Effects of liming on litter decomposition dynamics in a calcium deficient Southern Appalachian forest

Leaf litter decomposition is a critical component in nutrient cycling, ecosystem carbon budgets, and soil formation. Liming forest soil combats negative effects of acidic deposition: such as low soil pH, cation depletion, and aluminum mobilization. However, decomposition rates and nutrient dynamics following liming are poorly known. A litter bag study with limed and natural treatments was initiated in November 2012 at four sites within the Nantahala National Forest, NC, to examine the effects of liming on litter decay rates and nutrient dynamics in a northern hardwood forest affected by acid deposition. Litter bags consisted of mixed species leaf litter specific to each site and a single species reference litter collected offsite. Percent mass loss, decay rate, percent lignin and percent cellulose, CO2 efflux, carbon, nitrogen, calcium, magnesium, and aluminum were determined for litter bags collected every three months for one year. Liming had no major impact on decay rates of chestnut oak or mixed litter, although limed litter typically had slower decay rates. Percent lignin and cellulose remaining, two recalcitrant components of leaves, fluctuated over time in limed and natural litter. Liming significantly reduced CO2 efflux from chestnut oak and mixed species litter mostly in the first six months of the study. Liming reduced immobilization of nitrogen in chestnut oak and mixed litter throughout decomposition and significantly decreased the carbon concentration. Calcium and magnesium concentration of limed litter was significantly greater than natural litter, while aluminum concentration was not affected by lime. This study suggests that applying lime to areas affected by acid rain may alter nutrient dynamics by impeding microbial decomposition of litter, but causes insignificant change to mass loss and associated decay rates. Future work should focus on carbon and nitrogen dynamics in limed versus natural leaf litter as well as different application rates of lime for a period that extends beyond one year.