Dune Complex Research Articles

Applicability of Synthetic Aperture Radar Data for the Study of Snow Dune Complexes and Snow Sheets in Antarctica and their Bearing on Paleo-Climatic Variability

Applicability of Synthetic Aperture Radar Data for the Study of Snow Dune Complexes and Snow Sheets in Antarctica and their Bearing on Paleo-Climatic Variability

Arizona Dune Complexes Resulting from Drainage Integration and Climatic Change: A Speculative Hypothesis

Arizona Dune Complexes Resulting from Drainage Integration and Climatic Change: A Speculative Hypothesis

Israelite Plain, southwestern Australia, a siliciclastic, late Quaternary Coorong analogue, without dolomite

The Israelite Plain, a narrow terrace at the western edge of the Great Australian Bight, is characterised by a series of schizohaline, ephemeral lakes leeward of a marginal marine eolianite dune complex that has many similarities to the Coorong Coastal Plain (CCP). The late Pleistocene and Holocene sediments are a mixture of dominantly quartzose sand and lesser carbonate components. Paleolagoon to shallow marine MIS 5e, mollusc-rich quartzose deposits are capped by calcrete or karst and contain a biota similar to the well-documented, coeval Glanville Formation on the CCP. Holocene sands with minor carbonate are also lagoonal and resemble many modern Coorong Lagoon deposits. Both deposits are interpreted to reflect marine accumulation during sea-level highstands. Lakes today range from dry to water-filled with most floored by calcareous quartzose sand. Microbial influenced sedimentary structures in the form of pustular to laminated mats veneer lake margin bedrock and sediment. Carbonate minerals are mostly calcite with abundant accessory magnesium-calcite, aragonite and traces of magnesite, monohydrocalcite and halite. Gypsum is minor but ubiquitous and floors one of the smaller, marginal-marine lakes. Although having a similar evaporative climate and evidence of groundwater resurgence like Coorong lakes, there is no significant synsedimentary dolomite. This aspect is interpreted to reflect the narrow width of the plain, and the Mg-poor source of groundwater from the nearby karst Nullarbor Plain to the north. The Israelite Plain, together with other coeval, young successions marginal to the Southern Ocean under a semiarid climate now illustrate the depositional variations and early diagenetic differences that can occur in similar environments adjacent to a cool ocean. KEY POINTS The Israelite Plain is a narrow, marginal marine terrace covered by Quaternary, lagoonal, eolian to lacustrine, calcareous siliciclastic sands, similar to several other calcareous terraces along the southern Australia coast. The interpreted sediment ages are late Pleistocene stage MIS 5e with the deposit sporadically overlain by similar Holocene deposits. Most 14C age dates are suspicious because of interpreted diagenesis or MIS 5e age, whereas U/Th age dates appear correct or altered by diagenesis. Pleistocene biota is dominated by the bivalve Anadara trapezia, whereas Holocene deposits contain a varied array of cooler water molluscs. The carbonates are similar to those on the Coorong Coastal Plain but do not contain any dolomite likely because of climate and lack of Mg-groundwater flow.

Observations and modeling of shear stress reduction and sediment flux within sparse dune grass canopies on managed coastal dunes

AbstractWind flow over coastal foredunes adapts to vegetation, resulting in spatial gradients in bed shear stresses that contribute to the formation of localized bedforms. Understanding, and having the capability to numerically predict, the distribution of sediment deposited within sparsely vegetated dune complexes is critical for quantifying the ecological, protective, and economic benefits of dune management activities. Data from wind tunnel experiments have indicated that there is a spatial lag from the canopy leading edge to a downwind location where sediment deposition first occurs. The length scale of this deposition lag is further quantified here using new field measurements of aeolian sediment transport across sparsely vegetated managed dune systems in Oregon, USA. We develop a deposition lag length scale parameter using both lab and this new field data and then incorporate this parameter into the process‐based aeolian sediment transport model, Aeolis, which also includes a new far‐field shear stress coupler. Results from numerical simulations suggest that the spatial deposition lag effect is significant for model skill in sparsely vegetated dunes. We observe with field and laboratory observations that, as canopy density increases, the length of the deposition lag decreases. As such, within the model framework the implementation of the deposition lag length does not affect the results of models of coastal dune geomorphological evolution within higher density canopies. Dune canopy density can vary due to natural (e.g., storm overwash, burial, die‐off) or anthropogenic (e.g., managed plantings, dune grading) processes.

