| | As part of the research to develop new varieties of smooth cord grass, which is the dominant species of the Louisiana marshes, Prasanta Subhudi applies pollen from one variety to another using a paint brush. (Photo by John Wozniak) |
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| | Steve Harrison evaluates sea oat plants on Holly Beach as part of coastal restoration efforts. (Photo by Mark Claesgens) |
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| | Coastal marshes help protect the rest of the state against storms, and vegetation helps build marshes. (Photo by Linda Foster Benedict) |
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Although Louisiana boasts 15,000 miles of shoreline and 40 percent of the nation’s wetlands, it loses an average of one acre of marsh lands every 20 minutes. These losses are being caused by factors that include the Mississippi River levee system, which prevents sediments and nutrients from replenishing adjacent marshes; high subsidence rates from the compaction and sinking of soft marsh soils, saltwater intrusion that has killed vegetation and accelerated erosion; and exotic species such as nutria that tear away at wetland vegetation.
To stem the relentless erosion of Louisiana’s coastal wetlands, the LSU AgCenter has been applying proven scientific techniques for more than a decade to improve native marsh and coastal plants, conducting educational programs for Louisiana’s youth and providing important information to the state’s public policy leaders.
Plant Breeding
Coastal marshes help protect the rest of the state against storms, and vegetation helps build marshes. Plants growing in the water trap sediment and cause it to settle and accumulate while plants on the shore trap blowing sand and help create protective dunes.
The AgCenter has been using traditional plant breeding techniques refined in years of agricultural use and applying them to develop plants to restore marsh and preserve the beaches. Traditional plant breeding can be used to rapidly and effectively produce plants for coastal revegetation. Scientists use knowledge of plants’ habitat, growth requirements and genetics to select and breed plants that meet specific characteristics.
Most coastal wetland plants reproduce and spread vegetatively. Although these plants will produce some seeds, production is generally low in both number and viability. AgCenter researchers through their breeding program are selecting individual plants that demonstrate superior seed characteristics. They use techniques such as selective crossing and tissue culture to develop improved lines of seed-producing species more effective in establishing marsh on a landscape scale.
The AgCenter has worked with the U.S. Department of Agriculture’s Natural Resources Conservation Service to evaluate and develop new varieties of Spartina alterniflora – also called smooth cordgrass. Although smooth cordgrass can tolerate a wide range of salinity and water depths, like many marsh species, it is a poor seed producer. Because it is the dominant species in Louisiana’s intertidal saline marshes, it is one of the primary species that AgCenter researchers are working with to develop a seed-based restoration program.
Recently, AgCenter researchers have focused on sea oats, which have the capacity to help stem erosion on Louisiana’s Gulf Coast beaches and dunes. While sea oats have the ability to trap and hold sand, native Louisiana sea oats are not good seed producers. Few are left in the wild because most of the state’s natural dunes have been lost.
To develop new lines of sea oats, AgCenter researchers planted hundreds of sea oat plants at Holly Beach on the Southwest Louisiana Gulf Coast. The plants came from seeds collected along the Gulf Coast from Texas to Florida and from the Atlantic Coast from Florida north. Federal and state agencies and park systems helped collect the seeds along the Gulf. North Carolina State University contributed seeds collected along the Atlantic Coast.
“What we had was about 1,000 plants, each of which was genetically different,” said Steve Harrison, LSU AgCenter plant breeder in the Department of Agronomy & Environmental Management. “What we were doing was comparing the survival, spread, vigor, seed production and aesthetic attributes of each of those plants and trying to narrow down the 1,000 to a list of maybe 100 that warrant additional study.”
Harrison and his research team collected parts of selected plants at Holly Beach and took them to a greenhouse in Baton Rouge to produce more plants for future testing. The researchers are looking for plants with the ability to accumulate sand, withstand burial and continue to grow.
In the aftermath of hurricanes Katrina and Rita, AgCenter personnel are evaluating the areas where they have planted spartina, sea oats, bitter panicum and black mangrove to see how these plants withstood the forces of nature.
Aerial photographs indicate some of the sea oats at Holly Beach may have survived, said Mike Materne, an LSU AgCenter coastal wetlands plant specialist. In other coastal plantings near Port Fourchon and Bayou Lafourche, the research has suffered a setback but not a complete loss. Researchers are hopeful that many plant roots survived and will sprout and grow again.
“The hurricanes rearranged the coast where it was heavily impacted,” Materne said. “Caernarvon was a tremendous marsh, and Hurricane Katrina set it back years. You can speculate there would have been even more damage had the marsh been like it was 10 years ago. There’s no question the restoration program lessened the severity of the hurricanes.”
Coastal Roots
Some of the coastal plants that helped buffer the Southeastern Louisiana coast were planted by youth groups participating in the Coastal Roots project, a combined effort of the LSU AgCenter and the Sea Grant College program. In the coastal areas of Terrebonne and Lafourche parishes, Hurricane Katrina with winds from the north brought storm surge and sea rise to the barrier islands while Hurricane Rita with winds from the south flooded areas south of Houma.
The Coastal Roots program included six school groups and one Boy Scout troop from Lafourche and Terrebonne parishes along with the Lafayette Middle School. Most groups numbered about 30 youths, but the last group from Lafayette had 88 students.
Students from 4th grade through high school in South Louisiana take part in this project by establishing plant nurseries at their schools. Students are growing native restoration seedlings they will plant in coastal wetland restoration projects. They have been planting seeds from black mangrove in the winter and growing them in containers. Later, in the spring and summer, the youths bring their plants to the coast and plant them in endangered areas, such as south of Bayou Dulage in Terrebonne Parish and on the hurricane protection levees in Montegut. Because black mangrove is salt-tolerant and thrives on the water’s edge, they were planted at the foot of levees to provide shoreline protection. Restoration plants established by students in the spring of 2004 were about a foot tall when hurricane Katrina hit Louisiana’s coast. Although there was some minor damage to the plants, most survived and are providing additional shoreline protection as mature plants.
“By those plants staying there and holding soil, it’s a good indication they did some good,” said David Bourgeois, an AgCenter fisheries and coastal issues agent, who leads the Coastal Roots program. “We’re picking native plant seeds and growing plants that won’t be a problem in the future,”
Read about the Marsh Maneuvers 4-H program in which young people learn about the coastal environment.