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The Critical Zone is an interdisciplinary theme for environmental research that considers the near surface environment of the Earth and interactions amongst rock, soil, water, air, and living organisms. Critical Zone research initiatives in the United States (US) have met with great success, with multiple Critical Zone Observatories located in a variety of regional field settings at their core. These initiatives have allowed for enormous advances in addressing interdisciplinary environmental science questions based on team collaborations involving experts from various disciplines. The Critical Zone initiative in the US is now being extended to several other countries, but Canada has not been a participant in initial meetings involving various national funding agencies and researchers from different countries. Because physical geographers study a wide range of topics falling under the banner of Critical Zone science (including soils, hydrology, geomorphology, climatology, glaciology, biogeography), they are well poised to be active participants in national strategies for Critical Zone science. Suggestions are provided for moving towards a national strategy for Critical Zone science initiatives in Canada that connect to recent international developments. Vers une stratégie pour la science de la zone critique au Canada La zone critique est un thème interdisciplinaire de la recherche environnementale qui examine le milieu de la proche surface de la Terre et les interactions entre la roche, le sol, l'eau, l'air et les organismes vivants. Les initiatives de recherche en zone critique aux États-Unis ont connu beaucoup de succès grâce à de nombreux observatoires de la zone critique situés au centre de divers dispositifs d'études régionales. Ces initiatives ont permis d'accomplir d'énormes progrès en abordant des questions de science environnementale interdisciplinaire fondées sur la collaboration d'équipes impliquant des spécialistes de diverses disciplines. Les initiatives américaines en zone critique sont maintenant étendues à de nombreux autres pays, mais le Canada n'a pas participé aux premières réunions impliquant divers organismes nationaux de financement ainsi que des chercheurs de différents pays. Comme les géographes spécialisés en géographie physique étudient un large éventail de thèmes placés sous la bannière de la science de la zone critique (y compris les sols, l'hydrologie, la géomorphologie, la climatologie, la glaciologie, la biogéographie), ils sont bien placés pour participer activement aux stratégies nationales pour la science de la zone critique. Des suggestions sont faites dans le but d'adopter une stratégie nationale pour les initiatives concernant la science de la zone critique au Canada qui se rattachent aux récents progrès internationaux. [ABSTRACT FROM AUTHOR]

Molluscs, sediment lithology, and published sub-bottom profiles are used to deduce sea levels, outline the influence of glacially induced crustal displacement, and reconstruct the paleoenvironment of the northeast Pacific late Quaternary coastline. Geo-spatial modelling shows subaerially exposed land that could have been inhabited by plants and animals, and also coastally migrating early North American peoples. Ice-free terrain, present by at least 13 790 ± 150 14C years BP, a land bridge, and edible molluscs are identified. Queen Charlotte Islands (QCI) late Pleistocene coastal paleogeography may assist in explaining the biogeography of many terrestrial plant and animal species along the broader northeastern Pacific margin and provide evidence for researchers seeking late Pleistocene – early Holocene glacial refugia. Late Pleistocene – early Holocene coastlines that are not drowned and that may harbour early archaeological sites are identified along the western QCI, where migrants probably first travelled and the westernmost British Columbia mainland, where the effects of glacial ice were reduced. [ABSTRACT FROM AUTHOR]

This paper presents data on and discusses the degree of postglacial stability of the northern Canadian tree limit. Holocene climatic changes have been both directional and synchronous for this region, though deteriorations/ameliorations either (1) lagged from west to east, (2) were buffered by local geographic factors, or (3) were not registered in the fossil record owing to the inherent persistence of the vegetation at some sites. The present northern tree limit in eastern Canada is in equilibrium with the prevailing climate, with the tree populations successfully regenerating both sexually and vegetatively. These tree stands are still occupying their maximum Hypsithermal positions. In contrast, the tree limit, tree line, and intervening forest-tundra ecotone in central and western Canada are out of equilibrium with today's climate. These populations are not sexually regenerative and apparently became established during warmer climates where the tree line was north of its present position. As such, they are susceptible to destruction by further climatic deterioration or anthropogenic disruption. [ABSTRACT FROM AUTHOR]