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1.
An association between salt pans or dry lake beds and distinctive crescentic lake-floor sand mounds (1–10 m high, tens to hundreds of metres wide) is commonplace in desert systems. In the Makgadikgadi Basin of northern Botswana, a debate about the formative processes of these landforms has persisted despite numerous morphometric, sedimentary and geochronological analyses, with mound landforms variously inferred to be aeolian dunes, subaqueous dunes, spring mounds or shoreline remnants. We propose a new formative mechanism which draws on the interaction between uneven moisture distribution on the pan surface and mobile aeolian sediments. We use a numerical model (ViSTA), which couples vegetation and aeolian sand transport dynamics, together with optically stimulated luminescence (OSL) dating of a mound in the Makgadikgadi Basin to investigate the feasibility of this ‘sticky mound hypothesis’. We find that under a range of modelled environmental conditions, uneven moisture distribution on the pan surface can lead to the development and stabilization of crescentic aeolian dunes, with these dunes growing upwind from the point of initial deposition, corresponding with the chronological data gained from OSL dating of a mound feature. On removal of this moisture, the modelled dunes erode and dissipate. These findings suggest that the formative mechanism of the mounds could be dependent on the interaction between differential drying of the pan surface and the competence of the aeolian sediment transport system across the pan floor.  相似文献   

2.
Biotic influences on geomorphology (and vice‐versa) are ubiquitous. This paper explores whether landforms may be extended (composite) phenotypes of biota, based on four criteria: process–form relationships between biota and landforms; evolutionary synchrony; selective pressure via ecosystem engineering and niche construction; and positive feedback benefitting the engineer organism(s). Coral reefs, peat bogs, biomantles, insect mounds, grassland soils, salt marshes, mangrove swamps, and some vegetation‐dependent sand dune types clearly meet these criteria. Karst landforms, meandering rivers, and tree uprooting pit‐mound systems meet the first three criteria, but positive feedback to engineer organisms has not been established. Research in biogeomorphology will surely identify other extended phenotypes. Implications are that biological evolution will continue to drive landscape metamorphosis, the appearance of new landform types, and presumably the disappearance of extended phenotypes associated with extinct species. Independently of extended phenotypes, tightly‐coupled geomorphological–ecological interactions such as coevolution, and biogeomorphic forms of ecosystem engineering and niche construction are common. The toposphere, encompassing Earth's landforms, is partly a biotic construct. Some elements would be present in an abiotic world, but the toposphere would not exist in anything resembling its contemporary state without a biosphere. This raises important questions with respect to Earth system evolution. The bio, litho‐, atmo‐, hydro‐, topo‐, and pedospheres coevolve at the global scale. Major biotic events have driven revolutions in the other spheres, but the atmosphere and the global hydrological system seem to have been relatively steady‐state at the global scale. The toposphere and pedosphere have not. This suggests that perhaps landforms and soils provide the major mechanisms or degrees of freedom by which Earth responds to biological evolution. Landforms and soils may thus be the ‘voice’ of the biosphere as it authors planetary change, even if clear biotic signatures are lacking. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

3.
Insects are the largest and most diverse group of living organisms on Earth, playing a critical but underestimated role as agents of geomorphic change. Burrowing insects create micro-scale landforms such as subterranean tunnels and surface mounds and, by this way, exert an influence on hydrology, soil erosion and sediment transfer at a wider landscape scale. However, social insects represented by ants and termites were the main taxa studied as geomorphic agents and ecosystem engineers. This article proposes an extended and critical literature review of insects as zoogeomorphic agents, with reference to various taxonomic orders and families of insects having a burrowing behaviour. It provides a large overview of their primary and secondary impacts on Earth surface systems, both supported by naturalistic evidence and available quantitative data. Some evolutionary insights are discussed based on fossil evidence of geomorphic work by insects and, at finer temporal scale, on recent advances in radiometric and luminescence dating of insect mounds. Finally, this article explores the fruitful links between geomorphology and entomology, and suggests several research perspectives in order to develop an integrated understanding of the importance of insects in Earth surface processes and landforms. © 2020 John Wiley & Sons, Ltd.  相似文献   

