Document Type



Paha are loess-capped ridges standing 10-30 m above the surrounding plain of the Iowan Surface. Although Iowa was almost entirely covered with prairie and wetlands just prior to Euro-American settlement, the paha are believed to have been forested based on soil types and on early vegetation maps. The objective of this study was to find evidence that paha were forested by measuring the δ13C value of humin, the fraction of soil organic matter that is insoluble in acid and base. Previous work has shown that humin retains the δ13C signature of vegetation on a 1000-year time scale, as opposed to the more mobile and soluble humic and fulvic acids that reflect the δ13C signature of more recent vegetation. Soil samples were obtained from Casey's Paha State Preserve in Tama County from four locations at depths ranging from 5-85 cm. Carbonates were removed with 1.0 M HCl and humic and fulvic acids were removed by repeated application of 0.5 M NaOH. The δ13C values of the humin fraction (-22.031% to -24.358%) were within or slightly above the upper range of δ13C values for woody vegetation (-23% to -34%) and well below the range for prairie grasses (-9% to -17%). Although it has been suggested that prairie fires bypassed the paha or that perched water tables maintained the forest, we suggest that the paha forests resulted from activity by Native Americans.

Publication Date

January-December 2008

Journal Title

Journal of the Iowa Academy of Science





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© Copyright 2009 by the Iowa Academy of Science, Inc.



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