The Role of Paleoecology in Elucidating the Spatiotemporal Dynamics of Tundra Fires

Abstract:

Tundra ecosystems are undergoing dramatic environmental change in response to amplified Arctic warming, including potentially novel disturbance regimes. Fires are an increasingly important component of a suite of climate-driven disturbances and feedbacks, yet observations are limited because tundra burning has been historically rare. Paleorecords of charcoal accumulation rates from lake-sediment archives provide evidence of past fires, and can be integrated with other techniques to elucidate the spatiotemporal patterns, drivers, and unique dynamics of tundra fire regimes. We review key lessons gleaned from Alaskan paleofire research over the past decade and consider ways to capitalize on paleorecords to better anticipate the patterns and impacts of future climate-driven disturbances in the Arctic.

Paleorecords from Alaskan tundra have been key for characterizing tundra fire regimes and the role of fire in the Arctic system. Both modern observations and charcoal records spanning the past 6-35,000 yr highlight the importance of summer temperatures for facilitating tundra fires and reveal distinct climate thresholds to burning. Recent fires in cold, low-flammability tundra can now be considered in the context of charcoal records that show fire-return intervals on the order of thousands of years. In flammable tundra, fire-climate relationships have been characterized by both the spatial variability of tundra burning along modern climate gradients, and through composite charcoal records that show temporal variability in burning associated with past climate change. Combining charcoal and pollen records has also helped identify relationships between changing vegetation and fire activity. These baseline estimates of climate-fire-vegetation relationships are critical for understanding spatiotemporal variability in the response of tundra ecosystems to climate change. Paleorecords also reveal how fire activity can facilitate erosion in ice-rich permafrost terrain, highlighting a key feedback between climate-driven disturbances in the Arctic. Ongoing research is combining paleorecords with satellite imagery and chronosequences to investigate disturbance interactions at multiple spatiotemporal scales and refine our understanding of landscape evolution in the rapidly changing Arctic.