Paleosols of kurgans of the Early Iron Age in the Transural steppe zone

Paleosol studies of archaeological monuments of different ages have been conducted on the Transural Plateau. The morphological and physicochemical properties of paleosols under burial mounds (kurgans) of the Early Iron Age (the fifth and fourth centuries BC) were compared with the properties of background surface soils. A paleosol of the Savromat epoch (2500 BP) is characterized by high contents of gypsum and soluble salts. The presence of humus tongues in its profile attests to the aridity and continentality of the climatic conditions during that epoch. Paleosols buried under kurgans of the Late Sarmatian epoch and the Hun epoch (about 1600 BP) are characterized by a higher content of humus and greater depth of the carbonate horizon, which attests to the humidization of climatic conditions. The evolution of soils as related to climate dynamics in the first millennium BC and the first millennium AD is characterized.     

Specific features of paleosols of burial mounds involved in current farming practices and their contemporary pedogenesis (using the early Alanian burial mounds in the North Caucasus region as an example)

Paleosols of three burial sites—Brut 1, Brut 2, and Beslan—in the Northern Osetia Republic (Alania) of the North Caucasus region were studied. A part of the Brut 2 burial site was subjected to intensive agricultural use (more than 30-year-long irrigation and regular tillage). This led to the leveling of the burial mounds and changes in some properties of the buried paleosols. A comparative analysis of paleosols of the same age under the burial mounds involved not included in the intensive agricultural use made it possible to determine the degree of preservation of the initial properties in the irrigated paleosols and to use them for reconstruction of the paleoclimates. Some specific features of the soil evolution were revealed, and paleoclimate reconstructions were performed for the period of the Early Alan civilization in the North Caucasus region (from the second half of the 2nd century AD to the middle of the 5th century AD).     

Dynamics of the properties of steppe paleosols of the Sarmatian time (2nd century BC-4th century AD) in relation to secular variations in climatic humidity

Paleosols buried under kurgans of the Early (2nd-1st centuries BC), Middle (1st-2nd centuries AD) and Late (2nd-IV centuries AD) Sarmatian epochs were studied in dry steppes and desert steppes of the Lower Volga region (the Privolzhskaya and Ergeni Uplands and the Caspian Lowland). It was found that temporal variations in the morphological, chemical, microbiological, and magnetic properties of the paleosols in the interval of 2200–1600 BP were characterized by the cyclic pattern related to secular dynamics of climatic humidity with changes in the mean annual precipitation of ±30–50 mm. These climate changes did not transform chestnut paleosols and paleosolonetzes at the type or subtype taxonomic levels. However, they led to certain changes in the humus, carbonate, and salt profiles of the soils; in the character of solonetzic horizon B1; and in the state of microbial communities. According to these data, the Sarmatian time was characterized by alternation of micropluvial and microarid stages lasting fro about 100–200 years. In particular, the stages of humidization were observed in the 1st century BC-1st century AD and in the 4th century AD; the most arid conditions were observed in the second half of the 2nd and the first half of the 3rd century AD.     

Humus in paleosols of archaeological monuments in the dry steppes of the Volga-Don interfluve

Traditional chemical methods and ¹³C-NMR spectroscopy were used to study the humus in chestnut paleosols buried under kurgans of different ages (the 16th–15th centuries BC; the 1st, 2nd–3rd, and 13th–14th centuries AD) and under the Anna Ioanovna Rampart (1718–1720) and in their recent analogues on virgin plots. It was found that the decrease in the humus content of the paleosols as a result of the diagenetic processes is exponentially related to the age of the soil burial. The loss of humus from the upper 30 cm of the paleosol buried 3500 yrs ago amounted to 76 ± 14%, and this system did not reach a stationary state. The constants of the humus mineralization in the paleosols were determined. A tendency for an increase in the degree of the organic matter humification in the chestnut soils during the past 3500 yrs was found. With an increase in the age of the burial, the portion of aromatic structures in the structure of the humic acids increased and the portion of aliphatic fragments decreased. The cyclic changes in the composition of the humus related to the secular variations in the climatic humidity were identified.     

Revealing of directed temporal changes in soils of short-term chronosequences upon the high spatial variability in the background soil properties

The properties of paleosols buried under the Filippovka group of kurgans in Orenburg oblast dating back to the second half of the fifth and to the fourth centuries BC were analyzed with the use of multivariate statistical methods. This made it possible to establish the relative chronology of construction of the kurgans, which was confirmed by the results of radiocarbon dating of the soil humus.     

