Aeolian Landscape Research Articles

Climate-driven changes to dune activity during the Last Glacial Maximum and deglaciation in the Mu Us dune field, north-central China

One significant change of terrestrial landscapes in response to past climate change has been the transformation between activity and stability of extensively distributed wind-blown sand dunes. The relations between the dynamics of the aeolian landscape and its drivers are not yet completely understood, however. Evidence of aeolian sand deposition during the Last Glacial Maximum (LGM) is scarce in many mid-latitude dune fields, whereas abundant evidence exists for aeolian sand accumulation during the deglaciation, i.e. after about 15 ka. Whether this contrast actually reflects changes in dune activity is still unclear, making paleoclimatic interpretation uncertain. Comprehensive field investigation and luminescence dating in the Mu Us dune field, north-central China, demonstrates that aeolian sands deposited during the LGM are preserved as fills in periglacial sand wedges and beneath loess deposits near the downwind dune field margin. The scarcity of LGM dune sand elsewhere in the dune field is interpreted as the result of intensive aeolian activity without substantial net sand accumulation. Increasing sand accumulation after 15 ka, reflected by much more extensive preservation, signals a change in sand supply relative to sand transportation through the dune field. Reduced wind strength and other environmental changes including regional permafrost degradation after 15 ka transformed the dune field state from net erosion to net accumulation; the dunes, however, remained largely mobile as they were in the LGM. Similar diverging patterns of dune sand accumulation and preservation before and after 15 ka in many mid-latitude dune fields imply broad climatic controls linked to the changes in high-northern-latitude forcing.

Characterizing instability of aeolian environments using analytical reasoning

AbstractThis short communication describes the development and application of analytical reasoning to quantify instability of an aeolian environment using scale‐dependent information coupled with conceptual knowledge of process and feedback mechanisms. Specifically, a simple Fuzzy Cognitive Map (FCM) for aeolian landscape instability was developed that represents conceptual knowledge of key biophysical processes and feedbacks. Model inputs include satellite‐derived surface biophysical and geomorphometric parameters. FCMs are a knowledge‐based artificial intelligence (AI) technique that merges fuzzy logic and neural computing in which knowledge or concepts are structured as a web of relationships that is similar to both human reasoning and the human decision‐making process. Given simple process–form relationships, the analytical reasoning model is able to map the influence of land management practices and the geomorphology of the inherited surface on aeolian instability within the South Texas Sand Sheet. Results suggest that FCMs can be used to formalize process–form relationships and information integration analogous to human cognition with future iterations accounting for the spatial interactions and temporal lags across the sand sheets. Copyright © 2014 John Wiley & Sons, Ltd.

CONTEMPORARY CHANGES OF THE CLIMATIC CONDITIONS OF THE CASPIAN SEMI-DESERT LANDSCAPES OF THE EASTERN CISCAUCASIA

The article analyzes the changes in the hydrothermal conditions within the pricaspian littoral plains accumulation and denudation-accumulative in places aeolian landscapes saltwort, saltwort-sagebrush deserts and semi-deserts in light chestnut soils based on data from weather stations "Makhachkala" for years 1945-2005.Tendencies of changes in temperature, precipitation, and hydrothermal coefficient and coefficient of moisture are shown. Tendency of modern fluctuations suggests that the climatic conditions of the last period contribute to the development of dry steppes and significant deviations from the conditions of the previous period do not occur.

