Sand Dune Ecology

Forests line the course of the Kuiseb River, an ephemeral river in the Namib Desert, and several areas of these forests are characterized by high concentrations of tree death (Mizuno, 2005; Mizuno & Yamagata, 2005). We sought to clarify the relationship between recent environmental changes and such tree deaths in the region. In November 2007, we examined the roots of a seedling of Acacia erioloba that was germinated by rainfall beginning in January 2006. The Acacia erioloba had grown to a height of 10cm and its roots to over 230cm, within two years. In the sapling (seedling) stage, Acacia erioloba extends its main roots deeply until it reaches a moist, fine-grained soil layer (sandy silt) and can absorb water through lateral roots. When it reaches the stage at which the water supply from the moist, fine-grained soil layer is insufficient for its growing size, the tree extends innumerable lateral roots within a 50cm depth from the land surface, where they absorb water that has been t...

The development of selective or sequential extraction procedures for geochemical exploration programs requires intensive chemical experimentation with special attention to factors such as leaching time, temperature, grainsize and the type and concentration of leachate used in the extraction experiment. Considerable experimental error is also introduced during the chemical reaction through differences in the leachability of trace elements from different minerals as well as resorption onto suspended clay particles during the extraction procedure. The current study examines the use of statistics for determining the residence phases of trace elements utilising alternative methodologies using whole-rock geochemical data analysed from pedogenic calcrete and parent material sampled in profiles from South and Western Australia. The aims being to determine the geochemical changes that occur in the zone of calcium accumulation, i.e. does the minor and trace element composition of pedogenic ca...

Magnetic resonance sounding (MRS) was performed to evaluate its applicability for characterising groundwater at selected locations in Aswan Governorate, Egypt. The MRS mainly detects a weak but noticeable alternating magnetic field as MRS signals when the proton spin in groundwater produces non-magnetic moments and rotates around the geomagnetic field, indicating the detection of groundwater. The MRS system was first correlated at a piezometer with a known water table depth (~80 m). Subsequently, three MRS sounding stations with unknown water tables were tested at Qism Aswan at ~ 18 km from the piezometer using NUMIS Auto magnetic resonance sounding system following the MRS site common practices. The MRS data were subjected to adaptive notch filtering to remove spiky noise and potential power line harmonics, and finally enhance the MRS signals at the selected stations. The water depth (~75-95 m) estimated from the MRS data around the piezometer largely coincides with the actual depth (~80 m) at the piezometer itself. A transient electromagnetic (TEM) profile performed near the measured MRS stations indicates no water content. Unlike the MRS data for NNL-1, the data for NNL-2 and NNL-3 match well with TEM data at shallow depths. The evaluation generally indicates that the MRS method is applicable for groundwater exploration at the selected piezometer and the other three stations. However, the method necessarily requires additional denoising efforts to comprehensively characterise groundwater occurrence and aquifer parameters.

We consider three case studies of long-term plant population dynamics in Makhtesh Ramon erosion cirque in the central Negev desert of Israel. We show that rainfall is the major driving variable in this system, and that it creates large temporal and spatial variation in plant species diversity and vegetation community composition. This variability makes it extremely difficult to distinguish `signal'

The ability to form symbiotic associations with soil microorganisms and the consequences for plant growth were studied for three woody legumes grown in five different soils of a Portuguese coastal dune system. Seedlings of the invasive Acacia longifolia and the natives Ulex europaeus and Cytisus grandiflorus were planted in the five soil types in which at least one of these species appear in the studied coastal dune system. We found significant differences between the three woody legumes in the number of nodules produced, final plant biomass and shoot 15 N content. The number of nodules produced by A. longifolia was more than five times higher than the number of nodules produced by the native legumes. The obtained 15 N values suggest that both A. longifolia and U. europaeus incorporated more biologically-fixed nitrogen than C. grandiflorus which is also the species with the smallest distribution. Finally, differences were also found between the three species in the allocation of biomass in the different studied soils. Acacia longifolia displayed a lower phenotypic plasticity than the two native legumes which resulted in a greater allocation to aboveground biomass in the soils with lower nutrient content. We conclude that the invasive success of A. longifolia in the studied coastal sand dune system is correlated to its capacity to nodulate profusely and to use the biologically-fixed nitrogen to enhance aboveground growth in soils with low N content.

The analysis of co-occurrence patterns between plant species is being increasingly employed to study biotic interactions at the community level. We investigated changes in such patterns along two different abiotic stress gradients in eight sand-dune plant communities of the western coast of Portugal. We sampled a total of 72 transects consisting on 25 1 m 2 quadrats each, and we calculated the standardized effect size for each transect (SES), i.e. the differences between the observed co-occurrence patterns and simulated patterns for a random co-occurrence. The relationships between the average SES values for each site and the abiotic stress gradients, defined by the north-south geographic gradient (a surrogate of the climatic stress) and total plant cover (a surrogate of productivity), were analyzed. The factors driving co-occurrence patterns at smaller spatial scale were also investigated by a stepwise multiple regression analysis. Average SES values were significantly higher than zero in five of the studied sites, indicating lower species co-occurrence than expected by chance. These results suggest that the studied sand-dune communities studied are structured mainly by competitive interactions. At the site scale, SES values were not related to plant cover or the location along the north-south gradient. However, at the transect scale, SES values were inversely explained by different abiotic factors (the geographic position along the northsouth gradient and the plant cover). Our results indicate that the magnitude and the shifts in co-occurrence patterns along environmental gradients varied with the spatial scale and the surrogate of abiotic stress considered.