4.
The growth of segregated ice lenses in frost susceptible sediments in the discontinuous permafrost zone is the dominant mechanism for the formation of permafrost mounds, such as palsas, lithalsas and permafrost plateaus. Thawing of these mounds creates thermokarst lakes, which are particularly abundant in Nunavik, east of the Hudson Bay area. The inception of the permafrost in mounds and their growth are regulated by climate conditions, by local Quaternary geology and by environmental factors such as topography, vegetation, snow cover and surface humidity. Variable sizes and morphology of the permafrost mounds can be attributed to local factors that affect the ice segregation process, particularly the supply of water needed for ice‐lens growth and grain‐size composition of the soil into which aggradation takes place. Computer image analysis of CT scans on high quality cores obtained from permafrost mounds and plateaus of various shapes reveal that the ice layer sequences and permafrost internal structure vary with landform types. A relationship therefore exists between different morphological type within a family of landforms and their microscale internal structure. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

5.
Sunset Crater in north‐central Arizona (USA) is a 900‐year‐old scoria‐cone volcano. Wind action has redistributed its widespread tephra deposit into a variety of aeolian dune forms that serve as a terrestrial analog for similar landforms and aeolian processes on Mars. Fieldwork was conducted to collect essential geomorphological and sedimentological data, and to establish a baseline for the type and morphometry of dunes, physical properties, interactions with topography, and saltation pathways. Our analyses focused primarily on coppice dunes, falling dunes, wind ripples, and sand streaks. For all collected volcaniclastic aeolian sediment samples, the sand‐size fraction dominated, ranging from almost 100% sand to 74.6% sand. No sample contained more than 1.6% silt. The composition is overwhelmingly basaltic with non‐basaltic particles composing 2 to 6% of the total. Coppice (nebkha) dunes form where clumps of vegetation trap saltating particles and create small mounds or hummocks. Mean grain size for coppice dune samples is coarse sand. Measured dune height for 15 coppice dunes ranged from 0.3 to 3.3 m with a mean of 1 m. Mean length was 6.7 m and mean width was 4.8 m. Falling dunes identified in this study are poorly developed and thin, lacking a prominent ramp‐like structure. Mean wavelength for three sets of measured ripples ranged from 22 to 36 cm. Sand streaks extend downwind for more than a kilometer and are up to 200 m in width. They commonly occur on the lee side of mesas and similar landforms and are typically the downwind continuation of falling dunes. Falling dunes, wind ripples, and sand streaks have been identified on Mars, while coppice dunes are similar to Martian shadow or lee dunes in which sand accumulates in the lee of obstacles. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

6.
Aeolian processes – the erosion, transport, and deposition of sediment by wind – play important geomorphological and ecological roles in drylands. These processes are known to impact the spatial patterns of soil, nutrients, plant-available water, and vegetation in many dryland ecosystems. Tracers, such as rare earth elements and stable isotopes have been successfully used to quantify the transport and redistribution of sediment by aeolian processes in these ecosystems. However, many of the existing tracer techniques are labor-intensive and cost-prohibitive, and hence simpler alternative approaches are needed to track aeolian redistribution of sediments. To address this methodological gap, we test the applicability of a novel metal tracer-based methodology for estimating post-fire aeolian sediment redistribution, using spatio-temporal measurements of low-field magnetic susceptibility (MS). We applied magnetic metal tracers on soil microsites beneath shrub vegetation in recently burned and in control treatments in a heterogeneous landscape in the Chihuahuan desert (New Mexico, USA). Our results indicate a spatially homogeneous distribution of the magnetic tracers on the landscape after post-burn wind erosion events. MS decreased after wind erosion events on the burned shrub microsites, indicating that these areas functioned as sediment sources following the wildfire, whereas they are known to be sediment sinks in the undisturbed (e.g. not recently burned) ecosystem. This experiment represents the first step toward the development of a cost-effective and non-destructive tracer-based approach to estimate the transport and redistribution of sediment by aeolian processes. © 2018 John Wiley & Sons, Ltd.  相似文献   

