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Space for dunes is often limited in developed areas, placing increased importance on human efforts to aid dune-building. This study assesses how different management strategies influence dune topography, surface cover and below ground biomass of vegetation on four dune segments in New Jersey in two successive years. Two segments are evolving without human actions, one with a cover of native vegetation ( Ammophila breviligulata ) and one with an invasive exotic ( Carex kobomugi ). Two segments are in developed areas and are maintained using sand fences, vegetation plantings and bulldozers; one of these segments uses bulldozers to bury a seawall. The foredunes evolving naturally are wider than foredunes in the developed segments and have more topographic variability alongshore. Foredunes in the developed segments are narrower because sand blown or washed landward is recycled. The naturally evolving A. breviligulata dune segment had the sparsest vegetation cover; the segment maintained mainly by sand fences and vegetation plantings had the densest cover. The crest of developed dunes can be higher than the crest of natural dunes with the same vegetation type and similar beach widths, but sediment volume may be restricted if the dune cannot migrate inland. Planting programs hasten dune accretion and are especially valuable on the dune ramp following wave erosion. Species dependent on mobile dunes can be favored where landward infrastructure is not threatened; species dependent on stable dunes can be favored in developed areas. Dune veneers placed over seawalls are temporary, but seawalls can favor evolution of stable-dune species landward of them.

Vegetation is an important feature of coastal dunes and is often managed to stabilize restored dunes and provide coastal protection. Despite a high investment in planting and management efforts, little is known about how vegetation is affected by wind and wave run-up. The objectives of this study were to 1) investigate the lift forces and drag moments experienced by coastal dune vegetation from wind and wave run-up and 2) relate them to flow properties and plant morphology. Panicum amarum, Ammophila breviligulata, A. arenaria and Cakile maritima were subjected to laboratory wind and wave run-up conditions. Measurements were taken of fluid velocity, run-up depth, Reynolds number, and plant biophysical properties. The plant lift and drag responses were recorded with the use of a novel sensor designed to address the complexities induced by the flexibility and morphology of real vegetation under varying conditions. Regression analysis was used to describe the relationships between plant response and plant structure and flow properties. Experiments showed that wind induced a constant lift force and drag moment on plants over time, whereas run-up induced plant response was time-dependent. Plant height (R2 = 0.64, p

As the land-sea interface, foredunes buffer upland habitats with plants acting as ecosystem engineers shaping topography, and thereby affecting storm response and recovery. However, many ecogeomorphic feedbacks in coastal foredune formation and recovery remain uncertain in this dynamic environment. We carried out a series of wind tunnel experiments testing how the morphology, density, and configuration of three foredune pioneer dune building plant species influence the most basic stage of dune initiation — nebkha formation around individual plants. We established monocultures of native Ammophila breviligulata and Panicum amarum and invasive Carex kobomugi in 1 m × 1 m planter boxes of sand to simulate approximate natural and managed densities and planting configurations on the US Mid-Atlantic coast. We subjected each box to constant 8.25 m/s wind for 30 min in a moveable-bed unilateral-flow wind tunnel with an unvegetated upwind sand bed. We quantified resulting topography with sub-millimeter precision and related it to plant morphology, density, and configuration. Plant morphology, density, and configuration all influenced the resulting topography. Larger plants produced larger nebkha with greater relief, height, and sand volume. However, nebkha area, height, and planform shape varied among species, and taller plants did not necessarily produce taller nebkha. The erect grasses, Ammophila and Panicum, produced more elongated, high-relief nebkha compared to the low-lying Carex, which produced lower and more symmetrical equant nebkha. A staggered planting configuration produced greater net sediment accumulation than non-staggered. We validated these results against high-resolution field topographies of foredune nebkha and found strong agreement between the datasets. Our results provide species-specific parameters useful in designing foredune plantings and beach management and can be used to parameterize vegetation in models of foredune evolution associated with different plant species. By first understanding the underlying ecogeomorphic feedbacks involved in nebkha formation, we can more effectively scale up to forecast coastal foredune evolution and recovery.

