Thirty-year effects of liming on soil and foliage chemistry and growth of northern hardwoods In Pennsylvania, USA

Background/Question/Methods

In 1985 a long-term liming study was initiated by the Pennsylvania Bureau of Forestry and the U.S. Forest Service, Northern Research Station, in the Susquehannock State Forest, Potter County, Pennsylvania. Poor woody regeneration and overstory sugar maple (Acer saccharum Marsh.) decline were prevalent in this region. A single application of dolomitic limestone (22.4 Mg ha-1) was used to reduce acidic soil conditions and improve nutrient status at four northern hardwood sites. Liming effects on soil and foliage chemistry, tree growth and mortality have been evaluated over thirty years (1986-2016). Three principal overstory species were evaluated: sugar maple, American beech (Fagus grandifolia Ehrh.) and black cherry (Prunus serotina Ehrh.). Mid-crown foliage was obtained in August by shooting small twigs and branches. In each of the four replications of the study, mineral soils were sampled by depth increments to a total depth of 55 cm. Forest floor organic layers (Oi, Oe, and Oa) and A horizon mineral soils were quantitatively sampled to assess liming effects on thickness, mass and nutrient content (element g m-2).

Results/Conclusions

In limed plots, soils sampled to 45-55 cm depth, and sugar maple and black cherry foliage had significantly (P ≤0.05) greater concentrations of calcium (Ca) and magnesium (Mg) through 2016 compared with samples from unlimed plots. Ca and Mg capitals (g m-2) in the Oi through A horizons combined were greater in limed plots than unlimed plots, largely due to increases in the thickness and nutrient concentration in the A horizon. Over 30 years, sugar maple basal area increment (cm2 yr-1 BAINC) was greater in limed plots (30.6 cm2 yr-1 vs. unlimed 13.3 cm2yr-1). American beech BAINC was unaffected by lime treatment, and black cherry BAINC was reduced in limed plots, 22.8 cm2 yr-1 compared with unlimed plots, 27.5 cm2yr-1. Cumulative mortality of sugar maple in limed plots was 14.9% compared with 42.3% in unlimed plots. Black cherry mortality was 30.7% in limed plots compared with 8.0% in unlimed plots. There is little sign that treatment effects are fading, suggesting a strong nutrient retention function for a forest recovering during a period of declining anthropogenic acid deposition. The sustained effect of this treatment over 30 years and suggests that this could be an important management tool.