Late Holocene temporal constraints for human occupation levels at the Bodo archaeological locality, east-central Alberta, Canada using radiocarbon and luminescence chronologies

The Bodo Archaeological Locality in east-central Alberta is one of the largest precontact (prehistoric) archaeological sites in the Canadian Prairie Ecozone. Situated at the transition between the aspen parkland and fescue grassland regions within a postglacial eolian dune landscape, the site has the potential to add to existing understandings of cultural–environmental dynamics as they relate to late Holocene hunter-gatherer settlement and subsistence patterns in the region. To that end, we present a composite stratigraphy for the locality constructed from five separate sampling pits, obtaining chronological control using accelerator mass spectrometry radiocarbon and luminescence ages. We identify three main periods of landscape stability and associated human occupation during the late Holocene: 750 to 400 cal B.C., 750 to 1000 cal A.D., and 1450 to 1750 cal A.D. Early Holocene eolian activity is documented, but the mid-Holocene stratigraphic record is absent, suggesting extensive sediment reworking. Evidence also exists of major cultural landscape changes that coincide with the arrival of Euro-Canadians.

Planetary dune analogues: a special issue on integrating models, remote sensing and field data

ABSTRACTThis article reports on the Special Issue of Earth Surface Processes and Landforms dedicated to planetary dune analogues and the advances that have been made through the integration of remote sensing and terrestrial field data to better model and understand aeolian systems. The 11 articles presented demonstrate a spectrum of analytical techniques that are employed to investigate ripples, dunes, draa and ergs across a variety of spatial and temporal scales. Nine of the papers involve innovative research about aeolian bedforms and processes, while the final two papers are examples of how vast quantities of data may be organized and scrutinized using a GIScience approach. Based on these 11 papers and the many abstracts archived in a series of three planetary dunes workshops at the Lunar Planetary Institute (http://www.lpi.usra.edu/publications/abstracts.shtml; LPI Contributions 1403, 1552, and 1673) it is evident that there exists diverse and complementary approaches to the comparative study of landforms and processes for terrestrial and extra‐terrestrial aeolian landscapes that is driven by a vibrant international community of scientists and educators that engage in the cross‐fertilization of ideas. Copyright © 2014 John Wiley & Sons, Ltd.

Turning Human-nature Interaction into 3D Landscape Scenes: An Approach to Communicate Geoarchaeological Research

Within an investigation on the geoarchaeological reconstruction of aeolian landscape development in Northern Germany, three different 3D visualization software products (Autodesk® 3ds Max®, Visual Nature Studiotm2.86, a3Dc) have been applied in order to visualize and, thus, communicate scientific results to the public and the scientific community alike. By using offline and online rendering systems, scientifically sound visualizations are presented on different geographical scales and with varying interactive functionalities. This bridging of geoarchaeological and geovisualization techniques will aid researchers and the broad public to gain a deeper insight into humaninduced changes of landscapes in the past.

A Conceptual Model for Dune Morphodynamics of the Corralejo Dune System, Fuerteventura, Spain.

ABSTRACT Malvarez, G., Jackson, D.W.T., Navas, F., Alonso, I., Hernandez-Calvento, L. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.), Proceedings 12th International Coastal Symposium (Plymouth, England), Journal of Coastal Research, Special Issue No. 65, pp. 1539–1544, ISSN 0749-0208.--> The Corralejo dune system in Fuerteventura in the Canary Islands (Spain) is an aeolian landscape whose genesis and evolution has commonly been associated with a traditional input-output model by which sediments entered from northern beaches and accumulation occurred in the southernmost (land-locked) sections of the dune field. Satellite images as well as aerial photographic evidence over the last 60 years, however, shows that the evolution of the dunes may reflect a more complex scenario in which under current settings and orientation of the coast, a sediment leakage back into the southern coastal environment is occurring. Under these circumstances, longshore currents can then transport this sedime...

Key variables for the identification of soil management classes in the aeolian landscapes of north–west Europe

