Periglacial fires and trees in a continental setting of Central Canada, Upper Pleistocene

• Published in: Geobiology
• Main Authors: Bélanger, N., Carcaillet, C., Padbury, G. A., Harvey‐Schafer, A. N., Van Rees, K. J. C.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2014
• Subjects: Canada; Ice Sheet
• Online Access: http://dx.doi.org/10.1111/gbi.12076; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fgbi.12076; https://onlinelibrary.wiley.com/doi/pdf/10.1111/gbi.12076

Abstract Fire is a key factor controlling global vegetation patterns and carbon cycling. It mostly occurs under warm periods during which fuel builds up with sufficient moisture, whereas such conditions stimulate fire ignition and spread. Biomass burning increased globally with warming periods since the last glacial era. Data confirming periglacial fires during glacial periods are very sparse because such climates are likely too cold to favour fires. Here, tree occurrence and fires during the Upper Pleistocene glacial periods in Central C anada are inferred from botanical identification and calibrated radiocarbon dates of charcoal fragments. Charcoal fragments were archived in sandy dunes of central S askatchewan and were dated >50 000–26 600 cal BP . Fragments were mostly gymnosperms. Parallels between radiocarbon dates and GISP 2‐δ 18 O records deciphered relationships between fire and climate. Fires occurred either hundreds to thousands of years after D ansgaard– O eschger ( DO ) interstadial warming events (i.e., the time needed to build enough fuel for fire ignition and spread) or at the onset of the DO event. The chronological uncertainties result from the dated material not precisely matching the fires and from the low residual 14 C associated with old sample material. Dominance of high‐pressure systems and low effective moisture during post‐ DO coolings likely triggered flammable periglacial ecosystems, while lower moisture and the relative abundance of fuel overshadowed lower temperatures for fire spread. Laurentide ice sheet ( LIS ) limits during DO events are difficult to assess in Central C anada due to sparse radiocarbon dates. Our radiocarbon data set constrains the extent of LIS . Central S askatchewan was not covered by LIS throughout the U pper P leistocene and was not a continental desert. Instead, our results suggest long‐lasting periods where fluctuations of the northern tree limits and fires after interstadials occurred persistently.