Long-term impact of liming on growth and vigor of northern hardwoods

Sugar maple (Acer saccharum Marsh.) is a keystone species in the northern hardwood forest, and decline epi- sodes have negatively affected the growth and health of sugar maple in portions of its range over the past 50+ years. Crown health, growth, survival, and flower and seed production of sugar maple were negatively affected by a widespread decline event in the mid-1980s on the unglaciated Allegheny Plateau in northern Pennsylvania. A long-term liming study was initi- ated in 1985 to evaluate responses to a one-time application of 22.4 Mg·ha -1 of dolomitic limestone in four northern hard- wood stands. Over the 23-year period ending in 2008, sugar maple basal area increment (BAINC) increased significantly (P ≤ 0.05) in limed plots from 1995 through 2008, whereas American beech (Fagus grandifolia Ehrh.) BAINC was unaf- fected. For black cherry (Prunus serotina Ehrh.), the third principal overstory species, BAINC and survival were reduced in limed plots compared with unlimed plots. Foliar Ca and Mg remained significantly higher in sugar maple foliage sampled 21 years after lime application, showing persistence of the lime effect. These results show long-term species-specific re- sponses to lime application.