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Riverbed topography in natural rivers commonly features sand dunes, whose morphological variations can alter the turbulent flow structure near the bed and thereby affect processes of channel scour, deposition, and sediment transport. In this study, a series of flume experiments was conducted using an acoustic Doppler velocimeter (ADV) to simulate fixed bedforms of different dune scales (ratio of wavelength to flow depth, λ/h) in a laboratory flume. Velocity measurements were taken along the water depth at the dune crest and trough for each test case. The near-bed distributions of mean flow velocity, Reynolds stress, turbulent kinetic energy (TKE), and turbulence intensity were obtained at the crest and trough under three flow conditions, allowing analysis of the vertical decay of turbulence intensity at different locations on the dune. The results show that the dune steepness (Ψ, defined as dune height over wavelength) is a key parameter controlling the near-bed flow structure. As Ψ increases, the near-bed velocity gradient, Reynolds stress, TKE, and peak turbulence intensity all increase significantly, with the peak positions shifting closer to the bed. The trough region, due to flow separation and vortex shedding, exhibits substantially higher values of all turbulence-related parameters than the crest, making it the primary zone of energy dissipation and turbulence production. This study provides experimental evidence and theoretical reference for understanding the mechanism by which sand dune morphology influences flow structure, and it offers insight for predicting riverbed evolution.

The Athabasca sand dunes in northern Saskatchewan and north‐east Alberta are a unique landscape of moving sand that hosts nine narrowly distributed endemic vascular plant taxa. We modeled the extent of habitat for each species, corresponding dune morphologies in species habitat, spatial and temporal variation in dune environments, and rates of woody vegetation encroachment at dune boundaries to support an assessment of long‐term threats for the Athabasca endemic dune flora. Landsat images were used to maximize the time spans and areal coverage of the study. The Athabasca sand dunes are currently active and characterized morphologically by crescentic ridge and morphodynamically by transverse form dunes. Longitudinal sand movement parallel to the dune axis resulted in the creation of new dune areas along the east and south‐east boundaries of the dune fields at a rate of 0.14 km2 year−1. Forest succession along the western boundaries of the dune fields resulted at an annual dune loss of 1.98 km2 year−1. The net extent of dune stabilization between 1985 and 2014 was 53.76 km2 or nearly 20 percent of the total open sand dune extent. All habitat modeling methods showed robust performance (>0.5 AUC), with the best performance in most cases from generalized linear models. Estimated total available/occupied habitat was comparatively low for the least abundant species Achillea millefolium (38.92 km2) and Armeria maritima (48.82 km2), and of those areas 53.5% and 16.29%, respectively, are influenced by dune stabilization. Continuing stabilization of the Athabasca sand dunes region may present conservation concerns for these narrowly distributed endemic taxa. This paper addresses the conservation concern of nine narrowly distributed endemic vascular plant taxa in the Athabasca Sand Dunes, Saskatchewan, Canada. We evaluated the extent of critical habitat for each species, dune morphologies, long‐term dune environment spatio‐temporal variation and rates of woody vegetation encroachment at dune boundaries to support a long‐term threats assessment for the Athabasca endemic flora. Remote sensing and GIS were key aspects of the study and Landsat images were used to maximize the time spans and areal coverage of the study. By estimating the distribution of the rare endemic taxa, we were able to show that a large proportion of the area of occupancy of some species is influenced by dune stabilization. Continuing stabilization of the Athabasca sand dunes region may present conservation concern for these narrowly distributed endemic taxa.

Coastal ecosystems such as mangroves, salt marshes, and seagrasses sequester large amounts of carbon per unit area due to their high productivity and sediment accumulation rates. However, only a handful of studies have examined carbon sequestration in coastal dunes, which are shaped by biophysical feedback between aeolian sediment transport and burial-tolerant vegetation. The goal of this study was to measure carbon storage and identify the factors that influence its variability along the foredunes of the US Outer Banks barrier islands of North Carolina. Specifically, differences in carbon stocks (above- and belowground biomass and sand), dune grass abundance, and sand supply were measured among islands, cross-shore dune profile locations, and dune grass species. Carbon varied among aboveground grass biomass (0.1 ± 0.1 kg C m −2 ), belowground grass biomass (1.1 ± 1.6 kg C m −3 ), and sand (0.9 ± 0.6 kg C m −3 ), with the largest amount in belowground grass stocks. Aboveground grass carbon stocks were comparable to those in eelgrass beds and salt marshes on a per-area basis, while sediment carbon values in our study system were lower than those in other coastal systems, including other dune locations. Additionally, sand carbon density was positively related to patterns in dune sand supply and grass abundance, reflecting a self-reinforcing vegetation-sediment feedback at both high and low sand accumulation rates.

