Individual study: Planting native shrubs and grasses to prevent common reed Phragmites australis reinvasion of restored brackish marshes near Salem, New Jersey, USA
Wang J., Seliskar D.M., Gallagher J.L. & League M.T. (2006) Blocking Phragmites australis reinvasion of restored marshes using plants selected from wild populations and tissue culture. Wetlands Ecology and Management, 14, 539-547
Although usually considered to provide valuable wildlife habitat, in some sitiuations common reed Phragmites australis may be considered invasive. This study tested a vegetation strategy for controlling common reed invasion into brackish marshes as an alternative to the usual technique of repeated herbicide spraying followed by burning. The strategy involves blocking P. australis spread by planting desired plants selected from wild populations and/or tissue culture regenerants at key points on the major routes of invasion.
Study area: The planting of native species was conducted at three upper marsh sites dominated by P.australis (before spraying with herbicide in 1999), near Salem, New Jersey, northeast USA.
Site 1 - (9 x 7.8 m) was bare after removing the dead reed canes before the planting in 2000, however there was live reed on the upper edge.
Site 2 - (7.5 x 3.5 m) reed had reinvaded before the planting in 2001.
Site 3 - (17.1 x 5.5 m) dominated by reed before the planting in 2002.
The above-ground reed at Sites 2 and 3 was cut prior to planting.
Plant selection and planting: Wild population selections (well established juveniles) of three upper marsh zone shrubs: bayberry Myrica cerifera, eastern baccharis Baccharis halimifolia and Jesuit's bark Iva frutescens; two cordgrass species: smooth cordgrass Spartina alterniflora and saltmeadow cordgrass S.patens; and two rushes, saltmarsh rush Juncus gerardi and black rush J.roemerianus, were planted according to their normal zonation positions.
Tissue culture regenerated plants of the two grasses and two rushes, and also sturdy bulrush Scirpus robustus, were also planted.
There was an approximate 100 cm distance between plants at Site 1, and 60–70 cm at Site 2. At Site 3, there was an approximate 100 cm distance between M.cerifera shrubs, and 60–70 cm for the other species. Planting was undertaken between June and October, dependant upon year and species.
Monitoring: Plant survivorship at each site was recorded in the second and third years after planting.The heights and circumferences of the surviving plants were measured each year.
Most B. halimifolia, I. frutescens, J. roemerianus and S.patens plants demonstrated a consistent vigorous growth at all three sites, whether or not the plants were from wild populations or were tissue culture regenerants. The ‘multi-layered’ stands of these plants that subsequently established were effective in controlling P.australis by restricting or inhibiting its spread.
Upon screening 48 regenerated S. patens plants at one of the three sites, some regenerants showed enhanced characteristics for blocking P. australis spread, such as greater expansion and a higher stem density. The availability of the tissue culture-regenerated plants of the native marsh species makes it possible to select lines from local genotypes that have desirable characteristics for wetland restoration projects, in this example, blocking P. australis reinvasion.
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