Coastal regions are inherently and increasingly vulnerable and geomorphologically unstable, yet are invaluable economic and residential hubs. Dunes are dynamic buffers to erosion and the most natural, economical, and effective defense for coastal communities. Vegetation is integral to dune structure as it facilitates accretion and stabilization. Differences in the vegetation and root density likely translate to variability in coastal erosion prevention, but this notion has been largely unconsidered. We directly compared stabilizing factors, depth and density, of the root systems of two dominant mid-Atlantic dune plant species, native American beach grass (Ammophila breviligulata) and invasive Asiatic sand sedge (Carex kobomugi). Despite high plant density, C. kobomugi is targeted for removal in restoration efforts as its roots are assumed to provide less effective stabilization than A. breviligulata. We collected 30 cores and hand dug 14 A. breviligulata ramets at Island Beach State Park, New Jersey to examine biomass, root:shoot ratios, and root density. C. kobomugi had a more extensive root system with a root:shoot ratio of 11.36:1 compared to 1.62:1 for A. breviligulata. Similarly, cores 60 cm deep and 7.6 cm wide were sufficient to attain fully intact A. breviligulata roots, which did not extend deeper than 40 cm, but insufficient for C. kobomugi roots which extended beyond the sampling system vertically and horizontally. Scaling these findings to m−2, aboveground biomass is relatively equal, but C. kobomugi had over 700% more root mass m−2 than A. breviligulata. These results have strong implications for dune management. The root system of C. kobomugi may be better adapted to stabilize dunes and thus protect coastal areas during small and large-scale perturbations than previously supposed. This is a unique situation whereby the creation of monocultures will hyperstabilize dunes and make them more resistant to erosion at the cost of reduced biodiversity within the framework of resiliency.

Non-native plant species can alter soil communities, which can lead to changes in their ecosystem functioning and facilitate invasive plant spread. In this study, we asked whether abundance, composition, or function of free-living soil nematode communities differed in association with two dune building grass species in US Pacific Northwest coastal dunes. In 2016, we surveyed soil nematode communities along foredune profiles at six sites in Oregon and Washington, USA, where the non-native beach grass Ammophila breviligulata co-occurred with the native dune grass Elymus mollis. We also measured plant-associated factors that might influence nematode communities, including plant tissue nitrogen, arbuscular mycorrhizal associations, litter production, and plant community diversity associated with the two grass species across the foredune profile. Elymus mollis plots had over twice as many nematodes on average as A. breviligulata plots and were also associated with a higher nematode enrichment index, especially on dune heels. This is possibly explained by higher percent leaf nitrogen content in E. mollis. Subtle differences in nematode community composition and plant tissue nitrogen between the two grass species indicate that A. breviligulata may be altering nutrient cycling across the dune profile, which could explain the arrested succession associated with this species on back dunes. However, overall, nematode communities shifted more in response to foredune cross-shore position and stabilization as opposed to changes in vegetation.

Ecomorphodynamic feedbacks play an important role in the susceptibility and response of barrier islands to disturbance by overwash. Dune-building grasses, like Ammophila breviligulata , can help to restore areas of high relief after overwash events (i.e., resist disturbance). If overwash recurs before dunes have reestablished, however, overwash-adapted “maintainer” species, like Spartina patens (upright variety), may preferentially survive. Maintainer species help to preserve low, flat topography, thereby increasing the likelihood of future overwash (i.e., reinforcing disturbance). Under frequent disturbance conditions, this positive feedback may lead to overwash persistence. We explore the potential influence of the maintainer feedback on two morphologically distinct barrier islands in the Virginia Coast Reserve (VCR), located in the Mid-Atlantic Bight of the U.S. East Coast. Combined topographic and vegetation surveys show that on Hog Island (high-relief, rotating), where dunes dominated by A. breviligulata are ubiquitous, overwash zones are currently limited in extent and related to beach width rather than dominance by S. patens . Historical aerial photos and stratigraphic evidence (ground-penetrating radar, cores) indicate that gradual recovery has taken place following overwash events on Hog Island, except where the beach is narrow and eroding. Conversely, on Metompkin Island (low-relief, transgressing), overwash is widespread and dominated by S. patens , particularly along the rapidly migrating northern half of the island, where shell armoring is also common. Overwash has generally been more prevalent and persistent here than on Hog Island. We present a new conceptual model of the response of barrier islands to disturbance incorporating ecological and physical processes. Our findings suggest that in barrier systems where both dune-building grasses and overwash-adapted maintainer species are common (like the VCR), the maintainer feedback is likely to be a more important dynamic on islands already susceptible to frequent disturbance because of physical factors. The maintainer feedback, therefore, has the potential to accelerate large-scale shifts from dune-dominated to overwash-dominated barrier morphologies as the effects of climate change (increased storm intensity, sea level rise) cause overwash to become more frequent.

