Paleoenvironmental Studies in Southwestern Yukon

Abstract

ABSTRACT. The St. Elias Mountain region has occupied an important place in the study of the Quaternary because it presents a relatively accessible non-polar icefield and an array of environments from tundra to boreal forest. Paleoenvironmental studies in southwestern Yukon have documented the broad-scale climatic changes of the past 20 000 years, although few studies exist with well-dated sequences at high temporal resolution. Picea glauca arrived across the entire region around 10 000 years ago; however, the details regarding its migration pathways are not well known. Available records indicate few major changes in the composition of the boreal forest vegetation since that time. A slightly more intense fire regime in the early to mid Holocene has been suggested, but this conclusion is based on only a few studies. Variations in the tree line during the Holocene have been examined, but these studies also lack details. There is no evidence for more extensive grasslands in the area during the Holocene. Paleolimnological studies indicate that changes in populations of aquatic organisms have occurred in response to either Holocene climates or watershed variability.Key words: Quaternary, Holocene, boreal forest, Yukon, Kluane Lake, paleoecology, pollen analysis, paleolimnology, climatic change, dendroclimatology, fire history RÉSUMÉ. La région du mont St. Elias occupe une place importante dans l'étude du Quaternaire parce qu'elle recèle un champ de glace non polaire relativement accessible ainsi qu'une panoplie d'environnements, allant de la toundra à la forêt boréale. Des études paléoécologiques effectuées dans le sud-ouest du Yukon ont permis de documenter les changements climatiques à grande échelle des 20 000 dernières années, et ce, même s'il existe peu d'études dotées de séquences bien datées de grande résolution temporelle. Picea glauca est arrivée dans toute la région il y a environ 10 000 ans. Cependant, les détails concernant sa voie de migration ne sont pas bien connus. Les données disponibles indiquent peu de changements majeurs dans la composition de la forêt boréale depuis cette période. Un régime des feux un peu plus intense de l'Holocène inférieur à l'Holocène moyen a été suggéré, mais cette conclusion ne repose que sur un petit nombre d'études. Les variations caractérisant la limite des arbres pendant l'Holocène ont été examinées, mais ces études ne sont également pas suffisamment détaillées. Il n'existe pas de preuve qu'il existait des prairies à plus grande échelle dans la région pendant l'Holocène. Des études paléolimnologiques indiquent que des changements caractérisant les populations d'organismes se sont produits en raison de la variabilité des climats ou dans des bassins hydrographiques de l'Holocène.

Optimizing extraction and targeted capture of ancient environmental DNA for reconstructing past environments using the PalaeoChip Arctic-1.0 bait-set

“…but also potentially pine ( Pinus sp. ), that is consistent with pollen records in southern Yukon for the expansion of forests (Gajewski et al, 2014) and the establishment of the northern boreal forest by ~9000 cal yr BP (Dyke, 2005). Assignments to Pinus sp.…”

Holocene climate changes in eastern Beringia (NW North America) – A systematic review of multi-proxy evidence

“…Specifically, the early Holocene expansion of Populus was 666 thought to reflect rising temperatures, with summers possibly warmer than at present (e.g., of P. glauca, P. mariana, and Alnus in Alaska have been interpreted to reflect increasing moisture during the middle and late Holocene (e.g., Anderson and Brubaker, 1993). The 674 synchronous increase in Picea at 10 ka across a large area of southern Yukon is interpreted as a response to a warming climate (Gajewski et al, 2014). 676…”

A middle Holocene steppe bison and paleoenvironments from the Versleuce Meadows, Whitehorse, Yukon, Canada

“…Paleoecological data from southern Yukon demonstrate the changes in vegetation cover following the retreat of the Cordilleran ice sheet after 11 000 years ago (Cwynar and Spear 1995;Gajewski et al 2014). Immediately after deglaciation, the landscape was covered by a herb tundra vegetation with abundant grass (Poaceae), sage (Artemisia), and forbs, transitioning to a more shrub-dominated tundra environment with abundant birch (Betula), some trembling aspen (Populus tremuloides), and juniper (Juniperus spp.)…”

“…Immediately after deglaciation, the landscape was covered by a herb tundra vegetation with abundant grass (Poaceae), sage (Artemisia), and forbs, transitioning to a more shrub-dominated tundra environment with abundant birch (Betula), some trembling aspen (Populus tremuloides), and juniper (Juniperus spp.) in the understory, and which dominated until around 10 000 or 9000 years ago (Gajewski et al 2014). White spruce forests were abruptly established after this time and continued to be abundant for much of the Holocene.…”