Coastal erosion is a natural process, that contributed to shaping the Nile Delta shoreline in Egypt over history. The objective of this research is to investigate shoreline changes, accretion, and erosion and to detect particularly vulnerable locations that require immediate attention. Another goal is to assess the efficiency of coastal installations that have been recently implemented along the study area and determine whether they have performed their role to the fullest or need additional modifications. Several Landsat images (TM, ETM + , and OLI) were utilized over 37 years to track the shoreline changes and were analysed using remote sensing (RS) and Geographic Information System (GIS). The digital shoreline analysis system (DSAS) was integrated with the LRR model for assessing historical changes for shorelines from 1985 to 2022 and forecasting future shoreline positions in 2030, 2050, and 2100. Most of the eight zones that make up the Delta region have lately seen the establishment of coastal projects, such as the development of the Abu Qir port's breakwater in 2021. From the results, it was found that the areas around Rosetta promontory, Burullus headland, and Damietta promontory experienced a significant and rapid retreat and with large rates over the study period, with average values of-15.7,-3.25, and-16.8 m/y, respectively. However, both the

The Hot Tubb locality, located in the Monahans Dunes just off the southern High Plains of west Texas, has yielded Folsom and Midland projectile points, as well as badly fragmented and occasionally burned remains of Bison antiquus. Because these materials occur primarily on the surface of a deflation basin within an active sand dune, which also contains artifacts of later age, the Paleoindian component cannot be easily isolated, nor have attempts to determine its radiocarbon age been successful. Nonetheless, the distribution and density of the bone and diagnostic Folsom material indicate there is spatial and possibly stratigraphic integrity to this component, which makes it possible to discern where and what Paleoindian activity may have occurred on site. We infer this was a small Folsom-age bison kill and processing locality of an estimated six animals. The lithic assemblage is marked by intensive reworking and even re-fluting of projectile points, suggesting that the supply of stone, originally acquired at sources at least 150 km distant, was low by the time of this occupation. That dearth of stone, the presence of Midland points, as well as a possible Midland point preform, may also shed some light on the longstanding 'Folsom-Midland Problem.

The Hot Tubb locality, located in the Monahans Dunes just off the southern High Plains of west Texas, has yielded Folsom and Midland projectile points, as well as badly fragmented and occasionally burned remains of Bison antiquus. Because these materials occur primarily on the surface of a deflation basin within an active sand dune, which also contains artifacts of later age, the Paleoindian component cannot be easily isolated, nor have attempts to determine its radiocarbon age been successful. Nonetheless, the distribution and density of the bone and diagnostic Folsom material indicate there is spatial and possibly stratigraphic integrity to this component, which makes it possible to discern where and what Paleoindian activity may have occurred on site. We infer this was a small Folsom-age bison kill and processing locality of an estimated six animals. The lithic assemblage is marked by intensive reworking and even re-fluting of projectile points, suggesting that the supply of stone, originally acquired at sources at least 150 km distant, was low by the time of this occupation. That dearth of stone, the presence of Midland points, as well as a possible Midland point preform, may also shed some light on the longstanding 'Folsom-Midland Problem.

The characteristic morphology of pedogenic calcic accumulations in the Argentinian Arguidolls were studied in the southern east part of the Buenos Aires province; their distribution down the soil profile and mechanism of their formation were examined. In the monolithic samples the carbonate collomorphic (cryptocrystallic) films and carbonate tubes were examined by scanning electronic microscope observations. The origin of these carbonate accumulations is chemical. Spheroid gypsum concentrations (framboids) located on the boundary between the A humus and Bt1 illuvial horizons are most likely biogenic. Two ways of formation for those spheroid gypsum concentrations are considered: accumulation of crystal "crusts" around less soluble mineral (probably calcite) by spherical cyanobacterial colonies or the spherical form of concentrations has been inherited from framboid pyrite concentrations from sea sediment which decayed by sulfate-reducing bacteria. It is suggested that gypsu...

The study is carried out in selected vulnerable localities in terms of shortage in water supply in the White Nile State, Sudan, which include El Salam, Guli, and El Gabalain localities. These locations are either situated on basement rocks or dominated by thick clayey deposits within the NW-trending isolated sedimentary rift basins. The primary goal of this study is to explore the groundwater potential zones in the selected areas. The methods of investigations are based on the integration of the processed satellite gravity data with the ground electrical resistivity survey using winner and Schlumberger configurations. The interpretation of satellite gravity data were done through the Residual Bouguer Anomaly (RBA) and second vertical derivatives (SVD) to define the configuration of the sedimentary basins as water-bearing formations. The high-density rocks are attributed to the basement rocks, where the low-density rocks are related to the sedimentary sequences in the (RBA) maps. The faults, plains, and deep fractures are delineated as sharp boundaries between different gravity anomalies in (VSD) maps. The conducted geo-electrical surveys were done on the gravity data findings, detecting the lateral and vertical variations of sub-surface geology that help to highlight the groundwater occurrences. The high resistivity values ≥ 200 Ώ m refer to the occurrences of basement rocks; the medium resistivity values 20-200 Ώ m refer to the aquifer zones, while the low resistivity values of ≤ 20 Ώ m refer to clayey sediments or to saline water in the region.

