A History Of Fire At Hitchcock Nature Center, Western Iowa, Reconstructed Through An Analysis Of Macroscopic Charcoal And Soil-Magnetic Properties

Abstract

We analyzed soil-magnetic properties and macroscopic charcoal abundances for two soil profiles located in Hitchcock Nature Center (HNC), Honey Creek, Iowa. Both profiles are located on valley bottoms in the Loess Hills of western Iowa and developed in redeposited Peoria loess. Site HNC 15D is located on an elevated stream terrace and contains a moderately well-developed modern soil. Site HNC 15G is located on a valley floor and consists of a poorly developed modern soil and a series of buried soil horizons. Both sites record consistently low charcoal concentrations of 0.5 mm2/g in prehistoric deposits. While site HNC 15D remains undated, age control at site HNC 15G is provided through four radiocarbon dates from charcoal and snail shell fragments. At site HNC 15G, late 19th century deposits are characterized by a marked increase in charcoal abundance to 3 mm2/g and charcoal abundances return to near prehistoric levels in recent sediment. We observe a similar increase in charcoal abundances below the modern soil at HNC 15D and an accumulation of charcoal at the surface of the profile. Soil-magnetic properties show moderate increases in magnetic susceptibility and ARM/IRM ratios when compared to loessic parent material and confirm moderate to weak soil development. High values for χARM/χFD (40-100) and χARM/χ (2-5) further suggest that regional fires have not been intense enough to significantly heat the topsoil horizons and allow for the formation of strongly magnetic secondary iron-oxide minerals.