Postglacial vegetational change and soil development in southeastern Labrador as inferred from pollen and chemical stratigraphy

• Published in: Canadian Journal of Botany
• Main Authors: Engstrom, D. R., Hansen, B. C. S.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1985
• Subjects: Tundra
• Online Access: http://dx.doi.org/10.1139/b85-070; http://www.nrcresearchpress.com/doi/pdf/10.1139/b85-070

Palynological and geochemical analyses of Holocene lake sediments are used to evaluate long-term interactions between vegetation and soils from four sites in southeastern Labrador, Canada. Changes in soil composition are inferred from the stratigraphy of humic materials and the elemental composition of authigenic and allogenic fractions of the sediment. Early Holocene lake muds deposited under tundra vegetation are predominantly inorganic and contain high concentrations of allogenic elastics derived from the erosion of barren soils. Concentrations of humic materials and redox–pH-sensitive elements (Fe, Mn, P, Al) of authigenic origin increase markedly with the subsequent invasion of spruce and fir (8000–7000 years BP). These changes represent decreased erosion of clastic minerals and increased mobilization of organometallic complexes from waterlogged soils produced through humus accumulation under coniferous vegetation. This transition of inorganic tundra inceptisols to humic-rich boreal spodosols contributed to the competitive replacement of Picea glauca and Abies balsamea by the more edaphically tolerant P. mariana between 6500 and 6000 years BP. A subsequent decline in sedimentary humic content and increase in allogenic components may signal a regional climatic cooling after 4000 years BP. Geochemical analyses of lake sediments reveal no stratigraphic changes in allogenic mineral composition that might indicate progressive soil weathering.