The tree seedling bank in an ancient montane forest: stress tolerators in a productive habitat

Abstract

Summary 1 Seedling banks, made up of small individuals of tree species in the understorey, are an important component of many forests. 2 We collected and aged 4992 individuals up to 1.3 m in height of Abies amabilis , Chamaecyparis nootkatensis , Tsuga mertensiana and T. heterophylla from the seedling bank of an ancient forest in coastal British Columbia, Canada. 3 Growth was extremely slow. Some individuals < 1.3 m tall were more than 150 years old. Very few plants attained an above-ground stem length of 1 m in less than 100 years. Regressions of above-ground stem length vs. age indicated that net terminal growth averaged only c . 2 mm per year up to age 50. 4 Although species differed in age structure, all had slow-growing, persistent individuals. 5 These trees can be considered to be adapted to survive for long periods under the high levels of biotically induced stress of the forest understorey. Such a high potential for stress tolerance in forest trees presents a challenge for the classification of life histories. 6 The seedling bank contributes to the canopy composition in ancient forests. Forest ecology must consider not only tree regeneration in relation to disturbance, but also the dynamics of tree populations under intact canopies.