Dune Complex Research Articles

Conservation of sand dune systems in Canada’s capital: a restoration model and case study of the Pinhey Sand Dunes complex

This paper is a case study of a Phase 1 restoration initiative of a natural inland sand dune complex, the Pinhey Sand Dunes (PSD), in the National Capital Region (NCR) of Canada. The 10,000 year-old dune complex lies on protected federal land, the National Capital Greenbelt, providing a favourable opportunity for study, restoration and conservation. A geological analysis of the PSD is provided, highlighting the unique qualities of an inland dune as compared to the more common coastal dune. Urban development and misguided tree planting programs in the 1950s are main causes of the degradation of this complex. A key component of this restoration/conservation project is the cooperation and collaboration of the National Capital Commission (NCC), responsible for the management of the land. A major focus of the initiative has been the education of the community, students at the elementary, high school and university levels and the general public. This educational component is designed to create a long-term strategy for conservation. The on-the-ground restoration process, biomonitoring, community and volunteer participation are all chronicled in this detailed case study. Lessons learned through Phase 1 of the project have been compiled and synthesised to create a dynamic restoration model that may serve to assist others in restoring similar habitats and lay a foundation of knowledge informing Phase 2 of the PSD restoration.

Implications of dune pattern analysis for Titan’s surface history

Analysis of large-scale morphological parameters can reveal the reaction of dunes to changes in atmospheric and sedimentary conditions. Over 7000 dune width and 7000 dune spacing measurements were obtained for linear dunes in regions across Saturn’s moon Titan from images T21, T23, T28, T44 and T48 collected by the Synthetic Aperture RADAR (SAR) aboard the Cassini spacecraft in order to reconstruct the aeolian surface history of Titan. Dunes in the five study areas are all linear in form, with a mean width of 1.3km and mean crest spacing of 2.7km, similar to dunes in the African Saharan and Namib deserts on Earth. At the resolution of Cassini SAR, the dunes have the morphology of large linear dunes, and they lack evidence for features of compound or complex dunes. The large size, spacing and uniform morphology are all indicators that Titan’s dunes are mature features, in that they have grown toward a steady state for a long period of time. Dune width decreases to the north, perhaps from increased sediment stabilization caused by a net transport of moisture from south to north, or from increased maturity in dunes to the south. Cumulative probability plots of dune parameters measured at different locations across Titan indicate there is a single population of intermediate-to-large-sized dunes on Titan. This suggests that, unlike analogous dunes in the Namib and Agneitir Sand Seas, dune-forming conditions that generated the current set of dunes were stable and active long enough to erase any evidence of past conditions.

Aeolian to shallow-marine shelf architecture off a major desert since the Late Pleistocene (northern Mauritania)

Continental shelves off major desert regions are not expected to host substantial amounts of sediments due to long-lasting and unfocused material supply and a high re-mobilization potential of aeolian material. This study, in contrast, demonstrates that significant volumes of sediments have accumulated on the northern Mauritanian shelf under the arid climate conditions and prevail over consecutive climatic cycles.Eight late Pleistocene to Holocene depositional units, each formed under contrasting depositional conditions, are identified in high-resolution seismo-acoustic data and dated sediment cores. These are: (1) a highly differentiated Pleistocene paleo-landscape older than the past climatic cycle, (2) a continental dune complex (MIS-4), (3) a thick regressive shallow-water clinoform (late MIS-3), (4) a regressive to lowstand shore deposit (latest MIS-3), and (5) a local transgressive cover (LGM to deglacial). Additionally, (6) an open-shelf highstand cover, (7) an outer-shelf highstand wedge and (8) mid-shelf mud depocenters have formed during the Holocene sea-level highstand.The common local offshore formation and preservation of confined stratigraphic units, in particular from during MIS-3, mark the interplay of: a) episodes of pronounced arid climatic conditions resulting in enhanced aeolian and coastal sediment input, b) shelf current patterns focusing sediment deposition locally, and c) early post-depositional sediment stabilization providing protection against erosion. Prominent internal surfaces at 63 and 115m modern water depths indicate widespread and intense erosional activity during late MIS-3 regression and MIS-2 lowstand to post-LGM transgression, hosting coarse shell sands and gravels from beach and shoreface paleo-environments. The reasons for the high preservation potential of confined stratigraphic units are: a) carbonaceous cementation, b) sediment composition (massive widespread shore-related gravel and shell beds with subtle minor admixtures of cohesive material), and c) morphological protection (inside seafloor depressions and behind sheltering relief).

