In Louisiana, human actions, such as levee construction for flood protection, have disrupted the connectivity between many rivers and their surrounding wetlands, leading to marsh degradation and land loss. River sediment diversions from the Mississippi River into adjacent wetlands are currently proposed as a large-scale wetland restoration technique. The reintroduction of sediment-rich waters into adjacent wetlands will also come with altered hydrology and nutrient loads. Despite hydrology and nutrient loading being central to many previous studies, many uncertainties remain regarding the marsh response to this type of large-scale environmental alteration.
To better understand the effect of river sediment diversion related increases in nutrient supply and altered hydrology on tidal freshwater marsh species specific responses and soil physico-chemical properties, we conducted a greenhouse experiment consisting of three common tidal freshwater and brackish marsh species (Panicum hemitomon, Sagittaria lancifolia, and Spartina patens). To mimic diversion specific conditions, we tested high and low nitrate loading rates (35 g N m2 y–1 and 0.25 g N m2 y–1, respectively) and two hydrologic regimes to compare diversion and non-diversion. Units were also set at two different soil surface elevations within each treatment, to simulate healthy and degraded marsh types.
Growth responses measured throughout the study differed between species, but were not influenced by the treatments. After 3 months, aboveground and belowground biomass was not impacted by the treatment for any of the species. Soil redox potential was influenced by changes in hydrology but recovered to pre-study conditions by harvest. This study provides an insight into how proposed river diversion conditions and subsequent recovery may influence the productivity of freshwater marshes. We also further highlight the need for a more complete understanding of how changes in flooding depth, duration, and nitrate load from proposed river sediment diversions will influence the productivity of marshes in receiving basins.
|Advisor:||Hester, Mark W.|
|Commitee:||Duke-Sylvester, Scott M., Howard, Rebecca J., Nelson, James A., Sloey, Taylor M.|
|School:||University of Louisiana at Lafayette|
|School Location:||United States -- Louisiana|
|Source:||MAI 58/05M(E), Masters Abstracts International|
|Subjects:||Biology, Ecology, Hydrologic sciences|
|Keywords:||Flooding, Louisiana, Nitrate loading, Nutrient, River diversion, Sediment|
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