Forest vegetation and soils still show evidence of industrial disturbance 120 years after abandonment from charcoal-iron manufacture

Background/Question/Methods

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 19^th century iron furnace sites in southeastern Ohio, USA.  Vegetation was censused in plots in undisturbed forest (controls) and in plots on a variety of microsites within the industrial zone including piles of slag, clinker, iron ore, access roads, terraces, and charcoal manufacturing pads.  In each plot, we measured twenty aspects of the microenvironment including twelve soil variables.  Plots were ordinated in vegetation space using Principal Component Analysis and microsite types were compared statistically on the basis of axis scores.  Influence of environmental gradients was assessed by correlations with axis scores.  Canopy age was assessed by coring prominent trees.  Site history was determined from historical records.

Results/Conclusions

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 history appears to be perpetuated by long-term persistence of species distributions and by hitherto unsuspected sensitivity to physical and chemical gradients.  Forest composition and spatial structure retain a distinctive industrial character even 120 years after abandonment.