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Fine-scale Composition Changes in the Mesophytic Forest, 1790-2100

Authors: James Dyer*, Ohio University
Topics: Biogeography, Physical Geography, Climatology and Meteorology
Keywords: witness trees, water balance, species distribution modeling, mesophication, microrefugia
Session Type: Paper
Presentation File: No File Uploaded

Topography exerts strong control on microclimate, resulting in distinctive vegetation patterns in areas of moderate to high relief. As climate changes, so too can abundance patterns within the forested landscape. This study examines fine-scale forest changes at two sites within the Mesophytic forest region: Appalachian Ohio (1790-2010), and central Indiana (1860-2100). In Ohio, fine-scale forest associations were defined by the topo-edaphic setting of 5765 witness trees, then compared to contemporary associations based on data from 547 FIA subplots. Shifts in the realized niches of dominant taxa are evident, with mesic species increasing in dominance across the landscape, while xeric species have become more restricted to higher-stress sites. At a ForestGEO site in Indiana, 3137 individual tree locations were linked to summer deficit using a GIS-based Water Balance Toolset. Using monthly climatic data for a significant drought year, modeled moisture patterns capture vegetation distributions described for the region, with beech and maple preferentially occurring in low-deficit settings, and oak and hickory dominating more xeric positions; mesic species in smaller size classes are expanding across all landscape settings. Topographic shifts observed in forest vegetation at both study sites is consistent with changing climate conditions over the past two centuries. Finally, future climate projections were modeled using downscaled GCM data. An end-of-century water balance scenario suggests severe deficit conditions, which should favor oak and hickory over more mesic species. Pockets of smaller deficit do persist on the landscape; identification of mesic habitat microrefugia has important implications for retreating species under altered climate.

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