Morphology and distribution of Martian wedge dunes and their terrestrial analogs

Wedge dunes are widespread on Mars and contain important information about Mars surface processes and environmental characteristics. These dunes are wedge-shaped in plan-view, similar in scale to a barchan dune, with two slip faces intersecting at an obtuse angle and extending outward toward the main ridge downwind. And, the length of its main ridge does not exceed its width. At present, our understanding of wedge dunes and their development in nature is limited. The type, morphology, distribution and spatial composition of wedge dunes on Mars and Earth were investigated using high-resolution satellite image data. The results reveal that wedge dunes are simple in type and similar in size to barchan dunes. Martian wedge dunes are similar in shape to terrestrial wedge dunes but larger in size. The average angles between the sub-ridges of Martian and terrestrial wedge dunes are similar, at about 116°. Martian wedge dunes are mainly located in Abalos Undae, Siton Undae, and Aspledon Undae in the North Polar region, accounting for about 5% of the total area covered by dune fields. Wedge dunes are rare on Earth and can only be found on the edge of a few contiguous dune fields. These dunes indicate acute bimodal or obtuse bimodal wind regimes. Wedge dunes have distinct transitional characteristics and may be the initial stage of the development of various dune patterns. The implications of these findings are discussed, in particular the periodic changes in the regional wind direction reflected by the wedge dunes, as well as the significance of the distinctive transitional features of the wedge dunes for improving our understanding of the genesis of complex dune patterns.

High-resolution OSL chronology of a well-preserved inland dune in the Lys valley (Sint-Martens-Latem, NW Belgium)

The inland dune “Molenberg” (Lys valley, NW Belgium) is an exceptionally well-preserved dune of more than 10 m high. To determine the phases of dune formation and identify possible levels for human occupation, this dune was sampled at closely spaced vertical intervals for Optically Stimulated Luminescence (OSL) dating (every 50 cm) and grain-size analysis (intervals of 10–25 cm) over its entire depth, including the top of the underlying sediments. The resulting ages show dune formation during the late glacial period (GI-1 and GS-1), with a probable extensive deposition during the Allerød (GI-1a-c) and Younger Dryas (GS-1). Interestingly, the OSL dataset for the main body of the dune shows significant cyclical age inversions that may be caused by reworking of sediment causing incomplete bleaching of sand grains. This may further indicate the potential of high-sampling resolution OSL to contribute to the reconstruction of complex dune dynamics. • High-sampling resolution OSL dating shows dune formation during the late glacial in the Scheldt basin of NW Belgium. • OSL chronology demonstrates the potential of these inland dunes as an archive for prehistoric sites. • Cyclic age inversions may be related to reworking of sediment in periods of reduced accumulation. • Potential of high-sampling resolution OSL as proxy for complex dune dynamics.

Numerical Simulation Analysis of the Formation and Morphological Evolution of Asymmetric Crescentic Dunes

Generally, typical crescentic dunes in the ideal state are symmetrical, but it is difficult to form crescentic dunes with two perfectly symmetrical horns under actual conditions. Among many environmental factors, bidirectional winds, the size of sand particles, topography, epiphyte vegetation, and dune collision are important reasons for the asymmetric evolution of sand dunes. Few existing studies have revealed the mechanism of the morphological evolution of asymmetric crescentic dunes, especially in regard to the role of wind in a complex dune’s morphology. In this study, we used the Reynolds Averaged Navier-Stokes (RANS) and mass balance models to simulate the asymmetric forms and flow fields of crescentic dunes and analyzed the potential causes of the asymmetry among the above aspects. The results showed that: (1) the angle of the bidirectional winds significantly changed the structure of vortices around the sand dune; (2) for crescentic dunes with coarser sand, the deposit continuity was better, the extension of the single horn was maintained for a long time, and the extended horn took longer to die out; (3) the crescentic dune deformed according to the direction of the inclination of the terrain, and the shear stress of a dune on a slope was related to the slope, width, or height; (4) whether there was epiphytic vegetation on a dune’s surface had a great impact on the dune’s migration; (5) the collision position of two dunes determined the shape of the two dunes after fusion. The simulation results indicated that the spatial–temporal differences in sand flux, caused by changes in flow fields that were induced by various factors, determined the evolutionary shape of crescentic dunes. These results can provide a reference for the study of the erosion of surface flow fields on various dunes and for the prevention and control of wind and sand disasters in the Gobi Desert area.

Propuesta metodológica para la caracterización y tipificación de las costas españolas. Aplicación a las costas de Galicia.

