Vertisol Research Articles

Pedogenesis of soils formed on jurassic calcareous sedimentary rock formations: A transect study in northern semi-arid highlands of Ethiopia

With the objective of examining soil characteristics, pedogenic processes and classification in association to local environmental and landscape attributes, a transect study was carried out in Hnitalo Wajerat district of Northern Ethiopia. Six pedons beded on shale and dolerite parent rocks were investigated. The soils were sandy loam to clay in texture, moderately porous, neutral to strongly alkaline, nonsaline, base-rich and calcareous. The dominant pedogenic processes prominent in soils of the area were calcification, vertization, argilluviation, melanization and colloidal eluviations. Mollic and ochric horizons were noticed on surface horizons, while cambic, calcic and vertic horizons were found to be the dominant subsurface horizons. Steep upslope areas were characterized by shallow gravelly soils with continuous hard rock. Shrink-swell cracks, colluvic materials and deep soils were prominent on flat areas. The soils of the area were classified as Leptosols/Entisols, Cambisols/Inceptisols, Calcisols/Aridisols and Vertisols. The study evidenced that the pedogenic processes and soil development were largely patterned by terrain positions, lithology and land use type.

Vertical distribution of soil seed bank and the ecological importance of deeply buried seeds in alkaline grasslands.

BackgroundSoil seed banks play a central role in vegetation dynamics and may be an important source of ecological restoration. However, the vast majority of seed bank studies examined only the uppermost soil layers (0–10 cm); hence, our knowledge on the depth distribution of seed bank and the ecological significance of deeply buried seeds is limited. The aim of our study was to examine the fine-scale vertical distribution of soil seed bank to a depth of 80 cm, which is one of the largest studied depth gradients so far. Our model systems were alkaline grasslands in East-Hungary, characterised by harsh environmental conditions, due to Solonetz soil reference group with Vertic horizon. We asked the following questions: (1) How do the seedling density and species richness of soil seed bank change along a vertical gradient and to what depth can germinable seeds be detected? (2) What is the relationship between the depth distribution of the germinable seeds and the species traits?MethodsIn each of the five study sites, four soil cores (4 cm diameter) of 80 cm depth were collected with an auger for soil seed bank analysis. Each sample was divided into sixteen 5-cm segments by depth (320 segments in total). Samples were concentrated by washing over sieves and then germinated in an unheated greenhouse. Soil penetration resistance was measured in situ next to each core location (0–80 cm depth, 1-cm resolution). We tested the number and species richness of seedlings observed in the soil segments (N = 320), using negative binomial generalized linear regression models, in which sampling layer and penetration resistance were the predictor variables. We ran the models for morphological groups (graminoids/forbs), ecological groups (grassland species/weeds) and life-form categories (short-lived/perennial). We also tested whether seed shape index, seed mass, water requirement or salt tolerance of the species influence the vertical distribution of their seed bank.ResultsGerminable seed density and species richness in the seed bank decreased with increasing soil depth and penetration resistance. However, we detected nine germinable seeds of six species even in the deepest soil layer. Forbs, grassland species and short-lived species occurred in large abundance in deep layers, from where graminoids, weeds and perennial species were missing. Round-shaped seeds were more abundant in deeper soil layers compared to elongated ones, but seed mass and ecological indicator values did not influence the vertical seed bank distribution. Our research draws attention to the potential ecological importance of the deeply buried seeds that may be a source of recovery after severe disturbance. As Vertisols cover 335 million hectares worldwide, these findings can be relevant for many regions and ecosystems globally. We highlight the need for similar studies in other soil and habitat types to test whether the presence of deep buried seeds is specific to soils with Vertic characteristics.

