Post‐Hypsithermal plant disjunctions in western Alberta, Canada

• Published in: Journal of Biogeography
• Main Authors: Strong, W. L, Hills, L. V.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2003
• Subjects: Canada; Peace River; permafrost
• Online Access: http://dx.doi.org/10.1046/j.1365-2699.2003.00838.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1046%2Fj.1365-2699.2003.00838.x; https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-2699.2003.00838.x

Abstract Aim Evaluate the hypothesis that nine disjunct vascular plant species along the eastern slopes of the Rocky Mountains and in the Peace River District of west‐central Alberta represent remnants of more southerly vegetation that occupied these areas during the Holocene Hypsithermal (9000–6000 yr bp ). Alternatively, these plants represent populations that became established because of independent chance dispersal events. Location This study focuses on the area east of the Rocky Mountain Continental Divide in the Province of Alberta and the State of Montana in western Canada and USA, respectively. Methods Disjunct species were identified and their distributions mapped based on a review of occurrence maps and records, botanical floras and checklists, herbaria specimens, ecological and botanical studies, and field surveys of selected species. A disjunct species was defined as a plant population separated from its next nearest occurrence by a distance of > 300 km. Evaluation of the hypothesis was based on a review of published and unpublished pollen stratigraphy and palaeoecological studies. The potential geographical distribution of Hypsithermal vegetation was based on modern regional‐based ecosystem mapping and associated monthly temperature summaries as well as future climatic warming models. Results The hypothesis was compatible with Holocene pollen stratigraphy, Hypsithermal permafrost and fen occurrence, and palaeosol phytolith analyses; and future global climatic warming models. Modelled regional Hypsithermal vegetation based on a 1 °C increase in July temperatures relative to current conditions, indicated that much of the boreal forest zone in Alberta could have been grassland, which would explain the occurrence of Prairie species in the Peace River District. This amount of latitudinal vegetation shift (6.5°) was similar to an earlier Hypsithermal permafrost zone location study. An equivalent shift in vegetation along the eastern Cordillera would have placed south‐western Montana‐like vegetation ...