Geomorphic Position Research Articles

Morphogenetic Features of Soils under Mountainous Larch Forests and Woodlands in the Subpolar Urals

On the basis of the profile-genetic approach, diagnostic features of poorly studied mountainous soils under larch forests and woodlands in different geomorphic positions of the Subpolar Urals were identified, and their classification position was determined. The morphological, physicochemical, and chemical characteristics of the studied soil profiles were described. It was found that the soil cover under blueberry–moss larch stands is mainly composed of iron-illuvial svetlozems and iron-illuvial podzols. Both soils were identified as Albic Podzols (Skeletic) in the WRB-2015 system. On the outcrops of calcareous rocks on slopes of river valleys, gray-humus soils (Calcaric Leptosols (Skeletic)) and iron-illuvial podzols were described. They occupy small areas and can be referred to as rare soils in the studied region. Near the upper treeline, lithozems (Lithic Leptosols (Skeletic)) and podburs (Entic Podzols (Skeletic)) are developed; these soils are common in the mountainous tundra landscapes. The accumulation of plant litter on the soil surface and its slow mineralization predetermine the raw-humus and peaty nature of the upper horizons with a broad C : N molecular ratio.

Late Quaternary slip rate of the Central Sierra Madre fault, southern California: Implications for slip partitioning and earthquake hazard

The Sierra Madre fault system accommodates contraction within a large restraining bend area of the San Andreas fault along the northern margin of the Los Angeles metropolitan area in southern California. Reverse slip along this fault system during earthquakes controls growth of the San Gabriel Mountains and poses a significant seismic hazard to the region. Here, we measure the late Quaternary slip rate of the Central Sierra Madre fault (CSMF) using analysis of high-resolution topography combined with cosmogenic 10Be surface exposure dating and post-IR IRSL geochronology. We mapped terrace and fan surfaces from three drainages that cross the CSMF and correlate them based on deposit character and geomorphic position. Cosmogenic nuclide and luminescence ages are consistent amongst the three prominent surfaces offset ∼5 to 28 m across the fault zone. Age estimates for these surfaces are 53 +21/−15 ka, 35 ± 9 ka, and 12±5 ka based on data from two dating methods at three locations, refined by inset age relationships. Estimated slip for these geomorphic markers is more uncertain than the measured vertical separation due to uncertainties in fault dip and ranges from 7.5 +5.4/−3.1 m to 58.5 +46.3/−14.4 m. Incremental dip-slip rate estimates from different age surfaces and locations overlap within uncertainty, with median values ranging from 0.6 to 1.1 mm/yr. The average slip rate for all three generations of markers is 1.1 +1.1/−0.4 mm/yr. This late Quaternary slip rate for the CSMF is slower than estimates based on interseismic geodetic data, and emphasizes the importance of contraction distributed across multiple structures south of the Sierra Madre fault when assessed against the geodetic shortening budget. Despite being the central portion of the broader Sierra Madre fault system, the CSMF has a slip rate similar to or lower than neighboring sections, suggesting that slip transfer onto other nearby faults control the along-strike pattern of deformation rate. Paleoseismic evidence indicates that the last earthquake on the CSMF was in the early Holocene, and the slip rate we estimate suggests that the accumulated elastic strain could produce many meters of slip in future earthquakes.

Flow Pattern and Hydraulic Parameter Characteristics of the Different Topographic Position in the Small Catchment

Flow pattern and hydraulic parameter characteristics of the different topographic position in the “slope-gully-basin” system under the rainfall intensities of 60, 90 and 120 mm/h using generalized small watershed model with the simulated rainfall experiment. The results show that the increase of the rainfall intensity will result in the increase of the Reynolds number. During the whole experiment, only when the rainfall intensity is 60 mm/h, the flow pattern of the hilly-slope is laminar flow. The flow patterns of the other geomorphic position are all turbulent flow. Moreover, the Reynolds number of slope flow is much less than that of channel flow. With the increase of rainfall intensity, flow patterns of the all different geomorphic position changed from the stratum flow into torrent flow. Furthermore, the Froude number increases first and then decreases with the increase of rainfall intensity. For the resistance coefficient of the overland flow, with the increase of rainfall intensity, the resistance coefficient of overland flow and channel flow decreases obviously. For the spatial distribution of resistance coefficient, the maximum occurs at the hilly-slope and the minimum at the channel.

