Whole plant traits of coastal dune vegetation and implications for interactions with dune dynamics

Abstract

Coastal dunes are important protective features against sea level rise and coastal storms. Interactions between dune plant aboveground structures and sediment trapping that allow for dune building and maintenance are well established. More recently, studies documenting belowground biomass for promoting erosion resistance in dominant dune species have been conducted, yet a knowledge gap remains regarding species-specific characterization of whole plants, specifically with respect to roots, rhizomes, and belowground stems.Our objective was to quantify above-and belowground traits of four dominant dune grasses to document the potential for species-specific effects on dune growth, maintenance, and erosion resistance. We examined above-and belowground traits among four prominent dune grasses of the Atlantic and Gulf Coasts of North America: Ammophila breviligulata, Panicum amarum, Spartina patens, and Uniola paniculata. Whole plant samples of each species were collected from the foredune at the US Army Engineer Research and Development Center's Field Research Facility in Duck, North Carolina, USA, and quantified for several above-and belowground traits (e.g., stem height, rhizome number and length, root surface area by diameter class, root tensile strength, and mycorrhizal percent infection). Belowground factors known to impact important dune processes, such as rhizome length, mycorrhizal percent infection, and root traits, differed substantially among species. When visualized in multivariate space, all species significantly differed in suites of aboveand belowground traits. When considering belowground only, Ammophila and Spartina were similar, despite differences in biomass allocation. Species separated along axes related to mycorrhizal association, biomass allocation, and root construction. The four co-occurring dune grass species were dissimilar in suites of plant traits. Belowground trait differences were driven by those describing root construction, biomass allocation, and mycorrhizal infection.

Drivers of dune formation control ecosystem function and response to disturbance in a barrier island system

“…Two decades prior, dunes on Hog were dominated by Ammophila and Spartina , with Panicum only comprising ~ 2% of dune relative cover 37 . By 2022 Panicum relative cover increased to > 40% on both Hog and Metompkin which has implications for overall dune structure as Panicum exhibits phalanx growth due to shorter rhizomes 39 and traps 50% less sediment than Ammophila or Spartina , forming smaller, hummocky dunes. Panicum has the potential to alter dune dynamics and growth from those previously documented in Virginia, creating new climate-vegetation scenarios that current models may not predict.…”

Impacts of Hurricane Isaias (2020) on Geomorphology and Vegetation Communities of Natural and Planted Dunes in North Carolina

“…Planting supplemental stabilizing plant growth forms may act synergistically with dune grasses to facilitate positive interactions, such as by providing additional sediment stabilization via rhizomes, sand trapping, and soil nutrients (Brown, Zinnert, and Young, 2018). Different plant growth forms and varied plant functional traits lead to a diversity of functional roles served in coastal vegetation communities and emergent interactions (Brown, Zinnert, and Young, 2018; Walker and Zinnert, 2022).…”

“…Recent work has also shown that functionally similar species, such as A. breviligulata and U. paniculata , have different strategies for surviving the dune environment, as evidenced by differences in plant functional traits. For instance, Walker and Zinnert (2022) found that while both A. breviligulata and U. paniculata had similar belowground biomass, they displayed markedly different root traits. Meanwhile, Spartina patens (salt hay), recently renamed Sporobolus pumilus (Peterson et al ., 2014), and Panicum amarum (bitter panicum) were 70% less massive underground despite serving similar functional roles as dune builders.…”

“…Meanwhile, Spartina patens (salt hay), recently renamed Sporobolus pumilus (Peterson et al ., 2014), and Panicum amarum (bitter panicum) were 70% less massive underground despite serving similar functional roles as dune builders. Both plant functional groups and plant functional traits, including above- and belowground traits, influence dune processes ( e.g ., sediment transport, sand accumulation, erosion) and morphology (Brown, Zinnert, and Young, 2018; Walker and Zinnert, 2022).…”

Alongshore Variable Accretional and Erosional Coastal Foredune Dynamics at Event to Interannual Timescales

“…The dune nourishment region initially included regular spacing of sprigs Ammophila brevigulata , with additional Uniola paniculata planted near the dune crest (CPE, 2017), with similar vegetation present in the other partially managed coastal sections as well. Conversely, there is a wider range of species present at the unmanaged FRF site including Panicum amarum , Spartina patens , Solidago sempervirens , Erigeron canadensis , and Smilax bona‐nox (e.g., Levy, 1976; Walker & Zinnert, 2022). Quadrat surveys of dune grass vegetation on the dune face in portions of the study site, as presented in White (2022), showed that the total living cover was about twice as high in Zone 2 than Zone 3 and that the species richness was higher in Zone 2 than Zone 3.…”