-1 Human facilitation of Phragmites australis invasions in tidal marshes: a review and synthesis David Bart 1,2, *, David Burdick 3 , Randolph Chambers 4 and Jean Marie Hartman 1 1 Graduate Program in Ecology and Evolution Rutgers, The State University of New Jersey, 113 Blake Hall, 93 Lipman Drive, New Brunswick, NJ 08901-8524, USA; 2 Current address: Department of Botany, University of Wisconsin-Madison, B239 Birge Hall, 1430 Lincoln Dr. Madison, WI 53706, USA; 3 Jackson Estuarine Laboratory, Department of Natural Resources, Center for Marine Biology, University of New Hampshire Durham, NH 03824, USA; 4 Department of Biology, VIMS College of William and Mary Williamsburg, VA 23187, USA; *Author for correspondence (e-mail: dbart@wisc.edu; phone: +608-469-0836; fax: +608-262-7509) Received 15 August 2003; accepted in revised form 17 February 2005 Key words: Anthropogenic influences, Control, Phragmites australis invasion, Prevention, Salt marshes Abstract Efforts to manage or prevent Phragmites australis invasion in salt and brackish marshes are complicated by the lack of a general causal role for specific human activities. The pattern of invasion within a marsh differs among sites, and each may have different causal histories. A review of the literature finds three estab- lishment/invasion patterns: (1) from stands established on ditch- or creek-bank levees toward interior portions of high marshes, (2) from stands along upland borders toward high marsh interiors, and (3) centroid spread from high marsh stands established in ostensibly random locations. Each invasion pattern seems to have different anthropogenic precursors, therefore preventing generalizations about the role of any one human activity in all sites. However, historical and experimental evidence suggests that regardless of invasion pattern, establishment is much more likely at sites where rhizomes are buried in well-drained, low salinity marsh areas. Any human activity that buries large rhizomes, increases drainage, or lowers salinity increases chances of establishing invasive clones. To integrate these patterns and improve our under- standing of the rapid spread of Phragmites, recent evidence has been synthesized into a dichotomous flow chart which poses questions about current site conditions and the potential for proposed activities to change site conditions that may facilitate invasion. This simple framework could help managers assess susceptibility and take preventative measures in coastal marshes before invasion occurs or before removal becomes very expensive. Introduction Invasion by Phragmites australis ((Cav.)(Trin. Ex Stuedel) (Common Reed, hereinafter referred to as Phragmites) is a wide-spread phenomenon affect- ing many East and Gulf Coast tidal marshes of the United States (Chambers et al. 1999). The invasion has been noted for almost 100 years in some marshes (e.g. Harshberger and Burns 1919). The plant is native to some East Coast tidal marshes (Niering et al. 1977) but there is some evidence suggesting that invasive stands are a new more aggressive genotype introduced from Europe (Saltonstall 2002). Managers and ecologists have Wetlands Ecology and Management (2006) 14:53–65 Ó Springer 2006 DOI 10.1007/s11273-005-2566-z