Origins and genesis of loess deposits in central Spain, as indicated by heavy mineral compositions and grain‐size variability

AbstractThe formation of loess deposits strongly depends on the availability of deflatable dust‐sized material. Identification of source areas and mechanisms of dust production is essential for an appropriate characterization of related palaeoenvironmental conditions. So far, little research has been done on loess deposits in the Mediterranean region and information about mechanisms of dust production is very rare. In this context, it is not clear from where the loess deposits from the upper Tagus Basin in central Spain originated. The main objective of this study was to find out whether these loess deposits were formed primarily by mountain processes and fluvial comminution, or whether they have their origin in the weathering of Tertiary marls in the centre of the Madrid Basin. A further concern was to link the determined source areas with loess formation mechanisms and concomitant environmental contexts. Following a comprehensive approach using heavy minerals and grain‐size data, together with information on stratigraphic features and geomorphic positions, different local loess sources could be identified. This study shows that during the last 35 kyr a major proportion of the Tagus loess deposits was deflated from river floodplains, while the mountain region of the Iberian Range was identified as a significant source of respective floodplain sediments. Based on heavy mineral compositions and dating results, it was found that during Heinrich Stadial 3, sediment supply from the Iberian Range strongly increased, suggesting an environmental shift from initially warmer towards colder temperatures in late Marine Isotope Stage 3. Furthermore, it was found that grain‐size patterns clearly indicate maximum wind strengths during Heinrich Stadial 3, followed by Heinrich Stadial 2 and Heinrich Stadial 1. These results demonstrate that the formation of dust‐sized particles in this part of the Mediterranean operated similar to many other places in temperate and continental regions, and that weathering processes linked to hot and dry environments were only of minor importance.

Hydroperiod, soil moisture and bioturbation are critical drivers of greenhouse gas fluxes and vary as a function of landuse change in mangroves of Sulawesi, Indonesia

The loss and degradation of mangroves can result in potentially significant sources of atmospheric greenhouse gas (GHG) emissions. For mangrove rehabilitation carbon projects, quantifying GHG emissions as forests regenerate is a key accounting requirement. The current study is one of the first attempts to systematically quantify emissions of carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) from: 1) aquaculture ponds, 2) rehabilitating mangroves, and 3) intact mangrove sites and frame GHG flux within the context of landuse change. In-situ static chamber measurements were made at three contrasting locations in Sulawesi, Indonesia. The influence of key biophysical variables known to affect GHG flux was also assessed.Peak GHG flux was observed at rehabilitating (32.8 ± 2.1 Mg CO2e ha−1 y−1) and intact, mature reference sites (43.8 ± 4.5 Mg CO2e ha−1 y−1) and a dry, exposed disused aquaculture pond (30.6 ± 1.9 Mg CO2e ha−1 y−1). Emissions were negligible at low productivity rehabilitating sites with high hydroperiod (mean 1.0 ± 0.1 Mg CO2e ha−1 y−1) and an impounded, operational aquaculture pond (1.1 ± 0.2 Mg CO2e ha−1 y−1). Heterogeneity in biophysical conditions and geomorphic position exerted a strong influence on GHG flux, with the longer hydroperiod and higher soil moisture content of seaward fringing mangroves correlated with decreased fluxes. A greater abundance of Mud lobster mounds and root structures in landward mangroves correlated to higher flux. When viewed across a landuse change continuum, our results suggest that the initial conversion of mangroves to aquaculture ponds releases extremely high rates of GHGs. Furthermore, the re-institution of hydrological regimes in dry, disused aquaculture ponds to facilitate tidal flushing is instrumental in rapidly mediating GHG flux, leading to a significant reduction in baseline emissions. This is an important consideration for forest carbon project proponents seeking to maximise creditable GHG emissions reductions and removals.

Landscape-dynamic aspects of soil formation in the Lena River Delta

This article provides data on the study of pedodiversity and pecularities of soils and their spatial distribution in the territory of the Lena River Delta (Siberia, Russia). Special reference to geogenic factors of soil formation in the pedoenvironment are made. The main patterns of soil distribution in different geomorphic positions for Samoilovsky, Arga-Belir-Aryta, Kurungnakh and Hardang islands are discussed. The soil catenas of the 4 investigated islands are given as a reliable representation of the formation of soils and the development of soil-forming processes in various types of relief and geomorphological features. Soils are represented mainly by the following groups: Fluvisols, Umbrisols, Podzols, Cryosols, Histosols, Gleysols, which are closely related to the geomorphic terraces of the delta.