. An excavation in a sand dune in southern Michigan revealed numerous, thin -3 mm clay-enriched strata between otherwise weakly stratified, clean, fine sand deposits. The parallelism of both the sandy and clayey strata suggest that they have direct geologic origins, having been deposited during formation of the dune. Although the clay-enriched strata and the intervening sandy layers are both within the sand textural class, the former contained between 3.0% and 5.4% clay, and the latter -1.8% clay. In areas of preferred leaching, such as below vertical root traces, the clayey strata thin out and become absent, or Abend downwardB, become wavy and contorted, and take on the appearance of typical pedogenic lamellae. These observations support a theory of lamellae genesis that is both pedogenic and geogenic. Thin sedimentary strata may be pedogeni-Ž . cally AtransformedB into features that would normally be described as entirely pedogenic lamellae. Thus, many thin lamellae in Pleistocene-aged soils may simply be deformed and pedogenically altered sedimentary strata. This conclusion has implications for the nature and cyclicity of clay deposition in environments where thin lamellae are common in sandy soils.

Accurate estimation of sediment transport is critical for many fluvial processes but remains challenging due to high-frequency dynamics. Using novel acoustic flow instrumentation, we quantified the contribution of turbulent bed and suspended sediment fluxes to the total sediment fluxes along an entire dune profile and over the full flow depth. We found that over the dune stoss side and in the bed load layer, the turbulent mean streamwise flux is negative and reaches up to 40% of the total mean streamwise flux. Over the lee side, where turbulent intensities are highest, the contribution of the turbulent mean streamwise flux to the total mean streamwise flux is larger and reaches up to 50%. The mean vertical turbulent flux along the entire dune bed and in the bed load layer reaches nearly 30% of the total mean vertical flux. Turbulent sediment flux may thus constitute a large component of the total flux.

Accurate estimation of sediment transport is critical for many fluvial processes but remains challenging due to high-frequency dynamics. Using novel acoustic flow instrumentation, we quantified the contribution of turbulent bed and suspended sediment fluxes to the total sediment fluxes along an entire dune profile and over the full flow depth. We found that over the dune stoss side and in the bed load layer, the turbulent mean streamwise flux is negative and reaches up to 40% of the total mean streamwise flux. Over the lee side, where turbulent intensities are highest, the contribution of the turbulent mean streamwise flux to the total mean streamwise flux is larger and reaches up to 50%. The mean vertical turbulent flux along the entire dune bed and in the bed load layer reaches nearly 30% of the total mean vertical flux. Turbulent sediment flux may thus constitute a large component of the total flux.

Climate warming may appear fatal for many plant species. Thanks to evolutionary formed mechanisms of resistance xerophytes possess high ability of adaptation to elevated temperature and water deficiency. That is why the knowledge of biology of drought resistant species seems very important for possible recovering of deserted regions in future. Antioxidant system is regarded to play an essential role in plant resistance against water deficiency. On the base of analysis of antioxidant system, stress-adaptation strategies of xerophytes, growing at two arid habitats of Georgiav. Udabno (Iori plateau) and Kotsakhura gorge (Kvernaqi hill), has been investigated. It was established that several mechanisms of antioxidant system are involved in stress-resistance of studied xerophytes. In some cases these mechanisms were similar in species of the same habitat and may be linked with environmental conditions; while in some cases the specific peculiarities of plants were revealed. In particular, ascorbate-tocopherol system was activated in most experimental species. Protective mechanism of phenolic substances accumulation was active in all species as well. Udabno plants were distinguished by the accumulation of osmoprotective soluble carbohydrates; while accumulation of another osmoprotectant-proline was common in both habitat plants.

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With its N-NW exposure, the western part of the Polish coast, between Niechorze and Swinoujscie, is subjected, like a whole Polish coast, to the action of the storm surges. In this area two types of coast may be distinguished: Pleistocene cliff coast made-up of clay and sand and a barrier dune coast built of Holocene sands. In particular, our study

Porto Primavera geosite comprises aeolian sandstones with tetrapod trace fossil cropping out at the Porto Primavera Hydroelectric Power Plant, São Paulo State, Brazil. The Upper Cretaceous Rio Paraná Formation, which contains these tracks, is composed of medium–fine quartzarenites well- sorted and supermature, with typically large tabular/trough cross-bedding.  They accumulated in complexes of large barchanoid dunes, moved by winds to the south-west. The Porto Primavera association consists of tracks of theropod dinosaurs and small mammals preserved in concave epirelief. These rare records in aeolian desert environments from the Late Cretaceous of Brazil indicate that even the interior Caiuá desert was occupied by organisms. The study focused on the characterization of the ichnofossils, assessing their susceptibility to degradation by natural and anthropogenic  processes, and proposing measures to manage the geosite. Because the risk of degradation of the geosite is high, it is prop...

