Environmental Description:  This is a wide-ranging alliance found in the central United States. Locations supporting this alliance are moist, poorly drained, sometimes alkaline areas along ephemeral, intermittent or perennial streams, and overflow areas of large river floodplains. Weaver (1965) reported that, historically, large stands of Spartina pectinata occurred on mudflats of the Missouri River. This alliance can also be found in swales, meadows, and on the margins of marshes, ponds or lakes. Sites are generally level to gently sloping. Jones and Walford (1995) found stands along highly meandering, narrow (<12.5 m wide) floodplains, and often the channel was deeply entrenched. The water table is typically high, within 1 m of the surface; the sites are typically flooded for part of the winter and spring. Soils are fine-textured, ranging from clays to silt loam (Weaver 1960, Steinauer 1989), and may be slightly to moderately alkaline (Ungar 1974b, Hansen et al. 1995, Jones and Walford 1995). Soil water movement is rapid enough to preclude the accumulation of salts in the surface horizon. In the east, stands can experience droughty conditions in the summer and fall (Comer et al. 1995b), while in the southern and central portion of this alliance''s range they can remain saturated for much of the growing season (Küchler 1974).