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Wednesday, April 11 • 10:45am - 11:00am
FOREST LANDSCAPE PROCESSES: Have the Realized Niches of Oaks and Maples Shifted over the Last Two Centuries?

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AUTHORS: James Dyer*, Ohio University; Todd Hutchinson, U.S. Forest Service Northern Research Station

ABSTRACT: Euro-Americans settled Appalachian Ohio c. 1800. Like most of the eastern deciduous forest, the region has undergone dramatic changes in forest composition and structure following widespread clearing and subsequent reforestation; mesic species such as maples have increased at the expense of oak and hickory species. Changes in land use, climate, and fire regimes have been presented as drivers of these observed changes. This study focused on intra-landscape changes in forest composition across a 5000 km2 area. The topo-edaphic setting of 5765 witness trees was used to define fine-scale forest associations, which were then compared to contemporary associations based on data from 547 FIA subplots. Ridges continue to support a distinct forest assemblage, which is more distinctive from slopes and valleys than was the case in the presettlement forest. 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. This pattern is borne out in a water balance analysis of a recent tree survey. Land use and climate data are available at different spatial scales and suggest a causative role in the observed changes; size-class analysis of witness trees suggest the possibility of an 18th century mesophication event. Fire-scar studies dating to the presettlement era are not common in the region, but do indicate the occurrence of fire. Tree-ring data are limited by small sample size but provide annual resolution of fire events. In contrast, line descriptions from the original land survey cover an extensive area, but represent a snapshot in time. Fire was noted in the original land survey, but resurveyed lines reveal that direct evidence of fire is no longer observed within 10 years. Multiple drivers are likely responsible for the oak-to-maple transition.

Wednesday April 11, 2018 10:45am - 11:00am CDT
Spire Parlor