La végétation et le climat postglaciaires du centre et de l’est de la Gaspésie, au Québec

• Published in: Géographie physique et Quaternaire
• Main Authors: Asnong, Hans, Richard, Pierre J.H.
• Format: Text
• Language: French
• Published: Les Presses de l'Université de Montréal 2003
• Subjects: geo; hist; Bouchard; Lac Bouchard; Noire; Dwarf birch; toundra; Tundra
• Online Access: https://doi.org/10.7202/010330ar; http://id.erudit.org/iderudit/010330ar

Pollen and macrofossil analyses were used to reconstruct the postglacial vegetation history in the central (Lac du Triangle [48° 42’ 36’’ N, 65° 24’ 50’’ W]) and the eastern (Petit Lac Bouchard [48° 51’ 14’’ N, 64° 35’ 52’’ W]) part of Gaspésie. A sparse dwarf birch tundra existed as early as 11 200 BP (calendar years). Afforestation occurred around 10 700 BP involving black spruce sometimes accompanied or not by aspen. Growth of black spruce populations slowed down or was even reversed around 10 000 BP, and green alder and aspen experienced increased abundance during a period of elevated fire incidence. It took 1000 years for closed forests to be installed in central Gaspésie but in the eastern region, the process lasted 2000 years. Such a delayed afforestation could be due to a cold maritime climate. During the forest phase, regional thermophilous taxa like white pine and yellow birch occupied the eastern area whereas central Gaspésie was dominated by boreal tree species: balsam fir, black spruce and, to a lesser extent, white birch. Jack pine, presently absent from Gaspésie, was present around Lac du Triangle between afforestation to about 3500 BP. In response to a cooler and wetter climate during the last 3500 years, black spruce and balsam fir became more abundant, while white birch decreased in the two regions, more so around the eastern site. A first paleohydrological reconstruction is proposed, based on lake level changes. L’analyse pollinique et macrofossile des sédiments de deux lacs a livré l'histoire postglaciaire de la végétation au centre (lac du Triangle [48° 42’ 36’’ N, 65° 24’ 50’’ O]) et à l’est (Petit lac Bouchard [48° 51’ 14’’ N, 64° 35’ 52’’ O]) de la Gaspésie. Une toundra éparse à bouleau glanduleux s'est installée dès 11 200 BP (années étalonnées). L’afforestation s’effectue par l’entremise de l’épinette noire accompagnée ou non de peuplier faux-tremble vers 10 700 BP. La multiplication des populations d’épinette noire s’est ralentie ou a cessé vers 10 000 BP au profit de l'aulne crispé ...