Soils and Vegetation of the Khaipudyr Bay Coast of the Barents Sea

Soils and vegetation of the coastal zone of the Khaipudyr Bay of the Barents Sea have been examined and compared with analogous objects in the Karelian coastal zone of the White Sea. The environmental conditions of these two areas are somewhat different: the climate of the Khaipudyr Bay coast is more severe, and the seawater salinity is higher (32–33‰ in the Khaipudyr Bay and 25–26‰ in the White Sea). The soil cover patterns of both regions are highly variable. Salt-affected marsh soils (Tidalic Fluvisols) are widespread. The complicated mesotopography includes high geomorphic positions that are not affected by tidal water. Under these conditions, zonal factors of pedogenesis predominate and lead to the development of Cryic Folic Histosols and Histic Reductaquic Cryosols. On low marshes, the concentrations of soluble Ca2+, K+ + Na+, Cl–, and SO2-4 ions in the soils of the Khaipudyr Bay coast are two to four times higher than those in the analogous soils of Karelian coast. Cluster analysis of a number of soil characteristics allows separation of three soils groups: soils of low marshes, soils of middle-high marshes, and soils of higher positions developing under the impact of zonal factors together with the aerial transfer and deposition of seawater drops. The corresponding plant communities are represented by coastal sedge cenoses, forb–grassy halophytic cenoses, and zonal cenoses of hypoarctic tundra. It is argued that the grouping of marsh soils in the new substantivegenetic classification system of Russian soils requires further elaboration.

Four-topic correlation between flood dendrogeomorphological evidence and hydraulic parameters (the Portainé stream, Iberian Peninsula)

Torrential floods are hazardous hydrological phenomena that produce significant economic damage worldwide. Flood reconstruction is still problematic in ungauged mountainous areas due to the lack of systematic data, so indirect techniques are required. This paper presents an integrated palaeoflood study of a Pyrenean stream that combines fluvio-torrential geomorphology, dendrogeomorphology, palaeoflood discharge estimation and flow hydraulics. The use of a total station and airborne LiDAR data allows detailed topography for geomorphological mapping and running a one-dimensional hydraulic model. Based on the height of scars on several damaged trees, we obtained palaeodischarges of 316m3s−1 and 314m3s−1 for the 2008 and 2010 floods. The hydraulic parameters were related to the geomorphic position of trees, showing a positive relation between most energetic geomorphic elements and both flow depth and velocity values. The most affected trees are located in intermediate energy geomorphic positions. Analysing variation in scar height and flow stage differences, we suggest that most reliable trees for peak discharge estimation correspond to those in areas related with fluvio-torrential processes of intermediate energy. This multidisciplinary palaeohydrological study relates flood hydrodynamics with the damage to trees and their geomorphological characteristics, focusing on the hydraulic parameters of the peak flow (depth, velocity and unit stream power), which has never been performed before. The proposed approach shows strong potential for palaeoflood analysis in ungauged mountain catchments with scarce non-systematic data.

What drives riparian vegetation encroachment in braided river channels at patch to reach scales? Insights from annual airborne surveys (Drôme River, SE France, 2005–2011)

AbstractUnderstanding riparian vegetation encroachment and its drivers is crucial for predicting alluvial river channel morphodynamics in different hydro‐climatic contexts. We investigated fine‐scale vegetation encroachment patterns and underlying physical controls along the Drôme River, France, following a 50‐year flood in 2003. Our study addressed the following questions: (a) What is the relative timing and the respective importance of vegetation patch recruitment versus patch expansion? (b) How well do regional/climatic factors explain the spatio‐temporal patterns of recruitment and expansion versus local and reach‐scale variation in geomorphic position and habitat? Along a 3‐km reach, we analysed a chronosequence of high‐resolution aerial images acquired yearly between 2005 and 2011. From each image series, we digitized patches of newly recruited vegetation and their lateral extent in following years to determine their expansion. This was complemented by elevation and plant structure data from airborne LiDAR data and field observations. The initial post‐flood vegetated area doubled within 6 years, with a pronounced recruitment peak in 2006–2007. Patch expansion showed a positive linear relationship to growing season temperature. Vegetation encroachment was greatest in a slightly aggrading sub‐reach compared to an incising sub‐reach. Initially, it occurred principally along low flow channel margins and on bar surfaces, later in intermittent channels. Our results confirmed that extensive recruitment can succeed floods with recurrence intervals smaller than 1‐in‐5 to 10 years, when the flood history resets the geomorphic framework. Recruitment extent depends in part on local hydrological connectivity, whereas higher temperatures can boost plant growth where there is a perennial water supply.