A free cellular model of dune dynamics: Application to El Fangar spit dune system (Ebro Delta, Spain)

Currently, dune field surveying is employed to assess dune net volume changes and their accretion and erosion patterns. In dune fields with complex sediment sources and sink interactions such as El Fangar Spit (Ebro Delta, Spain), it is difficult to establish the sediment input and output with only net volume changes estimated by dune field surveying. This work presents a free dune dynamic cellular model that incorporates algorithms that introduce wind data into the erosion and transport processes. The model can be applied to dune systems with variable wind regime. A calibration methodology based on the morphological reproduction of the observed dune field evolution is proposed. The model and the calibration methodology is applied to a region of El Fangar dune system surveyed with DGPS on 15th and 18th April 2012. The difference between the final measured dune state and the best morphological reproduction obtained with the model is employed to estimate the sediment flux. This operation yields an output sand flux of 98.8m3 and an input of 292.6m3. This algorithm could have a great impact on the study of complex dune systems where the dunes act as sinks and sources of beach sediments and in the characterization of the beach–dune interactions.

The utility of desert sand dunes as Quaternary chronostratigraphic archives: evidence from the northeast Rub' al Khali

The distributions of optically stimulated luminescence (OSL) ages from dunes are affected by palaeoenvironmental changes, complex dune dynamics and sampling strategy. Extracting the relative importance of these factors when interpreting discontinuous OSL chronologies from sand dunes has proven difficult, and is particularly hindered in contexts where the internal sedimentary structures of dunes are not visible. In this study samples for OSL dating were taken from three major dune exposures in the Rub' al Khali, United Arab Emirates, each showing clear internal structure, with the aim of addressing these problems. Specific objectives were to assess how ages of individual sedimentary units represent dune accumulation as a whole, and how the dune record in turn reflects known past environmental changes. Final ages were calculated using the OxCal software package, by incorporating the known relative stratigraphy through the application of Bayesian methods. The results show that stratigraphy alone is not sufficient at these sites to guide OSL sampling; that is, chrono- and lithostratigraphic boundaries do not necessarily coincide. Where chronological hiatuses are present, internal sediment stratigraphy can be a useful tool in identifying potential problems of under-sampling the full dune record. The implications of these findings for reconstructing Quaternary climates from dune chronologies are considered.

Assessing significant geomorphic changes and effectiveness of dynamic restoration in a coastal dune ecosystem

A shift from restoring coastal dunes as stabilized landscapes toward more morphodynamic ecosystems is underway. This paper uses results from a recent case study where invasive vegetation was removed from a coastal dune complex in western Canada as a first step in a dynamic ecosystem restoration project. Spatial statistical methods, used in the natural sciences to quantify patterns of significant spatial–temporal changes, are reviewed and the local Moran's Ii spatial autocorrelation statistic is explored for detecting and assessing significant changes. Cluster maps of positive (depositional) and negative (erosional) changes were used to derive statistically significant volumetric changes within discrete geomorphic units (beach, foredune, transgressive dune) over one year following vegetation removal. All units experienced net increases in sediment budgets compared to a pre-restoration surface. The beach experienced the highest episodic erosion and volumetric change and greatest net annual sediment budget. Compared to the beach, the annual sediment budget of the foredune was 19% whereas the transgressive dune was 33%. The foredune recovered rapidly to initial erosion during restoration and subsequent natural events with consistently positive sediment volumes and attained a form similar to that pre-restoration. Aeolian deflation and sand bypassing through the foredune was greatest in the two months following vegetation removal and peak accretion in the transgressive dune resulted from depositional lobes extending from the foredune, smaller dunes migrating within the complex, and growth of a precipitation ridge along the eastern margin.Several methodological and logistical considerations for detecting significant change in dynamic dune landscapes are discussed including sampling strategy design, data normalization and control measures, and incorporating uncertainty and inherent spatial relations within acquired datasets to ensure accuracy and comparability of results. Generally underutilized in coastal geomorphology, spatial autocorrelation methods (e.g., local Moran's Ii) are recommended over spatially uniform threshold approaches for the ability to detect local change processes and explore hypotheses on spatial–temporal dynamics.Finally, several key geomorphic indicators, that are believed to aid in re-establishing ecological conditions and processes that favor more resilient and natural dune ecosystems, are identified for assessing the effectiveness of dynamic restoration projects including: increased aeolian activity, enlarged active sand surface area, positive sediment budgets, increased dune morphodynamics, improved geomorphic diversity, and enhanced geomorphic resilience. Although limited in temporal scope, the case study results show that the initial phase of the restoration treatment was effective in enhancing all indicators except for increasing sand surface area. Given decadal scale observations of climatic changes and longer-term eco-geomorphic trajectory toward stabilization in the region, however, it is unlikely that the geomorphic effectiveness of this restoration effort will continue without continued frequent treatment interventions.

