Succession of vegetation in an evolving river delta, Atchafalaya Bay, Louisiana

Johnson, W; Sasser, Charles; Gosselink, James

Wetland vegetation found on islands in the Atchafalaya Delta are described in terms of principal components, allowing classification into species associations. These are relatively new islands that have appeared as a result of the increased flow from the Mississippi coming through the Athcafalaya (this century). Vegetation on the islands has been mapped annually with color infrared aerial photography. Vegetation sampling has also been done, with several sampling stations in place on the islands. Species found on these islands include wetland species common to the freshwater marshes of the Louisiana coast. Forty-five plants species were found. The three most common are: Sagittaria latifolia, Salix nigra, and Typha latifiolia. Distribution of species in wetland plant communities, as has been found previously, can be influenced by hydrology. Table 1: Frequency of occurrence of the most common vascular plant species at sites in the Atchafalaya River Delta in May and September. Table 2: Aerial standing crop biomass estimates of the most common species in each of the major vegetaion associations of the Atchafalaya Delta in May and September. Table 3: Conjunction coefficients showing the similarities between the plant associations of islands in the Atchafalaya River Delta, in May and September. Table 4: Percentage variation in soil variables in soils from islands in the Atchafalaya River Delta attributable to different sources. Figure 2: Illustration of a typical mouth-bar island in the Atchafalaya Delta, showing both aerial and cross-sectional views. Figure 3: Diversity characteristics of the important floral associations of islands in the Atchafalaya Delta. Figure 4: Change in Atchafalaya Delta vegetation associations from May to September.

Succession of vegetation in an evolving river delta, Atchafalaya Bay, Louisiana

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