2002 ARCSS All-Hands Workshop

An Integrated Approach to Understanding Climate-Vegetation-Fire Interactions in Boreal Forest Responses to Climatic Change

L.B. Brubaker¹, P.M. Anderson², F.S. Hu³, S Rupp⁴, T. Brown⁵, P.E. Higuera⁶, B. Clegg^7
1University of Washington, USA, Phone 206 543-5778, Fax 206 543-3254, lbru@u.washington.edu
²University of Washington, USA
³University of Illinois Champaign Urbana, USA
⁴University of Alaska Fairbanks, USA
⁵Lawrence Livermore National Laboratory, USA
⁶University of Washington, USA
⁷University of Illinois Champaign Urbana, USA

A major challenge in predicting boreal ecosystem responses to future climatic change is the extent to which shifts in P. glauca forests will be driven solely by climate or by feedbacks among climate, vegetation, and fire. Paleoecological records from central Alaska provide a unique, natural experiment to explore this question. P. glauca expanded rapidly in central Alaska ca. 9-8.5 ka (C14 yrs), declined within 500-1000 yrs across 9000 km², and did not recolonize the area until ca. 2000 yrs later. These dynamics could represent responses to 1) a regional climate oscillation, or 2) interactions of fire and vegetation with a unidirectional climatic change. The goal of this new ARCSS SIMS project is to assess the causes and processes of the early-to-mid Holocene fluctuation in P. glauca in central Alaska, as a means to better understand factors controlling the past, present, and future distribution of boreal forest. Specific research tasks are to describe: 1) vegetation and fire histories through fine-resolution pollen, macrofossil, stomate, and charcoal records (10-100s yrs, 10s km); 2) climate changes through oxygen-isotope and trace-element content of sedimentary carbonates (ostracodes and abiotically precipitated carbonate); 3) ecological processes associated with treeline changes through ALFRESCO simulations of past vegetation dynamics. During the first field season of this project we surveyed water chemistry and morphology of 19 lakes as potential coring sites. Sediment cores were also taken at several sites to define the overall sampling strategy, gain preliminary data on Picea dynamics, and confirm suitability of research techniques.

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