Geomorphic and sediment volume responses of a coastal dune complex following invasive vegetation removal

ABSTRACTThis paper documents application of an established geostatistical methodology to detect significant changes in a foredune–transgressive dune complex where Parks Canada Agency (PCA) implemented a dynamic restoration program to remove invasive marram grasses (Ammophila spp.) and enhance dynamic dune habitat for an endangered species. Detailed topographic surveys of a 10 320 m2 site in the Wickaninnish Dunes in Pacific Rim National Park, British Columbia, Canada for the first year post‐treatment are compared to a pre‐restoration LiDAR baseline survey. The method incorporates inherent spatial structure in measured elevation datasets at the sub‐landscape scale and models statistically significant change surfaces within distinct, linked geomorphic units (beach, foredune, transgressive dune complex). Seasonal and annual responses within the complex are discussed and interpreted.All geomorphic units experienced positive sediment budgets following restoration treatment. The beach experienced the highest differential volumetric change (+1656 m3) and net sediment influx (+834 m3, 0 · 19 m3 m–2) mostly from supply to the supratidal beach and incipient dune. This sediment influx occurred independent of the restoration effort and was available as a buffer against wave erosion and as supply to the landward dunes. The foredune received +200 m3 (0 · 13 m3 m‐2) and its seaward profile returned to a similar pre‐restoration form following erosion at the crest from vegetation removal and scarping by high water events. Sediment bypassing and minimal change was evident at the mid‐stoss slope with appreciable extension of depositional lobes in the lee. The transgressive dune complex experienced high accretion following restoration activity (+201 m3) and over the year (+284 m3, 0 · 07 m3 m–2) mostly from depositional lobes from the foredune, precipitation ridge growth along the downwind boundary, and growth of existing lobes within the complex. Further integration of this methodology to detect significant geomorphic changes is recommended, particularly for applications where sampling densities are limited or logistically defined. Copyright © 2013 John Wiley & Sons, Ltd.

Quantifying spatial and temporal trends in beach–dune volumetric changes using spatial statistics

Spatial statistics are generally underutilized in coastal geomorphology, despite offering great potential for identifying and quantifying spatial–temporal trends in landscape morphodynamics. In particular, local Moran's Ii provides a statistical framework for detecting clusters of significant change in an attribute (e.g., surface erosion or deposition) and quantifying how this changes over space and time. This study analyzes and interprets spatial–temporal patterns in sediment volume changes in a beach-foredune–transgressive dune complex following removal of invasive marram grass (Ammophila spp.). Results are derived by detecting significant changes in post-removal repeat DEMs derived from topographic surveys and airborne LiDAR. The study site was separated into discrete, linked geomorphic units (beach, foredune, transgressive dune complex) to facilitate sub-landscape scale analysis of volumetric change and sediment budget responses. Difference surfaces derived from a pixel-subtraction algorithm between interval DEMs and the LiDAR baseline DEM were filtered using the local Moran's Ii method and two different spatial weights (1.5 and 5m) to detect statistically significant change. Moran's Ii results were compared with those derived from a more spatially uniform statistical method that uses a simpler student's t distribution threshold for change detection. Morphodynamic patterns and volumetric estimates were similar between the uniform geostatistical method and Moran's Ii at a spatial weight of 5m while the smaller spatial weight (1.5m) consistently indicated volumetric changes of less magnitude. The larger 5m spatial weight was most representative of broader site morphodynamics and spatial patterns while the smaller spatial weight provided volumetric changes consistent with field observations. All methods showed foredune deflation immediately following removal with increased sediment volumes into the spring via deposition at the crest and on lobes in the lee, despite erosion on the stoss slope and dune toe. Generally, the foredune became wider by landward extension and the seaward slope recovered from erosion to a similar height and form to that of pre-restoration despite remaining essentially free of vegetation.

