© 2005 Blackwell Publishing Ltd www.blackwellpublishing.com/geb DOI: 10.1111/j.1466-822x.2005.00157.x 307 Global Ecology and Biogeography, (Global Ecol. Biogeogr.) (2005) 14, 307–313 RESEARCH PAPER Blackwell Publishing, Ltd. Late Holocene opening of the forest tundra landscape in northern Québec, Canada Hugo Asselin* and Serge Payette ABSTRACT Aim Previous studies conducted at the tree line in northwestern Québec suggested that the forest tundra was created over the last 3000 years by deforestation as a result of the combined action of forest fires and climatic cooling. Our objectives were to: (1) validate at a larger spatial scale the time frame of the last 3000 years; (2) verify if the opening process was more pronounced during particular time periods; and (3) confirm that fire was the triggering mechanism. Location Seventeen lakes from the forest tundra of northern Québec. Methods Pollen records were analysed to determine the date of landscape opening, as interpreted by the time of decrease towards present-day values of the ratio of Picea pollen percentage to pollen percentage of the taxa typical of open forest tundra landscapes (Betula, Ericaceae, Cyperaceae and Poaceae). Results Landscape opening in northern Québec started c. 3220 cal.  (calibrated years before present) and was more pronounced between c. 2040 and 890 cal. . No spatial pattern was observed in the dates of landscape opening. Main conclusions The suggestion that landscape opening in the forest tundra occurred over the last 3000 years was validated at the scale of northern Québec. A period of more pronounced opening was identified between 2040 and 890 cal.  and could be related to increased fire occurrence. Absence of a spatial pattern in the dates of landscape opening provides further confirmation that fire was the triggering mechanism. Keywords Black spruce, climate change, fire, forest tundra, landscape opening, Picea mariana, pollen. RÉSUMÉ Objectif Des études antérieures menées à la limite des arbres dans le nord-ouest du Québec ont suggéré que la toundra forestière aurait été créée au cours des derniers 3000 ans par la déforestation résultant de l’action combinée des feux de forêt et d’un refroidissement climatique. Nos objectifs étaient de (1) valider à une échelle spatiale plus importante la période des derniers 3000 ans; (2) vérifier si le processus d’ouver- ture du paysage a été plus prononcé à certaines périodes; et (3) confirmer que le feu a été le mécanisme déclencheur. Localisation Dix-sept lacs de la toundra forestière du nord du Québec. Méthodes Les enregistrements polliniques ont été analysés pour déterminer la date d’ouverture du paysage, telle qu’interprétée par le moment où survient une baisse marquée vers les valeurs actuelles du ratio du pourcentage de pollen de Picea sur le pourcentage de pollen de taxons typiques des milieux ouverts de la toundra forestière (Betula, Ericaceae, Cyperaceae et Poaceae). NSERC Northern Research Chair, Centre d’études nordiques, Université Laval, Québec (Québec), G1K 7P4, Canada *Correspondence: Hugo Asselin, Chaire industrielle CRSNG-UQAT-UQAM en aménagement forestier durable, Université du Québec en Abitibi-Témiscamingue, 445, boulevard de l’Université, Rouyn-Noranda (Québec), J9X 5E4, Canada. E-mail: hugo.asselin@uqat.ca