Table 1. Historical land use changes in Jean Lafitte National Park. 



were measured to the nearest centimeter on tide staffs secured in the clay layer beneath the marsh 

 or swamp surface. If the marsh surface was dry, the water level was assumed to be at the marsh 

 surface, and the marsh elevation was inferred by subtracting the water depth above the marsh from 

 the reading on the tide staff. Since marsh elevations could not be leveled to a common datum, 

 all marsh and water elevation changes are discussed in terms of yearly ranges about their relative 

 means. 



Salinity 



Marsh and canal salinity readings were obtained monthly. Interstitial soil salinity was obtained 

 at a depth of 15 cm below marsh surface, and when the marsh was flooded, surface water salinity 

 was also measured. Monthly mean and maximum salinities in Bayou Barataria at Lafitte were 

 obtained from U.S. Army Corps of Engineers data for 1956-80. 



Soil Characteristics 



Sedimentation was measured as accumulation over marker horizons established at 9 locations in 

 3 different environments: (1) streamside marsh or behind spoil banks, (2) inland marsh (both 

 behind spoil banks and in areas without spoil about 50 m from the water edge), and (3) inland 

 swamp. Marker horizons of feldspar chalk were established in June 1986 as described in Baumann 

 (1980), Swenson (1982), and Baumann et al. (1984), and sediment accumulation was measured in 

 August 1986. The marsh and swamp substrate was sampled for bulk density, percent organic 

 matter, mineral content, and percent water. Details of procedures for all field methods and 

 analytical and statistical analyses are described in Taylor (1988). 



RESULTS 



Soil Characteristics 



The soil results indicate that the sites near sources of mineral sediment generally experienced 

 greater vertical accretion rates and had higher bulk densities, lower organic content, and lower 

 water content than sites in the interior of the park or behind spoil banks. 



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