Carbon and nitrogen stocks and microbiological attributes of soil under eucalyptus cultivation in the Pampa biome of southern Brazil

In the south of Brazil, the intensification of eucalyptus planting can impact the local biome, characterized by grasslands that extends to Uruguay and Argentina. Thus, the objective of the study was to evaluate changes in soil carbon, nitrogen and their labile fractions and soil microbiological attributes due to the introduction of eucalyptus cultivation in the Pampa biome. The soils evaluated were Eutric Regosol (RG), Haplic Lixisol (LX), Dystric Leptosol (LP) and Pellic Vertisol (VR). For this, areas of homogeneous cultivation of Eucalyptus saligna (7 years old) and areas of grassland (native vegetation) were selected. Physical granulometric fractionation of soil organic matter (SOM) was performed in the 0–5, 5–10 and 10–15 cm soil layers, quantifying levels, stocks and distribution of total organic carbon (TOC) and total nitrogen (TN) in the labile and associated with minerals fractions, and the carbon management index (CMI) was calculated. In the 0–5 and 5–10 cm soil layers, microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), basal soil respiration, metabolic coefficient, MBC / TOC, MBN / TN, MBC / MBN ratios were also evaluated. Eucalyptus cultivation increased the TOC and POC carbon stocks by 8.7 and 21.7%, respectively (0-15 cm) in compared to grassland. It was also observed that the cultivation of eucalyptus increased 6.7% and 26.0% the stocks of TN and PN, respectively, compared to grassland in the pampa biome. Carbon stocks associated with minerals were not affected by eucalyptus cultivation. The cultivation of eucalyptus increased the basal respiration and the microbial biomass carbon in relation to grassland and there is a reduction of microbial biomass nitrogen in the soil. Thus, the cultivation of eucalyptus in the Pampa biome in southern Brazil demonstrates that it is a forest crop that can contribute to the increase in total and labile carbon stocks and also the biomass and microbial activity of the soil, which are important indicators of assessment of soil quality.

The Structural Characteristics of Organic-Inorganic Complexes and the Mechanism of Its Influences on Soil Color in the Calci-Aquic Vertisols

The Structural Characteristics of Organic-Inorganic Complexes and the Mechanism of Its Influences on Soil Color in the Calci-Aquic Vertisols

SOIL DENSITY AND OPTIMUM MOISTURE FOR SOIL COMPACTION IN FIVE SOIL CLASSES IN WESTERN BAHIA STATE

The transformation of natural ecosystems into agricultural environments modifies the soil structure and it may result in its compaction. Therefore, the objective of this work was to determine the optimum moisture for soil compaction (wot) and maximum soil compaction density (Dsmax) in different soil classes in western Bahia State. The samples were collected in five sites covering different soil classes: Orthic Quartzarenic Neosol (RQ), Orthic Ebanic Vertisol (VEo), Haplic Cambisol (CX) and two Red-Yellow Latosol, one already cropped (LVA) and another with native forest (LVA1). Wot and Dsmax were determined according to ABNT NBR 7182 (1986) standards. Data were submitted to a regression analysis and also to the analysis of the principal components (PCA). Wot presented a decreasing order: VEo> LVA> LVA1> CX> RQo, ranging between 8.20 and 15.00% and Dsmax showed the following order RQo> LVA> LVA1> CX> VE, ranging between 1.34 and 1,92 Mg.m-3. The wot was directly proportional to the clay content and the organic carbon and inversely proportional to the soil sand content. For Dsmax, the influence of the clay was inversely proportional whereas in wot, this variable promoted the growth.