Geostatistical facies modeling trends for oolitic tidal sand shoals

To assess prospective modeling trends for oolitic tidal sand shoals and explore potential patterns of reservoir heterogeneity, this study examines, quantifies, and models the cycle-scale architecture of the Holocene mobile oolitic tidal sand shoal complex at Schooner Cays, Bahamas. Process-based stratigraphic trends are captured in quantitative, geocellular models of the shoal from analyses of satellite imagery; two-dimensional, high-frequency seismic (chirp) data; and sediment cores. Data show that longitudinal tidal sand ridges extend up to 8 km (5 mi) along depositional dip, gradually transforming bankward into channel-bound, compound barforms consisting of linear, parabolic, and shoulder bars. These bars terminate into a laterally extensive (10 km [6 mi]), strike-elongate sand sheet. Each bar type includes distinct internal architecture, grain size, and sorting related to feedbacks among hydrodynamics, geomorphology, and sedimentology. Building on these data and concepts from the Holocene accumulations, this study demonstrates a methodology for quantifying and validating probabilistic stratigraphic trends prior to their inclusion in stochastic-based facies modeling algorithms. Inclusion of statistically robust facies probability volumes during truncated Gaussian simulation generated ordered and geologically accurate facies distributions relative to bar-crest centerlines, water depth, and geomorphic position. Petrophysical models that incorporate facies-specific porosity, permeability, and water saturation functions display pronounced cycle-scale heterogeneity that could provide insights into variable production rates and poor sweep efficiency commonly encountered during development of analogous oolitic reservoirs.

A Maize Experiment in a Traditional Zuni Agroecosystem

Maize has sustained the Zuni and other people in the arid American Southwest for many generations. In the traditional Zuni dryland agricultural system, fields are carefully placed on valley-edge landforms to tap into watershed hydrologic and ecosystem processes. In these geomorphic positions, field soils are managed to receive supplemental water and nutrients for crops by retaining storm runoff transported from adjoining uplands. Crop experiments were conducted to examine the effects of runoff on maize (Zea mays) productivity. Productivity of a Zuni maize cultivar and modern hybrid maize was evaluated with five treatment combinations of water and nutrient input sources in two traditional agricultural areas that have been cultivated for at least 1000 years. During the first year of the two-year experiment (1997–1998), one field received inputs from four runoff events, while the other field, with a larger watershed, received no runoff. In year two, the one remaining field (the other field was disrupted) had inputs from one runoff event. Growing season precipitation was above average for both years of the experiment. All treatments, including those receiving only precipitation, produced grain yields ranging from 852 to 3467 kg ha−1 for Zuni maize. Grain and biomass productivity tended to be greater in the irrigation-plus-fertilizer control treatment. Productivity differences among treatments are attributed primarily to differences in water inputs rather than nutrient supply. Although the more densely populated hybrid maize out-yielded Zuni maize on a land area basis, Zuni maize produced greater yields per plant and more biomass than did the hybrid maize.

Relating Intensity of Soil Redistribution to Land Use Changes in Abandoned Pyrenean Fields Using Fallout Caesium‐137

AbstractFallout caesium‐137 has been used to trace soil redistribution in abandoned fields located in the Central Spanish Pyrenees. A total of 28 fields with different lengths, slope angles and time since abandonment were selected on a representative south‐facing slope of the Estarrún valley. The local reference inventory and the magnitude and spatial distribution of 137Cs inventories within these fields were documented and used as a basis for assessing patterns of soil redistribution. The local reference inventory was estimated to be 4,500 Bqm−2. Within the fields, the average 137Cs inventory at the top of the slope was 3,920 Bqm−2, and accumulation of soil at the bottom of the slopes was demonstrated by an average 137Cs inventory of 5,320 Bqm−2. Deviations from the reference inventory were highest for fields with the longest slopes that had been abandoned for less than 30 years. Here, increases in the 137Cs inventory, relative to the reference inventory, in excess of 20% were found at the bottom of the slopes. Considering all the fields and all geomorphic positions within the fields, the greatest 137Cs losses and gains were found in the fields with the longest duration of abandonment, indicating more intense soil redistribution. Irrespective of the timing of abandonment, the ranges of 137Cs inventories in the fields were found to be proportional to the water erosion index. The 137Cs technique demonstrated that patterns of sediment redistribution were closely related to the topographic and physiographic characteristics of the slopes. Copyright © 2017 John Wiley & Sons, Ltd.