Undrowning a lost world — The Marine Isotope Stage 3 landscape of Gibraltar

The Rock of Gibraltar, at the south-western extreme of the Iberian Peninsula and 21km from the North African coast, is a 6-km long limestone peninsula which was inhabited by Neanderthals from MIS 5e until the end of MIS 3. A total of 8 sites, either with Neanderthal fossils or their Mousterian lithic technology, have been discovered on the Rock. Two, Gorham's and Vanguard Caves, are the subject of ongoing research. These caves are currently at sea level, but during MIS 3 faced an emerged coastal shelf with the shoreline as far as 5km away at times. They hold a unique archive of fauna and flora, in the form of fossils, charcoal and pollen, helping environmental reconstruction of now-submerged shelf landscapes. In addition, geological and geomorphological features — a 300-metre dune complex, elevated aeolian deposits, raised beaches, scree, speleothems — complement the biotic picture.The work is further complemented by a study of the ecology of the species recorded at the site, using present-day observations. The species composition in this fossil record closely matches the present day fauna and vegetation of the Doñana National Park, SW Spain: a mosaic of pine groves, coastal dunes, shrubland and seasonal wetlands and currently the richest reserve in terms of biodiversity in the Iberian Peninsula, located only 100km to the northwest from Gibraltar.All this information permits, for the first time, the quantification of the vegetation structure of the ancient coastal plain and the modelling of the spatio-temporal dynamics of the MIS 3 coastal shelf off Gibraltar.

Three-dimensional Computational Fluid Dynamic experiments over a complex dune topography

Wakes, S., 2013. Three-dimensional Computational Fluid Dynamic experiments over complex dune topography In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)For modeling coastal dune systems the topography is often complex with complicating factors such as dune vegetation, sediment transport and the sand properties. Strategies such as simplifying the geometry and vegetation and no sediment transportation have been applied and provided insight into mechanisms of flow over the coastal dunes at Mason Bay, Stewart Island, New Zealand. Simulations building on the complexity of this modeling process are undertaken with a targeted mesh. Included was surface roughness signifying areas of vegetation but no Aeolian sediment transportation. Comparing preliminary results against the existing two and three-dimensional simulations and field data shows that although the strategy of splitting the domain in order to achieve three-dimensional results originally is workable simulating the whole domain is ideal. Grid adaption allows targeting of mesh in areas of most interest, mostly close to the dune surface and within the first 10m above the surface but needs to be done with care. There were distinct differences in wind velocity profile when comparing the results. It is also showed that the model choice has significance for turbulence parameters, with possible implications for sediment transportation, particularly at lower heights. In spite of the complex topography, the flow is strongly two-dimensional in some parts of the domain whilst strongly three dimensional in other areas. Therefore each level of simulation has a role in understanding the underlying flow mechanisms involved and what insight to the flow is required. Understanding gained from the previous work was invaluable in the extension to full three-dimensional simulations.

Geomorphological and ecological features of blowouts in a western Mediterranean coastal dune complex: a case study of the Es Comú de Muro beach-dune system on the island of Mallorca, Spain

Many of the coastal dune systems along western Mediterranean shores are in an advanced state of fragmentation and show distinct signs of erosion, largely because of blowout development along the dune front. The Es Comu de Muro beach-dune system on the island of Mallorca (Spain) is a good example of this. In order to better understand and quantify the current situation, 58 blowouts along a ca. 1.5-km-long dune front were investigated. In each case, a number of morphometric and ecological variables were analyzed as a basis for comparison and classification, in particular blowout dimensions and orientation, inner morphometry and topography, morphological types, the role of vegetation in defining the state of the foremost dune line, and the link between vegetation and blowout typology. In comparison with a recent preliminary investigation, the results of the present study provide a more comprehensive picture of the advanced state of fragmentation along the dune front. The blowouts are not evenly distributed, highest densities occurring along the southernmost part of the beach, lowest densities along the northern part. The blowouts were subdivided into two categories on the basis of their shape and general structure, trough blowouts being the most prevalent, followed by mixed trough-saucer shapes. Distinctly saucer-shaped blowouts could not be distinguished. In addition, the blowouts were subdivided into two morphological categories, i.e. simple and branched. It was also possible to link the morphological state of the dune front to certain ecological parameters, in particular vegetation which, in the present case, comprised herbaceous and woody plants. Cluster analyses of species associations (Bray-Curtis similarity indices) were carried out on the basis of the presence/absence of each species. It is shown that, on account of presence counts and the degree of similarity of species associations, some species play a more important role in stabilizing the mobile dune sands than others, a foremost candidate being Ammophila arenaria. It is concluded that active support for such plants should form part of any management strategy aiming to reduce and reverse coastal dune fragmentation processes.