Characteristics of microbial communities in steppe paleosols buried under kurgans of the Sarmatian time (I–IV centuries AD)

Microbiological studies of paleosols buried under steppe kurgans of different ages of the Middle (I–II centuries AD) and Late Sarmatian (II–IV centuries AD) time in different regions of the Lower Volga steppes were carried out. The regularities of the soil microbial communities’ development were determined in the I–IV centuries AD by the climate dynamics and the replacement of the relatively humid conditions (the I century to the first half of the II century) by dry (the second half of the II century to the first half of the III century) and then again by humid (the end of the III century to the IV century) conditions. In the humid climatic periods, the active biomass of the microorganisms and its portion in the total microbial biomass and the C_org of the soil increased, the portion of microorganisms consuming plant residues increased in the ecological-trophic structure of the microbial community, and the index of oligotrophy decreased. These changes had an opposite direction in the arid climatic periods. The variations of the microbiological parameters relative to the century-long dynamics of the climate over the historical time were synchronous and unidirectional, though the studied soils were found in different soil-geographical zones (dry and desert steppe), natural regions (the Privolzhskaya and Ergeni uplands and the Caspian Lowland), and landforms (watersheds, river terraces, marine plains).     

Paleosol and paleoenvironmental conditions in the Lower Volga steppes during the Golden Horde period (13th–14th centuries AD)

Paleosols buried under steppe kurgans of the Golden Horde period (13th–14th centuries AD) in the Lower Volga basin are characterized by an increased humus content, lower salinity and gypsum content, and higher magnetic susceptibility of the soil material in comparison with the paleosols buried in the preceding period and the background surface soils. A comparative analysis of the morphological, chemical, and magnetic properties of the buried and surface soils allows us to conclude that an increase in climatic humidity within this dry region took place in the period of the high Middle Ages, with a peak in the 13th–14th centuries AD. The climatic change was manifested in the soil evolution at the taxonomic levels of soil genera and soil subtypes (in the ecotone zones). On the basis of measured magnetic susceptibility values, the mean annual precipitation levels in the Golden Horde period have been reconstructed. According to our estimates, the mean annual precipitation in the Lower Volga basin in that time was 30–80 mm higher than at present. The favorable paleoenvironmental and paleosol conditions of the Golden Horde period were important factors that affected the ethnic and political situation in the Lower Volga region.     

Short chronosequences of paleosols from the Skvortsovka kurgans in the Buzuluk River valley of Orenburg oblast

Paleosols buried under kurgans of the Yamnaya (the third millennium BC) and Srubnaya (the 18th–17th centuries BC) cultures within the Skvortsovka group of kurgans in the Buzuluk River valley in Orenburg oblast have been studied. This is the area of the dry steppe zone. The changes in the paleosol properties make it possible to distinguish between relatively short-term chronointervals separately for the Yamnaya and Srubnaya cultures. The paleosol data and radiocarbon dating have been used for revealing the relative order of the construction of the kurgans within these chronointervals and for the paleoclimatic reconstruction. Quite definite changes took place in the soil formation from the beginning to the end of the particular chronointervals: the contents of humus and exchangeable bases and the portion of calcium ions in the composition of the exchangeable cations increased in parallel with the enhanced leaching of carbonates and the enhanced biological activity. These changes attest to the increasing amount of precipitation. In general, the climate of the Srubnaya cultural epoch was less continental, whereas the climate of the Yamnaya cultural epoch was relatively close to the modern climate. The ¹⁴C dates of the pedogenic carbonates in the upper meter of the paleosol profiles have been used as auxiliary data to confirm the sequence of the soil’s burial during the short chronointervals corresponding to the humid stages of the paleosol’s evolution, and the 14C dates of the diagenetic carbonates have been used to determine the dates of construction of the kurgans with due account for some time gap between the construction of the kurgans and the appearance of these carbonates in the buried soil profiles.     

Paleosol studies of burial mounds in the Ilovlya River valley (the Privolzhskaya Upland)

Paleosols buried under kurgans of the Bronze (end of the fourth and the third millennia BC), Early Iron (1st–3rd centuries AD), and Medieval (13th century AD) epochs have been studied on the Ilovlya River (a tributary of the Don River) terrace. The evolution of chestnut soils in the south of the Privolzhskaya Upland during the last 5000 years has been traced. It is shown that the mean weighted contents and distribution of soluble salts, gypsum, and carbonates in the soil profiles have been subjected to cyclic changes. The total microbial biomass and its trophic structure in the A1, B1, and B2k horizons of paleosols of different ages have been determined. A comparative analysis of the morphological, chemical, and microbiological data on the paleosols of different ages has been used to reconstruct the climatic dynamics for the last 50 centuries. The aridity of the climate in the studied region increased at the end of the third-the beginning of the second millennia BC and in the second and third centuries AD. The humidization of the climate took place in the 1st and in the 12th–13th centuries AD.     