Environment Quality: Impact From Traffic, Power Plant and Land Morphology, a Case Study of Prishtina

Abstract Environmental air pollution is a global health concern, a complex phenomenon which is directly reflected on public health, economic and human development. Environmental air pollution has been drastically multiplied, followed by the beginning of the new Millennia in Prishtina, the capital city of the Kosovo. The new millennium began as a crucial activity for the city of Prishtina in terms of demographic, human geography, social and economic phenomena. The presented study aims to determine prevalent traffic and land morphology composition attributes, which have influenced and continue to have environmental impact in the city of Prishtina. According to the conceptual findings from the empirical observations, the heavy city traffic and the land morphology structure, determine the urban air pollution level. Prishtina is generally polluted due to its geomorphic position in relation to the power plants Kosovo A, and Kosova B. The impact of the above cited factors, is even bigger when the dominant winds prevail through valley, which encompasses the city. The findings from this paper propose the necessity of careful driven urban solutions.

Magnetic susceptibility of soils along a lithotoposequence in southeast Iran

Magnetic susceptibility (χ) is a simple and quick technique to determine soil properties and to describe soil forming processes. Knowledge about factors affecting χ data helps better interpretation. Magnetic susceptibility of soils along a lithotoposequence was studied in this research in order to investigate the effects of soil forming factors (parent material and relief) and processes on the χ content and its vertical distribution. The study area is a transect from Jiroft to Kahnooj area, south Kerman Province, Iran. Rock pediment, mantled pediment, inselberg, alluvial fan, alluvial plain, and flood plain landforms with igneous parent materials (gabbro, diorite, and granite) were selected in the area. Thirteen representative pedons on different geomorphic positions were studied. Low frequency χ (χlf) values ranged from 193.1×10−8m3kg−1 to 2704.2×10−8m3kg−1 in studied soils and decreased with increasing diamagnetic material contents. Mean χlf values in soils formed on gabbro, diorite, and granite parent rock were >1700×10−8m3kg−1, 515.22×10−8m3kg−1, and 352.53×10−8m3kg−1, respectively. Frequency dependent χ of soils (in the range of 0.06 to 1.05%) showed that coarse multi domain grains inherited from igneous parent material were the main source of χlf in the area under study. Both increasing and decreasing trends of χlf with depth were observed. Decreasing trend of χlf with depth was due to illuviation of diamagnetic material into subsurface layers. On the other hand, increasing χlf with depth was attributed to the primary ferrimagnetic material inherited from igneous parent material. Alluvial plain (320.44×10−8m3kg−1) and mantled pediment (328.50×10−8m3kg−1) showed low values of χlf due to high amounts of soluble salts, anhydrite, and calcium carbonate investigated in these geomorphic positions. A positive significant relationship (R2=0.018; r=0.27, P<0.05) between χlf and Feo/Fed activity ratio was found. Soil χlf decreased with development and relative dating of soils. Results of the study showed that soil χlf values were highly affected by parent material, relief, and soil development.

Concentrations of trace elements and iron in the Arctic soils of Belyi Island (the Kara Sea, Russia): patterns of variation across landscapes.

