Invasive Spartina alterniflora: biology, ecology and management

Smooth cordgrass Spartina alterniflora Loisel., a perennial rhizomatous grass native to the Atlantic and Gulf coasts of North America, spreads rapidly in estuaries and coastal salt marshes in the Pacific coast of North America, Europe, New Zealand and China, and has caused considerable effects on the invaded regions. We here describe a comprehensive account of its biology and ecology, and discuss the management of this invasive plant. S. alterniflora was intentionally introduced to China in 1979 for the purposes of erosion check, soil melioration and dike protection. However, its rapid elongation rates, high leaf area indices, high photosynthetic rates, long photosynthetic season and clonal growth make S. alterniflora an aggressive competitor with native salt marsh plants in the coastal regions in China. The estimates made for the year 2002 show that S. alterniflora covered 112000 hectares throughout the eastern China, from Guangxi (21o N) to Tianjin (39o N), and is still spreading rapidly in the east coast of China. The successful invasion of S. alterniflora in non-native ranges is obviously the result of the interactions between its great invading ability and a high invasibility of the invaded ecosystems, which is further facilitated by human activities. On the basis of its population trend and potential impact on native ecosystems, S. alterniflora was officially placed on the list of most harmful invasive alien plants (nine species) in China in 2003. S. alterniflora invasions in the salt marshes have multiple effects on the abiotic and biotic properties and the functioning of the invaded ecosystems, including conversion of mudflats to Spartina meadows, loss of shorebirds' foraging habitats, alteration of ecosystem processes (e.g. carbon and nitrogen cycling), decrease in abundance of native species, degradation of native ecosystems and their functions, and considerable economic loss. It is predicted that the environmental changes driven by human activities in the coastal regions (e.g. eutrophication, sea level rise and saltwater intrusion) may favour its further invasions in coastal ecosystems in the future. Like other invasive species, it is quite difficult, expensive and even impossible to eradicate S. alterniflora once it has successfully invaded the coastal ecosystems. Obviously, further intentional introductions of S. alterniflora should be banned in China, and effective control