7.
This paper reviews the role of alluvial soils in vegetated gravelly river braid plains. When considering decadal timescales of river evolution, we argue that it becomes vital to consider soil development as an emergent property of the developing ecosystem. Soil processes have been relatively overlooked in accounts of the interactions between braided river processes and vegetation, although soils have been observed on vegetated fluvial landforms. We hypothesize that soil development plays a major role in the transition (speed and pathway) from a fresh sediment deposit to a vegetated soil‐covered landform. Disturbance (erosion and/or deposition), vertical sediment structure (process history), vegetation succession, biological activity and water table fluctuation are seen as the main controls on early alluvial soil evolution. Erosion and deposition processes may not only act as soil disturbing agents, but also as suppliers of ecosystem resources, because of their role in delivering and changing access (e.g. through avulsion) to fluxes of water, fine sediments and organic matter. In turn, the associated initial ecosystem may influence further fluvial landform development, such as through the trapping of fine‐grained sediments (e.g. sand) by the engineering action of vegetation and the deposit stabilization by the developing aboveground and belowground biomass. This may create a strong feedback between geomorphological processes, vegetation succession and soil evolution which we summarize in a conceptual model. We illustrate this model by an example from the Allondon River (Switzerland) and identify the research questions that follow. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

8.
Research into global hot spots of dust emission has focused on exposed fine‐grained sediments in palaeo‐ or ephemeral dryland lake basins including Etosha (Namibia) and Makgadikgadi (Botswana) in southern Africa. Namibia's western ephemeral river valleys are also known to produce dust but have remained largely overlooked as a regionally significant source. Nutrient enrichment of valley sediments and proximity to the South Atlantic suggests aeolian dust could play an important role in ocean fertilization. The fertility of valley dust is dependent on fluvial sediments originating in the upper catchments on the Southern African Central Plateau. In this study we investigate climate, geology, vegetation and land use variability and how these may influence the nitrogen, phosphorus and iron availability in the catchments. We intensely sampled the Huab, Kuiseb and Tsauchab river systems to map the spatial distribution of nutrients from upper catchments to river termini. Samples were analysed for the bioavailable fractions of iron, nitrogen and phosphorus as well as total nitrogen and phosphorus. Results show that the lower valley reaches are sources of aeolian dust enriched in nutrients. Nitrogen levels correlate with precipitation and vegetation levels and phosphorus levels with geology. However, differences in upper catchment sediment nutrient levels were not representative of downstream nutrient differences between valleys. Rather, it is the hydrological and geomorphological processes of the ephemeral river systems that are key for producing the enriched sediments in the lower reaches. We demonstrate that the ephemeral river valleys of western Namibia are an extensive and enriched source of mineral dust that could play a critical role in marine productivity of the southern Atlantic. © 2017 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.  相似文献   

9.
Cellular automaton modelling for the simulation of dune field formation and evolution has developed progressively in aeolian geomorphology in the last decade or so. A model that incorporates the effects of vegetation and its interactions with geomorphic landscape development – the Discrete Ecogeomorphic Aeolian Landscapes (DECAL) model – can replicate a number of important visual and qualitative aspects of the complex evolution of aeolian dune landscapes under the influence of vegetation dynamics in coastal environments. A key challenge in this research area is the analysis and comparison of both simulated and real‐world vegetated dune landscapes using objective and quantifiable principles. This study presents a methodological framework or protocol for numerically quantifying various ecogeomorphic attributes, using a suite of mathematically defined landscape metrics, to provide a rigorous and statistical evaluation of vegetated dune field evolution. Within this framework the model parameter space can be systematically explored and simulation outcomes can be methodically compared against real‐world landscapes. Based on a simplified scenario of parabolic dunes developing out of blow‐outs the resulting dune field realizations are investigated as a function of variable growth vigour of two simulated vegetation types (pioneer grass and successional woody shrub) by establishing a typological phase‐diagram of different landscape classes. The set of simulation outcomes furthermore defines a higher‐dimensional phase‐space, whose axes or dimensions can be interpreted by analysing how individual ecogeomorphic landscape metrics, or state variables, contribute to the data distribution. Principal component analysis can reduce this to a visual three‐dimensional (3D) phase‐space where landscape evolution can be plotted as time‐trajectories and where we can investigate the effects of changing environmental conditions partway through a simulation scenario. The use of landscape state variables and the construction of a 3D phase‐space presented here may provide a general template for quantifying many other eco‐geomorphic systems on the Earth's surface. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

