Interdunal Swales Research Articles

Evolution of a coastal transgressive dunefield to a parabolic dunefield, Canunda dunes, South Australia

Various studies have detailed the evolution of barchan dunes to parabolic dunes and a very few studies describe the evolution of coastal transgressive dunefields and continental sand seas to parabolic dunefields. This study examines the evolution and transformation of a 12 km long portion of a formerly large (~50 km along-coast), active, transgressive dunefield (coastal sand sea or erg) dominated by transverse dunes to a coastal barrier dominated by parabolic dunes. A GIS study of vegetation cover change from 1950 to 2017 was conducted, and a stereographic analyses of 1945 to 2020 aerial photography was carried out to determine morphological changes across the dune system. Historical rainfall, aeolian drift potentials, and rabbit numbers are examined as possible drivers of change, and rabbit numbers most strongly correlate with vegetation change. The vegetation cover of the greater dunefield increased in the study area from 26 % cover in 1950 to 54 % by 2020. A largely unvegetated transgressive dunefield dominated by transverse dunes evolved into a parabolic dunefield in <70 years. Vegetation colonisation primarily took place from landward slipfaces, by nebkha formation on dune lobe crests, from interdune swales and flats, and within deflation basins and plains. Vegetation colonisation also occurred above the backshore in the same period. Aeolian landform units such as marginal ridges, nebkha fields, deflation basins and plains, dune ridges, remnant knobs, parabolic dunes, and a foredune-blowout complex were formed as the dune field was colonised and stabilised by vegetation growth. The study provides far greater detail on how vegetational and morphological changes take place as a transgressive dunefield evolves into a parabolic dunefield.

Distribution, abundance, and ecology of the threatened Gibson’s Big Sand Tiger Beetle (Cicindela formosa gibsoni Brown) in the Elbow Sand Hills of Saskatchewan

Gibson’s Big Sand tiger beetle, Cicindela formosa gibsoni Brown, occurs primarily in the Saskatchewan sand hills and was recently listed as threatened in Canada due to habitat loss caused by dune stabilization. Herein, we report on a 3-year population study initiated in 2016 to better understand the distribution, abundance, and ecology of C. f. gibsoni in the Elbow Sand Hills, a large active dune complex in southern Saskatchewan. Estimated adult population size for the dune complex varied from a low of 1106 (95% confidence interval (CI) 975–1237) to a high of 1474 (CI 1350–1598), possibly due to inter-annual variation in May–June rainfall. Adult abundance varied substantially between interdunal swales (0–137 individuals), with the highest numbers occurring in sparsely-vegetated habitats on the stoss side of the dune complex where the rate of encroachment by vegetation is highest. Approximately a third of the total population is concentrated within a relatively small area (~ 6 ha) in the northwestern region of the dune complex, although the specific cause for this localized distribution is not clear. Our findings suggest that the distribution of C. f. gibsoni within the dune complex is not limited by prey availability or larval habitat quality but is instead related to the amount of sparsely-vegetated habitat. We hypothesize that sparsely-vegetated areas allow beetles to shuttle between exposed and shaded microhabitats, thereby assisting in thermoregulation and maintenance of high body temperatures that are optimal for foraging.

Bitter Panicgrass, Bitter Panicum, Panicum amarum

Bitter panicgrass is important in dune stabilization and building and often grows intermixed with sea oats onforedunes. It is also found spread throughout back dunes, interdunal swales, and coastal grasslands. This plantoccurs throughout coastal Florida, except for the Big Bend coast, west to New Mexico, and along coastal northeast states to Massachusetts. A significant proportion of bitter panicgrass reproduction is by vegetative spread; its seeds are often sterile.https://edis.ifas.ufl.edu/sg178&#x0D; This publication is derived from information in SGEB-75/SG156, Dune Restoration and Enhancement for the Florida Panhandle, by Debbie Miller, Mack Thetford, Christina Verlinde, Gabriel Campbell, and Ashlynn Smith. https://edis.ifas.ufl.edu/sg156.

