Recent advance of white spruce (Picea glauca) in the coastal tundra of the eastern coast of Hudson Bay (Québec, Canada)

• Published in: Journal of Biogeography
• Main Authors: M. Caccianiga, S. Payette
• Format: Article in Journal/Newspaper
• Language: English
• Published: Blackwell Publishing 2006
• Subjects: Forest tundra; Isostatic uplift; Macrofossil analysi; Picea glauca; Shrub tundra; Subarctic Québec; Tree colonization; Tree line; Tree-ring analysi; White spruce; Settore BIO/02 - Botanica Sistematica; Nunavut; Hudson Bay; Canada; Hudson; Nastapoka; Subarctic; Tundra
• Online Access: http://hdl.handle.net/2434/23836; https://doi.org/10.1111/j.1365-2699.2006.01563.x

Aim The species-specific response of tree-line species to climatic forcing is a crucial topic in modelling climate-driven ecosystem dynamics. In northern Quebec, Canada, black spruce (Picea mariana) is the dominant species at the tree line, but white spruce (Picea glauca) also occurs along the maritime coast of Hudson Bay, and is expanding along the coast and on lands that have recently emerged because of isostatic uplift. Here we outline the present distribution, structure, dynamics and recent spread of white spruce from the tree line up to its northernmost position in the shrub tundra along the Hudson Bay coast. We aimed to obtain a minimum date of the arrival of the species in the area and to evaluate its dynamics relative to recent climate changes. Location White spruce populations and individuals were sampled along a latitudinal transect from the tree line to the northernmost individual in the shrub tundra along the Hudson Bay coast and in the Nastapoka archipelago in northern Quebec and Nunavut, Canada (56 degrees 06'-56 degrees 32' N). Methods White spruce populations were mapped, and the position, dimension, growth form and origin (seed or layering) of every individual recorded. Tree-ring analyses of living and dead trees allowed an estimation of the population structure, past recruitment, growth trends and growth rate of the species. A macrofossil analysis was performed of the organic horizon of the northernmost white spruce stands and individuals. Radiocarbon dates of white spruce remains and organic matter were obtained. The rate of isostatic uplift was assessed by radiocarbon dating of drifted wood fragments. Results The first recorded establishment of white spruce was almost synchronous at all sites and occurred around AD 1660. Spruce recruitment was rather continuous at the tree line, while it showed a gap in the northern shrub tundra during the first decades of the 19th century. A vigorous, recent establishment of seedlings was observed in the shrub tundra; only wind-exposed, low krummholz ...