10.
Feedback between hydrogeomorphological processes and riparian plants drives landscape dynamics and vegetation succession in river corridors. We describe the consequences of biogeomorphological feedback on the formation and dynamics of vegetated fluvial landforms based on observations from the channelized Isère River in France. The channel was laterally confined with embankments and mostly straightened. From the beginning of the 1970s to the end of the 1990s, alternate bars were progressively but heavily colonized by vegetation. This context presented an exceptional opportunity to analyse temporal adjustments between fluvial landforms and vegetation succession from bare gravel bars to mature upland forest as the consequence of biogeomorphological interactions. Based on a GIS analysis of aerial photographs (between 1948 and 1996), we show that the spatiotemporal organization of vegetated bars within the river channel observed in 1996 resulted from a bioconstruction and biostabilization effect of vegetation and interactions between bars of varying age, size and mobility. Field measurements in 1996 reflected how a strong positive feedback between sedimentary dynamics and riparian vegetation succession resulted in the construction of the vegetated bars. A highly significant statistical association of geomorphological and vegetation variables (RV of co-inertia analysis = 0.41, p < 0.001) explained 95% of the variability in just one axis, supporting the existence of very strong feedback between geomorphological changes (i.e. the transformation of small bare alternate bars to fluvial landforms covered by mature upland forest, and vegetation succession). Such dynamics reflect the fluvial biogeomorphological successions model, as described by the authors earlier. © 2020 John Wiley & Sons, Ltd.  相似文献   

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

12.
The wide spatial coverage of sand dunes in continental interiors makes the understanding of their activity and accumulation history valuable for palaeoenvironmental reconstructions and the interpretation of landscape evolution. Nevertheless, the study of aeolian landscape development at the million-year timescale is hampered by the complex interaction of factors determining dune migration and the inherently self-destructive nature of their chronostratigraphy, thus limiting the applicability of traditional dating methods. This study presents a standalone program that simulates aeolian transport based on luminescence-derived chronologies coupled with numerical modelling of the accumulation of cosmogenic nuclides. This integrative approach to modelling the history of aeolian landforms reveals phases of emergence of aeolian sand into the landscape, and provides a data-based scheme that facilitates the morphodynamical study of aeolian processes over multiple timescales and up to several millions of years. The application of the program for reanalysing previously reported data from the Australian Simpson Desert reveals multiple pulses of sand dispersion into central Australia at 3.8–3.4, 2.9–2.5 and 1.5–1 Ma, corresponding to pronounced changes in climatic conditions and landscape deformation events. The synchronicity of the results with the established environmental framework that would promote the production and aeolian distribution of sand exemplifies the applicability of process-based modelling in constructing a timeframe of key landscape evolution events in arid environments by studying aeolian deposits. The dependence of the parameters used to determine environmental settings on sand transportation patterns additionally makes the program a powerful tool to further investigate the triggers and mechanisms of aeolian processes.  相似文献   

13.
Climate variability during the Mid‐Late Holocene has influenced the activity of geomorphic processes in the current periglacial belt of the Sierra Nevada. We studied two types of sedimentary records that reveal a synchronous timing for slope instability in this high semi‐arid massif: solifluction landforms and mountain lake sediments. Lithological and sedimentological properties of both records have recorded numerous cycles of different magnitude of slope processes in the massif. Solifluction deposits record seven phases of solifluction activity and soil development during the last 7 ka bp and lake sediments show evidence of eight periods with increased geomorphic activity in the catchments over the last 6 ka bp . Although present‐day climate conditions do not promote active solifluction processes in the Sierra Nevada, colder and wetter periods during the Holocene triggered solifluction and transported coarse‐grained sediments into the lakes. By contrast, warm phases favoured soil formation and spread an incipient vegetation cover over the headwaters of the highest valleys, diminishing the grain size of the particles reaching the lakes. Lake sediments record an aridification trend in the massif intensifying since 4·2 ka bp that has conditioned solifluction activity to shift gradually to higher elevations. During major cooler phases such as the Little Ice Age active solifluction was recorded back down to 2500 m altitude. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