Interpretation of the complex dune morphology on Mars: dune activity, modelling and a terrestrial analogue

ABSTRACTIn this work we analyze a dark erg on Mars that could be considered a mega‐dune (draa) where secondary dunes of different morphology are superposed over a main crescent‐shaped bedform (primary dune). The presence of a complex, multi‐directional wind regime is indicated as one of the main causes for the accumulation of a tall draa, presenting an analogy to the Great Sand Dunes in Colorado. In both cases, main regional winds from the SW blow in opposition to winds from the NE which are enhanced by the topography. Such a complex wind regime leads to the development of star and reversing dunes and is accurately predicted by atmospheric models on a regional and local scale. Signs of activity in the form of grainflow scars are also noted over the slip faces of many dunes, suggesting that easterly winds are actively shaping the study draa in the present‐day climatic setting. The presence of this draa on Mars suggests a complex interaction between regional and local topographically controlled flows and a consistent availability of sand. The future study of an analogue terrestrial site such as the Great Sand Dunes could be fundamental for understanding the evolution of similar Martian dune fields. Copyright © 2012 John Wiley & Sons, Ltd.

Recolonization after habitat restoration leads to decreased genetic variation in populations of a terrestrial orchid

Colonization is crucial to habitat restoration projects that rely on the spontaneous regeneration of the original vegetation. However, as a previously declining plant species spreads again, the likelihood of founder effects increases through recurrent population founding and associated serial bottlenecks. We related Amplified Fragment Length Polymorphism markers genetic variation and fitness to colonization history for all extant populations of the outcrossing terrestrial orchid Dactylorhiza incarnata in an isolated coastal dune complex. Around 1970, D. incarnata suffered a severe bottleneck yet ultimately persisted and gradually spread throughout the spatially segregated dune slacks, aided by the restoration of an open vegetation. Genetic assignment demonstrated dispersal to vacant sites from few nearby extant populations and very limited inflow from outside the spatially isolated reserve. Results further indicated that recurrent founding from few local sources resulted in the loss of genetic diversity and promoted genetic divergence (F(ST) = 0.35) among populations, but did not influence population fitness. The few source populations initially available and the limited inflow of genes from outside the study reserve, as a consequence of habitat degradation and spatial isolation, may have magnified the genetic effects of recurrent population founding.

Wood charcoal from an inland dune complex at Joldelund (Northern Germany). Information on Holocene vegetation and landscape changes

The charcoal content of an inland dune complex close to Joldelund in Northern Germany was analysed as part of a project which aims to reconstruct Holocene aeolian activity in high spatial and temporal resolution. The eleven investigated profiles contained numerous charcoal-enriched layers, providing evidence for the potential of inland dunes as palaeoarchives for anthracology. Earlier studies have found Late Roman Iron Age settlement activity and iron ore productions in the research area and in its vicinity. Charcoal assemblages date to Roman Iron Age as well as Early, High and Late Medieval Times, according to radiocarbon dating of single, species-identified charcoal fragments and the stratigraphic correlation of sedimentary units. The dominance of Quercus (oak) and significant proportions of Ericaceae-charcoal (probably Calluna vulgaris, heather) especially in the Early and High Medieval samples indicate the presence of a heathland with Quercus trees, which was managed by fire. In the younger layers of sand, a greater diversity of taxa were found, including the dominant Quercus, Fagus (beech), Alnus (alder), Betula (birch), Corylus (hazel), Fraxinus (ash), Salix (willow), Populus-Salix (poplar-willow-type), Acer (maple), Pinus (pine), Maloideae (apple subfamily), Tilia (lime), as well as some Ericaceae. The diversity of species indicates that some charcoals were transported by wind together with the sand from the surrounding areas, and do not represent the local vegetation on the dunes, but rather a nonspecific regional input. The differences in the charcoal assemblages and thus the possible correlation of aeolian units support the stratigraphic correlation of the sedimentary aeolian units. The comparison with the available pollen data from nearby mires showed a good agreement of the proportions of woody taxa, with only few exceptions.

