•Hydrogeological and microclimate yield wetlands in Brazilian semiarid.•C-rich dystrophic Gleysols occur in an atypical landscape of Caatinga.•Erosion of slope is frequent and buries histic and humic ...horizons.
Palm swamps are typical of the plateaus in the Brazilian savanna, but they are present in remnant in the Brazilian semiarid region, exceptionally in selective concave sectors of the edge and steep slopes at the Araripe Plateau. This study aimed to investigate the genesis and evolution of remnant wet soils under buriti palms/palm swamps in the Brazilian semiarid. Three pedons were selected, described, and classified according to the World Reference Base for soil resources. Soil samples were collected from the surface down to the lithic contact at each pedon. Morphology, chemical, and physical attributes were analyzed. Optically stimulated luminescence (OSL) dating was applied to buried horizons at soil profile soil profile number 1. Our results show that remnant wetlands are associated with dynamics of the hydrogeological conditions and the regional relief, strongly influenced by the morphostructure and the current morphogenesis of the Araripe Plateau. In clear contrast with typical semiarid soils, the hydrolysis and ferrolysis have produced acid, hyperdystrophic, and C-rich horizons. Evidence of colluvium and alluvium show that the soils are polycyclic. The ages between <200 to 850 yr reveal evidence of a parent material of colluvium/alluvial origin from a current sedimentation phase, attributed to erosion scarp, mass movements, and fluvial flow with low capacity.
Mottling and gleying remain important characteristics for the classification of soils in Canada. The development of criteria for the morphological description of these redoximorphic soil features, ...for soil horizon nomenclature, for the taxonomy of gleysolic and gleyed soils, as well as for soil drainage classification, began in the mid-1940s and continued for the next four decades. Despite advancements elsewhere, notably with Soil Taxonomy and the World Reference Base, there have been minimal refinements made in Canada, during the past quarter century. Various issues are identified, including the need for more succinct and clearer definitions, a revision of standards for the field characterization of redoximorphic features, as well as more consistency in the application of concepts across existing taxa and systems. A taxonomic framework to more effectively reflect redoximorphic features, such as a new “Redoximorphic Phase” is also discussed. Ultimately, it is recommended that a special committee to be established to conduct a thorough study and present recommendations.
The interface between wetlands and uplands is characterized by gradients in hydrological, soil and biological components. Consequently, the exact spatial distribution of this transitional area is not ...well known because it often occurs as a fuzzy moisture gradient. However, ecological assessment and conservation require mapping and characterizing this interface to better understand and model biotic and abiotic interactions between wetlands and uplands. To this end, in 2021 and 2022, we observed soil properties and vegetation types along soil moisture gradients throughout the Atlantic, Continental, Mediterranean and Alpine biogeographic regions of France. The dataset contains 2 236 georeferenced plots (accuracy ± 5 m) distributed along 1 088 transects placed along the slope at 377 sites. Each plot in the database is characterized by 21 fields that describe the vegetation habitat type based on the European Nature Information System (EUNIS) and soil properties (i.e. depth of appearance and thickness of redoximorphic features in the soil profile, moisture). These data are useful for researchers and engineers in a variety of disciplines (e.g. Earth and life sciences) to calibrate and validate models to predict the spatial distribution of habitats or to analyze flows.
Soil color patterns are essential to understand hydrologic regime and biogeochemical processes in wetland ecosystems. Munsell Soil Color Chart (MSCC) has been traditionally and predominantly used to ...identify and quantify hydric soil field indicators, but several simple, low-cost alternatives have become recently available to compare their efficacy in complementing the MSCC in soil color assessment. We conducted an intensive literature review on studies utilizing different methods to identify and quantify hydric soil colors and associated patterns; these include 1) the MSCC, 2) the Nix Color Sensor, 3) mobile phone camera (MPC) and medium-end digital camera photography, and 4) colorimetry and spectrometry. A review of these methods elucidates their respective strengths and weaknesses and highlights the importance of considering study-specific attributes in determining which method to choose for field studies of hydric soil colors. Redoximorphic features (RMFs) require methods capable of capturing small and heterogeneous soil surfaces and features such that the MSCC and digital photography are the most appropriate methods; on the other hand, the Nix Color Sensor provides rapid assessment of soil color that does not necessitate rigorous training to overcome biases that might come about in more subjective methods such as the MSCC. Overall, all alternative methods reviewed have their own merits and capacity to complement measurements made by the MSCC.
