Mechanisms inhibiting the forest development of historic charcoal hearths in southeastern Pennsylvania

Charcoal production associated with the iron industry had a pervasive influence on forests during the 17th and 18th centuries in the mid-Atlantic region of the eastern United States. In a recent study we reported the altered forest composition and soil properties on historic charcoal hearths in southeastern Pennsylvania. In this study, additional experimental results describe potential past and present mechanisms that may inhibit forest development. Nyssa sylvatica Marsh, wood samples taken from the first 15 years of growth on hearth sites contained roughly half the amount of P and Mn and nearly double the amount of K and Na relative to wood produced on nonhearth sites in the same period, consistent with initial pH elevation following hearth abandonment in 1883. In the greenhouse, Quercus alba L. and Quercus rubra L. showed a significant growth depression in hearth soil. When the proportion of charcoal soil varied from 0 to 100%, several growth parameters of Q. rubra declined significantly with increasing charcoal soil content. In situ foliar nutrient concentrations of Vaccinium corymbosum L. and Quercus velutina Lam. were significantly different in P, K, Ca, Mg, Mn, Fe, Na, and Cu on hearth versus nonhearth plots. The present inhibition of hearth regeneration appears to be the result of persistent differences in soil nutrient availability after more than a century.