Forest liming has been used to reduce acidic soil conditions resulting from acidic deposition and provide base cations necessary for species like sugar maple, but it is uncertain how long liming effects will persist in the soil and how deep in the soil profile the lime-induced changes occur. Forest Service scientists at the agency’s Northern Research Station recently reported the 21-year results from a single dolomitic limestone application of 22.4 Mg/ha (10 tons/acre) at four forested sites in Potter County, Penn., where soil, soil leachate, and sugar-maple foliar chemistry have been measured. The research team found that increases in exchangeable calcium and magnesium ions, and pH continued for 21 years (through 2006). Sugar maple foliage chemistry had elevated Calcium and Magnesium levels in 2006, indicating the persistence of the lime treatment. Comparisons of Calcium-aluminum ratios show inconsistent results when compared with published risk thresholds, suggesting species-specific thresholds should be developed. Forest liming can be used as a tool to remediate acidic soil conditions and provide long-term increases in base cations that maintain the health and growth of sugar maple.