Thursday, August 7, 2008

PS 59-82: Tundra fires in the Noatak National Preserve, northwestern Alaska, since 6000 yr BP

Philip E. Higuera, Montana State University and University of Illinois, Melissa Chipman, University of Illinois, Jennifer Allen, National Park Service, T. Scott Rupp, University of Alaska, and Feng Sheng Hu, University of Illinois at Urbana-Champaign.

Background/Question/Methods Fire and fuels management initiatives in Alaska are hindered by a limited understanding of fire history and the controls of fire regimes. This is especially true for tundra ecosystems that cover nearly one-third of the state. Over 4.1 million acres of Alaskan tundra have burned over the past 50 years, indicating the highly flammable nature of these ecosystems under warm and dry conditions. Land managers working within the tundra face decisions on fuels management, suppression tactics and pre-suppression staffing. However, these decisions are currently made in the absence of long-term fire history records and limited empirical knowledge on the relationships between fire, climate and vegetation. Current and future climatic change also challenge land managers as they consider the impacts of increasing temperatures on tundra fire regimes and the potential cascading effects on other ecosystem processes. We are utilizing macroscopic charcoal from lake-sediment cores to characterize the frequency component of fire regimes in shrub-dominated and herb-dominated tundra ecosystems in northwestern Alaska over the past 6000 years. Fire history records will provide context for resource management and serve to refine the tundra component of an ecosystem model designed to aid Alaskan land managers in assessing fuels and fire hazards. Results/Conclusions We present the first long-term records of fire history in the Alaskan tundra from lakes in the Noatak National Preserve, a region encompassing some of the most flammable tundra in Alaska. Preliminary results from one lake indicate that fire has been a consistent process in tundra ecosystems, with fire return intervals (FRIs) ranging from 40 to 500+ years over the past 6000 years. This record also suggests significant changes in historic FRIs at millennial time scales, likely related to climatic changes in the region. For example, from 1500 yr BP to present FRIs averaged 260 years (s.d. 170), while FRIs from 6000-4500 yr BP, a period of lower effective moisture and higher summer temperatures, averaged 120 (s.d. 81) years. In addition to providing some of the first estimates of long-term fire occurrence in modern tundra ecosystems, our results indicate that tundra fire regimes are sensitive past, and by inference, future climate change.

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