Novel Morphological Approach to Building Vegetation-Specific Paleofire Profiles of the Arctic Tundra

The effects of climate change are becoming more evident, particularly at high latitudes where the frequency and spatial extent of tundra fires are increasing. To prepare for coming changes in the Arctic tundra, paleoecological records can indicate the impacts of past climate, environmental, and ecological developments in the region. Charcoal found in lake sediment cores can indicate the occurrence and frequency of past wildfires in the tundra, but total charcoal accumulation rates only offer general records of fire history. Morphological classification methods have differentiated fuel types in forested environments, but these methods have not been applied in the tundra biome. For the present study, a classification scheme for Arctic tundra charcoal was developed by gathering morphology data (length/width ratios) of charcoal pieces from seven different plant species (five shrubs and two graminoids) produced in a muffle furnace. Our study aimed to make a morphological distinction between shrub species and graminoid species. Qualitatively, we found that grass charcoal tended to be more rectangular in shape, while shrub charcoal took on varied polygonal shapes with more curved edges. Grass charcoal is consistently more elongated (length:width = 6.771) while shrub and forb charcoal tends to have more similar length and width dimensions (length:width = 2.419). This distinction will allow us to differentiate between grass and shrub charcoal in sediment cores and future tundra fire reconstructions. In addition to the paleoecological analyses, we are undertaking organic geochemical approaches (PAHs, BPCAs) to further distinguish tundra fuels at a chemical level. The present study is important for providing the steps needed to construct a regional wildfire history and to understand how wildfire will impact the region in the present and future.