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In boreal systems, soil profiles typically consist of distinct stratified horizons, with organic layers at the surface overlying deeper mineral horizons providing microhabitat variation along a depth gradient, and vertical stratification of fungal communities along such soil profiles is commonly observed. We studied fungal community structure in a coastal pine forest along a gradient of decreasing influence from the coast. In this system, the vertical stratification pattern of soil microhabitats (defined here as organic, mineral with roots and mineral without roots: O, MR and MN, respectively) is non-uniform; organic horizons are sometimes buried under drifting sand dunes. Our results show that soil microhabitats are distinct with respect to physiochemical characteristics, community composition and OTU richness. While community composition was partly related to depth and distance from the coastal forest edge, microhabitat appeared to have the strongest influence. A closer inspection...

The activity concentration of natural radionuclides in soils and sediments is dependent on many factors, such as the rock parental material, pedogenic and weathering processes, physical and chemical properties of the environment, anthropogenic sources, among other aspects. There are few studies about the levels of natural radionuclides in reservoirs in both, international and national, literature. The objective of this paper was to evaluate the activity concentrations of 238U and 232Th by Instrumental Neutron Activation Analysis and 226Ra, 210Pb, 228Ra, 228Th and 40K by gamma spectrometry in two soil profiles and three sediment cores collected in the catchment area of Jundiai reservoir, located in the state of São Paulo, Brazil. Principal component analysis was applied to verify the correlation of the activity concentrations of the natural radionuclides with physical and chemical properties of soil and sediment samples.  The mean activity concentrations of the radionuclides in the s...

The decreasing groundwater level (GWL) in degraded tropical peatland areas during the dry season has been one source of annual peat fire disasters in Central Kalimantan. After the severe peatland fire in 2015, Peatland Restoration Agency's strategies' peatland restoration efforts enhance peat moisture and increase the groundwater level of the hundreds of deep wells and canal blocking in the burned area of 2015. This study examines the use of geoelectric resistivity methods in determining the attachment or position of layers and types of aquifers in transition and inland tropical peatland. The research was conducted on transitional peatlands in Sidodadi Village with 19 estimate points of resistivity geoelectric, nine estimate points in the inland swamp in Taruna Jaya Village, and 18 estimate points Kalampangan Village. This research used the quantitative approach is a one-dimensional (1 D) resistivity geoelectric, which using the Schlumberger array. While the qualitative process verified the result of sequences observation with two drill wells in Sidodadi, two drill wells in Taruna Jaya, 18 hand drill wells in Kalampangan, and geological stratigraphy. The research results obtained 4 (four) layers of composition with resistivities ranging from 1.224 -661.1 Ωm in Sidodadi, ranging from 3.37 -7,950 Ωm in Taruna Jaya Kalampangan ranging from 5.36 -16719 Ωm. The geoelectric data and field verification interpretation show that the soil/lithology layer consists of 4 (four) layers: peat, sand, sandy clay, and clay. The type of aquifer is an unconfined aquifer. The type of aquifer is an unconfined aquifer.

In Nigeria, desertification has become one of the most pronounced ecological disasters, with the impacts mostly affecting eleven frontline States. This has been attributed to a range of both nat-ural and man-made factors. This study applied a remote sensing-based change detection and indicator analysis to explore land use/land cover changes and detect major conversions from ecologically active land covers to sand dunes. Results indicate that areas covered by sand dunes (a major indicator of desertification) have doubled over the 25 years under consideration (1990 to 2015). Although about 0.71 km2 of dunes have been converted to vegetation, indicative of the success of various international, national, local, and individual afforestation efforts, conversely about 10.1 km2 of vegetation were converted to sand dunes, implying around 14 times more de-forestation compared to afforestation. Juxtaposing the progression of sand dune with climate records of the study area and examining the re...

Introduction: Sulfates on Mars have been directly studied or inferred from a variety of experiments. These include the in situ Viking Lander XRS experiments [1] and laboratory chemical analyses of martian meteorites [2, 3]. Mars Pathfinder [4] and more recently the MER rovers have measured sulfur with the alpha particle backscatter experiment. The sulfatecontaining rocks at Meridiani [5] have been found to contain the mineral jarosite, which can be uniquely identified with the Mossbauer instrument. The identification of jarosite at Meridiani was one of the early indicators of aqueous processes at that site [6]. Various Fe, Ca, and Mg sulfates have also been identified in the rocks of Columbia Hills [7], with varying degrees of aqueous alteration inferred in several different rock classes. Recent maps of hydrated and sulfate mineral distributions on Mars have been obtained from the Mars Express OMEGA experiment [8], and these together with additional data expected soon from the Mars Reconnaissance Orbiter will significantly enhance the site selection process for future surface landers, for either in situ exploration or sample return. The 2009 Mars Science Laboratory (MSL) [9] is designed to greatly expand our ability to identify minerals on Mars as well as associated organic or inorganic volatiles. Samples screened by MSL remote sensing and contact instruments can be processed and delivered to one of two locations in the MSL Analytical Laboratory (AL): the MSL CheMin (XRD/XRF) experiment will provide definitive mineralogy, while the Sample Analysis at Mars (SAM) instrument suite will measure the chemical and isotopic composition of volatile species. Evolved gas analysis by SAM: The Mars Science Laboratory utilizes a highly mobile rover and a sophisticated set of sample acquisition, screening, and processing tools. Selected samples will be examined with advanced laboratory-like analytical instruments to assess sites on Mars as potential habitats for past or present life, through the most comprehensive geological and chemical analysis possible within the constraints of in situ robotic investigation. The SAM instrument suite includes an evolved gas analysis (EGA) measurement mode in which volatiles released from rocks and fines are continuously sampled by a quadrupole mass spectrometer or a tunable laser spectrometer as sample temperature is raised from ambient to 1100 °C.

