Use of sediment amendment to rehabilitate sinking baldcypress swamps in coastal forests, Louisiana: 2. soil characteristics

Jiang, Ming; Middleton, Beth

Amendments of sediment from dredging activities have played an important role in raising the elevation of sinking coastal wetlands. Nevertheless, the usage of sediment amendments to rehabilitate coastal baldcypress (Taxodium distichum) swamps is untested, particularly with regard to the biogeochemical properties of sediment from dredging activities, which covers the original surface soil after application. This study compared the soil characteristics of coastal swamps treated with sediment amendments in the Barataria Preserve unit of Jean Lafitte National Historical Park and Preserve in treatment sites on Treasure Island with those in natural swamps. The sandy sediment amendments used in the coastal forests had different soil texture and characteristics than the more organic soils of the natural swamps. Three years after the application of these sediments on the coastal swamp of Treasure Island, dewatering and compaction of the sediment had occurred but the sediment still had high salinity and bulk density, and low organic matter content. For the natural swamps, percent organic matter decreased with depth to 20 cm; however, in the sediment amended swamps, the percent organic matter was low throughout the soil column (mean percent organic matter = 4.1% ± 0.5%). Ultimately, organic matter is a key factor in the biogeochemical properties of soils with respect to ion immobilization and water holding capacity. The future soil characteristics of the coastal swamps treated with sediment amendments are likely to depend on the ability of in-situ vegetation to produce organic matter. The two sediment amended swamps differed from each other in that Site 1 had a higher elevation (mean = 25 cm higher) and drier soil than Site 2. The effects of sediment in coastal forested wetlands require separate consideration from studies of salt marshes, e.g., the weight of the sediment might damage tree roots, or the amendments might influence soil stability during storms in a different way. 3 environments beneficial to these sinking baldcypress swamps in coastal Louisiana. Generally, this study suggested that shallower depths of sediment are more likely to yield environments beneficial to these sinking baldcypress swamps in coastal Louisiana.

Use of sediment amendment to rehabilitate sinking baldcypress swamps in coastal forests, Louisiana: 2. soil characteristics

Collections