Prasanta K. Subudhi and Herry S. Utomo

When storms threaten Louisiana’s coastal areas, the nation is hurt economically. Because of its significant contribution toward natural gas and oil production, tourism and waterborne commerce, the Louisiana coast needs resiliency to maintain economic vitality for national security.

Restoring Louisiana’s coast is more than just building levees. While the levees protect the vanishing landscape, sustaining these protected coastal areas is of paramount importance for long-term protection of communities, infrastructure and habitat. These wetlands serve as a buffer to protect coastal areas and provide winter habitat to millions of migratory birds. Although they constitute 40% of the total wetlands in the nation, Louisiana wetlands are vanishing at an alarming rate.

Native wetland plants efficiently capture sediment from water and help the wetlands grow by safeguarding levees and reducing storm surge. Using native plants in creating healthy and self-sustainable wetlands and rejuvenating existing wetlands is economically feasible, rapid and sustainable.

Potential Native Plant Species

Native plants constitute the major planting materials for restoration projects. The diversity of plant species is critically important because of irregular environmental disturbances. Smooth cordgrass is the most widely used native plant species in coastal restoration projects because of its tolerance of higher salinity levels. Several other native plant species, such as marshhay cordgrass, big cordgrass, black mangrove, saltgrass, California bulrush, seashore paspalum, bitter panicum and sea oats, are adapted to some coastal areas, depending on salinity, elevation and other factors, and can be used for wetland restoration.

Native Plant Diversity for Healthy Marshes

Both productivity and longevity of coastal wetlands largely depend on the quality of planting materials and the diversity of plant species. Equally, plant species diversity is critical for the sustainability of the unique coastal ecosystem. The different genetic makeup of individual plant materials can act as insurance against stresses from both living organisms and environmental factors. The brown marsh event in 2000 that led to the complete death of smooth cordgrass but not black mangrove plants prompted efforts to develop improved varieties of native plant species. Increased diversity enhances the chance that plants adjust to environmental disruptions, resulting in better vegetation survival, establishment and maintenance.

Because of the lack of diversity in plant materials that had been used in coastal restoration projects, LSU AgCenter researchers initiated the Coastal Plants Breeding Program in the late 1990s to develop improved plant materials. Three native plant species — smooth cordgrass, sea oats and California bulrush — were targeted for research. Conventional plant breeding was used, and after several years of field trials in marsh and controlled sites, AgCenter researchers released six smooth cordgrass clonal varieties with improved vigor, tillering, spreading habit, rust resistance and seed set. The clonal smooth cordgrass varieties were named Cameron, Terrebonne, Jefferson, St. Bernard, Las Palomas and Lafourche. Three clonal varieties of sea oats were also developed. And three superior salt-tolerant California bulrush varieties will expand the utility of California bulrush from freshwater to moderate brackish marshes for shoreline protection and rapid stabilization of newly created marshes. The environment also benefits from California bulrush because of its ability to efficiently remove industrial and agricultural pollutants.

Superior seed-producing smooth cordgrass breeding lines have been developed through many years of selection and trials. Superior polycross smooth cordgrass populations developed using known female parents and several male parents composed of sets of four, five and six fertile parental lines are being tested for release. The first polycross population was developed using 15 genetically diverse lines. On average, the seed set of the polycross populations was improved to 59% with a germination rate of 82%. In comparison, the widely used cultivar Vermilion has a seed set of 21% and germination rate of 35%. The polycross smooth cordgrass also has an inherently high degree of genetic diversity, a critical component for longevity and resiliency against coastal environmental fluctuations.

Aerial seeding, a novel approach for marshland development

Aerial planting can overcome many challenges associated with revegetation efforts and can also be used to re-establish new marshland. This planting technique can readily be scaled up as needed and is both practical and economical for reaching even the most remote areas. Extensive aerial seeding trials over newly constructed marshes in various places in Marsh Island and Belle Chasse areas demonstrated that aerial applications can deliver rapid stabilization of newly constructed marshes. Robust and healthy vegetation can be established in a single season. With the development of polycross populations as a reliable seed production system, an aerial seeding approach has great potential as a versatile tool in marshland development and habitat restoration projects.

Prasanta K. Subudhi is a professor in the School of Plant, Environmental and Soil Sciences, and Herry S. Utomo is F. Avalon Daggett Professor in Rice Research at the H. Rouse Caffey Rice Research Station in Crowley, Louisiana.

This article appears in the spring 2019 issue of Louisiana Agriculture.

New plots of California bulrush at the H. Rouse Caffey Rice Research Station. Photo by Herry S. Utomo

Advanced smooth cordgrass lines at the Belle Chasse testing site. Photo by Herry S. Utomo