Production of CO<Subscript>2</Subscript> by Paleosol Samples Taken in the Steppe Zone under Kurgans Constructed in the Periods of Relative Aridization and Optimum of the Climate

The studies of recent soils and paleosols buried under kurgans created in the periods of long-term aridization (3000–2000 BC) and climatic optimum (13th–14th centuries AD) were performed in steppes of the southeastern part of the East European Plain (Privolzhskaya Upland and Caspian Lowland) in order to determine the rate of carbon dioxide production by the soil samples at the natural moisture and after moistening up to 60% of the total moisture capacity. The CO₂ emission from the samples of paleosols corresponding to the period of climatic aridization in the Lower Volga River at their natural moisture status was lower than that from the samples of background surface soils, whereas the CO₂ emission from the samples of paleosols buried under optimum climatic conditions was higher than that from the samples of background surface soils. After moistening of the samples, the increase in the CO₂ emission from the paleosol samples depended on the actual humidity of the climate in the corresponding period.     

Late Holocene paleopedological records contained in tephra from El Chichón volcano, Chiapas, Mexico

High rates of pedogenesis on unconsolidated volcanic materials imply the accelerated generation of the soil memory. The purpose of this research was to extract the high resolution (centennial scale) paleopedological records from the Late Holocene paleosols of the El Chichón volcano formed during the last 2000 years. We studied buried monogenetic Andosols on the dated tephras and a pedocomplex formed from a set of thin ash layers deposited on older Acrisol derived from shales. Particle size distribution, DCB-extractable Fe, oxalate-extractable Fe, Al and Si, sand and clay mineralogy, organic carbon content and stable C isotope composition in humus were evaluated and interpreted as the elements of the soil memory. However, some differences were found in properties of two buried soils, especially in the kind of A horizons. We attribute such differences of individual Andosols to be caused by ancient human impact because it has been demonstrated that humid conditions persisted during the last 1300 years. Thus the drought that was supposed to provoke the collapse of the Maya civilization at the end of I millennium A.D., should have been a short-term event, below the resolution of this paleopedological record. The Andic Acrisol pedocomplex demonstrated the domination of the humid tropical climate over longer time intervals (probably major part of the Holocene) with possible minor dry episodes.     

Soil evolution and climate dynamics in dry steppes of the Privolzhskaya Upland during the last 3500 years

The investigation of paleosols of different ages buried under archaeological monuments of the Bronze (16th?C15th centuries BC), Early Iron (2nd?C3rd centuries AD), and Medieval (14th century AD) ages demonstrated that the evolution of chestnut soils and solonetzes in the dry steppes of the southern part of the Privolzhskaya Upland during the past 3500 years manifested itself at the level of the genus and species characteristics of the soils, such as the degree of the solonetzicity, the humus content, and the content and composition of the soluble salts. The revealed regularities of the variations of the morphological, chemical, and microbiological soil properties in time allowed reconstructing the secular dynamics of the climatic humidity in the region. It was found that the humidization of the climate with a decrease in the degree of the climatic continentality took place in the middle of the second millennium BC. The Late Sarmatian Time (2nd?C3rd centuries AD) was characterized by arid climatic conditions, whereas the Golden Horde time (13th?C14th centuries AD) was marked by the general humidization of the climate. A gradual aridization of the climate began in the second half of the 14th century and continued in the 15th century AD.     

Comparative characterization of microbial communities in kurgans,paleosols buried under them,and background surface soils in the steppe zone of the Lower Volga region

A comparative analysis of the state of microbial communities in kurgans, paleosols buried under them, and background surface soils in the dry steppe zone of the Lower Volga region has been performed. It is shown that the population density of microorganisms of various trophic groups in the kurgans is an order of magnitude lower than that in the A1 horizon of the corresponding buried paleosols and background surface soils within the areas of chestnut, light chestnut, and solonetzic soils. The respiration activity of the microbial communities in the upper layer of the kurgans is comparable with that in the A1 horizons of the background surface soils; it decreases in the deeper layers of the kurgans. In the A1 horizon of the buried paleosols, the respiration activity is approximately the same as in the deep layers of the kurgans. In the buried paleosols, the spatial variability in the numbers of soil microorganisms is approximately the same or somewhat higher than that in the background surface soils. The spatial variability in the respiration activity of the buried paleosols is two to four times higher than that in the background surface soils.     

