Spruce-seedbed interactions : is there facilitation of recruitment in the boreal forest-alpine tundra ecotone? (Mealy mountains, Labrador, Canada)

• Main Author: Wheeler, Julia A. C., 1985-
• Other Authors: Memorial University of Newfoundland. Dept. of Biology
• Format: Thesis
• Language: English
• Published: 2009
• Subjects: Black spruce > Effect of global warming on > Newfoundland and Labrador > Labrador; Black spruce > Newfoundland and Labrador > Labrador > Seedlings; Ecotones > Newfoundland and Labrador > Labrador; Forest soils > Newfoundland and Labrador > Labrador; Soil seed banks > Newfoundland and Labrador > Labrador; Newfoundland; Canada; Mealy Mountains; Newfoundland studies; Tundra; University of Newfoundland
• Online Access: http://collections.mun.ca/cdm/ref/collection/theses4/id/155476

Thesis (M.Sc.)--Memorial University of Newfoundland, 2009. Biology Includes bibliographical references As climates warm, black spruce (Picea mariana) is expected to expand its range into alpine tundra. Ecological factors such as seedbed and prédation may influence recruitment on regional scales. In the boreal forest, seedbed-seedling competition dominates but in the climatically-stressed Mealy Mountains forest-tundra ecotone (Labrador, Canada) the Stress Gradient Hypothesis (SGH) predicts facilitation as the dominant plant interaction. We investigated mechanisms of seedbed facilitation (temperature, water, nutrients, physical structure) in Pleurozium schreberi, Cladina spp., and mineral soil, and examined links between prédation and seedbed. Pleurozium seedbeds had strong positive effects on seedling growth (30.9%) and survival (55%). Conversely, seedlings recruited poorly on mineral soil, with lowest growth (20.5%) and survival (26%). Seed emergence was highest on Pleurozium (6.3%), and lowest on Cladina (0.3%). The physical structure of Pleurozium likely protects seedlings from exposure, temperatures extremes and predators. As climates warm and seed availability increases, Pleurozium may facilitate black spruce expansion.