At present, spatially very detailed data sets can be obtained about soil, landscape and crop variability. However, there is a need to select independent key properties to identify management classes needed for precise land management. In a previous study performed in the European loess belt, topsoil pH, apparent electrical conductivity (ECa) and elevation were identified as key properties. In this study we enlarged the number of soil properties by including gamma ray measurements and employed a similar methodology to a field in the sand belt of northern Europe. Based on a principal component analysis we identified the same three variables as key properties. This was surprising given the big differences in landscape topology and pedogenesis between the loess and sand areas. These three key variables were used to delineate management classes using a fuzzy k-means with extragrade classification procedure. This classification was evaluated by mapping the wheat grain yield in the year 2006. A multiple regression model could be constructed that predicted yield from ECa and elevation well (Radj2=0.88). To analyse the influence of ECa on crop yield in depth a boundary line analysis was conducted. The boundary line could be modelled with an excellent Radj2 of 0.98. It was concluded that ECa, elevation and pH are generic key variables for the delineation of management classes of the aeolian landscapes of north–west Europe. Given its integral nature and strong relationship with crop performances, the authors plea to upgrade ECa from a “secondary” (proxy) source of information to a “primary” variable which can be used directly as a basis for detailed soil mapping of the bulk soil.

Characteristics and dating of Quaternary aeolian landsca-pes in Arabia

Characteristics and dating of Quaternary aeolian landsca-pes in Arabia

Fluvial and aeolian landscape evolution in Hungary – results of the last 20 years research

AbstractPresent study provides a review of the latest results on fluvial and aeolian landscape evolution in Hungary achieved by our team during the last 20 years.– The Hungarian river terrace system and its chronology was described with special emphasise on the novel threshold concept. A revised terrace system was created by the compilation of novel terrace chronology and MIS data. Evolution of river terraces was not only governed by climatic factors but tectonic ones too. Incision rate of the Danube, and uplift rate of the Transdanubian Range (TR) was around 0.1-0.3 mm/a in the marginal zones of the TR (mostly based on the published U-series data) and was above 1 mm/a in its axial zone (based on 3He exposure age dating of strath terraces).– According to a detailed geomorphological investigation of the different channel-planform morphologies in the Middle Tisza region and Sajó-Hernád alluvial fan, six phases of river pattern change and four incision periods were detected during the last 20,000 years.– Wind polished rock surfaces dated by in situ produced cosmogenic 10Be suggest that deflation was active in Hungary as early as 1.5 Ma ago. According to these exposure age data, Pleistocene denudation rate of the study area (Balaton Highland) was 40-80 m/Ma.– In sand covered areas the alternations of wind-blown layers and buried fossil soils provide information about climate and environment changes. In this study, periods of sand movement were mostly determined by optically stimulated luminescence (OSL) dating methods and five aeolian sand accumulation periods were recognised during the last 25 000 years.– A new loess stratigraphical view was elaborated using the most recent dating methods (luminescence, AAR). The lower part of Mende Upper (MF1-2) pedokomplex is suggested to represent the last interglacial period (MIS 5e). During the last interglacial/glacial period (MIS 5 - MIS 2) several soil-forming periods existed but the preservation of these paleosoils is variable depending on their paleogeomorphological position.

Effects of river regulation on aeolian landscapes, Colorado River, southwestern USA

Connectivity between fluvial and aeolian sedimentary systems plays an important role in the physical and biological environment of dryland regions. This study examines the coupling between fluvial sand deposits and aeolian dune fields in bedrock canyons of the arid to semiarid Colorado River corridor, southwestern USA. By quantifying significant differences between aeolian landscapes with and without modern fluvial sediment sources, this work demonstrates for the first time that the flow‐ and sediment‐limiting effects of dam operations affect sedimentary processes and ecosystems in aeolian landscapes above the fluvial high water line. Dune fields decoupled from fluvial sand supply have more ground cover (biologic crust and vegetation) and less aeolian sand transport than do dune fields that remain coupled to modern fluvial sand supply. The proportion of active aeolian sand area also is substantially lower in a heavily regulated river reach (Marble–Grand Canyon, Arizona) than in a much less regulated reach with otherwise similar environmental conditions (Cataract Canyon, Utah). The interconnections shown here among river flow and sediment, aeolian sand transport, and biologic communities in aeolian dunes demonstrate a newly recognized means by which anthropogenic influence alters dryland environments. Because fluvial–aeolian coupling is common globally, it is likely that similar sediment‐transport connectivity and interaction with upland ecosystems are important in other dryland regions to a greater degree than has been recognized previously.

