Forest history of the last 12ensp;000 years based on plant macrofossil analysis of sediment from Marion Lake, southwestern British Columbia

摘要

The forest history around Marion Lake in southwestern British Columbia is reconstructed using plant macrofossil analysis. A comparison with a previous reconstruction based on pollen and spore analysis reveals a good correspondence between pollen and macrofossil zones. Significant improvements in the reconstruction of forest history are possible by combining the study of pollen and macrofossils.Thuja plicatamacrofossils do not appear at Marion Lake until 6000ensp;BP, contradicting previous suggestions of red cedar presence as early as 10ensp;000ensp;BP. Although not common at present,Taxus brevifoliamay have been an important component of the forest prior to the arrival ofThuja. Fluvial input of macrofossils is important at Marion Lake. Charcoal also appears to enter the lake primarily during periods of high runoff and erosion in the watershed, suggesting the need for caution in the interpretation of charcoal data from stream-fed lakes. Increases in total influx coincide with evidence for increased precipitation after 7000ensp;BP. Marked reductions in macrofossil influx coincide with periods of peat deposition upstream from the present lake. Relative percentages of conifer needles are unaffected by changes in influx.