Impacts of an invasive shrub, Buddleja davidii (butterfly bush), on plant succession on New Zealand floodplains.

摘要

Plant successional trajectories are driven in part by the interactions among the biotic and abiotic components of a plant community such that introduction of an invasive species may impact the recruitment of native species. Buddleja davidii Franchet (Family Buddlejaceae) is an ornamental shrub, native to China, able to rapidly colonize and dominate disturbed areas around the world. This study details the impact B. davidii has on several New Zealand floodplain communities and the recruitment, growth and survival of a native species, Griselinia littoralis, in natural settings and under controlled conditions in plots and treatments representative of a multi-stage (i.e., open, young, vigorous and mature) developmental chronosequence (i.e., time since disturbance by flooding). Although B. davidii was abundant on the floodplains studied from the open to vigorous stages, it was rarely present as a mature plant. Soil phosphorus and nitrogen concentrations increased along a developmental gradient which suggested that B. davidii augmented soil nutrients over time. Growth of G. littoralis transplants under a B. davidii canopy remained unchanged from the time they were initially planted in the open and young stages yet nearly doubled in height in the vigorous stage suggests that B. davidii may enhance the growth of G. littoralis transplants. The growth of the G. littoralis transplants under the B. davidii canopy may have been facilitated by increased soil moisture and nutrients. G. littoralis seedlings established naturally beneath the B. davidii canopy, yet did not establish in the open or young stages. It appeared that B. davidii did not inhibit G. littoralis establishment. B. davidii was not able to survive under the relative darkness of a simulated vigorous developmental stage. Growth of G. littoralis cuttings was suppressed by B. davidii in the open and young developmental stages yet G. littoralis mortality was not negatively impacted by B. davidii. Although B. davidii initially dominated the floodplain plant community, its influence may be temporary because it cannot tolerate the closed canopy community of the later stages of succession on New Zealand floodplains. Native species, able to tolerate a broader range of conditions dominated the later stages of succession.