We assessed hydro-physicochemical (HP) settings and soil color attributes including redoximorphic features (RMFs) at four forested wetlands in Northern Virginia, USA, to identify whether four simply ...measurable HP attributes—inundation/saturation frequency, bulk density, soil moisture, and percent sand—can provide an explanatory framework for characterizing and classifying soil color attributes related to hydric soil field indicators. Study plots (n = 16) were grouped by site for initial characterizations and comparisons of HP (n = 4) and color attributes (n = 11); each attribute was additionally characterized and compared between three HP-based clusters formulated through k-means clustering analysis. Whereas only one HP attribute (inundation/saturation frequency) significantly differed between sites, all HP attributes but percent sand differed between HP-based clusters (
p
< 0.05), with PCA Dimensions 1 and 2 explaining over 80% of variability in plot HP attributes. Moreover, more sets of color attributes were significantly different when plots were grouped by HP-based cluster (n = 5: frequency of concentrations, non-matrix color count, hue, chroma, and depth to concentrations) compared to by site (n = 3: value, frequency of depleted matrices, depth to depletions) (
p
< 0.10). Simply measurable HP attributes are thus closely associated with certain soil RMF and color characteristics beyond site identity, potentially serving as a suite of measurements that can be adopted to assess and monitor redoximorphic features indicative of wetland soils.
Redox processes, which are widespread in soils, need to be quantified for an improved comprehension of the dynamics of Fe- and Mn-oxides and their associated trace elements. The classical methodology ...used to study these redox processes generally relies on the quantification of all mineral species in the various pedological features that can be related to different redox stages. However, this approach usually encounters the difficulty of precisely quantifying the different forms of poorly crystallised Fe- and Mn-oxides.
In this study, we use the signature of rare earth elements (REEs) to visualise and, eventually, quantify the importance of redox processes in soils. Our approach relies on that developed by Laveuf et al. (2008) and the idea that the relative contribution to the mobilisation of REEs that is made by the primary minerals reactive to redox conditions depends on the following factors: (i) their initial proportion in the different pedological features that can be related to various redox processes, (ii) their relative mobilisation during the redox process in question, and (iii) their initial REE signatures.
The catena studied is characterised by two stages of redox conditions: the first is related to the formation and subsequent dissolution of Fe–Mn concretions, and the second is related to the bleaching of the soil matrix due to morphological degradation. In this soil, the main minerals reactive to redox conditions are Mn-oxides, ferrihydrite, goethite and (fluor)apatite. The results indicate that the primary redox conditions can be characterised by a positive Ce anomaly on the REE pattern, which has been attributed to a preferential immobilisation of this element, due to its association with Mn-oxides. The results also indicate that the secondary redox conditions can be characterised by depletion in medium REEs (MREEs) in the REE pattern, which has been attributed to a preferential release of these elements during the dissolution of (fluor)apatite and, to a lesser extent, of ferrihydrite.
These results emphasise the potential of REE signatures of the visualisation of the various redox processes that have been active in a soil. Additionally, REE signatures are a proxy of the frequency and intensity of the redox conditions.
► Identification of redoximorphic features. ► Speciation of rare earth elements in redoximorphic features. ► Impact of redox conditions on rare earth mobilization. ► Interpretation of changes in speciation and of fractionations. ► Use of rare earth elements as tracers of redox processes.
Raised field cultivation (camellones) is a Pre-Columbian technique, now abandoned, which is very extensive in the Llanos de Moxos (Bolivia). The objectives of the research were to understand the ...effects of human actions on the morphology, genesis and characteristics (especially redoximorphic features and chemical properties) of these soils on ridged fields and their past use. We studied five representative raised field (anthropogenic) soils and other non-anthropogenic soils around San Ignacio de Moxos and along the transect Trinidad-San Borja.
The non-anthropogenic soils are acidic, show a wide range of clay contents and different degrees of human activity according to their available phosphorus content. Soil-forming processes are related to fine fraction mobility and alternating redox conditions. Contrarily, the soils of the raised fields show a distinct pattern of redoximorphic features from ridge to channel. Moreover, ridges tend to be less acidic and have lower aluminium saturation than channels. Nevertheless, they have neither artifacts nor charcoal, and their colour and P content is similar to those of surrounding soils.
The raised fields appear to have been built to improve the drainage conditions. Chemical soil fertility was not the main issue and they were used for cultivation including maize. The set of characteristics encountered (differences in pH, and drainage status at a microscale) should be used to improve the classification of these anthropogenic soils.
•Anthropogenic soils were identified and studied in detail in the Llanos de Moxos.•Soil-forming processes are related to fine fraction mobility and redox conditions.•The raised fields appear to have been built to improve the drainage conditions.•Chemical soil fertility was not the main issue when managing the anthropic soils.•Phytolith studies reveal that they were used for cultivation including maize.
Land drainage is an operation which increases land production and ensures sustainable land use. Soil scientists attempt to arrive a scientific procedure for assessing the efficiency of drainage ...system, among the correlation between soil morphological characteristics, mainly soil color and redoximorphic features and water table behavior. The aims of this study were investigating the efficiency of drainage system through soil morphological and micromorphological characteristics and judge about the existence of episaturation or endosaturation, in Khuzestan sugarcane cultivated lands after years of artificial drainage. 5 pedons were dug and characterized based on their morphological and micromorphological features. The characteristics of redoximorphic features showed no considerable differences in drainage class between artificial drained field and virgin land. The only contrast was shallower ground water table in virgin lands. 4 pedons were classified as somewhat poorly drained and one as well drained. These drainage classes show that despite the existence of artificial drainage system, the problems haven't been eliminated yet. All pedons showed horizons with low chroma colours in deeper horizons and different types of redoximorphic feature. Micromorphological observations proved that the lands were involved in Endosaturation due to high ground water level.
