Identifying the tundra – forest border in the stomate record: an analysis of lake surface samples from the Yellowknife area, Northwest Territories, Canada

Abstract

Conifer stomata were identified in surface samples from lakes in the treeline zone near Yellowknife, Northwest Territories, to assess the potential use of fossil stomata for reconstructing past changes in the arctic tree line. Stomata of Larix, Pinus, Picea mariana, and Picea glauca were distinguished. Conifer stomata were absent in samples from tundra lakes, whereas they were generally present in forest–tundra and forest lakes. Stomate analysis recorded the presence of Larix trees in the area; in contrast, the pollen of this relatively common tree was infrequent in pollen surface samples from the same sites. Conifer stomate analysis, however, is not able to resolve differences between forest–tundra and closed forest. The potential of stomata for providing improved resolution of past locations of the tree line, coupled with the presence of stomata in lakes that would lack good macrofossil records, suggest that stomate analysis will become an important technique supplementing pollen analysis for reconstructing past tree-line changes. Keywords: Northwest Territories, conifer stomata and pollen, tree line, tundra, forest–tundra, closed forest.