Print PageThe Central Hardwood Region (CHR) has historically been dominated by oak forests, woodlands, and savannas. Through the clearing of land for agriculture and infrastructure, the amount of forested land in Indiana has been reduced, leaving small patches of remnant oak and oak/hickory old-growth forests often less than 30 ha in size. Fragmentation coupled with the removal of fire from the landscape is resulting in a compositional shift in these forests. Forests previously dominated by oak (Quercus) and hickory (Carya) species are shifting to dominance by maple (Acer saccharum and A. rubrum) and American beech (Fagus grandifolia). In order to gain a better understanding of long-term changes in old-growth forests of the CHR, permanent plots were established in five remnant old-growth forests throughout Indiana in 1992-93 and remeasured in 2011. Thirty plots were sampled in each forest. Data from these five forests will be used to examine overstory mortality, with a focus on the dominant oak cohort, and compare changes in the density and basal area between 1992-93 and 2011.
Results/Conclusions
Across the study sites overstory (stems ≥10 cm dbh) mortality ranged from 26% to 47% between 1992-93 and 2011. Along with high overstory mortality, we observed a decrease in the overstory density of white oak (Quercus alba), northern red oak (Quercus rubra), and sugar maple (Acer saccharum) at all of the sites where these species were present. Despite this decrease in density, all five sites experienced an increase in the overstory basal area of sugar maple and no significant change in the overstory basal area of white oak or northern red oak. Our results suggest that these forests are experiencing high rates of mortality in the dominant cohort. The end result of this mortality has been observed in hardwood forests throughout the CHR; succession towards composition dominated by late-successional shade-tolerant species.
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