Reconstructing Vegetation Past: Pre-Euro-American Vegetation for the Midwest Driftless Area, USA

摘要

Historical reference conditions provide important context for creating ecological restoration and management plans. The U.S. 19th Century Public Land Survey (PLS) records provide extensive ecological information for constructing such reference conditions. We used PLS records to reconstruct pre-Euro-American tree species cover class and vegetation structure types for the Midwest Driftless Area, a 55,000 km~2 region currently experiencing multiple conservation threats. We related cover classes to soil texture, topographic roughness, and distance from waterway. Our analyses revealed that the landscape of the Driftless Area was mostly composed of savanna, with two large patches of closed forest and smaller, scattered patches of closed forest, open woodland, and prairie. The Driftless Area was heavily dominated by a variety of oak communities, with bur (Quercus macrocarpa), white (Q. alba), and black (Q. velutina) oak by far the most dominant species across the region. A variety of non-oak communities occurred within the closed forest patches, along rivers, or in smaller areas near the periphery of the region. The prevalence of savanna and oak communities indicates that fire played a key role in mediating historical landscape patterns and ecosystem processes in the region. Variation in soil texture, topographic roughness, and distance from waterways additionally contributed to the diversity of cover classes present prior to Euro-American settlement. Restoration practitioners can use our reconstructions to inform regional and site-specific restoration planning. Because oaks tend to be foundational species within ecosystems and are currently in decline throughout the Driftless Area, restoration activities that encourage these species are urgently needed.