Invasive Characteristics of Chinese Privet (Ligustrum sinense Lour.) in a Bay Swamp in the Fall Line Hills of East-Central Alabama

Abstract

Exotic species often become invasive because of an ability to occur in many habitat types with a variety of environmental variables. One species of plant that is particularly invasive throughout the southeastern United States and in many habitat types is Chinese privet (Ligustrum sinense). Chinese privet can be found in dry upland sites and wet bottomland hardwood forests. In this study, characteristics of Chinese privet populations in a bay swamp and an upland site were compared in order to learn the effects of Chinese privet in bay swamp habitats, and to examine characteristics that make it successful at invading these sites. Quadrat and belt transect sampling were employed to discern plant density, diversity, and importance values in a bay swamp in east-central Alabama. An upland site was also sampled for Chinese privet in order to compare invasion success. Phenotypic plasticity was detected by comparing leaf measurements from both upland and bay swamp habitats, by transplanting of plants from the upland site to the bay swamp, and by comparison of biomass allocation. Allelopathy potential was investigated using tomato seed germination bioassays in five concentrations of Chinese privet leaf and root extracts. Invasion of Chinese privet in the bay swamp was found to be in an early stage, but beyond feasible treatment. The presence of Chinese privet appears to have had a larger effect on evenness than on species richness at this stage of invasion. Results of the belt sampling survey indicate that Chinese privet may be in direct competition with coastal doghobble (Leucothoe axillaris). Factors that allow Chinese privet to be a successful invader in many habitat types include high level of phenotypic plasticity in leaves and tremendous propensity for asexual reproduction. Another possible factor is that Chinese privet is potentially allelopathic.