Geochemical investigation of the South Wellesley Island wetlands: Insight into wetland development during the Holocene in tropical northern Australia

The South Wellesley Islands in the Gulf of Carpentaria, northern Australia, were the recent focus of a palynological investigation which found vegetation change during the Holocene was driven by coastal progradation and regional climate. Here, we present new elemental data from x-ray fluorescence core scanning which provides non-destructive, continuous and high resolution analysis from three wetlands across Bentinck Island, the largest of the South Wellesley Islands. Elemental data and grain size analyses are combined with lead-210 (210Pb) and accelerator mass spectrometry (AMS) carbon-14 (14C) dates. An open coastal environment was present 1250 cal. a BP on the south east coast of Bentinck Island, with sediment supply incorporating fluvial deposition and detrital input of titanium and iron from eroding lateritic bedrock. Prograding shorelines, dune development and river diversion formed a series of swales parallel to the coast by ~800 cal. a BP, forming the Marralda wetlands. Wetlands developed at sites on the north and west coasts ~500 and ~450 cal. a BP, respectively. Geochemical and grain size analyses indicate that wetlands formed as accreting tidal mudflats or within inter-dune swales that intercepted groundwater draining to the coastal margins. The timing of wetland initiation indicates localised late-Holocene sea level regression, stabilisation and coastal plain development in the Gulf of Carpentaria. Elemental data provide new records of wetland development across Bentinck Island, highlighting the value of a multi-proxy approach to understanding environmental change during the Holocene in tropical northern Australia.

Microsite and rooting depth are more important than water-holding gel for establishment of restoration plantings of Ilex vomitoria on barrier islands in the Gulf of Mexico

Restoration of woody plants to barrier islands requires development of production and outplanting protocols as well as determination of “safe sites” for reestablishment. Yaupon ( Ilex vomitoria Aiton [Aquifoliaceae]) is a shrub associated with scrub dunes and shallow, interdunal swales of barrier islands along the northern Gulf Coast. We studied the effect of microsite (lowest point of the depression within interdunal swale versus low dune ridge around swale), rooting depth (production container depth), and absorbing gel on seedling survival and subsequent growth of I. vomitoria planted at 5 sites associated with barrier island swales of Santa Rosa Island, Florida. Survival of I. vomitoria was greater in depressions than on ridges and with greater rooting depths. Survival on ridges did not improve with addition of hydrogel but survival for standard pots was increased in depressions. When outplanted in depressions with gel, plant height increased by as much as 6 cm (2.4 in) compared to all other out-planting combinations. Plants on ridges were half the height of plants in depressions in 2006 but no differences were found in 2007. Plants grown in Treepots were more than twice as tall as plants grown in round containers in 2006 but did not differ in 2007. Plants had greater canopy area in depressions than on ridges and with greater rooting depth. For establishment and growth on barrier islands, I. vomitoria should be grown in pots 35 cm (14 in) deep (for example, Treepots) and planted in centers of shallow swales.

Hydric Soil Field Indicators for Use in Mid-Atlantic Barrier Island Landscapes

Hydric soils in Holocene-aged barrier island landscapes in the Mid-Atlantic region of North America lack morphologies typically associated with saturated and reducing conditions. Furthermore, many better drained (nonhydric) soils have low chroma colors due to parent material effects, making identification and delineation of wetlands problematic. Our objective was to develop field indicators that could be used to effectively recognize hydric soils in these environments. Soils along 10 topographic transects were evaluated at Assateague Island National Seashore, Maryland. Transects spanned a gradient of topographic positions from dune crests to interdunal swales. Water tables and reducing conditions were monitored to determine hydric status. Soil descriptions along each transect were used to identify morphological features indicative of soil wetness. Of 16 monitored and documented hydric soils, only five met recognized field indicators. Hydric soils were best identified by the presence of matrix colors with chromas less than 2 in mineral soils or the presence of at least 1 cm of muck (Oa horizon). On the basis these characteristics, we propose two new indicators restricted for use in Holocene-aged barrier island landscapes in the Mid-Atlantic region. These indicators will allow identification of hydric soils, improving the accuracy and ease of delineation of wetlands.

