Long-term effects in vegetation and soils at two 19th century iron furnace sites in southeastern Ohio, USA

Deciduous forests are regenerating following industrial disturbance in large areas of eastern North America and western Europe. To understand the long-term process of forest regeneration, the microenvironment and flora of post-industrial plots were compared with non-industrial controls at two 19th century iron furnace sites in southeastern Ohio, USA. Post-industrial plots had a shrub and canopy structure similar to controls, and showed comparable litter cover, soil organic content, and bulk density. Post-industrial and control plots remained clearly distinguishable in soil moisture, pH, and cation concentrations, however, consistent with leaching from industrial waste. Post-industrial areas were dominated by shade-tolerant plant species typical of long-established second-growth forest in the region, suggesting functional suitability of the industrial soils and an abundance of potential colonists. Open-habitat species persisted in post-industrial plots, showing a significantly higher richness and abundance than control plots. Annual growth increments showed later establishment of canopy tree species in the post-industrial plots, suggesting that the presence of open-habitat species reflected delayed canopy closure in the post-industrial area. Slag, clinker, iron–ore, and terrace microsites consistently differed in species composition within the post-industrial areas despite their relatively small size and close proximity. Thus, industrial effects appear to be perpetuated by long-term persistence of species distributions and hitherto unsuspected sensitivity to physical and chemical gradients. Forest composition and spatial structure retain a distinctive industrial character even 120 years after abandonment.

► The capacity of forest communities to regenerate on post-industrial sites is unknown.
► Nineteenth century furnace sites have relatively benign soils and many forest herb species.
► Furnace sites have more open-habitat species than non-industrial forest controls.
► Industrial microsites are still vegetationally distinct after 120 years.
► Post-agricultural models of forest succession, stressing homogeneity, do not apply.