Transformation of carbonate pedofeatures in paleosols buried under kurgans in the North Caucasus region

Carbonate concentrations in a chronosequence of paleosols buried under kurgans in the North Caucasus region at the end of the 4th century and the first half of the 5th century AD have been studied with the use of a set of morphological and isotopic methods. It is demonstrated that morphologically different phases of calcite—the collomorphic phase and the crystalline phase—in carbonate pedofeatures (calcareous pseudomycelium) and in the calcareous horizon have different elemental compositions and different isotopic compositions of carbon. Hence, these forms of calcite should have different origins. An addition of colloidal carbonates migrating in colloidal solutions from the lower soil horizons to the surface horizons during the periods of climatic aridization to the acicular calcite may be responsible for a sharp and irregular increase in the radiocarbon age of the newly formed carbonate pseudomycelium.     

Temporal evolution of salts in Mediterranean soils transect under different climatic conditions

The research was conducted in Israel at three sites along a south–north axis, characterized by increasing annual rainfall, from 310 mm at site LAV in the south through 600 mm at site MAT (600), to 800 mm at site EIN in the north. At each site soil samples were taken during several seasons (September 2001 through April 2003), in three dominant microenvironments at 0–2 cm and 5–10 cm. The following microenvironments were selected at LAV and MAT: “Under Shrub” (US), “Between Shrubs” (BS), and “Under Rock fragments” (UR). At EIN the selected microenvironments were US, BS, and “Under Tree” (UT). In each soil sample electrical conductivity (EC), pH, and concentrations of several ions were determined. The objective was to analyze the effects of soil microenvironments and climatic conditions on the temporal dynamics of salt concentrations. In all microenvironments at all sites the minimal values of EC were found in the rainy season (January or April), and the maximal values in the dry season (September). In the rainy season the temporal variability of EC in the topsoil was regulated by: (1) clay, which restricted the leaching of salts from the topsoil when EC was low; and (2) surface features (microenvironment), when EC was high. In the UT, US, and UR microenvironments the rainy season could be divided into two periods with respect to their effect on salt movement in the topsoil: at the beginning of the rainy season (September–January) the reduction in EC was relatively moderate, especially with regard to ions involved in biotic activity (Mg⁺⁺ and K⁺), whereas, late in the rainy season (January–April) there was enhanced reduction in EC. In contrast, in BS the regulation of salt movement was weak at all sites. Hence, in this microenvironment the salts concentration (mainly Na⁺ and Cl⁻) responded rapidly to changes in rain amount and soil moisture and temperature. In the dry season (April–September) the temporal variation in EC varied not only between microenvironments but also between sites. In US, where local surface features were similar at all sites (the same shrub), the rise in EC was maximal at LAV (mainly Ca⁺⁺ and Na⁺), and gradually diminished toward EIN. Thus, the contribution of regional sources to the salts added to the soil diminished toward the humid site, EIN, where the EC hardly changed in any microenvironment. In BS and UR microenvironments the rise in EC (mainly in Ca⁺⁺, Na⁺, and K⁺) was greatest at site MAT, and decreased toward LAV and EIN. It seems that this pattern was affected also by changes in local biotic activity.     

Reconstruction of climate,soil, and vegetation conditions of the Srubnaya cultural epoch on the basis of kurgan studies in the Cis-Ural forest-steppe of the Republic of Bashkortostan

The reconstruction of soil, vegetation, and climatic conditions for the Srubnaya cultural epoch (3660 ± 40 (date wood), 3860 ± 120 (bones date) was performed on the basis of palynological and paleosol studies with radiocarbon dating of bones and wood fragments from two kurgans in the Cis-Ural forest-steppe of the Republic of Bashkortostan. Morphological features and chemical properties of the modern background soils, the soils formed on the surface of burial mounds (kurgans), and the soils buried under them were characterized. According to palynological data, the climate of this territory in the period of construction of these kurgans was more humid than the modern climate. The paleovegetation of the Srubnaya epoch was represented by mesophilic herbaceous steppes with a lower participation of xerophytic species as compared to the modern steppe and by small forest groves composed of birch and pine trees with some admixture of lime trees. The temperature conditions were close to those at present, or somewhat cooler, which is evidenced by the lower content of pollen of the broadleaved trees. The modern background soils and the soils buried under the kurgans are classified as thin light loamy typical calcareous chernozems; they have similar morphologies and physicochemical properties. However, the reconstructed organic matter content in the upper 50 cm of the buried paleosols is higher than that in the modern soils. This attests to more favorable climatic conditions during the Srubnaya epoch and is in agreement with palynological data.     