Hydrology in a patterned landscape is co-engineered by soil-disturbing animals and biological crusts

Water redistribution has a profound influence on dryland ecosystem function. This hydrological function is largely regulated by ecosystem engineers including biological soil crusts (biocrusts) which produce run-off, and burrowing animals, such as the greater bilby, whose pits capture water. We estimated the relative importance of these two ecosystem engineers in determining infiltration rates in a system where dune slopes shed water to adjacent interdune swales to maximize overall productivity. Also, we determined which biocrust property was most hydrologically important: total cover, composition, patch aggregation or spatial heterogeneity. While both biocrusts and burrowing animals equally affected the overall infiltration through macro- and micropores (under ponding), only biocrusts were important for the infiltration specifically via micropores (under tension). Of the studied biocrust properties, community composition was the strongest influence such that the greater the prevalence of early successional biocrust patches, the greater the infiltration rate. Greater total cover of biocrusts reduced infiltration, and the spatial properties were relatively unimportant. Although bilbies and biocrusts comparably influenced infiltration under ponding at the microscale, realistic cover of bilby pits at the landscape scale is unlikely to strongly impair the hydrological function of dunes. Reintroduction of the endangered bilby may enhance nutrient cycling and plant recruitment via its seed and resource capturing pits, without a concomitant disruption of hydrological function. In contrast, removal of biocrusts caused by, e.g., livestock trampling, is expected to strongly enhance infiltration in the run-off areas, strongly reducing ecosystem productivity at the landscape scale.

Rediscovery and Habitat Associations of Photuris Bethaniensis McDermott (Coleoptera: Lampyridae)

Photuris bethaniensis McDermott, 1953, is recorded only from Sussex County, Delaware, from the original species description. In 1998 we relocated P. bethaniensis near the type locality. From 1998 through 2000, Photuris bethaniensis was found exclusively within freshwater interdunal swales occurring within Delaware's backdune depressions. The species was discovered in 7 of 18 swales surveyed within a 25-km stretch of Atlantic shoreline. Photuris bethaniensis was most common in swales with dense shrub thickets. The temporal stability of freshwater interdunal swales may be an important factor influencing the distribution of this species.

The activity of Sand Goannas Varanus gouldii and their interaction with reintroduced Greater Stick-nest Rats Leporillus conditor

The activity pattern of the Sand Goanna Varanus gouldii in northern South Australia was estimated by radio telemetryduring the summer months. Individuals were located within the Arid Recovery Reserve where introduced European Rabbits Oryctolagus cunniculus, Feral Cats Felis catus and European Foxes Vulpes vulpes were removed. Interaction between the re-introduced Greater Stick-nest Rat Leporillus conditor and the Sand Goanna, a potential significant predator in the absence of cats and foxes, was examined. Mean activity area for Sand Goannas was 5.9 ha (�1.0, n = 9), and their summer activity was concentrated on sand dunes rather than the adjacent inter-dunal swales. Tracks of Sand Goannas were found more often around Greater Stick-nest Rat nests than control sites. However, Sand Goanna predation on re-introduced Greater Stick-nest Rats could not be confirmed and most deaths of radio-collared Greater Stick-nest Rats coincided with a period of exceptionally high maximum temperatures and were probably due to heat and dehydration. Sand Goannas scavenged Greater Stick-nest Rat carcasses, and analysis of scats and stomach material revealed that although invertebrates were the most common prey item, mammal material (hair and bones) was present in 20% of scats.

