Soils and quaternary environments of northwestern Canada

土壤和古土壤-过去的土壤-是加拿大西北部长期环境变化的丰富档案。土壤证据将被用来回答关于东白令陆桥环境历史的两个重要问题——育空和阿拉斯加的无冰川地区与西伯利亚的低海平面相连。考虑到加拿大北部最近和预计的变暖幅度，这项研究计划是及时的，因为它将提供陆地生态系统如何对过去同样重大的环境变化作出反应的直接证据。首先，土壤及其风化产物是否表明更新世早期间冰期气候比现在更温和？将对育空中西部地区的土壤、古土壤及其母质的矿物学和地球化学进行研究，以确定：(1)前冰期风化的遗传影响；(2)早更新世和上新世冰川沉积物形成的土壤性质的区域格局；(3)土壤风化产物稳定同位素组成中保存的过去气候特征；(4)无冰川高地深度风化基岩上土壤形成的景观和历史格局。其次，森林和草原-苔原植被之间的变化是否影响了粉质风吹沉积物（黄土）的沉积及其随后通过土壤形成的修饰？在育空西南部的Kluane湖，全新世黄土沉积形成了森林-草地嵌合体，为白令陆桥东部的许多冰期和间冰期植被类型提供了类似物。对黄土和相关斜坡沉积物上发育的土壤的研究将解决以下问题：(1)与斜坡位置和植被类型相关的黄土厚度和形态差异；(2)通过埋藏木炭的放射性碳定年重建的火灾后黄土再分布的历史记录；(3)与植被类型相关的黄土在斜坡上再分布机制的微形态学证据。

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.