Articles | Volume 12, issue 13
Biogeosciences, 12, 4017–4027, 2015
Biogeosciences, 12, 4017–4027, 2015

Research article 03 Jul 2015

Research article | 03 Jul 2015

Spatiotemporal patterns of tundra fires: late-Quaternary charcoal records from Alaska

M. L. Chipman1, V. Hudspith2,a, P. E. Higuera3, P. A. Duffy4, R. Kelly2,b, W. W. Oswald5, and F. S. Hu1,2,6 M. L. Chipman et al.
  • 1Program in Ecology, Evolution, and Conservation Biology, University of Illinois, 505 S. Goodwin Ave., Urbana, Illinois 61802, USA
  • 2Department of Plant Biology, University of Illinois, 505 S. Goodwin Ave., Urbana, Illinois 61802, USA
  • 3College of Natural Resources, University of Idaho, P.O. Box 441133, Moscow, Idaho 83844, USA
  • 4Neptune and Company, Inc., 1435 Garrison Street, Suite 110, Lakewood, Colorado 80215, USA
  • 5Institute for Liberal Arts and Interdisciplinary Studies, Emerson College, 120 Boylston St., Boston, Massachusetts 02116, USA
  • 6Department of Geology, University of Illinois, 605 E. Springfield Ave., Champaign, Illinois 61820, USA
  • anow at: Department of Geography, University of Exeter, Laver Building 440, Exeter, EX4 4QE, UK
  • bnow at: Nicholas School of the Environment, Duke University, Box 90338, Durham, North Carolina 27708, USA

Abstract. Anthropogenic climate change has altered many ecosystem processes in the Arctic tundra and may have resulted in unprecedented fire activity. Evaluating the significance of recent fires requires knowledge from the paleofire record because observational data in the Arctic span only several decades, much shorter than the natural fire rotation in Arctic tundra regions. Here we report results of charcoal analysis on lake sediments from four Alaskan lakes to infer the broad spatial and temporal patterns of tundra-fire occurrence over the past 35 000 years. Background charcoal accumulation rates are low in all records (range is 0–0.05 pieces cm−2 yr−1), suggesting minimal biomass burning across our study areas. Charcoal peak analysis reveals that the mean fire-return interval (FRI; years between consecutive fire events) ranged from ca. 1650 to 6050 years at our sites, and that the most recent fire events occurred from ca. 880 to 7030 years ago, except for the CE 2007 Anaktuvuk River Fire. These mean FRI estimates are longer than the fire rotation periods estimated for the past 63 years in the areas surrounding three of the four study lakes. This result suggests that the frequency of tundra burning was higher over the recent past compared to the late Quaternary in some tundra regions. However, the ranges of FRI estimates from our paleofire records overlap with the expected values based on fire-rotation-period estimates from the observational fire data, and the differences are statistically insignificant. Together with previous tundra-fire reconstructions, these data suggest that the rate of tundra burning was spatially variable and that fires were extremely rare in our study areas throughout the late Quaternary. Given the rarity of tundra burning over multiple millennia in our study areas and the pronounced effects of fire on tundra ecosystem processes such as carbon cycling, dramatic tundra ecosystem changes are expected if anthropogenic climate change leads to more frequent tundra fires.

Short summary
Tundra fires may have increased as a result of anthropogenic climate change. To evaluate this hypothesis in the context of natural variability, we reconstructed fire history of the late Quaternary in the Alaskan tundra. Fire-return intervals are spatially variable, ranging from 1648 to 6045 years at our sites. The rarity of historical fires implies that increased fire frequency may greatly alter the structure and function of tundra ecosystems.
Final-revised paper