Assessing a multi-species planting approach on the vegetative development of created thick-mat floating marsh, Louisiana, USA

The benefits of using multi-species planting approaches to achieve goals associated with wetland restoration are well demonstrated, particularly if those species exhibit different growth forms, or belong to different functional groups. Such efforts not only have the potential to accelerate ecological succession, but simultaneously, they increase species richness, a particularly beneficial quality if what is being restored is naturally biologically diverse. We developed and evaluated a multi-species planting approach within the context of creating thick-mat floating marsh, a widely distributed freshwater wetland type in coastal Louisiana. This research, and the larger collaborative project to which it is linked, represents the first attempt to create this wetland type. In all, 7 vegetative combinations were tested, all of which included Panicum hemitomon, the dominant macrophyte of thick-mat floating marsh. Additional species assessed included Althernanthera philoxeroides, Hydrocotyle ranunculoides, Ludwigia peploides, and Sagittaria lancifolia. After 5 months of growth it became clear that more than one species significantly enhanced overall floating marsh mat development, but not necessarily more than two. The combination of Panicum hemitomon and Ludwigia peploides was superior to any other two-species combination, as well those treatments that combined 4 and 5 species. We base these conclusions on the fact that Ludwigia peploides was highly resilient to transplant shock, grew most vigorously in a lateral fashion, produced significantly more root biomass than any other secondary species, and ultimately, contributed positively to overall mat buoyancy, a key metric regarding successful thick-mat floating marsh creation.