Mapping functional vegetation abundance in a coastal dune environment using a combination of LSMA and MLC: a case study at Kenfig NNR, Wales

The interactions between wind-blown sand transport, pioneer vegetation and succession vegetation in coastal dune fields play an important role in landform development and determine the balance between stabilization and re-activation of these aeolian landscapes. High-resolution mapping of vegetation communities across a dune field – in particular, the mixture of different functional plant types such as pioneer versus succession species – is critical for the calculation of landscape metrics that enable a rigorous and quantitative testing of numerical simulation models, as well as for informing targeted land management actions that maintain biodiversity and ecological functions. This article presents a method of using maximum likelihood classification (MLC) to inform linear spectral mixture analysis (LSMA) for quantifying sub-pixel abundance of sand, pioneer and succession vegetation in a coastal dune area in Wales, from archived imagery obtained from the Compact Airborne Spectral Imager (CASI) in 1997. LSMA is first applied to derive sub-pixel fractional abundances of soil, green vegetation (GV) and non-GV elements. An MLC is developed separately for automatically identifying pixels believed to contain a mixture of the two functional vegetation types, and this then serves as a basis for applying a transform that interprets the LSMA results in terms of sand and pioneer and succession vegetation communities. Very high resolution (0.1 m pixels) colour aerial photography, taken simultaneously with the CASI data, and field survey data from both 1997 and 2009 were used to aid the MLC and the transform algorithm and were also used for a limited validation exercise. The LSMA abundance maps achieved an overall accuracy of 82.7% (kappa coefficient κ = 0.78). The reduced MLC vegetation maps (four classes) achieved an overall accuracy of 98.2% (kappa coefficient κ = 0.96). Although it was not possible to validate the final pioneer and succession vegetation abundance maps quantitatively, a qualitative review of the results for selected locations within the dune field indicates the viability of applying MLC to help direct a transformation of LSMA abundance maps into functional vegetation abundance data.

Lateglacial soil paleocatena in inland-dune area of the Toruń Basin, Northern Poland

The buried toposequence of soils (paleocatena) dated to the Alleröd interstadial has been researched in this work. Studies were carried at the Katarzynka site located in the inland-dune area of the Toruń Basin, Northern Poland. Paleosols developed on the slope dividing two glaciofluvial terraces, and were buried under dune sands during the Younger Dryas (ca 11100 BP; uncal.) The paleocatena consists of weakly developed Podzolic (Usselo) soil at the upper slope, Gley-Podzolic soil at the lower slope and humus-enriched Gleysol at the bottom of the sequence. In some parts, the paleosol also has the morphology of the ‘Bwb’ horizon typical for the so-called Finow soil. In the uppermost topographical position, the buried soil mantle is eroded by wind activity and shows disturbances typical for periglacial conditions.Usselo and Finow soils are usually considered to be marker stratigraphical horizons for Lateglacial aeolian landscapes of Western and Central Europe, although their genesis and paleoenvironmental significance are still controversial. The occurrence in paleocatena pattern and morphological, chemical and micromorphological features indicate their pedogenic nature. The Podzolic (Usselo) soil, Gley-Podzolic soil and Gleysol show clear effects of soil-forming and diagenetic processes varying along the buried slope. The origin of ‘Bwb’ Finow soil horizon seems to be a post-burial process similar to illuvial lamellae formation, masking the effects of former pedogenic features. In all probability, this process was preceded by alterations of soil morphology caused by permafrost development at the onset of the Younger Dryas, immediately before burial. The variety of soils forming the paleocatena is clear evidence of landscape diversity during the Alleröd.