The concentrations of several trace elements and iron were determined in 26 soil samples from Belyi Island in the Kara Sea (West Siberian sector of Russian Arctic). The major types of soils predominating in the soil cover were sampled. The concentrations of trace elements (mgkg-1) varied within the following ranges: 119-561 for Mn, 9.5-126 for Zn, 0.082-2.5 for Cd, <0.5-19.2 for Cu, <0.5-132 for Pb, 0.011-0.081 for Hg, <0.5-10.3 for Co, and 7.6-108 for Cr; the concentration of Fe varied from 3943 to 37,899mgkg-1. The impact of particular soil properties (pH, carbon and nitrogen contents, particle-size distribution) on metal concentrations was analyzed by the methods of correlation, cluster, and factor analyses. The correlation analysis showed that metal concentrations are negatively correlated with the sand content and positively correlated with the contents of silt and clay fractions. The cluster analysis allowed separation of the soils into three clusters. Cluster I included the soils with the high organic matter content formed under conditions of poor drainage; cluster II, the low-humus sandy soils of the divides and slopes; and cluster III, saline soils of coastal marshes. It was concluded that the geomorphic position largely controls the soil properties. The obtained data were compared with data on metal concentrations in other regions of the Russian Arctic. In general, the concentrations of trace elements in the studied soils were within the ranges typical of the background Arctic territories. However, some soils of Belyi Island contained elevated concentrations of Pb and Cd.

Characteristics of soil seed banks at different geomorphic positions within the longitudinal sand dunes of the Gurbantunggut Desert, China

Understanding the characteristics of soil seed banks in sand dunes is crucial to stabilize the dune systems and maintain the plant populations in deserts. In this study, we conducted a survey investigation in the field and a seed germination experiment in the laboratory to explore the characteristics of soil seed banks at various geomorphic positions of longitudinal sand dunes in the Gurbantunggut Desert, China. Totally, 17 plant species belonging to 17 genera and 9 families were identified in soil seed banks, and 35 plant species belonging to 34 genera and 17 families were identified in aboveground vegetation. Plant species richness in soil seed banks decreased with increasing soil depth. The highest species richness was presented in the upper slope of the windward slope and the lowest species richness was presented in the base of the windward slope. There was no significant difference in seed density of soil seed banks among the examined seven geomorphic positions. The highest seed density occurred in the lower slope of the leeward slope while the lowest occurred in the crest. Moreover, seed density decreased with increasing soil depth, being the highest in the upper soil layer (0–2 cm). For both soil seed banks and aboveground vegetation, there was no significant difference in Simpson’s diversity index among the seven geomorphic positions; however, Shannon-Wiener diversity index and Pielou’s evenness index showed significant differences among the seven geomorphic positions. Those results showed that although there was no significant difference in seed density of soil seed banks among the seven geomorphic positions, the geomorphic positions significantly affected the species richness, diversity and distribution of soil seed banks. Therefore, understanding the characteristics of soil seed banks at different geomorphic positions of sand dunes is essential to vegetation restoration or reestablishment. Furthermore, the Jaccard’s similarity coefficients of plant species between soil seed banks and aboveground vegetation at the seven geomorphic positions were low, suggesting that vegetation restoration or reestablishment processes should be promoted through adding seeds to surface layers.

Soil and desert varnish development as indicators of landform evolution in central Iranian deserts

Desert varnish (or rock varnish) and soils of Jiroft area, south central Iran play a crucial role in the evolution of landforms in this arid setting containing mantled pediments, rock pediments, inselbergs, alluvial fans, alluvial plains, and flood plains. Mantled pediment contains three stable, semi-stable, and unstable surfaces as indicated by desert varnish and soil development properties. However, alluvial fan could be divided into apex and mid fan settings based on slope position. Mid-fan settings include both stable and unstable surfaces, based on varnish properties. About 100 rocks containing varnish were selected randomly on each geomorphic surface. In addition, a representative soil pedon was described and sampled on each surface for a total of 10 pedons. Results of the study show that brown to black coatings of varnish with the cation exchange capacity (CEC) range of 8.5–21cmolckg−1 were composed of <0.2–50μm particles. Magnetic susceptibility of varnish samples fluctuated between 300 and 185510−8m3kg−1 and Si, Ca, Al, Fe, and Mg concentrations were 26.4, 3.9, 3.8, 3.1, and 2.2%, respectively. Age and development indices such as cation-ratio of desert varnish (with the range of 6.14 to 14) and activity ratio of Feo/Fed (with the range of 0.03 to 0.35) of soils decreased with increasing stability of geomorphic surface and soil development. Chlorite, smectite, illite, palygorskite, and kaolinite clay minerals exist in the clay fraction of studied soils. In addition, chlorite, smectite, vermiculite, sepiolite, illite, palygorskite, kaolinite together with zeolite, quartz, and feldspar tectosilicates were found in desert varnish. Cation-ratio of varnish and activity ratio of Feo/Fed in different geomorphic positions together with soil properties provide a simple method to study the evolution of landforms in this warm desert setting.