Time-averaged windspeed profiles at eight locations over a relatively high (8 m), vegetated, topographically simple foredune were measured using cup and ultrasonic anemometry during an onshore wind event in May 2002. The experiment was part of a largerstudyonthesedimentarydynamicsofabeach–dunecomplexintheGreenwichDunes,PrinceEdwardIsland(PEI),Canada. The foredune is vegetated with Ammophila breviligulata, and vegetation density ranged from 0% on the foredune ramp to upward of 70% at the dune crest. Topographic forcing and resulting flow acceleration was observed distinctly in windspeed profiles, and linear speedup occurred for all elevations above the vegetation canopy. A distinct inflection point is evident in normalized windspeed profiles over the dune indicating a net momentum sink below the vegetation canopy top, and systematic speed-down within the vegetation was observed up the foredune stoss slope. Wind speed profile structure was consistent for the range of incident wind speeds measured. A comparison of normal and slightly oblique incident winds indicated that for similar approach winds, wind speeds are consistently higher during oblique flow conditions. The implications for foredune morphodynamics and sedimentation are discussed. D 2004 Elsevier B.V. All rights reserved.

The ability of several sand dune-inhabiting plant species to successfully colonize dune sites appears to depend upon the presence in the soil of arbuscular mycorrhizal fungi (AMF) that form mutualistic associations with roots. Dune sites barren of vegetation lack these fungi whose large spores are not readily dispersed to the root zones. Despite the absence of these beneficial fungi from barren sites, however, plantings made in AMF-free dune soils eventually form the mycorrhizal association. Examination of planting stock of several species of plants that are used to vegetate barren sand dunes and dune flats of the eastern seaboard of the U.S.A. revealed that AMF were routinely present in the planting materials prior to outplanting. AMF occurred in planting stock of seven varieties of Ammophila breviligulata , and in Prunus maritima , Rosa rugosa , and Spartina patens , but were absent from Myrica pensylvanica . In a field planting in a previously barren deflation zone in the large parabolic dunes of Cape Cod National Seashore, Massachusetts, culms of A. breviligulata that were inoculated with native species of AMF produced more tillers and inflorescences than did non-inoculated plants, even though 78% of the latter had become mycorrhizal 47 weeks after planting. In greenhouse experiments, P. maritima was found to have an absolute requirement for AMF and Solidago sempervirens was not. The significance of the presence of AMF in planting stock for revegetation and restoration of previously unvegetated sites lacking in AMF is discussed.

The vertical growth of shoots of the seagrass Thalassia testudinum Banks ex Konig in four meadows, along a range of exposure to waves, in the Mexican Caribbean was examined to elucidate its magnitude and its relationship to sediment dynamics. Average internodal length varied between 0.17 and 12.75 mm, and was greatest in the meadow which experienced the greatest burial by sand waves moved by Hurricane Gilbert (September 1988). Internodal length showed annual cycles, confirmed by the flower scars always preceding or coinciding with the annual minimum internodal length. These annual cycles on the shoot allowed estimation of annual leaf production, which varied, on average, between 14.2 and 19.3 leaves per shoot year-1. High vertical shoot growth was associated with long internodes and high leaf production rate, which increased with increasing vertical shoot growth to a maximum of approximately 25 leaves per shoot year-1, with vertical growth of about 30 mm year-1 or more. Average internodal length showed substantial interannual differences from perturbations derived from the passage of Hurricane Gilbert. The growth response of the plants surviving moderate burial and erosion after the hurricane involved enhanced vertical growth and increased leaf production, and reduced vertical growth, respectively, after 1988. The variability in shoot vertical growth of T testudinum can be separated into seasonal changes in plant growth, and long-term variability associated with episodic perturbations involving sediment redistribution by hurricanes.

