Grant: Discovery Grants Program - Individual

Soils and paleosols - soils of the past - are a rich archive of long-term environmental change in northwestern Canada. Soil evidence will be used to answer two important questions about the environmental history of eastern Beringia - the unglaciated region of Yukon and Alaska joined by lowered sea level to Siberia. Given the magnitude of recent and projected warming in northern Canada, this research program is timely as it will provide direct evidence of how terrestrial ecosystems responded to equally significant  environmental changes in the past.        First, do soils and their weathering products indicate that early Pleistocene interglacial climates were more temperate than at present? The mineralogy and geochemistry of soils, paleosols, and their parent materials in the west-central Yukon will be examined to identify: (1) inherited influences of preglacial weathering, (2) regional patterns in the properties of soils formed on early Pleistocene and Pliocene glacial deposits, (3) signatures of past climates preserved in the stable isotope composition of soil weathering products, and (4) landscape and historical patterns of soil formation on deeply weathered bedrock in unglaciated uplands.      Second, did shifts between forest and steppe-tundra vegetation influence the deposition of silty wind-blown sediments (loess), and its subsequent modification by soil formation? At Kluane Lake, southwestern Yukon, Holocene loess deposition has occurred in a forest-grassland mosaic that provides analogues for many glacial and interglacial vegetation types in eastern Beringia. Examination of soils developed on loess and associated slope deposits will address: (1) differences in loess thickness and morphology in relation to slope position and vegetation type, (2) the historical record of loess redistribution after fires, as reconstructed by radiocarbon dating of buried charcoal, and (3) micromorphological evidence for the mechanisms of loess redistribution on slopes in relation to vegetation types.