Dunes help protect communities from storms, and vegetation helps stabilize dunes by reducing wind and water erosion and by trapping and accumulating new sediment. While the importance of aboveground plant structures in dune dynamics is well known, the role of roots is less understood. A recent NCCOS-funded study began examining the influence of root and below ground plant structures on dune dynamics.

The findings of this study may have important implications for what plant species are used in dune plantings and may inform strategies for how dune nourishments are completed, as man-made dunes typically lack the internal plant structure that naturally-occurring dunes offer. Incorporating a deeper understanding of the role plants play in dune processes into coastal models can also allow us to better predict dune performance during storms, and help coastal managers more effectively assess alternative management strategies for protecting communities from flooding and storm surge.

Figure 1. Schematic of the similarities and differences above and below ground of the four dune grass species examined. (a) Ammophila breviligulata, (b) Panicum amarum, (c) Spartina patens, and (d) Uniola paniculata.

Researchers examined the whole plant traits (above- and below-ground plant characteristics) for four dominant dune grasses in the U.S. Atlantic and Gulf Coasts (Figure 1). They found that these four co-occurring species are not similar in their vegetative traits, suggesting that they each have different approaches to surviving in the dune environment. For example, Panicum amarum has fewer, smaller, and shorter roots, suggesting it grows more slowly as a way to conserve resources, and as a result is more reliant on symbiotic relationships with belowground fungi to gather resources and survive. Ammophila breviligulata, on the other hand, has many long, thin roots that, along with its longer rhizomes, suggest it can quickly colonize dune systems after disturbance.

The study found that it is important to quantify both above- and below-ground plant traits in order to fully understand how a plant species contributes to ecosystem services and processes. By considering the full characteristics of a species, instead of just what exists above the sand dune, a more mechanistic understanding of plant behavior is reached. For example, Ammophila breviligulata has longer leaves and accumulates biomass quickly. When this information is combined with the fact that Ammophila has belowground traits that encourage rapid growth, it helps explain the ability of Ammophila to capture and retain more sediment and drive quicker dune building relative to other grasses. A healthy belowground dune-root composition also helps dunes withstand erosion during storm events.

This study was supported by the NCCOS Effects of Sea Level Rise (ESLR) project “Is an Old Dune a More Resilient Dune? Assessing How Dune Formation Affects Coastal Protection from Storms and Sea Level Rise in North Carolina,” which is led by scientists from the Virginia Institute of Marine Science, the U.S. Army Corps of Engineers Engineer Research and Development Center–Field Research Facility, and Virginia Commonwealth University.

Citation: Walker, Shannon L., and Zinnert, Julie. 2022. “ Whole Plant Traits of Coastal Dune Vegetation and Implications for Interactions with Dune Dynamics.” Ecosphere 13( 5): e4065. https://doi.org/10.1002/ecs2.4065