Paleosols in an outcrop of red beds from the Upper Cretaceous Yaojia Formation, southern Songliao Basin, Jilin Province, NE China

Paleosols in an outcrop of fluvial–lacustrine red beds have been recognized in the Upper Cretaceous Yaojia Formation in southern Songliao Basin, Songyuan City, Jilin Province, NE China. They are recognized in the field by pedogenic features, including root traces and burrows, soil horizons and soil structures. Root traces are remnants of small herbaceous plants, elongating and branching downwards in the red paleosols. They are filled by calcite, analcime, and clay minerals in spaces created by the decay of the plant roots. Burrows are found near the root traces with backfilled cells made by soil-dwelling insects. Soil horizons include calcic horizons (Bk horizon) with continuous calcareous layers, argillic horizons (Bt horizon) with clay films and dark brown to black iron-manganese cutans, vertic horizons (Bw horizon) with slickensided claystone, and deformed soil structure and gleyed horizons (Bg horizon) with mottles and reticulate mottles. Soil structures of the paleosols include pseudo-anticlinal structures, subangular blocky structures, and angular blocky structures. The micro-pedogenesis characteristics are also observed, including micrite pedogenic minerals and clay skins. Based on the pedogenic features above, paleosols types including Aridisol, Alfisol, and Vertisol are interpreted in the red beds of the Yaojia Formation. Forming in the Late Cretaceous, the paleosols can provide more details about the seasonal climate conditions and terrestrial sedimentary system in lacustrine basin.

Physical Indicators and Mechanism of Vertisolization: A Case Study of the Cis-Caucasian Vertic Chernozem

Vertisolization —the development of vertic properties and vertic horizons—is a widespread process leading to adverse physical and technological properties of chernozems.. There is still no generally accepted theory of the genesis of this phenomenon, although it is a priori clear that the physicochemical mechanisms of the interaction between fine particles and soil water in swell–shrink cycles are the underlying factors. Patterns of the dynamics of the main categories of soil porosity in dependence on the soil water content have been studied at a quantitative level in the genetic horizons of a Cis-Caucasian vertic leached chernozem (Luvic Chernozem (Epiloamic, Katoclayic, Aric, Novic, Bathyvertic)) in comparison with a chernozem without vertic properties. The physical state of vertic soils is represented by structural diagrams of porosity as a function of the specific volumes of various pore categories depending on the volumetric water content. The diagrams are constructed using the experimental data on the textural porosity of aggregates obtained by saturating individual aggregates with a nonpolar liquid (toluene) and humidification with hot water vapor and a fundamental ionic electrostatic model of the disjoining pressure. Vertisolization is characterized by a significant reduction in the textural porosity and a predominance of specific volumes of the external pore space (cracks and interaggregate voids) in the overall structure of the porous dispersed system. The most likely cause of vertisolization is a sharp (twofold) decrease in the effective width of the electrical double layer in the dispersed system with an increase in the particle interaction through stable layers of liquid phase (compaction effect). In turn, this brings about adverse technological properties of the vertic chernozems and lumpy fragmentation upon drying with the formation of large cracks, which complicates their tillage and agricultural activities in general.

Shrinkage curves of monoliths from genetic horizons of Vertic Solonetz

Statistical cumulative distributions of indices for shrinkage curve of 324 monoliths from Vertisols and Vertic Solonetzes are created. Natric and vertic horizons have similar range of shrinkage indices, with that natric ones have higher values of pore volume weakly changed during water evaporation and lower bulk density at shrinkage limit.

Morphological diversity of chernozemic soils in south-western Poland

Abstract Diverse chernozemic soils featured by thick mollic horizon, rich in humus, dark-coloured, structural, and saturated with base cations are relatively common in the loess-belt of SW Poland. It is postulated, that most of these soils may have similar initial (chernozemic) history of thick humus horizon, related to climate conditions and vegetation in the Late Pleistocene and the Neolithic periods. However, these soils exist on various bedrocks and under different moisture conditions that led to the development accompanying features and variable classification of soils, both in Polish and international soil classifications. The aim of the paper is to presents the most important variants of loess-derived chernozemic soils of SW Poland, in relation to local conditions, which influenced soil transformation and present spatial diversification. ‘Typical’ chernozems (WRB: Calcic Chernozems), which have a mollic horizon and secondary carbonates, but are free of strong redoximorphic features, are rather uncommon in the region. Whereas, the black earths (WRB: Gleyic/Stagnic Chernozems/Phaeozems), featured by the presence of mollic horizon and strong gleyic or stagnic properties in the middle and bottom parts of the profiles, are predominant loess-derived chernozemic soils in SW Poland. Their most specific forms, developed on the clayey bedrock, are black earths with a vertic horizon (WRB: Vertic Stagnic Phaeozems). The strongly leached chernozemic soils developed over permeable subsoils, lacking carbonates and free of (strongly developed) stagnic/gleyic properties are called grey soils, often featured by the presence of subsurface diagnostic horizons cambic or luvic (WRB: Cambic/Luvic Phaeozems).

