hw2_primary_succession_of_subarctic_vegetation_and_soil

hw2_primary_succession_of_subarctic_vegetation_and_soil -...

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ORIGINAL ARTICLE Primary succession of subarctic vegetation and soil on the fast-rising coast of eastern Hudson Bay, Canada Ann-Catherine Laliberte ´ and Serge Payette* NSERC Northern Research Chair, Centre d’e´tudes nordiques and De´partement de biologie, Universite´ Laval, Que´bec, Canada *Correspondence: Serge Payette, NSERC Northern Research Chair, Centre d’e ´tudes nordiques and De ´partement de biologie, Universite ´ Laval, Que ´bec G1K 7P4, Canada. E-mail: serge.payette@bio.ulaval.ca ABSTRACT Aim The objectives of the study are: (1) to evaluate the dynamics of the maritime tree line and forest limit of white spruce, Picea glauca , within the dual framework of primary succession induced by the rapid post-glacial land emergence on the eastern coast of Hudson Bay and the impacts of recent and past climate changes; and (2) to determine the time lapse between land emergence and seedling, tree, and forest establishment in the context of the primary chronosequence occurring on rising, well-drained sandy beaches and terraces. Location The study area was located on the eastern coast of Hudson Bay (56 Ŷ 20 ¢ N, 76 Ŷ 32 ¢ W) in northern Que ´bec, Canada. Methods We evaluated the colonization dynamics of white spruce as seedlings, tree-line trees and primary-forest trees at eight sites distributed along a 200-km latitudinal gradient based on a mean land emergence rate of 1.2 m century ) 1 .A 30-m wide by 140–300-m long quadrat was positioned at random at the centre of each site. The elevation above sea level, position and age of all individuals of spruce present in the quadrat areas were determined, and the soils of each chronosequence were described. Results The main stages of primary succession along the emerging coast were common to all the sites, regardless of latitude, but occurred at different elevations above sea level (a.s.l.). White spruce seedlings colonized near-shore beaches 2 m a.s.l., whereas the tree line and forest limit tended to form only at about 3–4 m and 4–8 m a.s.l., corresponding approximately to 180–825 years and 310– 1615 years after land emersion, respectively. White spruce establishment at the tree line occurred about 50 years ago. Climatic conditions at this time were probably more favourable to tree colonization than when the species established at the forest limit. Soil formation was inFuenced primarily by distance from the seashore and elevation above sea level, with podzolization being accelerated by white spruce cover. Main conclusions The current tree-line and forest-limit positions on the rising coast of eastern Hudson Bay correspond to ecological limits established during the course of primary succession within a context of changing climatic conditions. The recent establishment of trees at the tree line and forest limit at relatively old coastal sites is associated with warmer conditions over the last 100 years. Although white spruce was present nearby, coastal sites were devoid of trees before the 20th century.
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