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IMPACTS ON FLOODPLAINS BY AN INVASIVE SHRUB, BUDDLEJA DAVIDII
Citation:
TALLENT-HALSELL, N. G. AND L. Walker. IMPACTS ON FLOODPLAINS BY AN INVASIVE SHRUB, BUDDLEJA DAVIDII. Presented at American Water Resources Association 2008 Summer Specialty Conference, Virginia Beach, VA, June 30 - July 02, 2008.
Impact/Purpose:
Presentation
Description:
Despite its popularity, the ornamental, Buddleja davidii, a woody shrub of Asian origin, is considered problematic because of its ability to rapidly colonize and dominate floodplain and riparian ecosystems. Dominance during early succession may influence community dynamics and ecosystem processes. This study documented plant succession on floodplains dominated by Buddleja in seven New Zealand catchments. I aimed to determine the differences among successional stages in biotic and abiotic factors on a four-stage developmental chronosequence: open, young, vigorous and mature. Furthermore, I verified whether patterns of succession were consistent among our environmentally diverse catchments. Buddleja biomass increased significantly from open to vigorous stages before decreasing in the mature stage. Stem density progressively declined from the open to the mature stages suggesting that self-thinning had occurred. Species richness and the percentage of non-indigenous species did not differ among stages. The percentage of grasses and forbs decreased from the open to the mature stage while the percentage of woody species decreased. There was a sequential increase in foliar nitrogen of Buddleja from the open to vigorous stages before stabilizing. Foliar phosphorus of Buddleja remained the same in the open and young stages before increasing in the vigorous and mature stages. Soil pH progressively decreased from the open through the mature stages. Soil nitrogen pools remained the same in the early and young stages, yet, doubled in the vigorous stage, before tripling in the mature stage, when compared to the earlier stages. Soil phosphorus pools were equal in the open and young before increasing by factors of three and four in the vigorous and mature stages, respectively. These patterns are consistent with the general patterns of succession observed in New Zealand floodplains, with and without Buddleja. Whether Buddleja modifies the rate of change in community dynamics has yet to be determined. However, there were significant departures in community composition and soil fertility from the generalized patterns among the catchments that were correlated with island-wide differences in annual average precipitation. Similar patterns in succession between native and invasive-dominated floodplains suggest that Buddleja does not alter successional trajectories.