Environmental determinants of Phragmites australis expansion in a New Jersey salt marsh: an experimental approach

Abstract

Interdependence among disturbance events, ecosystem properties, and biological invasions often make causal relationships difficult to discern. For example, Phragmites australis invasion in mid‐Atlantic salt marshes is often associated with disturbances that create well‐drained features as well as with low sulfide concentrations, but explanations of these associations have been elusive. We tested experimentally: 1) that disturbances increasing wetland drainage facilitate Phragmites invasion by altering sulfide concentrations and salinity; 2) that translocation allows plants to spread beyond drainage areas; and 3) that plants can then lower edaphic stress through pressure ventilation of the rhizosphere and promote further expansion. At the invasion front, treatments of 1) severing rhizomes to halt translocation and 2) combined severing with clipping dead culms to limit ventilation of the rhizosphere killed most culms, but did not affect pore water chemistry. In already invaded areas, severing and clipping reduced culm height and panicle production, severing alone and in combination with clipping also raised sulfide and ammonium concentrations in the root zone. There were no treatment effects on plant performance or pore water chemistry along mosquito ditches, where sulfide concentrations were negligible. Small‐scale hydrological alterations such as ditches appear to provide suitable sites for the establishment of Phragmites because soils are well‐drained and are low in free sulfides. Subsequent expansion into more hostile areas occurs through translocation, with well‐drained areas acting as sources for essential substances. Once established, the plant increases rhizosphere oxygenation and lowers sulfide concentrations.

Does the invasive plant Elymus athericus modify fish diet in tidal salt marshes?

“…The invasion pattern of Elymus athericus (Valéry et al, 2004) is similar to the invasion of Phragmites australis (common reed) in salt marshes along the North American Atlantic coast (see for example Bart and Hartman, 2000). In fact, P. australis in North American salt marshes has changed recently from a species with a limited distribution to an invasive species producing dense monospecific stands.…”

The biology of Canadian weeds. 129. Phragmites australis (Cav.) Trin. ex Steud.

“…Habitats created by small-scale hydrological alterations, such as ditches with well-drained soil and low free sulfides, provided suitable habitats for P. australis growth and served as source areas for colonization of more hostile habitats (Bart and Hartman 2000). Oxygen demand, loss on ignition and mineral nutrient levels were highest in a soil composed of black mud with high litter content in eutrophic fishponds of the Czech Republic.…”

Uptake and distribution of N, P and heavy metals in three dominant salt marsh macrophytes from Yangtze River estuary, China

“…Recent investigations demonstrate that concentrations of metals in plant tissues are highly variable between species (Fitzgerald, Caffrey, Nesaratnam, & McLoughlin, 2003;Ye, Baker, Wong, & Willis, 1997). Differences in uptake rates and allocation patterns between species can generate different rates of metal retention in salt marsh vegetation and perhaps further influence the biogeochemistry of salt marshes (Windham et al, 2003;Burke, Weis, & Weis, 2000;Weis & Weis, 2004;Ornes, Sajwan, Loganathan, & Chetty, 1998 australis expansion could alter edaphic conditions (Windham & Lathrop, 1999;Bart & Hartman, 2000), accelerate nutrient cycling (Windham, 1999;Meyerson, Saltonstall, Windham, Kiviat, & Findlay, 2000), and increase metal bioavailability (Weis & Weis, 2004;Windham et al, 2003). The genus Spartina is native to the Atlantic and Gulf Coasts of North America, but it has been introduced to many coastal and estuarine regions of the world (Daehler & Strong, 1996;Chen, Li, Zhong, & Chen, 2004 (Daehler & Strong, 1996;Levin, Neira, & Grosholz, 2006).…”