Viscoelastic Behavior of Vertic Solonetz in the Kamennaya Steppe

The aim of this work is to determine viscoelastic behavior parameters of soil pastes and micromonoliths of natric and vertic horizons in the profile of Vertic Solonetz from the Kamennaya Steppe (Voronezh oblast, Russia) and to use rheological properties to explain the formation of three irregular alteration structures with different wavelengths and deformation patterns of the soil mass. The rheological parameters of six soil horizons were determined by the amplitude sweep tests using an MCR-302 rheometer with parallel plates. The general features of viscoelastic behavior of soil pastes and micromonoliths, the correlation between the storage modulus G'LVR in the linear range of viscoelastic behavior of pastes and micromonoliths with their moisture, the distribution of rheological properties in the soil profile, and the relationship between the content of exchangeable sodium and the integral Iz used for the evaluation of structural stiffness are discussed. Rheological properties of Vertic Solonetz are compared with published data on Vertisols from Brazil, Russia, and USA and on saline clay alluvial soil from Spain. A hypothesis of formation of the profile of Vertic Solonetz with the gilgai microtopography as dependent on the rheological characteristics of the viscoelastic behavior of the studied soil horizons is proposed.

Past and current geochemical conditions influence silicon isotope signatures of pedogenic clay minerals at the soil profile scale, Ethiopia

Soil processes strongly govern silicon (Si) mobility in terrestrial environments and its relation to other global biogeochemical cycles. The nature of inherited soil clay minerals can be highly diverse given the variability of their weathering environment. The influence of Si isotope fractionation factor in the initial geochemical conditions of clay precipitation can therefore be still expressed in inherited clay minerals in their new environment. We studied top- and subsoil of an Ethiopian Vertic Planosol derived from parent materials of similar sources of volcanism. The selected Planosol has an abrupt textural change at a depth of ~40 cm separating a bleached, silty (25 ± 1.8% clay) ash-derived soil horizon with a crumby structure from a heavy clayey (68 ± 3.4% clay) lacustrine-derived vertic soil horizon. The mineralogical assemblage of the clay fraction in top- and subsoil is characterized by similar proportions of 1:1 (kaolinite) and 2:1 (illite and smectite) layer-type clay minerals. This specific soil profile provides a unique opportunity to elucidate the influence of clay formation processes (inheritance versus neoformation) on the Si isotope signature of pedogenic clay minerals. Minerals of the clay fraction in the clayey vertic horizon are significantly enriched in light Si isotope (δ30Si = −1.41 ± 0.02‰) compared to the bleached, silty horizon (δ30Si = −0.69 ± 0.03‰). These results are corroborated by the preferential enrichment in Ge, relative to Si, in the clay fraction of the clayey subsoil compared to the silty topsoil (Ge/Si = 6.3 ± 0.14 and 4.0 ± 0.10 μmol mol−1, respectively). Our results demonstrate that geochemical conditions in lacustrine environment favor kinetically-driven Si isotope fractionation factor leading to lower Si isotope ratios in 2:1 clay minerals inherited in the new soil profile environment. The inherited soil textural conditions in the soil profile also contribute to on-going processes that result in larger Si isotope differences between the soil solution (CaCl2 extractable) and clay minerals. This implies that Si isotope signatures of clay minerals in the studied soil profile are influenced by a combination of inheritance processes in lacustrine environment and on-going neoformation processes in the soil profile. This finding has important implications for environmental studies using geochemical and Si stable isotope tracers to better understand current soil processes, to model elemental cycling in soil-plant systems and to quantify land-ocean element mass-balances.

