Investigating dune‐building feedback at the plant level: Insights from a multispecies field experiment

Abstract

Coastal foredunes provide the first line of defense against rising sea levels and storm surge and for this reason there is increasing interest in understanding and modeling foredune formation and post‐storm recovery. However, there is limited observational data available to provide empirical guidance for the development of model parameterizations. To provide guidance for improved representation of dune grass growth in models, we conducted a two‐year multi‐species transplant experiment on Hog Island, VA, U.S.A. and measured the dependence of plant growth on elevation and distance from the shoreline, as well as the relationship between plant growth and sand accumulation. We tracked total leaf growth (length) and aboveground leaf length and found that Ammophila breviligulata (American beachgrass) and Uniola paniculata (sea oats) grew more than Spartina patens (saltmeadow cordgrass) by a factor of 15% (though not statistically significant) and 45%, respectively. Our results also suggest a range of basal/frontal area ratios (an important model parameter) from 0.5‐1 and a strong correlation between transplant growth and total sand deposition for all species at the scale of two years, but not over shorter temporal scales. Distance from the shoreline and elevation had no effect on transplant growth rate but did have an effect on survival. Based on transplant survival, the seaward limit of vegetation at the end of the experiment was approximately 30 m from the MHWL and at an elevation of 1.43 m, corresponding to inundation less than 7.5% of the time according to total water level calculations. Results from this experiment provide evidence for the dune‐building capacity of all three species, suggesting S. patens is not a maintainer species, as previously thought, but rather a moderate dune builder even though its growth is less stimulated by sand deposition than A. breviligulata and U. paniculata. © 2019 John Wiley & Sons, Ltd.

Spatial Variability of Coastal Foredune Evolution, Part A: Timescales of Months to Years

“…The high-resolution terrestrial lidar measurements collected in this study demonstrate the important role of dune grasses on trapping wind-blown sediment and its potential beneficial use in dune management. Consistent with numerous other works (e.g., [65,[88][89][90]), grass planting may be an effective measure in limiting aeolian transport to homes adjacent to the beach and enhancing coastal resilience to flooding by promoting natural dune growth (Figures 9, 10 and 12). However, morphological feedbacks similarly have an important role in influencing dune dynamics ( Figures 7, 8 and 13).…”

Species-Specific Functional Morphology of Four US Atlantic Coast Dune Grasses: Biogeographic Implications for Dune Shape and Coastal Protection

“…Spartina patens shoots were also relatively short and very thin compared to the other species, likely explaining the lower sand accretion values similar to P. amarum and U. paniculata (Figure 8). Interestingly, a recent field experiment by Mullins et al [37] demonstrated that although S. patens is less efficient in accreting sand than A. breviligulata and U. paniculata, it, too, functions as a dune builder, contrary to previous thought [38,39].…”

Sediment availability provokes a shift from Brownian to Lévy‐like clonal expansion in a dune building grass

“…Previous studies have demonstrated that the engineering ability of species can be related to its species‐specific expansion strategy (Hacker et al ., 2012; Bouma et al ., 2013; Schwarz et al ., 2018; Mullins et al ., 2019; Reijers et al ., 2019b). However, so far in the field of ecosystem‐engineering and biogeomorphology, engineering traits have been mostly considered as invariant properties of species, even though intraspecific variability and environment‐dependent trait expression can have far‐reaching consequences for ecosystem dynamics and functioning (Hughes & Stachowicz 2004, de Battisti et al 2020).…”