Tidal Marshes across a Chesapeake Bay Subestuary Are Not Keeping up with Sea-Level Rise.

Sea-level rise is a major factor in wetland loss worldwide, and in much of Chesapeake Bay (USA) the rate of sea-level rise is higher than the current global rate of 3.2 mm yr-1 due to regional subsidence. Marshes along estuarine salinity gradients differ in vegetation composition, productivity, decomposition pathways, and sediment dynamics, and may exhibit different responses to sea-level rise. Coastal marshes persist by building vertically at rates at or exceeding regional sea-level rise. In one of the first studies to examine elevation dynamics across an estuarine salinity gradient, we installed 15 surface elevation tables (SET) and accretion marker-horizon plots (MH) in tidal freshwater, oligohaline, and brackish marshes across a Chesapeake Bay subestuary. Over the course of four years, wetlands across the subestuary decreased 1.8 ± 2.7 mm yr-1 in elevation on average, at least 5 mm yr-1 below that needed to keep pace with global sea-level rise. Elevation change rates did not significantly differ among the marshes studied, and ranged from -9.8 ± 6.9 to 4.5 ± 4.3 mm yr-1. Surface accretion of deposited mineral and organic matter was uniformly high across the estuary (~9–15 mm yr-1), indicating that elevation loss was not due to lack of accretionary input. Position in the estuary and associated salinity regime were not related to elevation change or surface matter accretion. Previous studies have focused on surface elevation change in marshes of uniform salinity (e.g., salt marshes); however, our findings highlight the need for elevation studies in marshes of all salinity regimes and different geomorphic positions, and warn that brackish, oligohaline, and freshwater tidal wetlands may be at similarly high risk of submergence in some estuaries.

Sedimentation patterns across a Coastal Plain floodplain: The importance of hydrogeomorphic influences and cross-floodplain connectivity

The floodplains of large Coastal Plain rivers in the southeastern U.S. are important long-term storage sites for alluvial sediment and nutrients. Yet considerable uncertainty surrounds sediment dynamics on many large river floodplains and, in particular, the local scale factors that affect the flux of sediment and nutrients from rivers onto their floodplains and their subsequent deposition. This research quantifies short-term rates of sediment deposition from 2012 to 2014 on floodplain sites at Congaree National Park using feldspar pads. Sediment deposition rates ranged from 0.1 to 15.6cm (median=1.46cm) and were closely associated with inundation frequency and geomorphic position. Cross-floodplain distributary channels served as particularly important conduits for moving sediment onto the floodplain. Physical and chemical analyses of soil samples demonstrated that the most flood-exposed sites had higher major nutrient and micronutrient levels (especially of phosphorus) and more diverse nutrient compositions. This research advances current understandings of lateral floodplain connectivity by demonstrating the complex effects of regional hydrology and local floodplain environmental characteristics on the supply of sediment and nutrients.

MIS3 paleosols in the center-north of Eastern Europe and Western Siberia: Reductomorphic pedogenesis conditioned by permafrost?

The MIS3 paleosol units comprise a prominent element of the loess-paleosol sequences throughout the Eurasian Loess Belt. To the north of the loess regions, the findings of MIS3 paleosols were few: it was supposed that geomorphic processes related to the extensive ice cover of the Last Glacial Maximum destroyed the earlier soil mantle. Recently, much smaller extent of continental ice in the east of Northern Europe and ice-free West Siberian Plain during MIS2 has been hypothesized, supposing preservation of MIS3 and earlier paleopedological records. We discovered in the center-north of European Russia (Upper Volga basin) and Western Siberia (Middle Ob basin), MIS3 paleosols within the Late Pleistocene alluvial and lacustrine sequences and correlated the studied profiles on the basis of macro- and micromorphological characteristics and radiocarbon datings of the paleosol organic materials. Paleosols are represented by hydromorphic profiles with Histic horizons and gleyic color pattern. Conspicuously, they are developed in the well drained geomorphic positions, where modern soils are non-gleyic. We suppose that the presence of permafrost was responsible for water logging and generation of reductomorphic soil environment. We further hypothesize a northern zone of MIS3 soil mantle, comprised of Histic and Reductaquic Cryosols different from synchronous Cambisols and Chernozems formed within loess sequences to the south.