Biomass accumulation and potassium concentrations in tissue of Teff (Eragrostis tef Zucc. Trotter) at three growth stages in Vertisols and Nitisols of the Central Highlands of Ethiopia

Understanding the physiology and time-course of above ground biomass (AGBM) and potassium (K) accumulation pattern in plants and removal from soil is essential to simultaneously increase crop yield and synchronize K demand and K supply, thereby predict crop yield. It is also an essential criterion for optimizing fertilizer practices, and may help to enhance soil and crop quality. A pot experiment was conducted using teff (Eragrostis tef Zucc. Trotter) to determine AGBM, K concentration and uptake at three growth stages. Two soil types (Vertisols and Nitisols) and four K levels were used. Soil samples (120) were collected at planting and three stages while plant samples (160) were collected at the three growth stages. Above ground biomass increased as growth stage advances regardless of K levels in both soil types. Maximum AGBM was observed at tillering stage and at 120 kg K ha-1 and was higher in Vertisols at all growth stages. The study concluded that sufficient supply of nutrients from soil/fertilizers at early growth stages is required for higher yields. The study suggested that determining the right rate for different soil and crops is required. Repeating the experiment at field condition to draw sound conclusions was also recommended. Key words: Growth stages, potassium concentration, biomass, teff, Vertisols, Nitisols, Central Highlands.

Response of new groundnut entry K 1641 to Spacing and nutrients in vertisol during rainy season under rainfed farming

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Vertic soils and Vertisols in cryogenic environments of southern Siberia, Russia

Vertisols and vertic soils are known in a wide range of bioclimatic environments. The aim of this research was to identify possible vertic features in ultra-continental climate with gelic soil temperature regime with MAAT <1°C. Detailed morphological investigation supported by micromorphological and physical attributes identified vertic features both at the order and subgroup levels in Buryatia (Trans-Baikal region), where soils are formed under MAAT −4.2°C, and are underlain by permafrost. Vertisol was found in the shoulder position, while the soils of the summit and the backslope position were classified as vertic intergrades of Phaeozem. Vertisol has cracks on the surface, slickensides and wedge-shaped aggregates within the profile, 47–55% of clay, extremely high smectite contents (up to 98% of clay fraction). Vertic Phaeozems on the summit and backslope positions have similar morphological attributes but at the initial stage of formation, and without the formation of vertic horizon. Both Vertisol and Vertic Phaeozems have vertic features at microlevel such as a variety of striated b-fabrics, an open porphyric c/f-related distribution, planar voids, a blocky microstructure, wedge-shaped microaggregates. These soils have been formed under the joint impact of deep winter freezing, permafrost formation, and shrink-swell processes, and show the combination of primary cryogenic features and cryogenic features transformed by the shrink-swell and shearing processes.We found that Vertisols can form not only in cold environments, but also in ultra-continental cold environments with permafrost and negative mean annual air temperatures. However, their areas in Buryatia are limited in size to the warmest and driest positions in the landscape, namely south facing slopes. The discovery of Vertisols in ultra-continental climates will be a challenge for current soil classification systems, like Soil Taxonomy, which will need a provisional taxonomic category to accommodate such soils under gelic temperature regimes. We propose to introduce Gelert suborder and Vertic subgroup to Haplogeloll great group.

