Blocking Phragmites australis reinvasion of restored marshes using plants selected from wild populations and tissue culture

Abstract

This study tested a vegetation strategy for controlling Phragmites australis invasion into brackish marshes as an alternative to the current technique of repeated herbicide sprays followed by burning. This strategy involves blocking P. australis by planting desired plants selected from wild populations and/or tissue culture regenerants at key points on the major routes of P. australis invasion. The planting of native species was conducted at three sites in a herbicide-treated P. australis marsh near Salem, NJ. Wild population selections of three upland marsh shrubs, Myrica cerifera, Baccharis halimifolia, and Iva frutescens, as well as two grass species, Spartina alterniflora and Spartina patens, and two rushes, Juncus gerardi and Juncus roemerianus, were planted according to their normal zonation positions. Tissue culture regenerated plants of the two grasses and two rushes, and the sedge species Scirpus robustus, were also planted. Plant growth at each site was monitored each year after planting for up to 3 years. Most plants of B. halimifolia, I. frutescens, J. roemerianus, and S. patens demonstrated a consistent vigorous growth at all three sites, whether or not the plants were collected from wild populations or were tissue culture regenerants. These multi-layered walls of plants demonstrated effectiveness in controlling the P. australis by restricting or inhibiting its spread. Upon screening 48 regenerated plants of S. patens at one of the three sites, we found that some regenerants showed enhanced characteristics for blocking P. australis, such as greater expansion and a high 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, such as blocking P. australis reinvasion.

Can Plant Competition and Diversity Reduce the Growth and Survival of Exotic Phragmites australis Invading a Tidal Marsh?

“…Unlike our experiment, previous field experiments utilized naturally growing established stands of native plants instead of manipulating native plant diversity by transplantation. More recently, Wang et al (2006) examined the ability of Phragmites to re-colonize a marsh after it was removed by burning and herbicide application. Similar to our results, they found that Phragmites was less successful at colonizing a marsh if native grasses or shrubs were planted immediately after restoration.…”

“…For instance, Konisky and Burdick (2004) found evidence that Phragmites was a superior competitor to most native species, but was still slightly inhibited by interspecific competition. Other studies have found more pronounced effects of native competitors on Phragmites leading to slower expansion (Amsberry et al 2000;Minchinton 2002;Minchinton and Bertness 2003) and reduced colonizing success (Wang et al 2006).…”

Plant functional group identity and diversity determine biotic resistance to invasion by an exotic grass

“…Few studies have tested the relevance of biotic resistance to the restoration of wetland communities (Wang et al . ; Carlson, Kowalski & Wilcox ; Peter & Burdick ).…”

“…Phragmites australis is being controlled often through the use of chemicals with little consideration for fundamental ecological principles or knowledge of species interactions. In areas where biodiversity is considered valuable or where P. australis is a major nuisance, for instance within or near protected reserves, restoring invasion-resistant wetland plant communities could be an innovative complementary management strategy to constrain P. australis expansion (Wang et al 2006;Carlson, Kowalski & Wilcox 2009). Even in situations where control is not an option, it is fundamental to understand how communities at risk of invasion assemble after disturbances.…”

Expansion ofPhragmites australisin the Liaohe Delta, north‐east China

“…Various methods to suppress P. australis have been applied, such as spraying of herbicides (Derr, 2008), clearing young seedlings, burning off dead canes during spring (Alistock et al. , 2001) and replanting of native plants in areas where P. australis is encroaching (Wang et al. , 2006).…”