In this report, we re-examine the debate over the origin of the Martian polar chasmata based on new imaging data provided by the Thermal Emission Imaging System (THEMIS) [1], topographic data from the Mars Orbiter Laser Altimeter (MOLA), and high resolution images from the Mars Orbiting Camera (MOC) . Our primary focus is the north polar region of Mars, including Chasma Boreale, largest of the Martian polar re-entrants, and two adjacent smaller chasmata (Figure ). We conclude that a model for chasmata formation that emphasizies long-term aeolian erosion and modification of the polar layered material best explains the available data. We focus our analysis on the aeolian depositional and erosional features within and surrounding the chasmata and the stratigraphic and morphologic relationships exposed within walls of the arcuate and sinuous head scarps. Cap unit of sinuous scarp Remnant conical mounds and plates derived from cap unit 20 km Lunar and Planetary Science XXXVIII (2007) 1342.pdf

FEW OTHER SITES IN THE HISTORY of Oceanic archaeology have spawned as much research investment as the Sigatoka Sand Dunes on the Coral Coast of Viti Levu in Fiji (Figure ). Continuous erosion on the face of this extraordinary geological feature over the past half-century has exposed a wide array of archaeological materials dating from the initial period of Fijian settlement up to and including the historic era. Numerous archaeologists have conducted surveys, surface collections, or excavations here, and each has used his or her results to create or refine our understanding of the site and Fijian prehistory. As was illustrated in pivotal excavations at the dunes in the mid 1960s by Lawrence , the ability to delineate cultural complexes at Sigatoka is greatly enhanced by large volumes of temporally diagnostic ceramics, including restorable vessels, by a rapid burial of archaeological remains and by consequential separation of cultural strata by sterile lenses of sand. Yet, and in spite of the large number of projects, the Sigatoka Sand Dunes archaeological record remained enigmatic, if not problematic, at the turn to the twenty-first century (see . Notwithstanding the literally hundreds of thousands of ceramic sherds recovered from the site and the widespread occurrence of human burials (Best 1989;, only limited evidence for sustained occupation was present . Indeed, prior to 2000 architectural or habitation features were rarely encountered, faunal material of any substance was nonexistent, and the nonceramic artifact assemblage amounted to little more than the occasional adze or grinding stone (Birks 1973: 47-50). And in a recent review of Sigatoka archaeology by Marshall et al. (2000: 5-8), even the usefulness of the Sigatoka ceramic sequence for modeling Fijian culture history was challenged. In this paper, I present initial results of an excavation project undertaken on the eastern end of the Sand Dunes in May and June of 2000. Recovered materials resolve many of the incongruities as given, and they provide a new and important data set by which to reconfigure an understanding of mid-sequence occupations

The overall design of the BEMA rotary actuators and associated challenges of developing a severely massconstrained solution with a common architecture for the Deployment (DEP), Steering (STR), and Drive (DRV) actuators is presented throughout this paper. While all three types of actuators are similar in design, some distinct variations were necessary due to the requirements on each to perform the driving, steering, deployment, and wheel walking operations of the ExoMars Rover. The actuators performance and qualification environments are summarized against the stringent requirements of the ExoMars mission. Furthermore, the test-as-you-fly philosophy will be discussed, together with methodologies adopted for actuator subassembly testing. Testing across a number of hardware prototypes included static loading, vibration, shock, low pressure thermal cycling in N2, life cycling in CO2, and exposure to dust and soil. Hardware was also exposed to Dry Heat Microbial Reduction (DHMR). The les...

Intraspecific competition and predation are core interests of ecology due to their ability to influence population dynamics. While these interactions have been investigated at length, non-lethal effects of predation and their interaction with intraspecific competition are still poorly understood. In this study, we placed two species of gerbils (Gerbillus andersoni allenbyi and Gerbillus pyramidum) in a vivarium where we could manipulate predator (barn owl, Tyto alba) presence and gerbil density, while keeping both species isolated. In that setting, we quantified gerbil foraging behavior by measuring the time they spent in food patches and the vigilance they employed in those patches. Food patches varied in risk (probability of being preyed upon), depending on moonlight and presence of owls. We expected that increased competition would decrease gerbil vigilance and lead them to use more dangerous patches. We found support for that expectation. Intraspecific competition suppressed the response to predators in contrast to a predator-mediated competition, where predation suppressed competition. Both species of gerbils behaved differently at highdensity with no predators, with G. a. allenbyi decreasing vigilance in the face of predators while G. pyramidum increased vigilance in predators' absence. This difference may be caused by G. a. allenbyi facing stronger intraspecific competition than G. pyramidum. If it were subjected to high degrees of intraspecific competition, G. a. allenbyi may experience less interruptions in foraging bout when the owl is present as it might reduce the number of confrontations with competitors.