Nitrogen response of sweet sorghum genotypes during rainy season

Sweet sorghum ( Sorghum bicolor (L.) Moench) is a smart biofuel crop, which can be grown under tropical rainfed conditions without sacrificing food and fodder security. Three sweet sorghum cultivars (viz. ICSA 52 × SPV 1411, CSH 22 SS and ICSV 93046) were grown under six nitrogen levels (0, 30, 60, 90, 120, 150 kg ha -1 ) on Vertisols during two rainy ( kharif ) seasons at ICRISAT, Patancheru, India. The results from two-year trial indicated that out of three sweet sorghum cultivars evaluated, sweet sorghum hybrid CSH 22 SS produced highest green stalk (46.90 t ha -1 ) and ethanol yield (1940 l ha -1 ) compared to other cultivars. The three cultivars responded well to applied N doses up to 150 kg ha -1 , however, application of N beyond 90 kg ha -1 did not result in any significant increase in grain yield and economic returns. Net economic returns of Rs 32,898 ha -1 (US$ 601.21 ha -1 ) were significantly higher with 90 kg N ha -1 application as compared to other levels of fertilization. It is concluded that for obtaining the highest green stalk yield, ethanol yield and thereby maximum economic returns, sweet sorghum cultivar, viz. CSH 22 SS should be fertilized with 90 kg N ha -1 .

QUANTITATIVE METHODS OF PEDOLOGICAL DROUGHT ANALYSIS IN THE NORTHEASTERN PART OF ROMANIA (1961 – 2006)

In the context of desertification and climate changes, under the pressure of a growing need for food all over the world, the increasing frequency and severity of droughts becomes an intensely debated subject by a great number of stakeholders, scientists, planners and decision makers. The aims of this study are to establish a good correlation between the atmospheric and soil pedological within the northeastern part of Romania, by modeling the role of different soil properties on drought propagation. Here, the authors present the results of Standardized Precipitation Index, Palfai Aridity Index and Palmer Drought Severity Index, indices that were computed using data of temperature and precipitation from four meteorological stations, evenly spread within the study area. Significant correlations were found between the above mentioned indices, hence the Palmer Drought Severity Index was modified by replacing the standard soil available water content with the real value obtained from 7 soil profiles (Chernozem, Phaeozem, Luvisol, Preluvisol, Vertisol and Gleysol) situated within the study area. Finally, based on a diagram between the water content and the wilting point the results of the study led to the identification of the most susceptible soil to drought, as an important preliminary step to drought risk management.

Landscape planning for agridevelopment at regional scale: an example from cotton growing Yavatmal district, Maharashtra, India

The basaltic landscape planning on the hot semiarid ecosystem in cotton growing Yavatmal district, Maharashtra tends to concentrate on 52 per cent of total cultivated area with 43 per cent of rural families living below poverty line posing major problem for environmental protection and resource management. Concepts of sustainable development at regional-level planning suggested that there is a growing concern for the landscape community to develop a strategic regional agricultural planning perspective in order to assist landscape planning goals. These challenges were explored with particular reference to the cotton growing Yavatmal district in Maharashtra through baseline land resource / agronomic surveys and assessing the production potential of regional rural landscapes for crop planning. Landscape analysis, premised on the geopedological and elevation constructs, culminated in a spatial coverage of hills and ridges (12.6 per cent of total area) in northern and central parts whereas plateaus (29.3 per cent) in association with isolated hills, mesas and butte and escarpments (17.7 per cent), pediplains (28.8 per cent) and plains (8.1 per cent) in south western parts of the district. Regional level analysis revealed spatially variable soil typologies dominated by vertisols and vertic intergrades. An exploration and brief account of integration landscape planning was discussed with some reflections on the experience and highlighting some of the problems and potentials of this approach within the regional context.