Analyzing dune dynamics at the dune-field scale based on multi-temporal analysis of Landsat-TM images

Studying dune dynamics at the dune-field scale requires intensive fieldwork and a relatively huge dataset. However, this is not always possible with the high cost and the limited availability of data. Here, we present a technique based on the analysis of multi-temporal Landsat-TM images for studying the dynamics of different dune morphologies from five dune-field sites around the world. A pair of Landsat-TM images for each site has been used after performing several steps of image pre-processing and enhancement (i.e. image co-registration, radiometric calibration and histogram equalization). RGB-clustering is a commonly used algorithm for data compression and iso-clustering. In this study, we implemented this technique as an unconventional change-detection algorithm with 32 clustering partitions per band. A bi-temporal layerstack of the near-infrared bands was the input for the RGB-clustering process. RGB-clustering produced thematic maps that gave an immediate insight into the dune dynamics at the dune-field scale given the availability of Landsat images. The technique gave the best results with dunes developed under uni-directional wind pattern. In addition, it was also easier to detect migration of simple dunes than in compound or complex dunes. These maps can be used as a bi-temporal digital atlas of large dune-systems and help in defining areas for detailed field measurements on dune dynamics and migration. Moreover, it can be implemented in analyzing aeolian systems where field measurements are practically impossible (i.e. large and extra-terrestrial aeolian systems).

Population Variation in Dune-Dwelling Lizards in Response to Patch Size, Patch Quality, and Oil and Gas Development

We studied relationships between quality and quantity of habitat and conversion of land to caliche roads and well pads associated with oil and gas development. We asked how these factors affected abundance of dune-dwelling lizards, with emphasis on a habitat specialist, the dunes sagebrush lizard Sceloporus arenicolus. Open depressions in dune complexes are a critical landscape feature for S. arenicolus, and extensively used by all species; thus, size and total area of open depressions in a study site were our measures of habitat quality and quantity. There were significant differences in habitat quality among sites, and habitat quality and quantity were correlated significantly. Abundances of all lizards, including S. arenicolus, varied significantly among sites and this variation could be explained by amount of habitat at a given site. Relationships between oil and gas development, quantity and quality of habitat, and abundances of lizards likely occur on different spatial scales constraining our ability to detect direct effects of oil and gas development alone. Our research is the first to investigate effects of oil and gas development on an assemblage of dune-dwelling lizards.

Biological Flora of Coastal Dunes and Wetlands: Uniola paniculata L

Uniola paniculata C. Linnaeus is a New World, tropical-, subtropical-, and temperate-zone, rhizomatous grass that is often a dominant species on foredunes and on the primary dune complex. Uniola paniculata L. has low freshwater-moisture requirements, tolerates aerosol salt spray, has low nutrient level requirements, tolerates high sand temperatures, and provides extensive sand coverage. Also known as sea oats, this grass inhabits mobile and semistable dune systems and plays a significant role in trapping sand and building primary dunes. Caryopsis production is low. However, germination is enhanced by cutting into the endosperm and leaching the caryopses. Northern populations require cold treatment before germination, but southern populations are not dependent on cold treatment before exposure to a germination protocol with a 35/25°C thermoperiod.

