Liming legacy effects associated with the world's largest soil liming and regreening program in Sudbury, Ontario,...

Limestone is a common amendment used to counteract soil acidity and metal pollution. Understanding the legacy effects of a one-time soil limestone application and subsequent afforestation is needed to evaluate the long-term success of remediation efforts. In this study, soil and tree chemistry were measured across 15 limed sites that were treated and planted 14 to 37 years ago in Sudbury, Ontario, along with two untreated sites. Soil pH and exchangeable base cation (calcium (Ca) and magnesium (Mg)) concentrations were generally elevated especially in surface organic [FH] horizons up to 37-years post limestone treatment. High site-to-site variation however, obscured clear patterns over time and base cation mass budgets were generally unable to account for the mass of added Ca and Mg. Metal partitioning (K_d) in soil was most influenced by soil pH rather than organic matter (OM) showing that metal availability increases as liming effects fade. This study shows that the legacy effects of soil liming can persist for several decades and are most apparent in the forest floor (FH), but legacy effects are quite modest, and it is likely that a considerable amount of limestone has been lost through erosion.