Crop water productivity for sunflower under different irrigation regimes and plant spacing in Gezira Scheme, Sudan

Two field experiments with Sunflower on deep cracking soil with heavy clay (vertisol) were conducted at Gezira Research Station Farm during two executive winter seasons, in WadMedani, Sudan. The crop was sown in the third week of November and in the first week of December for seasons 2012 and 2013 respectively. The experimental design was split plot design with three replicates. The Sunflower hybrid tested in the study was Hysun 33. The objective of this study was to determine the effect of three different irrigation intervals of 10, 15 and 20 days and two intra-row plant spacings of 30 cm and 40 cm on yield and yield components of Sunflower. The seed yields obtained from the different treatments were in the ranges of 1890-3300 kg/ha and 1590-3290 kg/ha for the first and second season respectively. The corresponding computed on average crop water productivity was in the range of 0.31-0.43 kg/m3. The study clearly indicated that the highest seed yield was obtained when the crop was sown at 40 cm plant spacing and irrigated every 10 days. The highest crop water productivity was achieved from irrigation every15 days in both planting spacings

Mineralogy and Micromorphology Characteristic of Vertisol Lying on Limestone Parent Rocks at Jeneponto District of South Sulawesi Province, Indonesia

The objective of this is paper is to determine the mineralogy and micromorphology characteristics of vertisol in the limestone parent rock at Jeneponto district of South Sulawesi Province, Indonesia. The pedons represent deposits of volcanoes basalt. The study consisted of field and laboratory research. Field research comprises of soil profile descriptions and soil sampling, while laboratory analysis consists of clay minerals analysis using X-rays, as well as sand and rock mineral. Micromorphology analysis undisturbed soil samples were taken from identifiable horizon for thin section preparation. X-ray analysis revealed that clay minerals of the vertisol mainly consists of montmorillonite group. While the mineral composition of parent rock (limestone) generally consists of foraminifera fossil, calcite, dolomite, clay minerals, orthoclase, opaque minerals and quartz. The mineralogy of sand fraction generally consists of easily weathered minerals like pyroxene, feldspar, hornblende, plagioclase, biotite and hard weathered mineral (quartz and opaque). Soil micromorphology analysis revealed that raw material, in general is dominated by coarse material which is consist of quartz mineral mixed with other minerals such as pyroxene and plagioclase. On the other hand, organic coarse-sized components are not found and the microstructure of the soil is generally in the loose form (massive), and the type of soil pore vary from vugh to channels pore.

Vertic features in a soil catena developed on Eocene marls in the Inner Depression of the Central Spanish Pyrenees

Scientific interest in marls has expanded in recent years especially in regard to erosion rates, weathering processes and stabilization of the resulting sediments. However, information regarding the properties and evolution of overlying soil is relatively scarce.This work analyzes the relationship between mechanical properties and standard properties of soils developed on Eocene marls in mountainous regions of the southern Central Spanish Pyrenees. It also examines whether these soils have the vertic features traditionally ascribed to them and how these features may vary along a catena.The water holding capacity of the soils exhibits a typical catena-related trend that increases progressively from low values in upper slope profiles to higher values for the middle slope and valley. The soils have a high percentage of silt-sized particles. Quartz and calcite are the main mineralogical components of the fine earth fraction. Illite represents the major component of the clay fraction. The linear extensibility and Atterberg limits are positively and significantly correlated to clay content. Low liquid limit (usually less than 30%), low soil aggregate stability (lower than 25% in Ap horizons), and high subsidence values (n>0.7) are likely factors in the high dispersivity and sliding risk observed for the soils. These factors also explain the presence of buried soils and lithological discontinuities in lower slope profiles as well as the relatively limited degree of soil evolution, despite a relatively humid climate. Low porosity, mainly of vesicular type, and a poor structure facilitate saturation in the wet season and lead to soil reduction processes, especially within deep soil horizons along lower parts of hillslopes. Simulated wetting and freezing treatments were shown to fracture the unaltered marls into small fragments, demonstrating the soil's susceptibility to physical weathering. Given moderate clay content, absence of smectites and moderate soil extensibility (COLE <0.06cmcm−1 in most horizons), topsoil cracking in lower slope profiles is apparently caused by high rates of evaporation during the dry season. The soils described here did not meet the requirements of vertic horizons but most meet the diagnostic criteria of having a protovertic horizon, despite the absence of swelling and shrinking clays.