Hay varias clasificaciones costeras. La mayoría de ellas han sido elaboradas a nivel mundial utilizando criterios tectónicos, climáticos, topográficos u oceanográficos. Otras clasificaciones han sido elaboradas a mayor escala y han sido enfocadas a catalogar las formas costeras: acantilados, playas, estuarios, lagunas o complejos dunares.Este trabajo analiza los tipos de litoral, entendiendo como tal cada sector que presenta determinadas condiciones topográficas marcadas por la elevación y pendiente, y que se modeló sobre un tipo concreto de roca en un entorno climático y marino específico. Se describe un enfoque metodológico para una clasificación a escala detallada. Este enfoque se basa en la delimitación de los diferentes sistemas costeros, ejemplificados en acantilados y playas de cantos rodados, playas de arena y dunas. En este caso las plataformas costeras, marismas y lagunas no han sido consideradas por los problemas técnicos derivados de la fuente de datos LiDAR, de la cual se derivan los modelos digitales del terreno (MDT) de resolución espacial de 2 m.El primer paso en la clasificación fue una delimitación manual que combinaba MDT y ortofotografías. Posteriormente, se realizó otra tipificación mediante la creación automática de Unidades Topográficas Litorales (UTC). Este índice es la combinación de dos variables: elevación costera y pendiente. La posible integración de otras, como la orientación o la litología, es posible, pero generan un número muy elevado de unidades y dificultan su interpretación. Por esta razón, este estudio no consideró más variables.En este proyecto se generaron 30 UTC, y luego se seleccionaron solo aquellas que aparecen en los sectores de acantilados, playas de cantos rodados, playas de arena y dunas costeras. La posibilidad de visualizar una o varias UTC en cualquier sector de la costa permite conocer con mayor precisión las condiciones de cada sector y estas categorías podrían mejorar los planes de gestión costera.

What sets aeolian dune height?

Wherever a loose bed of sand is subject to sufficiently strong winds, aeolian dunes form at predictable wavelengths and growth rates. As dunes mature and coarsen, however, their growth trajectories become more idiosyncratic; nonlinear effects, sediment supply, wind variability and geologic constraints become increasingly relevant, resulting in complex and history-dependent dune amalgamations. Here we examine a fundamental question: do aeolian dunes stop growing and, if so, what determines their ultimate size? Earth’s major sand seas are populated by giant sand dunes, evolved over tens of thousands of years. We perform a global analysis of the topography of these giant dunes, and their associated atmospheric forcings and geologic constraints, and we perform numerical experiments to gain insight on temporal evolution of dune growth. We find no evidence of a previously proposed limit to dune size by atmospheric boundary layer height. Rather, our findings indicate that dunes may grow indefinitely in principle; but growth depends on morphology, slows with increasing size, and may ultimately be limited by sand supply.

Shaping effects of sand flow channels on aeolian geomorphology – a case study of the Badain Jaran, Tengger, and Ulan Buh Deserts, northern China

Based on the interactions between mountains, we identified three sand flow channels in the Badain Jaran, Tengger, and Ulan Buh Deserts, northern China. We found that the height difference of the terrain in these areas provided favorable conditions for the transportation of sand. Owing to the venturi effect of their geomorphologies, airflow was compressed in these channels, and their wind regimes were strong and unimodal. Compared with the interior of the desert, the sand transport potential was relatively large in these areas, and westerly and northwest winds prevailed. We found that the wind accelerated in the sand flow channels, resulting in faster-moving dunes. The dune types that developed in these channels were relatively simple owing to the unimodal wind regimes; they mainly comprised barchan and transverse dunes. We also identified a transition landscape from barchan dunes to transverse, or complex dunes. Based on their sediment characteristics and the prevailing wind directions, we found that the sand flow channels provided a direct sand supply between the three deserts. The sand flow channels connected these independent deserts to an entire desert system. Similar sand flow channels can also be found in other deserts globally. Collectively, these sand flow channels reflect interactions between deserts.