Origin and age of the Lower Bavarian sand dune landscape around Abensberg and Siegenburg

The Lower Bavarian aeolian sand areas and sand dune landscape in the Abensberg/Siegenburg area (county/Landkreis Kelheim, Lower Bavaria) originated in an area where the Late Tertiary deltaic sediments of the Ur-Naab are overlain by a complex system of Pleistocene Danube gravels as well as those of the Abens river, deposited by in parts widely-shifting Quaternary river courses, mainly during the Riss glacial. This explains the absence of any significant loess cover of the area. The sand dunes and aeolian sands occurring there have been known for a long time, and their mostly late glacial age origin can be stratigraphically inferred. During the Holocene there were repeated phases of aeolian remobilisation, each of them related to an overexploitation of the carrying capacity of the landscape. It can be excluded that remobilisation was caused by changing climate. Today the dune fields, up to 10 m high, have partly been set aside as nature reserves, or are being used for agriculture and forestry. Based on geophysical prospection, at four selected dune chains and their surroundings, a distinction has been made between the underlying aeolian sand sheet, the dune cores, and younger aeolian accumulation bodies, and they have been sedimentologically characterised. The dune sands have been dated by OSL, macro-remains and the humous material of fossilised soil horizons by the radiocarbon method. Forest clearing of much of the landscape began during the Neolithic period, related to the operation of a flintstone mine at Arnhofen. Two significant phases of sand dune growth have been dated to the Bronze Age and the High Middle Ages, largely determining the aspect of the present dune landscape. There is evidence of younger remobilisation phases up to the 1950s. With reduced settlement pressure, each time the dune landscape returned to a phase of morphodynamic stability, without any evidence of directed reforestation or dune stabilisation measures of the sands. Today, under the name of Durnbucher Forest, the former hunting preserve of the Wittelsbach noble family, the Abensberg/Siegenburg dune landscape is one of the largest contiguous forest areas of Bavaria.

Evolution of aeolian landscapes in north-eastern Estonia under environmental changes

Evolution of dunes and other aeolian landforms is characterized by phases of sand drift, alternated with geomorphic stability. F ormation of wind-blown landforms in Estonia is strongly controlled by land uplift, climate, parent deposits, re-advance of ice-dammed lakes, as well as the Baltic Sea and Lake Peipsi water level changes. Different aeolian formations, such as cover- sand hillocks, blowouts, deflation hollows, foredunes, inland and coastal dunes, and wind-eroded plains are encountered. Forest cuttings and fires, military actions and other human activities trig- gered the movement of surficial sand, but wet environmental conditions, sparse population and rapid spreading of vegetation prevented extensive redistribution of loose sandy sediments by wind. In north-eastern Estonia, inland parabolic and transversal dunes were formed in severe climatic conditions of the Younger Dryas. Influence of climate is well seen also at the northern coast of Lake Peipsi, where rhythmically changing water level has caused aeolian redistribution of sediments.

Ecogeomorphic state variables and phase‐space construction for quantifying the evolution of vegetated aeolian landscapes

AbstractCellular automaton modelling for the simulation of dune field formation and evolution has developed progressively in aeolian geomorphology in the last decade or so. A model that incorporates the effects of vegetation and its interactions with geomorphic landscape development – the Discrete Ecogeomorphic Aeolian Landscapes (DECAL) model – can replicate a number of important visual and qualitative aspects of the complex evolution of aeolian dune landscapes under the influence of vegetation dynamics in coastal environments. A key challenge in this research area is the analysis and comparison of both simulated and real‐world vegetated dune landscapes using objective and quantifiable principles. This study presents a methodological framework or protocol for numerically quantifying various ecogeomorphic attributes, using a suite of mathematically defined landscape metrics, to provide a rigorous and statistical evaluation of vegetated dune field evolution. Within this framework the model parameter space can be systematically explored and simulation outcomes can be methodically compared against real‐world landscapes. Based on a simplified scenario of parabolic dunes developing out of blow‐outs the resulting dune field realizations are investigated as a function of variable growth vigour of two simulated vegetation types (pioneer grass and successional woody shrub) by establishing a typological phase‐diagram of different landscape classes. The set of simulation outcomes furthermore defines a higher‐dimensional phase‐space, whose axes or dimensions can be interpreted by analysing how individual ecogeomorphic landscape metrics, or state variables, contribute to the data distribution. Principal component analysis can reduce this to a visual three‐dimensional (3D) phase‐space where landscape evolution can be plotted as time‐trajectories and where we can investigate the effects of changing environmental conditions partway through a simulation scenario. The use of landscape state variables and the construction of a 3D phase‐space presented here may provide a general template for quantifying many other eco‐geomorphic systems on the Earth's surface. Copyright © 2010 John Wiley & Sons, Ltd.

