Postglacial vegetation community change over an elevational gradient on the western Kenai Peninsula, Alaska: pollen records from Sunken Island and Choquette Lakes

• Published in: Journal of quaternary science 2019-05, Vol.34 (4-5), p.309-322
• Main Authors: Scott Anderson, R., Berg, Edward, Williams, Chris, Clark, Tami
• Format: Article
• Language: English
• Subjects: Alaska biogeography; Deglaciation; fire history; Forests; Glacial periods; Holocene; Kenai Peninsula; Lake levels; Lake sediments; Lakes; Lowlands; paleoecology; Pollen; pollen analysis; Poplar; Prominences; Tundra
• ISSN: 0267-8179; 1099-1417
• DOI: 10.1002/jqs.3102

The Kenai Peninsula of south‐central Alaska is a region of high topographic diversity with a complex glacial history. The sedimentary record of two small lakes [Sunken Island (SIL; 76 m a.s.l.) in the Kenai Lowlands; Choquette (CL; 527 m a.s.l.) in the Caribou Hills upland] exemplifies the postglacial development of the conifer–hardwood forest over an elevational range there. A herb–shrub tundra was established at both sites after deglaciation. By ~10.7 ka, poplar (Populus sp.) and alder (Alnus) dominated the lowland forest, while alder with minor poplar occurred at the upland site. Lake levels lower than today occurred during the early Holocene until ~8 ka. Subsequently at SIL, the near‐modern Kenai birch (Betula kenaica) – white spruce (Picea glauca) forest maintained prominence throughout the Holocene. However, at CL, alder dominated with dwarf birch and other subshrubs; small amounts of white spruce arrived ~5.2 ka. Black spruce (Picea mariana) grew around SIL by ~4 ka, but never gained prominence at CL. Fire, a prominent agent of disturbance in the Kenai Lowlands since ~8 ka, was essentially absent at the hardwood‐dominated upland site before ~6 ka, and rare thereafter. This suggests an important link between fire and spruce in Kenai forests.