Écologie des populations d’aulne vert (Alnus crispa (Ait.) Pursh) à la limite des forêts, Québec nordique

• Published in: Géographie physique et Quaternaire
• Main Authors: Gilbert, Hélène, Payette, Serge
• Format: Text
• Language: French
• Published: Les Presses de l'Université de Montréal 1982
• Subjects: envir; geo; Arctic; Rivière aux Feuilles
• Online Access: https://doi.org/10.7202/032472ar; http://id.erudit.org/iderudit/032472ar

Populations of green alder (Alnus crispa (Ait.) Pursh) growing on south-facing and well-drained terraces in the Rivière aux Feuilles area (Northern Québec: 58°15' N, 72° W), located above the local forest line, present a disjunct distribution, isolated from the well-established alder stands found along the river. These populations are the result of an important range expansion of the species in the XXth century, during a warmer period between 1920 and 1960. Most of alder stands appeared after 1920, under suitable seed germination conditions on periglacial barren soils (frost boils, gélifluction lobes, etc.). During succession, the initial low shrub-lichenic vegetation gradually changed, within a few decades, into a scarce under canopy vegetation controlled by the thick litter produced by alder. The gradual development of alder populations has also caused important changes in soil properties: thickening of the organic horizon related to strong alder litter accumulation, increase of organic matter, CEC, total bases and N, and lowering of C/N ratio and pH. Vegetative regeneration is virtually the only reproductive mode for alder, since germination conditions changed drastically during the successionnal process. Similar situations in such alder populations have been observed elsewhere in the Hemi-arctic, and indicate 1) that green alder responds directly to climatic changes in this major biota of the Québec-Labrador peninsula, and 2) that it represents a general phenomenon for which there is a need for more detailed studies, in particular for paleoecological and palynological purposes. Des populations d'aulne vert (Alnus crispa (Ait.) Pursh) de la région de la rivière aux Feuilles (58°15' N, 72° O) sont particulièrement bien développées sur les versants bien drainés exposés au sud et situés au-delà de la limite locale des forêts. Ces populations correspondent à une importante expansion de l'espèce surtout au cours du XXe siècle, entre 1920 et 1960. L'essentiel des populations d'aulne vert sont apparues après 1920, ...