Modern pollen and conifer stomates from north-central Siberian lake sediments: Their use in interpreting late quaternary fossil pollen assemblages

To determine the modern relationship between pollen and stomate deposition and vegetation, surface sediments from 26 lakes along the Lena River in nor theastern Siberia were analyzed for pollen and conifer stomate content. The lakes sampled, crossed a vegetation gradient from tundra, forest-tundra, t o closed boreal forest. The pollen spectra of tundra lakes are dominated by Betula and Alnus. Cyperaceae and Poaceae are also abundant. Forest-tundra lakes are dominated by Betula and Alnus, but contain lower percentages of A rtemisia than tundra lakes. Forest pollen spectra are also dominated by Bet ula and Alnus pollen, however, forest lakes contain greater percentages of Larix pollen. Principal components analysis indicates that forest and tundr a sites were distinct from one another, but considerable overlap exists bet ween forest-tundra and forest and tundra pollen assemblages. Larix stomates were abundant in all samples from regions where trees are currently presen t except for one lake. Small numbers of Larix stomates were found in tundra lakes, likely due to the redeposition of older material from eroding peat banks. It is likely that this process also contributed some older pollen to modern lake sediments as well. Principal components analysis was used to c ompare fossil samples from a lake-sediment core to the modern spectra. Earl y Holocene vegetation assemblages, dominated by herb and Betula shrub tundr a and subsequent Larix forests, do not have modern pollen analogs in the lo wer Lena River region. Modem pollen analogs developed after 6 ka BP, when f orest vegetation developed around the site. This was gradually replaced by modern tundra after 3.5 ka BP.