In order to develop a model of the spatial dispersion of populations of vesicular-arbuscular mycorrhizal fungal (VAMF) spores within a root zone, we hypothesized that their spatial pattern would be correlated with the below-ground architecture (growth and structure) of the root system. Detailed excavation and mapping of the roots within the vicinity of three clusters of Ammophila breviligulata ramets (culms) revealed a network of rhizomes, many of which were not connected to the original plant. The species richness of VAMF for the three plots ranged from six to nine, including five genera. A high degree of spore clumping was not significantly correlated with the location of roots, nor with any of the physical soil parameters tested, or with the abundance of spores in adjacent sampling areas. The abundance of spores at a particular location in the soil generally was not a good predictor of spore populations only 10 cm distant. Since such spores are not readily dispersed from the point of sporulation, it is likely that some spore aggregations formed previously in association with fibrous roots that have subsequently decayed and are no longer detectable in the soil profile.

Long-term human trampling on coastal dune vegetation was analysed using eight 100 × 100 m study areas ranging in trampling intensity from little or no past trampling pressure to severe trampling pressure. All trampling levels significantly reduced species diversity. Total vegetation cover was significantly reduced only in areas with severe and heavy trampling pressure. Where long-term moderate trampling did not affect total cover, it appears to have favoured Ammophila breviligulata over other more sensitive species. The data suggest that long-term trampling pressure has caused a shift in the horizontal pattern of vegetation, i.e. expanding the width of the foredune plant community, while restricting the interdune community to a narrow strip at the base of the backdune ridge.

We examined the effects of an experimental oiling with natural gas condensate on three plant communities on Sable Island, a sandy, temperate island located 160 km east of Nova Scotia in the Atlantic Ocean. The plant communities were: (i) a dune grassland dominated by Ammophila breviligulata ; (ii) a herbaceous beach community dominated by Honckenya peploides ; and (iii) a heath dominated by Empetrum nigrum, Myrica pensylvanica, Rosa virginiana , and Vaccinium angustifolium . The experimental treatments were: (i) control; (ii) sprayed with 6·3 litres of condensate/25 m 2 and (iii) sprayed with 12·5 litres/25 m 2 . Initially, in all three communities there was a severe herbicidal effect on most above-ground plant tissues that were directly impacted by the condensate. However, below-ground perennating tissues were little affected by the hydrocarbon treatment, and the vigorous regeneration that issued from these tissues allowed an essentially complete recovery of most species after one or two post-spill growing seasons.

Ammophila breviligulata is the most common grass stabilising dunes north of Cape Hatteras on the eastern shore of the United States. Various levels and types of pedestrian traffic were tested to determine their effects on the standing crop of A. breviligulata . Levels of use as low as 200 shod passages in 45 days significantly reduced plant mass. The results of these tests are used to develop both formulae for predicting visitor impact and recommendation for controlling it.

There is speculation concerning the origin of the large foredunes on Fire Island National Seashore, New York. A number of sedimentological techniques were employed to address this question. Samples were taken from the dune top, dune base (of unknown origin), and mid-tide beach area at 30 locations along the seashore for comparison purposes. Cumulative weight percentages for each sample were calculated and plotted on probability paper. The majority of unknown sands have one saltation population, like the dune sands, whereas beach sands characteristically have two saltation populations with a break at or around 2 φ. Statistics show clear separation of the two (aeolian and hydraulic) environments. In all cases, the unknown sands group together with the dune sands, leaving beach sands clearly separate. Linear discriminant analysis and the Mahanalobis D 2 statistic proved to be conclusive techniques, clearly placing the unknown sands in the dune environment. Heavy/light mineral ratios were compared, indicating that dune and unknown sands are of the same origin. Roundness counts were made, but no statistically significant difference in roundness values was found between the environments. Grain surface textures were studied by the S.E.M. in an attempt to establish distinctive surface feature differences. A definite qualitative difference is observed, but this is not substantiated quantitatively. Structural analysis of the dunes proved to be of little significance because few cross-beds and only a small number of sand ripples were found. Where measured, small ripple numbers indicate an aeolian origin for the foredunes. Finally, inferences were made concerning the aeolian nature of the foredunes from a study of Ammophila breviligulata rhizomes and buried tire tracks.

Five species of Gigaspora were found in association with roots of Ammophila breviligulata in the Cape Cod dunes. Comparison is made with previous findings in Rhode Island dunes.