التغيرات البيئيه للمسطحات المائيه في جنوب العراق إعتمادا على الدراسات البالينولوجيه

Palynological techniques are useful in reconstructing past environments, especially when other sources of information are lacking. We have embarked on a palynological study of the wetlands in Southern Iraq in an attempt to determine the nature and extent of past plant communities and other conditions prior to the drying of the wetland in the 1990s. Ten 1-m depth cores were collected from selected locations in marshes and shallow open water wetlands in Mesopotamian wetlands of Southern Iraq. Pollen diagrams from three short cores from the Hawizeh wetlands serve as a reference because this site has not been drained. The palynomorphs in these cores were Gramineae, Chenopodiaceae, Typha, Isonandra lanceolata, Bursarea, Artocarpus, Ireantea, Arenga, Crinum, Palmae, Navia, Tofieldia, Ipomorea, Xyris, and Morus. Fungal spores including Polyporisporites, Pluricellaesporites palyadosporites, Fusiformisporites, Spegazzinites indicus, Diporisporites, Plochmopellinites, Lycoperdon, Miliolinites, Dryadosporites constrictus, and Trichothyrites padapakarensis were noteworthy. Charcoal was scattered through the cores and indicate activities associated with human settlements. Many other forms of cuticles, filaments, insects, algae, and foraminifera test linings were also recorded. A second set of pollen samples were analyzed from 160 soil samples from eight cores collected from the wetland area which was dried during the 1990s. These data show a mixture of pollen and spores that could be used to evaluate past vegetation, climatic, and ecological changes. Preliminary results indicated that chenopodiaceous have increased while germinate types have declined which probably reflected desertification and a trend towards a more aeolian landscape during the 1990s. It is hoped that these studies will be useful in establishing conditions of the wetlands prior to destruction and will assist in setting restoration goals in the future. Case studies of one deep borehole (153 m) near Amara city for evaluating late Quaternary history and dig of 3 m depth to evaluate ancient desertification by wetland dryness were taken for correlation and connection with this recent sediment.

The Early Mesolithic Haverbeck site, Northwest Germany: evidence for Preboreal settlement in the Western and Central European Plain

Archaeological sites dating from the Preboreal are of special interest since they mark the turning point in the transition between the cultures of the Late Pleistocene and the Holocene. In spite of their relevance only few sites in the Western and Central European Plain have become known, thus providing an inhomogeneous basis for further hypotheses. In particular, sites in the widespread aeolian landscapes have been neglected for a long time due to their uncertain genesis, dating problems and obviously insufficient preservation. Our investigations of the Haverbeck site, situated in sandy aeolian substrate, seek to enhance knowledge about the Preboreal Mesolithic. The well-preserved archaeological spatial, technological and functional patterns and the geoarchaeological site formation were studied. Sedimentological and palaeopedological analyses, supported by 14C and OSL dating results, revealed that artefacts were deposited during the Preboreal on sands which had accumulated during the Younger Dryas and were reactivated in subsequent periods (Atlantic, Subboreal, Subatlantic). In spite of these processes, the artefacts remained unimpaired in their relative horizontal positions, enabling spatial analyses, which show a zonal differentiation and a prevalence of retooling and replacing activities. These results offer an insight into spatial and functional differentiations of the local Early Mesolithic subsistence, evidently including particular places for gathering and processing raw material. A comparison between the microlithic spectrum left behind and the number of points produced as concluded from the microburins indicates a greater typological differentiation than previously assumed for the Early Mesolithic. The remarkable variability of scraper forms obviously intentionally abandoned in a high number and replaced by new tools emphasizes the strong influence of functional elements on the typological assemblage composition. It is suggested that Early Mesolithic assemblages could display rather functional requirements or tasks performed than significant chronological or regional influences. In addition, the combination of 14C, OSL and pedology helped to reconstruct the aeolian accumulation/erosion dynamics and to present a considerable sequence of processes, some of which are closely connected with human activities.