El desconocimiento sobre la ecologia de las especies invasoras limita el desarrollo de estrategias para evitar su propagacion, que es la segunda mayor causa de perdida de la biodiversidad y de extincion. En este estudio se describen la estructura macroscopica, microscopica y la dinamica de los ovarios de Hemidactylus mabouia , se establece el patron reproductivo de las hembras de una poblacion de este geco en La Habana, y se relaciona con factores ambientales. Entre mayo y diciembre de 2007 se recolectaron 41 hembras de esta especie en La Habana. La menor hembra sexualmente activa capturada tuvo una longitud hocico-cloaca de 51,6 mm. Los ovarios se clasificaron en cinco categorias reproductivas que, unidas al comportamiento mensual del peso ovarico, permiten afirmar que las hembras siguen un patron reproductivo ciclico. Los meses con mayor actividad reproductiva fueron mayo y junio, mientras que los de menor actividad fueron septiembre, octubre y noviembre. No se observaron huevos o...

Climate change scenarios for NW Scotland and the Western Isles envisage a combination of rising sea level, increased winter precipitation, and increased frequency and severity of winter storms. The flat, low-lying machair lands of the Uists are thus particularly vulnerable, not only from marine overtopping of coastal dune ridges, but also from inland flooding and restricted drainage, which may enhance the duration and area of seasonal standing waters within the machair lands. The drainage network of the Uist machairs is a legacy of historic drainage of a more extensive loch network, which now forms an intricately balanced complex of linked water bodies exhibiting a wide range of pH and salinity. Any future change in water levels would impose significant environmental shifts. The conservation importance of machair is significantly augmented by a pattern of rotational cultivation that largely employs traditional methods and provides species-rich fallows. This tradition is already unde...

Les missions de recherches dans les sites mauritaniens de l'Azrag ont permis une première description d'empreintes de pas humains observées dans les sédiments de la sebkra El Azrag, située à 30 km de la ville minière de Zouérate en République islamique de Mauritanie. Cette vaste cuvette peu profonde de 6 km de long sur 1,5 km de large s'intègre dans un vaste ensemble de dépressions qui se succèdent selon un axe Nord-Est/Sud-Ouest sur plus de 25 km, en bordure du massif dunaire d'El Hammami. L'étude anthropologique de 118 empreintes a été effectuée par mesures directes et par méthode photogrammétrique. Les mensurations des empreintes montrent une variabilité qui ne peut s'expliquer que par la présence d'enfants et d'adultes des deux sexes. L'aspect morphologique des empreintes est compatible avec des populations de type leucoderme, avec une arche plantaire marquée. La comparaison des empreintes de l'Azrag avec les populations actuelles d'Afrique de l'Ouest montre que les Peuls et les Maures de l'Adrar sont les populations morphologiquement les plus proches en particulier pour la longueur et la largeur du pied. Onze pistes de pas ont été étudiées, la plus longue comportant 21 empreintes. L'appui plantaire et l'asymétrie des empreintes droites et gauches d'une piste de pas sont en faveur d'une anomalie des membres inférieurs.

* Mean annual values over the simulated 30 year time period, e.g. mean of the annual minima. These give an indication of long-term sustainability under a changing climate ** The maximum/minimum value for the 30 year time period, i.e. highest and lowest records. These indicate the effect of extreme events (floods/droughts) under a changing climate

Groundwater in the Gaza Strip is the only source of water for domestic, agricultural and industrial uses. Extensive pumping has caused serious quantitative and qualitative problems in the aquifer. The hydrochemical facies are evaluated using the trilinear diagram for 200 water samples. Groundwater in the north and west is mostly characterized by Ca-Mg-HCO 3 facies (alkaline water), and in the south and east by Na-Cl-SO 4 facies (saline water). Sand dunes and rainfall are the major factors controlling the distribution of hydrochemical facies. The eastern edge of the sand dune belt is considered the barrier that separates the two major facies. Brackish water flowing from the east is mixed with rainwater which infiltrates through the sand dunes to the aquifer. Other factors, e.g. seawater intrusion and extensive pumping, play a minor role in the distribution of the hydrochemical facies.

In this paper we describe the sedimentary characteristics of the 2004 Indian Ocean tsunami deposits in and around Periya Kalapuwa Lagoon, Sri Lanka. Periya Kalapuwa is a coastal lagoon of about 13 km 2 area and has an average depth of about 1 m. It is separated from the Indian Ocean by coastal barrier sand dunes of up to 9m elevation through which two inlet channels open the lagoon to the ocean. This region was hit by three waves during the 2004 Indian Ocean tsunami. The second wave was largest (4-6 m) and entered the lagoon not only via the two inlet channels, but also by flowing over the sand dunes. Erosive scars were found on the sand dunes adjacent to the two inlets. Twenty-seven core samples, along with trenching and hand-auger data, show that the tsunami deposits are 9 cm thick on average (up to 35 cm in the lagoon and up to 66 cm on the shore) and are composed mainly of medium sand (mean grain size 1.06 φ) with low mud content (0.61 wt.%), which is similar to the composition of sand from near the erosive scars in the sand dunes (mean grain size 0.94 φ), but different from the lagoon deposits (mean grain size 1.68 φ; mud content 4.7 wt.%). The distribution of the tsunami deposits was limited to within about 1 km from each inlet. The tsunami deposits become thinner and finer grained with increasing distance from the inlets. Most of the tsunami deposits are massive, but some show sedimentary structures: single or multiple-graded bedding structures, parallel laminations defined by layers of heavy minerals, and muddy laminations. Our observations and analyses suggest that the tsunami deposits were formed mainly from sand eroded from sand dunes near the two inlets. We estimated the total volume of tsunami sediments to be 83 000 m 3 . By assuming that the sediments of the tsunami deposits were supplied only by erosion of sand dunes from near the two inlets, this is equivalent to erosion of 83 m 3 of sand per meter of sand dune traversed by the tsunami wave.

