how sugar maple will respond to climate change, the climatic factors affecting seedling recruitment at its northern range limit was studied. The hypothesis tested is that seedling recruitment in sugar maple populations at its northern range boundary is limited by unfavourable climatic factors during winter and the growing season, thus preventing migration and colonization of new habitats further north. Five sugar maple populations were sampled along a latitudinal gradient, in western Quebec, extending from 45º50’N (sugar maple-yellow birch domain) to 48º10’N (balsam fir-white birch domain). In each population, the age structure of seedlings (<120 cm height) was analyzed using a model assuming decreasing mortality with age (power function). Preliminary results show significantly fewer seedlings, higher mortality rate, and lower seedling growth within the northernmost sugar maple seedling populations compared to populations in the sugar maple-yellow birch domain. Correlation with climatic data further supports our hypothesis but migration and colonization of sugar maple might also be limited by unavailability of suitable habitats further north of the actual range limit.