The influence of different environmental and climatic conditions on vegetated aeolian dune landscape development and response

Aeolian dune field development in coastal and semi-arid environments is a function of complex ecogeomorphic interactions which are sensitive to fluctuations in climatic and environmental conditions. We explore the relationships between ecological and geomorphic processes in the development of these landscape patterns and speculate on their response to variations in vegetation vitality and sediment transport capacity, indicating possible consequences of climate and land use change, using the Discrete ECogeomorphic Aeolian Landscape (DECAL) cellular automaton algorithm. This algorithm models dune field behaviour that reflects long-term trends prevalent in palaeo-records, but also elucidates possible evolutionary progressions, relaxation period sequences and threshold sensitivities. The landscape response is sensitive both to the perturbation itself and the state of the system when the disturbance occurs. Response amplitude decreases in simulated systems with reduced mobility unless an external disturbance mimicking fire or land clearance is applied concurrently with a reduction in growth vigour triggering a threshold type response when sufficient vegetation is removed. The model demonstrates that the relative response characteristics of the multiple vegetation types and their mutual feedback with geomorphic processes impart a significant influence on landscape equilibrium or attractor states. Fast growing vegetation enables the formation of hairpin (long-walled) parabolic dune systems, which eventually become sediment starved and stabilise, whereas inhospitable conditions inhibiting vegetation growth contribute to the development of active transgressive transverse dune fields. This simple vegetated dune model illustrates the power and versatility of a cellular automaton approach for exploring thresholds, sensitivities and possible evolutionary trajectories associated with the interactions between ecology, geomorphology and climatic conditions in complex earth surface systems.

Groundwater salinity as a control on development of eolian landscape: An example from the White Sands of New Mexico

The White Sands of southern New Mexico form the largest field of gypsum dunes in the world. The juxtaposition of several different types of dunes within the field has long been recognized and has generally been attributed to changes in the rate of sand transport across the dune field. However, Steven Fryberger [Fryberger, S.G., 2003. Geology of White Sands National Monument, web page www2.nature.nps.gov/geology/parks/whsa/] recently hypothesized, however, that a primary control is groundwater salinity. The White Sands dune field is underlain by saline waters. Fryberger proposed that parabolic dunes could form in topographic highs that accumulated a lens of fresher water derived from precipitation. Water with lower salinity allowed vegetation to grow, and stabilized the sand except for the active noses of the parabolic dunes. This study is a test of that hypothesis. A study transect was established across the boundary between parabolic and barchan dunes. Groundwater and soil at six sites were sampled during December, 2004 and March, May, and June of 2005. Two sites were established in the parabolic field, two in the barchans, and two in the transition zone between them. Groundwater was found to be three times more saline in the barchan area. Conductivity and chloride decreased across the transition zone. A GPS topographic survey revealed two abrupt topographic steps, one at the boundary between the barchans and the transition zone and a second at the edge of the parabolic field. A second, larger topographic step was found outside the study area defining a higher parabolic dune field. These data indicate that Fryberger's (2003) hypothesis is correct and groundwater is controlling the dune field morphology. The dune field did not begin to form until the Mid-Holocene (6500 years ago). A compilation of dates shows that the parabolic dune field has probably been stable for the last 3500 years. In contrast, the barchan area has been recently deflated and exposed 2000 year old sediment near the surface.