Introduction.

        Forty percent of coastal wetlands occur in Louisiana. The state has more coastal wetlands than any other. Such wetlands are economically important for storm protection, recreation, and seafood production. At present, approximately 25-30 square miles of wetlands are lost annually. The coastal wetlands were formed by distributaries of the Mississippi River during the past 12,000 years. Deltas were formed as the river lost its sediment load; such activities also resulted in the river changing courses many times. At least 9-12 identifiable, previously formed deltas are evident. The oldest is the Maringouin; the current active deltas are the Belize (birdfoot) and the Atchafalaya.

Wetland loss/ erosion.

        Wave energy causes coastal erosion. Most land loss, however, is due to subsidence which is a lowering of land due to compaction and oxidation of organic matter. Subsidence generally results in open water replacing the land. Certain ratios of open water to land are essential for a productive habitat.

        The coastal marshes are no longer natural systems. Levees for flood protection prevent river deposition of sediment in the marshes. Canals for petroleum exploration and extraction have resulted in higher salinities penetrating deeper into the marsh. Canal construction has also increased mechanical erosion. Sulfur is abundant in brackish marsh soils, and it relatively inert under anaerobic conditions. However when disturbed, sulfur is oxidized to sulfuric acid that may lower soil pH to 2.5. Marsh soils may contain high amounts of water and become too fluid to support vegetation. The "N value" is a measure of soil fluidity. Coastal soils have a very high in organic content compared to upland soils where organic content is less than 5%. Nutria, an exotic rodent, can eat vast amounts of marsh vegetation causing considerable wetland damage.

Golden Meadow.

        The Center for Plant Materials is located in Golden Meadow; it consists of about 100 acres of test plots, production fields, and greenhouse facilities. Native species rather than exotics are used in restoration work. Various ecotypes for certain species are tested for desirable properties such as higher salt tolerance and the ability to grow in deeper water.

Primary species used for coastal restoration are the following:
 

1.  Spartina alterniflora
2.  Panicum amarum var. amarum
3.  Avicennia germinans
4.  Paspalum vaginatum

       1.  Spartina alterniflora "smooth cordgrass"

• Major method of reproduction is vegetative by rhizomes
• Grows in open water up to about 20 inches deep
• Tolerates fairly high salt concentrations; shows stress at 50 ppt
• High stem density and large root mass makes the plant good for dissipating wave energy
• Effective at filtering water; aids in sedimentation
• In certain situations this grass is an effective, less expensive alternative to levees that serve to reduce wave fetches.
• 2.  Panicum amarum var. amarum "bitter panicum"

• Grows at higher elevations in deep sands; withstands sand burial; nodes once buried will produce new roots; produces no or few seeds; major method of reproduction is vegetative by rhizomes.
• Provides for dune stabilization
• Dunes form one of the first lines of defense against hurricanes
• One mile of vegetated coast will reduce tidal surges by one foot
• The Isles Dernieres, once a single barrier island have been breached in numerous places by hurricanes where vegetation was absent or sparse.
• Panicum amarum var. amarulum "coastal panic grass" differs from the typical variety in several ways.
• This variation is a bunch grass due to its short rhizomes; it also produces viable seeds; its roots penetrate deep into sandy soils to collect moisture.

1. 3.  Avicinnia germinans "black mangrove"

• It is one of the few shrubs that has high salt tolerance; it produces many seeds with essentially 100% germination; the plants are easy to grow commercially.
• Black mangrove grows in the intertidal zone and can form large colonies; it produces pneumatophores (somewhat analogous to cypress knees) that function in gas exchange.
• provides good wildlife habitat; especially important as nesting habitat for brown pelicans that prefer to build nests off of the ground.
• Lycium carolinianum "matrimony vine; wolfberry" is another shrub that is salt tolerant and has many of the same characteristics as black mangrove for providing habitat for wildlife.

1. 4.  Paspalum vaginatum "seashore paspalum"

• Produces stolons (above ground rhizomes) and can quickly carpet bare soil; the plants will tolerate salt in the range of 6-12 ppt.
• In time seashore paspalum normally will succeed to other kinds of plants resulting in various kinds of natural communities.
• Seashore paspalum is good for wildlife in that it harbors insects and other small creatures that in turn serve as food for birds, etc.

The center is interested in finding ecotypes with high biomass production, tolerances for higher salt, sulfur, water depth, and sand burial, and certain other characteristics in prevailing environments. Living samples are obtained from many populations of test species from the Atlantic and Gulf Coasts and planted in a common garden. Differences in biomass production in Spartina patens were shown as an example. Ecotypes with desirable qualities are then used for coastal protection and restoration.

Techniques for using plants in coastal restoration and protection.

        One technique is to construct levees in a rectangular pattern so that the ends do not touch one another. This method allows marine animals to move about. If the corners of the rectangles were enclosed, animals would be excluded. Vegetation is planted on the levees to protect them from erosion and to produce biomass. Tides move sediment into the leveed areas which is then deposited due to the quiet waters within. This results in building marsh where open water previously existed. One big disadvantage to this technique is the expense in levee construction.

        Attempts at reducing the cost of levee construction make use of plants to create levees. In this technique California bulrush was used because it will grow in water as much as 36 inches deep. Plants were planted in rows on 10 ft. centers with rows 25 feet apart. Rhizomes spread underwater resulting in increased density of stems that will trap sediment. Cost for such installation is about $1 per linear foot. Such levees are self maintaining which provides another cost advantage. One problem encountered is that California bulrush will tolerate salt concentrations from 8-12(18) ppt and will be killed at levels of 24 ppt. The latter levels of salt concentration were attained in certain planting areas due to the drought that began in 1998.

        Spartina spartinae can tolerate high salt and high sulfur levels. It is useful on levees where sulfur occurs in high concentrations. It is readily eaten by nutria and may need protection from them.

        Uniola paniculata requires high beaches and dunes. Populations decreased in abundance along the Louisiana coast as soils became wetter. Ecotypes from Louisiana performed better along our coast than material from other localities.

        Zizaniopsis miliacea "giant cutgrass" is of great interest in fresh water restoration techniques. The species produces by vegetative and sexual means. Vegetative reproduction involves layering. As stems become heavier and lodge into the water or on moist soils new plants develop at the nodes. The plants provides excellent cover on spoil banks and on levees where they grow into open water. Its high stem densities are effective at reducing wave and water erosion and for high sediment capture.