14.
Vegetation plays an important role in shaping the morphology of aeolian dune landscapes in coastal and semi‐arid environments, where ecogeomorphic interactions are complex and not well quantified. We present a Discrete ECogeomorphic Aeolian Landscape model (DECAL) capable of simulating realistic looking vegetated dune forms, permitting exploration of relationships between ecological and morphological processes at different temporal and spatial scales. The cellular automaton algorithm applies three simple rules that lead to self‐organization of complex dune environments, including nebkhas with distinctive deposition tails that form in association with mesquite‐type shrubs, and hairpin (long‐walled) parabolic dunes with trailing ridges that evolve from blowouts in association with vegetation succession. Changing the conditions of simulations produces differing landscapes that conform qualitatively to observations of real‐world dunes. The model mimics the response of the morphology to changes in sediment supply, vegetation distribution, density and growth characteristics, as well as initial disturbances. The introduction of vegetation into the model links spatial and temporal scales, previously dimensionless in bare‐sand cellular automata. Grid resolutions coarser than the representative size of the modelled vegetation elements yield similar morphologies, but when cell size is reduced to much smaller dimensions, the resultant landscape evolution is dramatically different. The model furthermore demonstrates that the relative response characteristics of the multiple vegetation types and their mutual feedback with geomorphological processes impart a significant influence on landscape equilibria, suggesting that vegetation induces a characteristic length scale in aeolian environments. This simple vegetated dune model illustrates the power and versatility of a cellular automaton approach for exploring the effects of interactions between ecology and geomorphology in complex earth surface systems. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

15.
Soil‐disturbing animals play a critical role in many ecosystem processes. The loss of native soil‐foraging mammals (e.g. greater bilby Macrotis lagotis; burrowing bettong, Bettongia lesueur) throughout vast areas of Australia has altered fundamental soil processes such as decomposition. Little is known about whether surviving native soil‐disturbing animals (e.g. short‐beaked echidna, Tachyglossus aculeatus) produce soil disturbances that are functionally equivalent to those of locally‐extinct native animals. We used a litter bag study to compare abiotic and biotic mechanisms of decomposition within the foraging pits of two native mammal species. We compared decomposition rates between landforms, which we used as a surrogate for soil texture; grass species Austrostipa scabra subsp. scabra and Triodia scariosa subsp. scariosa, which we used as our substrates; and the effects of chemically excluding fungi and/or termites. There were initial differences in the organic mass loss between echidna and bilby/bettong foraging pits, with bilby/bettong pits losing more over 30 days, and echidnas losing more over 63 days. However, over 396 days there was no significant difference between the two pit types. Landform (soil texture) and chemical exclusion of termites and fungi did not affect our measures of decomposition until the final stage of the study. The two grass species lost significantly different amounts of organic material at each collection interval, with Austrostipa losing more at 30, 63 and 130 days and Triodia losing more at the final 396 day collection. This provided the most consistent effect on decomposition. Our results highlight the temporal idiosyncrasies in the various drivers of decomposition in this dune‐swale system. Overall, this study provides evidence that the foraging pits of the short‐beaked echidna do not differ markedly from those of the locally extinct greater bilby and burrowing bettong in terms of their capacity to maintain rates of decomposition at an annual scale. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

16.
Aeolian sand landforms in the Yarlung Zangbo River valley can be divided into 4 classes and 21 types. The river valley has favourable environment conditions for the development of aeolian sand landforms. Simulation of MM4 mid-scale climate model showed that the near-surface flow field and wind vector field during the winter half year in the river valley are generally favourable for the aeolian sand deposition and as a whole they also affect the distribution mneu and sites of aeolian sand landforms. Sand dunes and sand dune grouup in the river valley developed mainly in three ways, namely windward retarding deposition, leeward back flow deposition and bend circumfluence deposition. Through alternating positive-reverse processes of sand dune formation under wind actions and sand dune vanishing under water actions, sand dunes developed fmm primary zone thmugh main-body zone then to vanishing zone where climbing dunes and falling dunes are declining and are even disappearing. Project supported by the National Natural Science Foundation of China (Grant No. 49471009) and Xi’an State Key Laboratory of Loess and Quaternary Geology (Grant No. 9401)  相似文献   

