Session Information
| Session | Poster Session | | Date | Monday (2008-04-07) | | Time | 5:00 PM - 7:00 PM | | Room | Grand Terrace |
Presentation Information
| Presenter | Elizabeth Lynch | | Title | Historic vegetation composition and structure at the prairie-forest border in northeastern Iowa | | Affiliation | Luther College | | Authors | Elizabeth Lynch, Stephanie Tomscha, Lisa Schulte | | Keywords | Disturbance, Driftless Area, Historic vegetation, Iowa, PLS | | Presentation Type | Poster | Abstract:
The pre-Euro-American settlement (A.D. 1848-1853) vegetation of two counties in northeastern Iowa was analyzed using the original Public Land Survey (PLS) witness tree records. Although the records were originally compiled for administrative rather than scientific purposes, the surveys comprise a rich resource for reconstructing historical vegetation. Our objectives were to (1) inform land management and restoration efforts and (2) document the spatial configuration of the historical prairie-forest border in the region. All ecological information within the PLS records for the two counties was transcribed into a GIS database. The distributions of vegetation types (prairie, savanna, open woodland, and forest) and tree taxa were mapped and visually compared with topographic and soils data.
Of the 4,144 quarter corner and section corner points, 29% were classified as prairie, 49% as savanna, 10% as open woodland, and 12% as forest. Extensive prairie areas occurred only in southwestern Winnesheik County on the Iowan Erosion Surface. Here trees were restricted to riparian areas and areas immediately to the lee of rivers. On the more dissected terrain of the Paleozoic Plateau, small prairies occurred on flat uplands and along wide river bottoms. Upland prairies throughout the study area were common on mollic hapludalfs, forest soils with a significant influence of grasses. Most forests were in small isolated patches, with the exception of a 300 km2 area in the lower Yellow River valley. Of 6,167 trees, 86% were identified as oaks; primarily white and bur (Quercus alba and Q. macrocarpa), but also black and red oaks (Q. velutina and Q. rubra). Bur oak was most common in the western part of the study area, while white oak was more abundant in the east. Red/black oaks occurred primarily in areas of steep topography along the major rivers. Hickory (Carya) was the second most abundant (3%) tree, and was common only on uplands in the eastern part of the study area. Fire-sensitive mesic taxa were rare except in the Yellow River valley.
The composition and structure of the vegetation suggest that fires were frequent in much of the region. However, the relationship between prairie and soil types suggests that forest cover had been more extensive prior to the PLS survey. The expansion of prairie during several centuries of cool/moist ‘Little Ice Age’ climatic conditions suggests either an increase in the extent or frequency of anthropogenic fires prior to Euro-American settlement and/or fine-scale heterogeneity in ‘Little Ice Age’ climate. |
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