Background/Question/Methods
Griselinia littoralis, a native New Zealand shrub, was planted into a chronosequence (0 to 8 yrs since flooding) dominated by the non-indigenous shrub, Buddleja davidii in three New Zealand floodplains to determine to what extent facilitation and competitive inhibition  may influence the establishment of the native species. Buddleja, an aggressive, highly invasive, ornamental shrub of Asian origin, may be suppressing slower-growing native species on New Zealand floodplains, thus altering successional trajectories. Griselinia transplants (600) were planted in Buddleja-dominated communities representative of three successional stages (open, young and vigorous) for two growing seasons.  Growth responses (i.e., above and below ground biomass, specific leaf area and height) between stages were compared using an analyses of variance.
Results/Conclusions
Height, above-ground biomass and specific leaf area of Griselinia transplants remained unchanged from when initially planted in the open and young stages yet were nearly doubled in the vigorous stage, suggesting that the conditions in vigorous stage support Griselinia development.  Increased soil moisture, organic matter and nutrients in addition to protection from herbivores (i.e., feral sheep, hares) may have facilitated survival and growth of the Griselinia transplants under the Buddleja canopy.  The presence of Griselinia seedlings that have established naturally beneath the Buddleja canopy yet not in the open or young stages provided additional support that Buddleja does not inhibit establishment by Griselinia.  Rather, the decreasing light levels, unsuitable for Buddleja, may be facilitating its eventual replacement by Griselinia. Although this work was reviewed by the US EPA and approved for publication, it may not necessarily reflect official Agency Policy.