Agroecological sub-zone based sustainable land use in arid Rajasthan (India)

The arid region of Rajasthan has been classified into unique agro-ecological sub-regions, zones, and sub-zones (indicated by their code number in this abstract) for which sustainable land use has been suggested based on the potentials and constraints. 2.1, 2.2 and 3.1 sub-zones need dune stabilization, silvopastural farming, and kharif cultivation in interdunes; khadin water harvesting system, as well as solar farming. 4.1 and 4.2 sub-zones need rainfed cropping under conserved moisture, agroforestry and limited irrigation, cultivation of low water requiring crops, such as mustard, cumin in rabi. In 4.3 sub-zone under conserved moisture and winter rainfall pulses and mustard are suggested. In 5.1 and 5.2 sub-zones kharif season crops and wheat, mustard, cumin, and condiments irrigated with brackish groundwater by adopting gypsum treatment are suggested. In the canal command area, the micro-irrigation system is doing well in the sandy plain and dune complex area, but in the Ned area irrigation needs to be restricted/avoided. In 5.3 and 5.4 sub-zones, rainfed irrigated crops and fruit cultivation is suggested. In 6.1 sub-zone dune stabilization is suggested; 6.2 and 6.3 sub-zones require erosion control and irrigation water management for the cultivation of cotton, paddy, groundnut, sugarcane, and kinnow.

Sedimentary dynamics and topographic controls on the tidal-dominated Zagra Strait, Early Tortonian, Betic Cordillera, Spain

Abstract The approximately 350 m-thick stratigraphic succession of the Zagra Strait records an important oceanographic phase of basin interconnection between the Atlantic Ocean (Guadalquivir Basin) and the Mediterranean Sea through the Betic Cordillera (southern Spain) during the early Tortonian. The Zagra Strait developed as a narrow structurally controlled marine corridor. The sedimentary dynamics of the Zagra Strait were interpreted from the sedimentological features observed in six sections at well-exposed outcrops. Large-scale (>10 m high) compound dunes and compound–dune complexes moved parallel to the strait margins under strong tidal currents generated by tidal amplification at the strait entrance and exit. Dune distribution can be divided into three sectors with different palaeocurrent migration, lithological and topographical characteristics. The northern and central sectors were separated by a deep depression (>75 m water depth) where tidal currents were weaker and dunes were not generated. The southern sector records a relative decrease in current strength compared with the northern and central sectors, and a significant increase in the bioclastic content in the sediment. Terrigenous content generally increases towards the strait margins, and reciprocally, carbonates towards its axis. The closure of the Zagra Strait resulted from tectonic uplift of that part of the Betic Cordillera before the late Tortonian.

The Rapid Effects of Yellow-Legged Gull (Larus michahellis) Colony on Dune Habitats and Plant Landscape in the Atlantic Islands National Park (NW Spain)

The Atlantic Islands of Galicia Maritime/Terrestrial National Park hosts one of the largest breeding colonies of yellow-legged gull (Larus michahellis) in the world. In 2002, a new yellow-legged gull breeding colony was established on the Punta Muxieiro dune complex, which also harbors rare and threatened plant species and habitat types of community interest according to Directive 92/43/EEC. This study assesses the effect of this colony on two habitats of community interest: white dunes and grey dunes. For this purpose, plant cover and soil properties, composition, and nutrient content were monitored in plots with different gull densities. Moreover, historic aerial images were compiled to observe changes in the plant landscape of the dune system. The results showed that, despite the recentness of the occupation of the dune system by yellow-legged gull species, significant changes in acidic–alkaline processes and nutrient availability were already observed in soils. Soils in plots with higher gull density showed more acidic pH values and a higher content of the most labile N and P fractions. Moreover, a decrease in plant cover and number of species was also demonstrated in plots with higher gull densities. Finally, the presence of ruderal and alien species such as Urtica membranacea and Parietaria judaica was also observed.

Effects of wind patterns and changing wind velocities on aeolian drift potential along the Lake Michigan shore

Climate influences the amount of wind energy available to transport sand in coastal dune complexes. Wind data from meteorological stations were used to calculate aeolian sand drift potential along the Lake Michigan shore and surrounding region. Data from 11 nearshore stations were used to identify 83 potential aeolian transport events during 2015. All events were associated with the passage of cyclones and anticyclones with the strongest pressure gradients occurring when the lake was between high- and low-pressure centers. There are statistically significant correlations between the positions of cyclones and anticyclones and the orientation of the shores with onshore drift potential. There is enough variability in cyclone and anticyclone tracks to drive aeolian activity on the north, east and south coasts, not all of which can be explained by the regional “prevailing” winds. Wind data from seven airports were used to examine changes in regional drift potential since 1948. Total drift potential decreased over this time, including a decrease of approximately 40% over the period 1961–2019. Trends in directional drift potential are less clear and appear to indicate a decrease in the proportion of onshore drift potential for the east and north shores and an increase for the south shore. This decrease in the ability of winds along Lake Michigan shores to transport sand should contribute to a stabilization of the coastal dunes. Shifts in the tracks of cyclones and anticyclones associated with climate change are anticipated to shift the relative amounts of aeolian activity associated with shores of different orientations.