Background Understanding the dynamics of species and functional diversity and their interrelationships during vegetation restoration is essential for assessing the effectiveness of ecosystem restoration. Yet, the mechanistic links between species diversity and functional diversity during vegetation restoration remain uncertain, with community-level functional traits likely mediating this relationship. Methods We studied a chronosequence of Artemisia ordosica -dominated dryland communities, including semi-fixed (D1), fixed (D2), soil-biocrusted fixed (D3), and shrub-herbaceous-fixed sand-dunes (D4). Thirteen leaf functional traits were measured, including leaf tissue density (LTD), and leaf dry matter content (LDMC). Community-weighted mean leaf functional traits (CWM-LFTs) were calculated using importance value-weighted averages. Results Species and functional diversity increased progressively from stages D1 to D4, with the coefficient of variation for CWM-LFTs ranging from 7.71% to 57.27%. Changes in species diversity during sand dune stabilization were linked to a strategy of slow growth and cumulative increases in LTD, LDMC, and leaf carbon content (LCC), improving the community’s physical defense and nutrient retention. Leaf structural traits mirrored diversity patterns, with LDMC most strongly linked to functional evenness, functional divergence and Rao’s quadratic entropy. Conclusions Our results show that both species and functional diversity increased progressively with sand-dune stabilization. The plant community followed a trajectory of increasingly complex strategies, shifting from stress-tolerant traits toward competition-adapted traits in later stages. The LDMC was strongly correlated with both species and functional diversity, serving as a key trait that mediates competitiveness and defense in resource-limited ecosystems. These findings highlight the importance of trait-based assembly in vegetation restoration and offer new insights for desertification control.

McGuirk, M.T.; Kennedy, D.M., and Konlechner, T., 2022. The role of vegetation in incipient dune and foredune development and morphology: A review. Journal of Coastal Research, 38(2), 414–428. Coconut Creek (Florida), ISSN 0749-0208. Vegetation is the principal boundary condition on the coast for foredune development, both by trapping sand and protecting it from erosion. Plants that colonise beaches and dunes grow in a variety of forms and have different life cycles. Plant characteristics (e.g., leaf length, width) are important in the initiation of a dune, and their interaction with sand being transported inland from the beach is highly variable. This review aimed to identify gaps in knowledge regarding the influence of specific plant species on dune morphological processes. Many studies that relate the influence of vegetation on dune morphology are of a descriptive and qualitative nature. These studies record elements of plant architecture and species presence on the dune. Quantitative studies have primarily focused on exotic species growing on the U.S. Pacific Northwest coast, whilst numerical modelling of dune growth incorporating vegetation has parameterised the plant drag coefficients. In these highly numeric investigations, the parameters used are derived from desert vegetation or artificial proxies such as rigid cylinders. Direct measurements derived from dune vegetation are often lacking. Biogeomorphologists and ecological engineers have placed coastal vegetation into a variety of categories related to their growth form and response to abiotic factors. A consensus on the categories for plant functional and engineering groups used for research and planning purposes is necessary, for example, sand stabilisers and sand accumulators. There is an urgent requirement for quantitative data on the growth and sand-capture ability of coastal plants. This is necessary because dune responses to climate change will be a function of their floral communities. In many instances, these floral communities are undergoing rapid change due to exotic invasions, which means that the resilience of the dunes may change faster than climate-driven change.

Mega-dunes in the lake group area of the Badain Jaran Sand Sea, China, are generally taller than dunes in the non-lake group area. This spatial distribution of dune heights may provide a new perspective on the controversy regarding the dunes’ formation mechanism. In this study, we calculated the relative heights and slopes of individual dunes based on a digital elevation model, and we confirmed the height distribution of abnormally tall dunes in the lake group area of the sand sea. It was also found that slopes of more than 10° in the lake group area are more common than those in the non-lake group area. Based on meteorological observations, coupled with the measurement of water content in the sand layers, we propose a conceptual model demonstrating that moisture exchange between the lakes and soil via non-rainfall water will humidify dune slopes and form a more favorable accumulation environment for aeolian sand, thus increasing dune heights. Although long-term observations are yet to be carried out, the present study can be used as evidence for understanding the basis of dune formation in the lake group area and assessing groundwater utilization in deserts.

