Comparison of Callery pear (Pyrus calleryana, Rosaceae) leaf decomposition rates with those of the invasive shrub Amur honeysuckle (Lonicera maackii, Caprifoliaceae) and two native trees, red maple (Acer rubrum, Sapindaceae) and American sycamore (Platanus occidentalis, Platanaceae)1

Abstract

Invasive plants can alter nutrient cycling rates, because the leaves of many invasive species decay more quickly than those of native plants. Pyrus calleryana (Callery pear) is a relatively new woody invader in the eastern USA that rapidly colonizes open and disturbed areas. Invasive woody plants can alter forest nutrient cycling, yet the leaf decomposition rates of P. calleryana have not been previously determined. In this study, Pyrus calleryana leaf decomposition rates were compared against two widely distributed native trees, Acer rubrum (red maple) and Platanus occidentalis (American sycamore), with different levels of nitrogen (N), carbon (C):N, lignin, and lignin:N. It was also compared to that of the invasive shrub Amur honeysuckle (Lonicera maackii), which is known to have very fast decomposition rates. Litter bags were placed in four locations in a Callery pear-dominated stand in northern Kentucky in November 2014 and sampled at 3, 90, 12, and 18 mo. Dry weight and %N measurements were fit to a single exponential decay equation. Mass and N loss of P. calleryana leaf litter were both similar to those of A. rubrum, and they were lower than those of L. maackii; however, lignin and lignin:N levels were most similar to L. maackii. Platanus occidentalis decayed very slowly and immobilized rather than mineralized N. Pyrus calleryana is thus not predicted to greatly alter leaf litter decomposition in invaded forests, although litter decomposition dynamics might be different in mixtures with native species and in other locations.