Microhabitat Segregation of Two Utah Sand Dune Tiger Beetles (Coleoptera: Cicindelidae)

The Coral Pink Sand Dunes tiger beetle (Cicindela limbata albissima) exists only within the Coral Pink Sand Dunes in southwestern Utah. It is currently a candidate for listing as an endangered species. Cicindela tranquebarica occurs throughout the southwestern United States, including the Coral Pink Sand Dunes. We examined microhabitat differences between C. l. albissima and C. tranquebarica. Results of June 1999 adult counts and measurements of percent soil moisture and salt content in 53 interdune swales indicated a significant negative correlation between soil moisture and an index of the relative number of adult C. l. albissima to C. tranquebarica, and a significant positive correlation between soil moisture and direct counts of adult C. tranquebarica. The index of relative number of adults of the 2 species was unrelated to salt content. The relative ratio of larvae of the 2 species in a given swale was significantly correlated to the relative ratio of adults of the 2 species. The cause of the observed microhabitat differences for relatively moist or dry soil could be due to a number of as yet unstudied factors including oviposition preference by the females and larval competition.

Species Distributions in Interdunal Swale Communities: The Effects of Soil Waterlogging

The influence of soil waterlogging in determining plant species distributions among interdunal swales and between dunes and swales on Cape Cod was investigated employing field and greenhouse experiments. Most species exhibited significant responses to experimental treatments that closely matched their distributions in the field. In general dune species such as Ammophila breviligulata and Solidago sempervirens grew poorly under waterlogged conditions. When transplanted to the dry sand dune all species grew poorly or died. Swale species exhibited a range of responses to waterlogging conditions. Growth of Juncus canadensis, Scirpus pungens and Vaccinium macrocarpon increased with waterlogging. Cyperus dentatus, Juncus pelocarpus and Solidago tenuifolia grew equally well across all waterlogging conditions and are present in most swales. Juncus greenei and Myrica pensylvanica grew best in drier swales and their distributions appear to be restricted to the perimeters of swales.Soil waterlogging is an important determinant of species distributions among swales and between swales and dunes. However, the effect of biotic factors such as competition, seed dispersal, soil seed banks and seedling recruitment needs to be examined as well to show how swale communities change over time.

Pleistocene Calcarenite Lithosomes of Bermuda: ABSTRACT

Bermuda's subaerially exposed limestones consist of eolianites, littoral calcarenite lithosomes, and accretionary soils deposited during Pleistocene high sea levels. The geometry and structure of these deposits were studied to evaluate sea-level fluctuations during Pleistocene high stands, and to provide criteria for recognizing the eolian-marine facies in surface and subsurface rocks of earlier age. Eolianites are dune ridges trending parallel with the present coastline and arranged in decreasing age from the center of the Bermuda islands outward. Eolianites are subdivided into 2 structural lithosomes: foreset wedge and windward-topset wedge. The foreset wedge is characterized by strata steeply inclined (35°) landward and concave and downward. Foreset curvature is used to divide the wedge into a row of adjoining lobate bodies that represent the hillocky coastal dunes from which the dune ridge was constructed. The windward-topset wedge is characterized by complexly festooned cross-stratification in the part and more regular, seaward-dipping, gently inclined (5-15°) cross-stratification near the dune crest. Littoral calcarenites that overlie or are transitional with windward eolianite strata are termed seaward shore whereas those that onlap foresets are called inland shore. Seaward-shore calcarenites are subdivided into (1) depositional coastline deposits that represent beaches fed by reef-derived detritus, and (2) erosional coastline deposits that represent pocket beaches fed by erosion of headlands. The former are wedge-shaped bodies of regular, seaward-dipping, gently inclined cross-strata and interfinger with eolianites. The latter are conglomeratic pods overlain by accretionary soils and found between eolianites. Accretionary soil is unbedded, uncemented, organic-rich calcarenite containing land snails and rhizoconcretions. The soil records invasion of vegetation and land crabs onto freshly deposited calcarenite. Environments of soil development include the supralittoral of pocket beaches, interdune swales, and the slopes of inactive, unlithified dune trains. Analysis of the carbonate eolian-marine facies in Pleistocene and older rocks can provide data necessary to interpretation on a worldwide basis of (1) sea-level End_Page 873------------------------------ fluctuations, (2) shoreline position and physiography, (3) paleowinds and paleoclimates, and (4) sediment sources. End_of_Article - Last_Page 874------------