Stratégie de tolérance au vent chez Salix uva-ursi, une espèce de la toundra du Nouveau-Québec (Canada)

Abstract

Salix uva-ursi Pursh is a prostrate shrub typical of windy arctic–alpine tundra sites of eastern North America. According to Grime's thesis, plants living in growth-limiting conditions should satisfy the following criteria: (1) limited growth rate, (2) extended individual longevity, (3) reduced allocation to reproduction, (4) infrequent reproduction, (5) regeneration by vegetative multiplication or seedling bank rather man seed bank, (6) reduced plasticity, and (7) persistent leaves. Salix uva-ursi displays a few of these criteria (1, 2, 4) and is capable of layering (5). However, contrary to Grime's conditions (3, 6, and 5, respectively), allocation of annual biomass to reproduction is considerable, structure is variable, depending on wind exposure, and a seedling bank is absent and regeneration depends in part on a large number of small, wind-dispersed seeds. Thus S. uva-ursi takes advantage of wind, which is usually a limiting factor, to reach the few favorable microhabitats of an otherwise inhospitable environment. Finally, the leaves of S. uva-ursi die each fall (contrary to 7) but remain attached to the plant for several years. This may increase the boundary layer in winter and allow for protection against snow erosion. Salix uva-ursi dominates sites with very high levels of stress but its biology is not always consistent with Grime's predictions of the stress tolerance strategy.