Abstracts

SEARCH Open Science Meeting

October 27, 2003
Seattle, Washington, USA

Paleo Investigations of Climate and Ecosystem Archives (PICEA): Holocene Fire and Vegetation History from Ruppert Lake, Brooks Range, Alaska

Philip Higuera1, Linda B. Brubaker2, Patricia M. Anderson3, Feng Sheng Hu4, Ben Clegg5, Tom Brown6, Scott Rupp7
1Division of Ecosystem Sciences, University of Washington, College of Forest Resources, Box 352100, Seattle, WA, 98195, USA, Phone 206-543-5777, phiguera@u.washington.edu
2Division of Ecosystem Sciences, University of Washington, College of Forest Resources, Box 352100, Seattle, WA, 98195, USA, Phone 206-543-5778, lbru@u.washington.edu
3Quaternary Research Center, University of Washington, 19 Johnson Hall, Box 351360, Seattle, WA, 98195, USA, Phone 206-685-7682, Fax 206-543-3836, pata@u.washington.edu
4Plant Biology, University of Illinois, 265 Morrill Hall, 505 S. Goodwin Ave., Urbana, IL, 61801, USA, Phone 217-244-2982, Fax 217-244-7246, fshu@life.uiuc.edu
5Plant Biology, University of Illinois, 265 Morrill Hall, 505 S. Goodwin Ave, Urbana , IL, 61801, USA, Phone 217-244-9871, bclegg@students.uiuc.edu
6Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA, 94550, USA, Phone 925-423-8507, Fax 925-423-7884, tabrown@llnl.gov
7Department of Forest Sciences - Forest Soils Laboratory, University of Alaska, Fairbanks, PO Box 757200, Fairbanks, AK, 99775, USA, Phone 907-474-7535, Fax 907-474-6184, srupp@lter.uaf.edu

A major unresolved issue in predicting arctic ecosystem responses to future climatic change is the extent to which shifts in boreal forest will be driven solely by climate or by feedbacks among climate, vegetation, and fire. The PICEA project utilizes paleoecological records from north-central Alaska and a model of boreal ecosystems to document patterns and identify causes of past ecosystem change.

An initial goal of the project is to understand how fire regimes changed in relation to vegetation and existing interpretations of Holocene climate. A ca. 10,000 year old sediment core from Ruppert Lake provides a continuous record of macroscopic charcoal accumulation with an average temporal resolution of 25 years, and fossil pollen provides a broad-scale record of Holocene vegetation change. Charcoal accumulation rates suggest that fire was a component of the ecosystem when Betula shrub tundra dominated ca. 10,000 calibrated years before present (yr BP). Similar evidence of fire exists as small populations of P. glauca first invaded Betula shrub tundra ca. 9000 yr BP and with the addition of Alnus, ca. 7600 yr BP. Increases in both charcoal accumulation and the frequency of distinct charcoal peaks ca. 5000 yr BP suggest an increase in the size, frequency and/or severity of fires. This change coincides with a regional addition of P. mariana and a shift from P. glauca- to P. mariana-dominated forest communities. Forest composition changed little throughout the late Holocene, but charcoal accumulation at Ruppert Lake decreased again ca. 2500 yr BP. Independent climate proxies for this period suggest a shift to cooler temperatures.

Our results support the concept that fire regimes in boreal forests are broadly controlled by climate. However, links between forest change and changes in fire regimes suggest that vegetation can play an important intermediary role between climate and fire.

Abstract Categories: Biological Feedbacks, Student Poster

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