A palynological study of postglacial vegetation changes in the University Research Forest, southwestern British Columbia

摘要

The postglacial vegetation history of the University of British Columbia Research Forest was investigated using percentage and absolute pollen analysis, macrofossil analysis, and radiocarbon dating. A marine silty clay deposit records the oldest (12ensp;690ensp;plusmn;ensp;190 years before present (B.P.)) assemblage of terrestrial plant remains so far recovered from the postglacial of south-coastal British Columbia. Lodge-pole pine (Pinus contorta) dominated this early vegetation, although someAbies, Picea, Alnus, and herbs were also present. Sediment cores from two lakes were also studied. The older is Marion Lake, where five pollen assemblage zones are recognized, beginning with a previously undescribed assemblage ofPinus contorta, Salix, andShepherdiain clay older than 12ensp;350ensp;plusmn;ensp;190ensp;B.P. The pollen diagram from Surprise Lake (11ensp;230ensp;plusmn;ensp;230ensp;B.P.) is divided into three pollen zones which show the same major trends of vegetation change as the Marion Lake diagram.The first report of the postglacial vegetation history of cedar (Thujaand perhapsChamaecyparis) in southwestern British Columbia is presented from pollen and macrofossil analyses.At about 10ensp;500ensp;B.P. in both lakes, pollen of Douglas fir (Pseudotsuga menziesii) began a rapid increase, probably in response to climatic amelioration. The palynological evidence, supported by well-preserved bryophyte subfossils, suggests that humid coastal conditions have prevailed in the study area since about 10ensp;500ensp;B.P., with virtually no evidence for a classical Hypsithermal interval between 8500ensp;B.P. and 3000ensp;B.P.