Fences are commonly used in coastal regions to control wind-blown sand. Sand-trapping fences and sand-stabilizing fences have been installed at the Tottori Sand Dunes, Tottori Prefecture, Japan, to prevent damage by wind-blown sand; however, the effectiveness of these fences has not previously been quantitatively evaluated. This study analyzed the effects of sand fences on sand trapping using field observations of blown-sand flux and unmanned aerial vehicle (UAV) photogrammetry. The estimated total blown-sand flux in the near-ground surface observed inside and outside the sand fences indicated that wind-blown sand was effectively trapped by the sand fences at wind speeds lower than 17 m s−1, reducing sand flux by more than 80%. The UAV photogrammetry results demonstrated that large amounts of sand were transported from the dune to the fenced area during March and April, and sand initially accumulated on the lee side of the sand-trapping fences, forming a new foredune. Sand accumulated on the existing foredune during April and May, and the vertical accretion around the foredune was two to four times the sand deposition within the sand-stabilizing fences. This indicated the effectiveness of sand-trapping fences for controlling wind-blown sand; however, their efficiency was reduced as they were gradually buried, with sand being trapped by the sand-stabilizing fences.

Understanding aeolian sediment transport and wind erosion enhances our knowledge of desert dune formation and sand migration. The Makran region of southern Sistan and Baluchistan is prone to wind-driven erosion alongside frequent sand and dust storms (SDSs). Hourly wind data from two meteorological stations spanning 1994–2020 were analyzed to study erosive winds and sand transport. Wind energy analysis using drift potential (DP) indicated low energy (DP < 200 in vector unit) and minimal spatial variation across the Makran dune fields. The effective winds transporting sand particles were towards the east from November to May, and in the northwestern direction from June to October. The DP showed a gradual decline in the study area from 1990 to 2022, with no significant temporal trends. The sand dune morphology analysis indicates that bimodal wind regimes primarily form linear dunes and sand sheets, while crescentic, transverse, and topographic dunes are also present.

Coastal foredunes form via biophysical feedbacks between sand accretion and burial‐tolerant vegetation and can protect coastlines from hazards such as extreme storms and sea level rise. Predicting how coastal dunes, and the services they provide, will change in the future requires an understanding of the relative roles of the physical and ecological processes that shape their structure and function. Here we assess the relative roles of sand supply, beach morphology, and vegetation in determining foredune morphology, and its change, along a 300‐km stretch of the US Central Atlantic coast. In particular, we used the spatial variability inherent in beaches and dunes of this region to determine the relative importance of shoreline change rate (SCR; a proxy for sand supply to the beach), beach morphology, and grass density of four widespread dune grasses (Uniola paniculata, Ammophila breviligulata, Panicum amarum, and Spartina patens) to foredune morphology metrics (height, width, and aspect ratio) along the North Carolina Outer Banks barrier islands. Foredune morphology and change metrics are correlated with three main factors: multidecadal SCR (1997–2016), beach slope, and dune grass density and species identity. Multidecadal SCR and beach width explained the most variation in, and were positively correlated with, foredune height and width, and were negatively correlated with foredune aspect ratio (height divided by width). In addition, grass density and changes in grass density contributed significantly to foredune morphology change. We found a positive relationship between change in A. breviligulata density and foredune width, which aligns with previous studies on the US Atlantic and Pacific Northwest coasts. Our results demonstrate the interactive roles of beach sand supply and dune grass functional morphology in dune building processes on highly vulnerable coastlines.

The Deliblato Sands is among the largest uniform dune fields of Europe, with a very pronounced topography reflecting extensive past aeolian events. Although lacking numerical age data, previous researchers have hypothesized various periods of dune formation. Our research goals were to map the main morphological units of the Deliblato Sands, and to provide the first optically stimulated luminescence (OSL) ages for the major dune types. Mapping was carried out using digital elevation models, satellite images, and GPS profiles. Dune development was investigated using OSL. Several tests were performed concerning thermal treatment, signal characteristics, dose recovery, and dose distributions to assess the suitability of sediments for luminescence dating. Based on our results, two dune generations could be identified that differed in morphology and age. Older dune forms are primarily low sand-supply, hairpin-like parabolic dunes that developed from the last glacial maximum until the end of the early Holocene, then became stabilized. Younger, superimposed parabolic dunes record an intensive aeolian signal from the eighteenth and nineteenth centuries. The history of the Deliblato Sands fits with those from other European sand dune areas, and provides further details to understand paleoenvironmental changes in the region.