Impacts of early selective logging on the dendroecology of an old-growth, bottomland hemlock-white pine-northern hardwood forest on the Allegheny Plateau

The temporal variation in species recruitment was examined in relation to a nnual dendrochronological data to determine the historical development and disturbance history of an old-growth bottomland hemlock-hardwood forest in the Cook Forest State Park in Northwestern Pennsylvania. This 15 ha forest, located at the headwaters of a stream, contains a mixture of Tsuga canaden sis (hemlock), Fagus grandifolia (beech), Quercus rubra (northern red oak), Pinus strobus (white pine), and Acer rubrum (red maple). The present age s tructure indicates that a cohort of Quercus alba (white oak) established be tween 1680 and 1710, and that the oldest hemlocks became established in the early 1700s. A period of almost 100 years followed in which there was virt ually no recruitment. Tree recruitment resumed about 1800 and consisted pri marily of hemlock and beech until 1855. A period of episodic recruitment as sociated with a concomitant radial growth increase, indicative of a major d isturbance, began in many of the oldest trees in the stand during the 1850s and persisted for 70 years. Approximately two-thirds of all trees aged in this study became established between 1855 and 1930. The presence of decaye d, cut stumps of several different species scattered throughout the stand i s evidence that selective logging occurred, probably during the middle to l ate 1800s. This activity greatly altered the structure and composition of t he forest and created conditions favorable for the establishment of even-ag ed cohorts of relatively shade intolerant Q., rubra and P. strobus, not rec orded in the stand prior to cutting, as well as cohorts of late-successiona l tree species. In response to canopy closure and a large increase in deer populations, few new trees were recruited since 1930. Therefore, this fores t has experienced dramatic changes following Euro-American settlement of th e region that continue to the present, despite the fact that it retains man y old-growth characteristics. This study represented a rare opportunity to investigate the impacts of direct and indirect anthropogenic influences on an old-growth forest. The results are relevant for the restoration ecology of other eastern forests, because they point out that certain silvicultural techniques may differ broadly from natural disturbances and result in uniq ue and uncharacteristically diverse assemblages of species.