Pedogenesis, soil mass balance, phosphorus dynamics and vegetation communities across a Holocene soil chronosequence in a super-humid climate, South Westland, New Zealand

This study quantifies progressive pedogenesis under a super-humid climate on the west coast of South Island, New Zealand. It focuses on soil morphology, pedogenic oxides, soil mass balance, phosphorus transformation and linking pedogenesis trajectories to vegetation communities. The study comprises a set of dune ridges of a coastal sand dune complex covered by unmodified conifer (podocarp)-angiosperm forest. The surface ages of the chronosequence range from 370 y to 6500 y. Rapid podzolisation is characteristic for the study area. Within 1000 y, soils reach the Spodosol stage with typical eluvial–illuvial horizons and mobilisation of Fe and Al. This period is also characterised by the most rapid losses of total phosphorus at a rate of 110 g m − 2 ky − 1 , a relative loss of 41%. Beyond 3000 y changes in soil chemistry and losses for all nutrients markedly slow. Soil mass balance shows that the 6500 y soil has lost 75% total P, 62% K, 52% Ca and 54% Na. Soil P fractions substantially change across the gradient. High leaching losses of apatite and non-occluded P in the first hundreds of years coincide with accumulation of organic and occluded inorganic forms in the topsoil and subsoil, which mitigate total P loss. Beyond 1000 y of pedogenesis, all P fractions decline at similar rates to low, more persistent levels with apatite/non-occluded P being the dominant P form after 6500 y of pedogenesis. This incipient steady state is assumed to be sustained by the advection of parent material-derived P through surface lowering and reduced biological cycling. Vegetation communities change from more diverse communities on young and less impoverished soils in the first 1000 y to less diverse and less variable communities beyond 1000 y of ecosystem development. The soil evolution-correlated vegetation changes documented in this study are consistent with general schemes of vegetation succession for the west coast of South Island.

Freshwater recharge into a shallow saline groundwater system, Cooper Creek floodplain, Queensland, Australia

Freshwater lenses have been identified as having penetrated the shallow regional saline groundwater beneath the Cooper Creek floodplain near Ballera (south-west Queensland). Piezometers were installed to evaluate the major-element chemistry along a floodplain transect from a major waterhole (Goonbabinna) to a smaller waterhole (Chookoo) associated with a sand dune complex. The floodplain consists of 2-7m of impermeable mud underlain by unconsolidated fluvial sands with a saline watertable. Waterholes have in places scoured into the floodplain. The transect reveals that groundwater recharge takes place through the base of the waterholes at times of flood scour, but not through the floodplain mud. Total dissolved solids rise with distance from the waterhole and independently of the presence of sand dunes. Stable water isotopes (δ2H and δ18O) confirm that recharge is consistent with, and dependant on, monsoonal flooding events. Following floods, the waterholes self-seal and retain water for extended periods, with sulfate-δ34S and δ18O isotopes suggesting bacterial reduction processes within the hyporheic zone, and limited interaction between the surface water and groundwater during no-flow conditions. The area occupied by the freshwater lenses (TDS <5000 mg/L) is locally asymmetrical with respect to the channel flow direction, extending down gradient along distances of ∼300 m.

Resource Management Domain (RMD)—A Concept for Sustainable Agricultural Development in Hot Arid Regions of India

The northwestern hot arid region of India has been classified in 15 resource management domains (RMDs) by integrating biophysical resources and socio-economic indicators. Each RMD is uniform with respect to the natural resource base and socio-economic indicators, thus, these have similar potential/constraints and social status. The RMDs, (1) Western dune complex-livestock based livelihood, (2) Hard pan soil-livestock based livelihood, (10) Coastal rocky upland-labor based livelihood, and (11) Coastal ranns and mud flats-labor based livelihood, have severe biophysical constraints and low socio-economic status. The RMDs with moderate biophysical constraints and medium socio-economic status are (3) Sandy plain-rainfed farming and livestock, (4) Eastern sandy plain under rainfed/limited tube well irrigation, (5) Luni basin alluvial plain rainfed/brackish water irrigation, (6) Luni–Banas pediment-rainfed/limited dug-well irrigation, (12) Kachchh mainland-rainfed/limited irrigation (13) Santhalpur aeo-alluvial plain-rainfed farming, (14) Basaltic rocky/gravelly upland rainfed farming/labor based livelihood, and (15) Basaltic piedmont/valley fill with rainfed/limited irrigation. The RMDs associated with negligible biophysical constraints and high socio-economic status are (7) Dune complex with limited canal irrigation, (8) Canal irrigated aeolian plain, and (9) Intensive canal irrigated Sutlej-Yamuna river plain. Priority areas for research and development of each RMD have been suggested. Change analysis with respect to land use, area under different crops, and crop production revealed that the region is heading towards intensification and higher yields.