The installation of desalination plants close to ecosystems of interest may have environmental impacts that make corrective measures necessary. Especially, wetlands (which are water-dependent ...ecosystems) are prone to degradation. This is the case for the Agua Amarga salt marsh (SE Spain), that includes an abandoned solar saltworks and surrounding, topographically higher zones, in which the groundwater withdrawal to supply two desalination plants has led to a drop of the piezometric levels and the desiccation of the ecosystem. To overcome these problems, a programme to irrigate the marsh with seawater was established. This paper reports some soil characteristics of the marsh in relation to the different types of vegetation/environment identified and the seawater irrigation programme, with the objective being to propose some guidelines to improve the management of the site. Surface and subsurface samples were taken from 63 plots and the depth of the water level and the soil redox potential (Eh), moisture, electrical conductivity (EC), CaCO3, organic carbon, nitrogen and bulk density were determined. Also, the soil texture, structure, consistence, accumulation of salt crystals and redoximorphic features – indicative of reduction-oxidation processes – were described. The poor structure (weak, granular, subangular and angular blocks, very fine and fine) showed that the soils were hardly developed. The periphery (mainly colonised by Suaeda vera, Lygeum spartum and Limonium spp.) was less saline (EC 1:5 in the upper layers ~0.4 to ~4dSm−1) and drier (water level>−1.5m depth) than the abandoned saline ponds (EC 1:5 in the upper layers ~2 to ~9dSm−1 and water level between −1m depth and +0.2m above the soil surface), mainly colonised by Sarcocornia fruticosa, Arthrocnemum macrostachyum, Salicornia patula, Phragmites australis and Ruppia maritima in the flooded ponds. The soils of the periphery were always oxic (Eh>+500mV), but most of the abandoned saline ponds had suboxic (~+100mV<Eh<~+350mV) and even anoxic conditions (Eh<~+100mV), as shown by the existence of gley colours and redoximorphic features. The soil bulk density of the surface and subsurface layers showed that the most impermeable ponds were located in the centre of the marsh, where it is possible to maintain a surface water sheet during prolonged periods, suitable for the development of submerged plant species such as R. maritima and for waterbirds. Part of the seawater poured into more permeable ponds, such as those located in the southern and northern zones of the marsh, is lost by infiltration due to the lower bulk density of these soils. The latter facilitates the recovery of the piezometric levels and the growth of terrestrial plant species. Monitoring of redoximorphic features in the upper soil layers, in combination with symptoms of damage in the plants, could be used as a visual indicator of oxygen limitation due to excessive soil moisture. This would permit the regulation of the irrigation programme, hence optimising the energy and economic resources applied to maintain the ecosystem.
•Poor soil structure development was influenced by the former use as solar saltworks.•Impermeable ponds with the highest bulk density suitable for Ruppia maritima growth•Infiltration and seedling growth are facilitated in ponds with lower bulk density.•Soil redoximorphic features could be used as indicators to regulate the irrigation.•Salt marsh management should consider hydrology, soils and vegetation.
Pockmark fields occur throughout northern North American temperate estuaries despite the absence of extensive thermogenic hydrocarbon deposits typically associated with pockmarks. In such settings, ...the origins of the gas and triggering mechanism(s) responsible for pockmark formation are not obvious. Nor is it known why pockmarks proliferate in this region but do not occur south of the glacial terminus in eastern North America. This paper tests two hypotheses addressing these knowledge gaps: 1) the region's unique sea-level history provided a terrestrial deposit that sourced the gas responsible for pockmark formation; and 2) the region's physiography controls pockmarks distribution. This study integrates over 2500km of high-resolution swath bathymetry, Chirp seismic reflection profiles and vibracore data acquired in three estuarine pockmark fields in the Gulf of Maine and Bay of Fundy. Vibracores sampled a hydric paleosol lacking the organic-rich upper horizons, indicating that an organic-rich terrestrial deposit was eroded prior to pockmark formation. This observation suggests that the gas, which is presumably responsible for the formation of the pockmarks, originated in Holocene estuarine sediments (loss on ignition 3.5–10%), not terrestrial deposits that were subsequently drowned and buried by mud. The 7470 pockmarks identified in this study are non-randomly clustered. Pockmark size and distribution relate to Holocene sediment thickness (r2=0.60), basin morphology and glacial deposits. The irregular underlying topography that dictates Holocene sediment thickness may ultimately play a more important role in temperate estuarine pockmark distribution than drowned terrestrial deposits. These results give insight into the conditions necessary for pockmark formation in nearshore coastal environments.
► We address the role of sea-level history and physiography on estuarine pockmarks. ► Eroded paleosols suggest methane is not from drowned terrestrial deposits. ► Bathymetry and subsurface data indicate pockmarks relate to underlying topography. ► Underlying topography is more important than gas origins to pockmark distribution.
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