DENDROCHRONOLOGICAL ANALYSIS OF THE CANOPY HISTORY OF 2 OHIO OLD-GROWTH FORESTS

This study examined the temporal patterns of establishment, suppressio n, and release of major tree species in two old-growth Ohio forest rem nants as a means to determine the past disturbance history of these fo rests. Increment cores were taken from a total of 154 trees from two w ell-drained, upland plots and two poorly-drained, bottomland plots in each of the two forested areas. Acer saccharum and Fagus grandifolia e xhibited multiple episodes of suppression and release prior to becomin g canopy trees, and could tolerate suppressions as long as 84 years. I n contrast, Quercus macrocarpa, Q. muehlenbergii, Prunus serotina, and Acer saccharinum rarely exhibited any tolerance to suppression and ap peared to have entered the canopy after single disturbances had opened large areas of canopy. There was clear synchrony in the temporal patt ern of establishment and final release from suppression among trees fr om bottomland plots scattered throughout the stands, indicating that r elatively large disturbances were important in these poorly- drained a reas. In contrast, there was little synchrony among trees from well-dr ained upland plots, except in a single instance where selective cuttin g of Quercus trees opened the canopy. Thus, the canopy of upland site was likely subjected only to small disturbances resulting from the dea th of one or a few trees. At the whole of forest level, there was evid ence of episodic recruitment of canopy trees in both forests. Establis hment of Fraxinus spp. and Quercus spp. were particularly episodic, an d few Fraxinus or Quercus trees alive today established during the las t century. These data suggest that large disturbances have affected ca nopy dynamics of both upland and bottomland areas prior to 1900 and in bottomland forests through this century. In contrast, disturbances in upland areas during this century have been restricted to small, treef all-generated canopy gaps.