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I I I I I I I I I I I I I I, I I I I I of the trail between Lamar, Colorado, and Council Grove, Kansas. Wagon trains made use of the wood for fuel and wagon repairs and the stand steadily decreased in size. The last of the large trees were gone by 1863, and the reach downstream from Caddoa was virtually treeless for some period thereafter. Smaller, less spectacular cottonwood stands recolonized the area such that, by the 1 940s, they occupied about 40 acres per river-mile (Snyder and Miller 1991). Salt cedar, a deciduous, needle-leaved tree, was introduced into the United States from Eurasia in the early 1800s (Robinson 1965). This species was first noted in the Arkansas Valley near Lamar in 1913 and had spread substantially by 1923 (Niedrach, cited in Lindauer 1970). Local residents noted that salt cedar spread extensively throughout the valley after the large floods of 1921 and 1937 (Lindauer and Ward 1968). Bittinger and Stringham (1963) found that woody phreatophyte stands (primarily salt cedar) increased by about 43% (or approximately 52 acres/year) from 1936 to 1957 in the floodplain between La Junta and Las Animas. By 1967, woody riparian cover in Bent and Prowers Counties occupied an average of 143 acres per river-mile, 93% of which was monotypic or mixed stands of salt cedar (Lindauer and Ward 1968). Salt cedar has become established in the understory of existing cottonwood galleries, but, more extensively, has replaced broad expanses of riparian grassland communities. Salt cedar is a fast-growing species and is tolerant of saline soils, shallow groundwater, and poor water quality. It exudes a salty secretion which, when accumulated on the soil surface, suppresses other seeds from germinating. These properties give salt cedar a competitive advantage over native riparian plants and enable it to form dense stands with low plant species diversity. While it provides wildlife with shrub cover, its food value is low. Salt cedar provides lower quality wildlife habitat than native cottonwood-willow communities (Anderson et at. 1977, Engel-Wilson and Ohmart 1978, Hink and Ohmart 1984). Additionally, salt cedar root systems are extensive and can reach a depth of 25 feet or more, contributing to relatively high transpiration rates. Conservative estimates indicate that dense stands can utilize 42 to 60 inches of water per year (Robinson 1952, Fletcher and Elmendorf 1955, Bittinger and Stringham 1963). The width of historic riparian communities along the Arkansas River is not well documented in accounts from the 1800s. Bent noted that the "Big Timbers" stand in 1853 was about two miles wide (cited in Grinnell c. 1920). Currently within the five problem areas studied, the band of riparian vegetation varies from 250 to 4,000 feet wide. Although salt cedar coverage has increased dramatically, the overall areal extent ofriparian vegetation has decreased over the past 100 years due to urban and agricultural development with the floodplain and the reduced effective discharge associated with irrigation and flood control storage in John Martin Reservoir. Additionally, flood control operation has significantly reduced large flood events which formerly scoured extensive areas, creating suitable substrates for cottonwood and willow seed germination. Currently, riparian vegetation along the Arkansas River below John Martin Dam is largely restricted to the 3,000 cfs floodway. From Lamar downstream through Problem Areas 3 and 4, fairly dense sandbar willow occupies the immediate riverbank and mature 27