Waxing and waning slacks: The changing ecohydrology of interdunal wetlands/slacks in a Lake Michigan coastal dune complex during rising Lake Michigan-Huron levels

Since 2016 we have studied the largest interdunal wetlands/slack lying within a deflated parabolic dune east of Lake Michigan. Geologic cross-sections show ∼ 15 m of sand and gravel beneath the dunes, creating an aquifer hydraulically connecting Lake Michigan-Huron (MH) with the water table/shallow groundwater influencing the slack. Lake Michigan-Huron (MH) water levels have risen ∼ 1 m from 2016 to 2020, increasing water levels within and around the slack ∼ 1 m. Color-infrared images and vegetation quadrat sampling show water appearing, then significantly expanding with the main slack and upland/dune vegetation transitioning to wetland vegetation in response to this rise. Monitoring well data show slack water levels rise in spring as Lake MH rises. Levels drop as the growing season begins while Lake MH continues to rise through summer. Short-term slack water level increases occur due to local rain events, but significant water level declines follow due to evapotranspiration. Slack water levels begin to rise again in late summer and into fall as the end of the growing season arrives, evapotranspiration decreases, and heavier, more frequent rain events occur. Together, these factors push slack water levels to their highest point of the year while Lake MH levels are decreasing. In late fall–winter, slack water levels drop in concert with Lake MH levels. Climate change effects, increased transpiration from higher temperatures, summer drought, and greater variability in lake level fluctuations, may make it more difficult to maintain wet growing conditions for hydrophytic vegetation. Hence, climate change poses risks to the existence of this imperiled ecosystem.

Using photographic measurement and gigapixel panoramas to study changes in a Lake Michigan sand dune

Detailed measurements of changes in aeolian landscapes help researchers better understand aeolian processes and monitor the effects of climate change in these systems. This study focuses on a photographic method to measure sand surface changes. It introduces custom erosion pins (photoscale pins) designed to allow proper scaling of measurements taken from digital images or high resolution (gigapixel) panoramas. Furthermore, this study discusses errors associated with measuring photoscale pins photographically. Resolution errors arise when marking object boundaries on digital images. These typically affect measurement precision, but even so, differences between repeated measurements of the same pin average 0.58 mm. Perspective errors arise when pins are tilted relative to the camera’s line of sight and introduce bias, affecting measurement accuracy. Photographic measurement can allow remote surveillance, reduce site disturbance, increase the frequency of observation, and reduce measurement error compared to manual measurement of erosion pins. A study of sand movement in a dune complex on the southeastern shoreline of Lake Michigan provides an example of the method’s application. Photoscale pin measurements that bracket a wind event associated with Hurricane Sandy show average surface elevation changes of 3.97 cm/pin. Regional wind data, pin measurements, and surface changes recorded in gigapixel panoramas suggest that vegetation baffling, recirculation eddies, and topographic steering played roles in sand deposition and erosion at the site. Photographic measurement of erosion pins can complement wind instrumentation and other tools as aeolian research increasingly incorporates multiple techniques to study surface changes in greater detail both in time and space.

EEG Fingerprint Methodology Application to the Motor Cortices

The controls on the evolution of linear dunefields are poorly understood, despite the potential for reactivation of dunefields, which are currently stabilized by vegetation, under the influence of 21st century climate change. The relative roles of local influences (i.e. boundary conditions) and morphodynamic influences (i.e. emergent properties) remain unclear. Chronostratigraphic and sedimentological analyses were conducted on two pairs of linear dunes exhibiting different spatial patterning in the Strzelecki Desert of central Australia. It was hypothesized that morphodynamic influences, via pattern-coarsening, would mean that dunes from the simpler pattern, defined in terms of the frequency of defects (i.e. junctions and terminations), would be more mature, older landforms. Optically Stimulated Luminescence (OSL) dating of full-depth, regularly-sampled profiles was used to establish accumulation histories for the four dunes, and supported by sedimentological analysis to investigate possible compositional differences and similarities between the dunes. Whilst three of the dunes (the two more simply-patterned dunes, and one of the more complex dunes) have accumulation histories beginning between ~ 100 ka and 150 ka, and document sporadic net accumulation throughout the last interglacial/glacial cycle to the late Holocene, one of the dunes (with relatively complex patterning) reveals that the majority of the dune accumulation (> 7 m) at that site occurred during a relatively short window at ~ 50 ka. There is no clear sedimentological reason for the different behaviour of the younger dune. The data suggest that small-scale and essentially stochastic nature of the aeolian depositional/erosional system can overprint any large-scale morphodynamic controls. The concept of dating landscape change by pattern analysis is thus not supported by this study, and would require very careful interpretation of the scales being considered. This further suggests caution when interpreting dune chronostratigraphies palaeoenvironmentally, as different dunes are able to respond very differently to the same external stimulus (e.g. climate). In the case studied here, a mechanism is proposed to account for the rapid accumulation of the anomalous dune by avulsion of the local aeolian accumulation from one dune ridge to another.

