Expansion Dynamics and Performance of the Dwarf ShrubEmpetrum hermaphroditum(Ericaceae) on a Subarctic Sand Dune System, Nunavik (Canada)

Many tundra plant species rely more heavily on clonal propagation than on sexual reproduction. However, if reproduction bottlenecks are alleviated, shifts in the balance between these strategies can occur. To better understand the colonization and expansion dynamics of clonal dwarf shrubs in a rapidly changing environment, we monitored a crowberry population (Empetrum hermaphroditum) on a sand dune system in subarctic Quebec. Our objectives were to quantify survival, recruitment, and growth and to determine whether performance varied across a topographic and successional gradient. In 2012, we resurveyed a 6-ha plot where all individuals had been counted in 2007. Along the successional gradient, we measured vegetation cover, soil characteristics, shoot elongation, and seed germination. Over the 2007–2012 period, the population continued to experience abundant recruitment, fast growth, and low mortality, resulting in a 40% increase in population size and a 244 m2 increase in cover. Performance patt...