The coastal dunes belong to the most important ecosystems in the Netherlands, but they have also suffered from prolonged desiccation, changes in land use, diminished coastal dynamics, and acidification. Environmental management is applied to counteract the deterioration of threatened dune vegetation and to maintain biodiversity. An efficient and reliable monitoring system is necessary to investigate autonomous vegetation development and to evaluate the effects of nature conservation and restoration measures such as cattle grazing. Monitoring of the vegetation is supported by the classification of remote sensing images. As the spectral characteristics of vegetation change during the growing season, the discrimination between vegetation types may vary too. In order to determine an appropriate period for collecting hyperspectral imagery of coastal sand dunes, a GER field spectrometer was used to collect reflectance data of several dune grassland types in the Amsterdam Water Supply Dunes in different periods from May to July 2001. The data were transformed into the spectral configuration of a hyperspectral GER EPS-A scanner, which was used to make a hyperspectral image of this area (1). The reflectance spectra were analysed for statistically significant differences between vegetation types. The results illustrate that the spectral characteristics of dry dune vegetation do change during the growing season. It is concluded that the best discrimination is achieved by the end of May and that a field spectrometer can help to determine a convenient period for hyperspectral imagery.

Topographic variations affect the reflectance properties of the Earth's surface and are often removed in remote sensing studies, especially when significant terrain variations exist. In this study, however, we show that shading effects assessed by Landsat can be treated as a signal that stores important topographic information, especially when the spectral characteristics of a surface are homogenous. The coastal transverse dunes of the Ashdod area, and the desert linear dunes of Nizzana (both located in Israel), were selected to investigate the abovementioned idea. The dune heights in these areas are 10 m on average (relative to their surroundings) and have maximum slopes of 33j. An innovative method for extracting slope, aspect, and height data for sand dunes using Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) images was developed, based on the regularity and periodicity of dunes' landscapes. Using two Landsat images representing different sun zenith and azimuth angles, reflectance values of each image were converted to cos(i) values (i = incident angle between the surface normal and the solar beam radiation), applying histogram matching methods. The slope and aspect of each pixel were determined as those that give the best prediction of the observed value of cos(i). Height profiles were then extracted, using simple trigonometric relationships. The accuracies of heights and slopes along selected profile lines were to the order of 1 m and 3j, respectively (at a spatial resolution of 15 m). Best results were obtained when the images included one from the summer and the other from the winter, corresponding to maximum difference in solar zenith and azimuth angles. Errors in heights were attributed to surface heterogeneity (e.g., presence of biogenic soil crusts in the rainy season), geometric correction errors, cast shadows, and Bidirectional Reflectance Distribution Function (BRDF) effects. Comparison to Advanced Thermal Emission and Reflection Radiometer (ASTER) 3D information showed that the proposed method is better in representing the topographic variation of the area than the digital elevation model (DEM) produced by ASTER.

The coast of Ceará State in NE Brazil is covered by vast fields of active and stabilized coastal sand dunes. Its tropical climate is characterized by two seasons, wet and dry, with wind intensity determined by the meridional shift of the Intertropical Convergence Zone. The wind power is negatively correlated with precipitation, and precipitation is negatively correlated with the difference between sea surface temperatures of the tropical Atlantic north and south of the equator. We present a model suggesting that during the Late Pleistocene wind power determined the mobility and stability of the dunes. Sand dunes accumulated during periods of high wind power (as it is today) and stabilized when wind power was low. Once the dunes were stabilized by vegetation they could not be activated even by increased wind power. Samples that were taken for luminescence dating from 25 stabilized dunes along the coasts of Ceará gave ages ranging from135 ka to < 100 yr. We postulate that these lum...

Soil rubification is defined as a pedogenesis stage in which iron is released from primary minerals to form free iron oxides that coat quartz particles in soils with a thin reddish film. This study used an airborne hyperspectral sensor to spatially map soil rubification on the surface of coastal sand dunes in Israel. The area selected for this study is located south of the city of Ashdod, Israel, and is one of the last remaining coastal sand dune areas in the country. The study area occupied about 60 km 2 , and was covered by two flight lines of the CASI 48-channel sensor from an altitude of 2650 m, providing a pixel size of about 3 m. A traditional way to estimate rubification is to chemically measure the iron oxide concentration in the sand. The Dithionite Citrate Bicarbonate (DCB) method, which is a laboratory bwetQ-based procedure, was used to precisely measure the free iron oxide status of selected locations along the area. The soil reflectance properties of these samples were measured in the laboratory across the Visible and Near InfrarRed (VIS-NIR) region and was used with the DCB-Fe data to evaluate a spectral-based model for assessing the rubification extent solely from spectroscopy. After the CASI data were atmospherically, BRDF and geometrically corrected, they were run against the spectral model on a pixel-by-pixel basis, generating a rubification map from a far distance. Spectral validation of independent samples and field measurements of dune movement over 17 months showed that the map is reliable and significantly correlated with known stabilization processes throughout the area (the overall accuracy estimated as 78%). It was concluded that soil spectroscopy, either from field or air, enables the detection of small changes in the Fe absorption feature across the VIS region that provides information regarding the iron oxide minerals and content. This supports the utilization of a sensitive airborne hyperspectral sensor to rapidly and quantitatively evaluate spatial information concerning important pedogenic processes.

