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|Title:||Functional comparison of created and natural wetlands in the Atchafalaya Delta, Louisiana|
|Authors:||Louisiana State University (Baton Rouge, La.). Wetland Biogeochemistry Institute.|
Wetlands Research Program (U.S.)
Faulkner, Stephen P.
Poach, Matthew E.
|Publisher:||Environmental Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
Abstract: Functional assessment of created wetlands in comparison with natural wetlands of the same ages was undertaken in the Atchafalaya Basin, Louisiana. Overall objectives were to characterize the structural components (soils and vegetation) of created and natural wetlands of similar age classes, compare and contrast selected wetland functions, and quantify any structural and functional changes that may occur as a function of time. The Atchafalaya Basin was selected for this study because it is one of the few locations in the United States with newly forming natural wetlands and a number of created/restored wetlands available for comparison. Aerial photography, satellite imagery, and Corps records were used to select one natural and one created wetland for each of three age classes: young (1 to 3 years), intermediate (5 to 10 years), and old (15 to 20 years). An additional natural "old" wetland was added to assure a valid comparison. Soils were evaluated for bulk density, pH, moisture content, particle size, phosphorus content, and nitrogen (N-mineralization, total N, carbon, nitrous oxide, and denitrification enzyme activity) content. No seasonal differences for the three age classes were found in the N, P, pH, particle size, and moisture content samples; however, a trend of increasing soil N with increasing elevation was noted for the older marshes. Bulk density was highest in the young age class and lowest in the old age class. Phosphorus concentrations were similar in both created and natural marshes at lower elevations, but were higher at higher elevations. A total of 53 plant species were found in all wetlands studied, with a clear separation by elevation. The lowest level was unvegetated mud flats, followed by distinct zonations. Old wetlands were different from new wetlands in dominant species, and created wetlands of all ages had a higher diversity of species. Total aboveground biomass was lower on created wetlands, but may have been due to nutria herbivory. Presence of woody vegetation that could not be destructively sampled complicated vegetation biomass data comparisons. New created marshes had obvious differences attributable to the dredging process necessary to create the wetland. These initial differences were overcome through time with deposition of fine-textured, nutrient-rich suspended sediments on the soil surface during flooding events. A similar convergency of vegetation characteristics took place during this same interval. Results indicated that it takes from 5 to 10 years for a created wetland in the Atchafalaya Delta to develop similar soil and vegetation characteristics to a natural reference wetland of the same age. NOTE: This file is large. Allow your browser several minutes to download the file.
|Appears in Collections:||Technical Report|