Postglacial vegetation history of the Mariana Lake region, Alberta

Abstract

A fossil pollen record extending from 11 300 BP to the present was recovered from Mariana Lake, Alberta (55°57′N, 112°01′W). Initially, the region had a sparse vegetation dominated by forbs and graminoids, which at approximately 10 500 BP succeeded to Picea glauca forest. Picea mariana – Sphagnum peatlands began to develop between 10 000 and 9500 BP. After 9000 BP Sphagnum-dominated sites decreased; P. glauca declined while Betula increased. From 7500 to 5500 BP Populus reached its maximum Holocene representation in the vegetation. Sphagnum-dominated peatlands almost disappeared. The changes following 9000 BP were likely caused by increased aridity. However, the presence of P. mariana, Abies, and Larix in the pollen record suggests that mesic sites remained. Beginning at 6500–6000 BP the extent of Sphagnum peatlands began to increase. Abies declined in importance following 5000 BP, possibly due to paludification of mesic sites. The expansion of parkland into central Alberta during the mid-Holocene did not extend to Mariana Lake. However, Mariana Lake records changes in vegetation resulting from increased aridity in the early to mid-Holocene which are not apparent at more northerly sites in Alberta.