Leaf Litter Decomposition of Native vs. Invasive Plant Species along an Urbant to Rural Highway Gradient

Relatively unmanaged forests growing along interstate highways provide ecosystem services such as nutrient cycling, and removal and filtration of roadside pollutants. They also provide wildlife habitat and corridors that facilitate plant and animal movement. Since chemical quality of dead leaves controls their decay rates, invasion of highways by Lonicera maackii (Amur Honeysuckle) may alter nutrient cycling and leaf litter layer thickness in these forests with implications for future forest regeneration, use by wildlife, air quality and human health. This study compares the leaf litter decomposition of the native tree, Acer saccharum (Sugar Maple) and invasive shrub, L. maackii, along Interstates 71 and 64 in Louisville, Kentucky. The experiment occurred from January 25th to July 9th, 2007. Fourteen 10 x 10 m plots were established at varying distances (up to 22 km) from the city center along both highways. The Honeysuckle litter decay rate (-0.695% per day) was ten times faster than that of the reference litter, Sugar Maple (-0.0743% per day). This study detected an urban-to-rural gradient effect on litter decomposition rates along highways for Sugar Maple, but not Honeysuckle. Honeysuckle litter contained about twice the initial N content of Sugar Maple (x% vs. y%, respectively). Leaf litter nitrogen concentration increases during the first stages of decomposition (90 days) for both litter species, but Honeysuckle litter gained nitrogen 2.4 times faster than the Sugar Maple. Knowledge of decomposition dynamics along forested interstates and effects of invasive Honeysuckle on this process can inform management plans for these habitats