Geomorphology and dynamics of a coastal transgressive dune system, central California

ABSTRACT The Callendar dunes are located within the Santa Maria dune complex in south-central California and have been studied repeatedly since the pioneering work of Bowen and Inman in the 1960's. Previous conceptual models of the system’s Holocene evolution relate variations in dune morphologies to changes in sediment supply and sea level. In the years since their studies, conceptual frameworks of coastal and continental transgressive dune systems provide useful avenues for re-visiting the morphodynamic history of the Callendar dunes. Our study presents grain size and dune spacing data collected by Tchakerian and Mulligan in 1981, while working under Orme as graduate assistants. These data, when considered in light of the more recent conceptual frameworks mentioned above, suggest that the Callendar dunes may exhibit some elements of self-organization. With this in mind, we apply a conceptual model of coastal transgressive dune systems to help elucidate some of the historical morphodynamics influencing the modern arrangement of morphologies at the Callendar dunes.

Drought coincident with aeolian activity in a Great Lakes coastal dune setting during the Algoma Phase (3.1–2.4 ka), southwest Michigan

Aeolian studies of Lake Michigan’s coastal dunes have yet to elucidate what factors control their episodic activity over the past 5000 years. High lake levels exposing sand along with increased storminess is generally accepted for high perched dunes. This hypothesis, however, remains poorly tested for low perched dunes along the southeast Lake Michigan coastline. Here, small lakes in the lee of dune complexes contain aeolian sand and various biological proxies. Age and sedimentation rate models from Gilligan Lake cores guide analysis of aeolian sand, charcoal, pollen, and diatoms at high resolution (1 cm [10.4 yr/cm]) during the high-water Algoma Phase (3.1–2.4 ka) of the upper Great Lakes. The diatoms record a transition from a deep, more acidic lake to a shallower, more alkaline lake with fewer wetlands. This transition is accompanied by a stepped increase in the amount of aeolian sand. There is a weak correlation (R2 0.5, p < 0.01) between increasing abundances of charcoal chunks and sand. Peaks of sand follow peaks in charcoal threads and sheets, suggesting fire played a role in removing vegetation, presaging the landscape for increases in storminess. Arboreal pollen records a transition from a mesic forest Fagus-Acer-Quercus-Abies assemblage suggestive of moister conditions to one richer in mesic hardwoods tolerant of drier conditions. Together, the environmental proxy data record a shallowing lake concomitant with increasing aeolian sand, suggesting that drought-like conditions along the coastline conditioned the landscape for renewed aeolian activity. Once initiated, increased storminess and shoreline erosion maintained dune activity through increased sediment supply.

Two centuries of forest succession, and 30 years of vegetation changes in permanent plots in an inland sand dune area, The Netherlands.

There are not many sites in densely populated temperate Europe where primary forest succession has a chance to run without direct human intervention for a long time and over a relatively large area. The extensive drift sand area of the Veluwe, central Netherlands, provided an opportunity to study succession in a formerly open and dynamic inland sand dune system combining chronosequence and permanent plot approaches. Different successional stages, aged up to 205 years since the first tree individuals established, were identified and vegetation studied using 1200 permanent plots established in 1988 in three adjacent sand dune complexes of different successional age, and resampled during the past three decades. After two centuries, forest succession has proceeded to a pine forest with gradually increasing participation of native deciduous trees. However, their expansion has been arrested by browsing of wild ungulates. Species diversity peaked after about 40 years of forest succession, then declined, and increased again after 100 years. During the past three decades, the herb layer has differentiated in the oldest plots, and the spontaneous forest succession is still in progress. Besides open drift sand with early successional stages, also the spontaneously established late successional forests are valuable from the conservation point of view.