17.
The ability to continuously monitor the dynamic response of periglacial landforms in a climate change context is of increasing scientific interest. Satellite radar interferometry provides information on surface displacement that can be related to periglacial processes. Here we present a comparison of two‐dimensional (2D) surface displacement rates and geomorphological mapping at periglacial landform and sediment scale from the mountain Nordnesfjellet in northern Norway. Hence, 2D Interferometric Synthetic Aperture Radar (InSAR) results stem from a 2009–2014 TerraSAR‐X dataset from ascending and descending orbits, decomposed into horizontal displacement vectors along an east–west plane, vertical displacement vectors and combined displacement velocity. Geomorphological mapping was carried out on aerial imagery and validated in the field. This detailed landform and sediment type mapping revealed an altitudinal distribution dominated by, weathered bedrock blockfields, surrounded primarily by slightly, to non‐vegetated solifluction landforms at the mountain tops. Below, an active rockslide and associated rockfall deposits are located on the steep east‐facing side of the study area, whereas glacial sediments dominate on the gentler western side. We show that 2D InSAR correctly depicts displacement rates that can be associated with typical deformation patterns for flat‐lying or inclined landforms, within and below the regional permafrost limit, for both wet and dry areas. A net lowering of the entire landscape caused by general denudation of the periglacial landforms and sediments is here quantified for the first time using radar remote sensing. Copyright © 2018 John Wiley & Sons, Ltd.  相似文献   

18.
Sediment distribution is investigated applying grain size analysis to 279 surface samples from the transitional zone between high mountains (Qilian Shan) and their arid forelands (Hexi Corridor) in north‐western China. Six main sediment types were classified. Medium scale (103 m) geomorphological setting is carefully considered as it may play an important role concerning sediment supply and availability. A tripartite distribution of sedimentological landscape units along the mountain to foreland transition is evident. Aeolian sediments (e.g. loess and dune sands) are widespread. They are used to identify aeolian transport pathways. The mU/fS‐ratio (5–11 µm/48–70 µm) among primary loess opposes the two grain size fractions being most sensitive to varying accumulation conditions. The first fraction is attributed to long‐distance transport in high suspension clouds whereas the latter represents local transport in saltation mode. The ratio shows strong correlation with elevation (R2 = 0.77). Thus, it indicates a relatively higher far‐traveled dust supply in mountainous areas (>3000 m above sea level [a.s.l.]) compared to the foreland. The contribution of westerlies to high mountain loess deposits is considered likely. Hereby, the influence of the geomorphological setting on grain size composition of aeolian sediments becomes apparent: the contribution from distant dust sources is ubiquitous in the study area. However, the far‐distance contribution may be reduced by the availability of fine sand provided in low topography settings. Plain foreland areas support fine sand deflation from supplying river beds, allowing the formation of sandy loess in foreland areas and intramontane basins. In contrast, high mountain topography inhibits strong sand deflation into loess deposits. Eastern parts of the Hexi Corridor show higher aeolian sand occurrence. In contrast, the western parts are dominated by gravel gobi surfaces. This is attributed to higher sand supply in eastern parts provided by the Badain Jaran Desert and fluvial storages as sand sources. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

19.
Soils along catenas of Pinedale (15–20 ka) and Bull Lake (100–130 ka) age moraines at Whiskey Basin in the Wind River Range, Wyoming, USA, were sampled to assess the effects of aeolian processes on soil development here. Aeolian processes appear to have in?uenced soils by both depositing sediments and eroding topsoils. Pedogenic silt (often used as an indicator of wind deposition) accumulated in the Bull Lake soils moderately correlate with pedogenic clay accumulated, suggesting that ?ne sediments may have been deposited and incorporated into soil formation here. Following removal of previous topsoil by wind during Pinedale glaciation, Bull Lake B horizons have developed into contemporary A horizons. These data further link aeolian processes to soil development on piedmont moraines throughout the Wind River Range. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

20.
Whilst earth surface landforms evolve largely as a result of the activity of certain living organisms, the biologically driven geomorphic changes have evolutionary consequences on organisms and ecological communities. Recognition of complex biotic–abiotic feedbacks may lead to deep changes in our understanding of geomorphology. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

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