The changes in color of sand dunes from white to yellow or red is often interpreted to signify their age or their source materials. In this study we demonstrate the effect seasonal inter-dune freshwater ponds have on the bleaching of the color of sand dunes by iron reduction in the anaerobic conditions they create. By combining spectral measurements of field samples of dune sand together with the analysis of satellite images covering three dune fields in NE Brazil (Lençóis Maranhenses, Jericoacoara and Canoa Quebrada) we demonstrate its existence in the field. In areas where ponds cover 41% of the dune field (as in Lençóis Maranhenses) an almost total bleaching in the color of the sand occurs after which the dunes remain white with no relation to distance from the coastline. In areas with less ponds (e.g. Jericoacoara or Canoa Quebrada) dune whitening is less active, and there are areas where dune rubification occurs. As this process may have occurred in other dune fields during past climate conditions that may have been different from current ones, interpretations of dunes age based on their color should be handled with care.

To study the environment of the Kipushi mining locality (LMK), the evolution of its landscape was observed using Landsat images from 2000 to 2020. The evolution of the landscape was generally modified by the unplanned expansion of human settlements, agricultural areas, associated with the increase in firewood collection, carbonization, and exploitation of quarry materials. The problem is that this area has never benefited from change detection studies and the LMK area is very heterogeneous. The objective of the study is to evaluate the performance of classification algorithms and apply change detection to highlight the degradation of the LMK. The first approach concerned the classifications based on the stacking of the analyzed Landsat image bands of 2000 and 2020. And the second method performed the classifications on neo-images derived from concatenations of the spectral indices: Normalized Difference Vegetation Index (NDVI), Normalized Difference Building Index (NDBI) and Normalized Difference Water Index (NDWI). In both cases, the study comparatively examined the performance of five variants of classification algorithms, namely, Maximum Likelihood (ML), Minimum Distance (MD), Neural Network (NN), Parallelepiped (Para) and Spectral Angle Mapper (SAM). The results of the controlled classifications on the stacking of Landsat image bands from 2000 and 2020 were less consistent than those obtained with the index concatenation approach. The Para and DM classification algorithms were less efficient. With their respective Kappa scores ranging from 0.27 (2000 image) to 0.43 (2020 image) for Para and from 0.64 (2000 image) to 0.84 (2020 image) for DM. The results of the SAM classifier were satisfactory for the Kappa score of 0.83 (2000) and 0.88 (2020). The ML and NN were more suitable for the study area. Their respective Kappa scores ranged between 0.91 (image 2000) and 0.99 (image 2020) for the LM algorithm and between 0.95 (image 2000) and 0.96 (image 2020) for the NN algorithm.

The origin of extensive sand terrains which lie inland from the coastal margin of Western Australia is contentious, with the debate centering around an in situ vs. an aeolian origin. To resolve this debate the shape and surface features of sand grains are reported for sandplains, sand dunes and bedrock for the Victoria Plateau sandplain, which lies in the central west coastal region of Western Australia. All three components of the Victoria Plateau are similar in grain shape and microtexture. Quartz grains show a combination of chemical dissolution and precipitation micromorphology. Characteristics of dissolution include etch patterning, triangular shaped etch pits and solution features. Precipitation forms include edge rounding, silica veneers and plate-and sheet-like structures. Features such as peeling plates, complex precipitation forms projecting from grain surfaces, adhering particles and preserved grain contact faces indicate stability rather than a transport dominated environmental history. The combination of preserved dissolution and precipitation forms, a dearth of mechanically derived features and a correspondence between grains in rock and overlying sands points to local siliceous sedimentary rocks as the source of the sands.

Metriorrhynchus rhipidius (Macleay) (Coleoptera: Lycidae) has been observed feeding and presumably pollinating the flowers of a number of heathland plants on sand dunes in central, coastal New South Wales. These species are: Leucopogon lanceolatus (Sm.) R.Br., Leucopogon virgatus (Labill.) R.Br., Brachyloma daphnoides (Epacridaceae), Leptospermum polygalifolium Salisb. (Myrtaceae) and Conospermum taxifolium (Proteaceae). The beetles were aggregated in various areas where the food plants were profusely flowering and were absent from most areas within the sand dune system. The mouthparts of Metriorrhynchus are suitable for obtaining nectar from the more tubular-shaped flowers of Leucopogon, Brachyloma and Conospermum. The open bowl-shaped flowers of Leptospermum are easily accessible for the Metriorrhynchus beetles.