Nitrogen, sulfur and phosphorus dynamics in decomposing deciduous leaf litter in the southern appalachians

Abstract

The decomposition rates and N. S and P dynamics of flowenne dogwood ( Cornus florida). red maple ( Acer rubrum) and chestnut oak ( Quercus prinus) litter were examined during 2 years in a mixed deciduous forest in the southern Appalachians. Litter of the three species decomposed in the following order (fastest to slowest): flowering dogwood > red maple > chestnut oak. Initial mass losses (first 6 months) were most highly positively correlated with concentrations of ethanol-soluble and total soluble components. First-year annual decay rates were most highly negatively correlated with initial % lignin and lignin-to-N ratios. Second-year decay rates were significantly slower than first-year rates for flowering doewood and red maple litter, but not for chestnut oak. This was apparently due to the greater proportion of labile materials initially present in flowering dogwood and red maple litter Relative concentrations of N, S and P increased during the decomposition of each litter type. following any initial leaching losses. In all cases, the increases in N. S and P concentrations exhibited negative linear relationships to % mass remaining. For all three elements the slopes of these relationships were correlated with decay rates, indicating a greater increase in N. S and P concentrations per unit mass lost in faster decomposing litter types. Changes in the absolute amount of N (net immobilization or net release) followed a typical three component curve (leaching, immobilization and release phases). Nitrogen release began when C-to-N ratios decreased to between 25 and 34, Patterns of P and S fluxes varied more among litter types. Only flowering dogwood litter, with a final C-to-P ratio of 305 appeared to release P by the end of the study. Flowering dogwood litter also had a low initial C-to-S ratio (236) and displayed an immediate net release of S which continued throughout the study. The other litter types, which had higher initial C-to-S ratios, immobilized S throughout the study.