The morphology of cells and the biomass of microorganisms in the buried paleosols and modern steppe soils of the Lower Volga region

The morphology of microbial cells was studied, and the biomass of microorganisms was estimated in the modern steppe soils and paleosols buried under kurgans in the Lower Volga region with the methods of electron microscopy. The shape and ultrastructure of the cells in the modern soils and paleosols were similar, though their average volumes differed (0.37 and 0.28 μm³, respectively). The portion of cells with a volume above 1 μm³ in the surface soils and paleosols reached 10.9 and 9.2%, respectively, and the portion of cells with a volume less than 0.01 μm³ in the surface soils was 10% lower than that in the buried paleosols. It was found that the cells of the microorganisms have an external organomineral layer, which increases the cell volume by 4.9 times, and this fact was taken into account in the calculation of the microbial biomass. In the chestnut and light chestnut paleosols, the latter comprised 1500 and 230 μg of C/g soil, respectively.     

Microbiological investigations of paleosols of archeological monuments in the steppe zone

Microbiological studies of the paleosols of archeological monuments (burial mounds) of the Neolithic, Bronze, Early Iron, and Middle Ages (the fourth millennium BC to the fourteenth century AD) located in the dry and desert steppe of the Lower Volga River basin were conducted. The microbial communities that existed at the time of creating the burial mounds were shown to be preserved up to the present time. This fact was confirmed by the regularities of the distribution of the microorganisms in the “mound-buried soil” system and by the data on the determination of the age for the microbial fraction of the paleosols using the method of ¹⁴C atomic mass spectrometry. The total biomass of the microbial communities in the paleosols amounted to 20–40% of the microbial biomass in their background analogues. In all the paleosols, a special pool of viable microorganisms was present. In the microbial community of the paleosols, the biomass of the active microorganisms corresponded to 0.30–41.0% of the biomass in the present-day soil; the content of mycelium of microscopic fungi composed 43–50% of that in the recent soil. In the mycelium structure in the paleosols, the share of the dark-colored mycelium increased to 98–100%. The microbiological parameters that give a contrasting characterization of the state of the microbial communities in the soils during the arid and humid climatic periods were revealed. The changes of the arid and humid climatic epochs were reflected in the structure of the microbial communities in the paleosols at the ecological-trophic, metabolic, and genetic levels.     

Physical properties of tsunami-affected soils in Aceh, Indonesia: 2½ years after the tsunami

On 26 December 2004, a tsunami caused extensive loss of life, damaged property and degraded agricultural land in the province of Aceh, Indonesia. While some of the associated soil chemical changes have been documented, information on soil physical properties is sparse. The objective of this study was to quantify physical properties of some tsunami-affected upland agricultural soils in Aceh, Indonesia. Soil was sampled approximately 21/2 years after the tsunami, from the 0–0.1 m, 0.1–0.3 m and 0.3–0.5 m depths in four sites in the villages of Kling Cot Aroun in Aceh Besar sub-district, Kuta Kruen in Aceh Utara sub-district, Udjong Blang Mesjid in Bireuen sub-district and Meue in Pidie Jaya sub-district on the east coast of Aceh. These sites were located within 1 km from the sea at elevations ranging from 0 to 5 m ASL. The soils were Ultisols except for Meue, which was an Entisol. Soil properties measured were bulk density, structural stability and particle size distribution. Soil water retention, pore-size distribution and saturated hydraulic conductivity were estimated by inserting the values of bulk density, clay, sand and silt contents into pedotransfer functions from the literature. The analyses conducted during this study did not permit us to ascertain what proportion of the soil particles were of tsunami-origin. Nonetheless, deposition of finer-textured material may have occurred in two of the sites. In comparison with the greyish-white, coarse textured soil in the rest of the profile, a finer-textured yellow horizon was present in the lower slopes of the Udjong Blang Mesjid site. At Meue, clay and silt contents were higher in the surface 0.3 m than in the 0.3–0.5 m depth, although a distinct horizon was absent. Particle size distribution in all sites was dominated by the sand fraction, although clay and silt contents were relatively high (20–30 g 100 g^− 1) at Kuta Kruen. Among the sand fractions, fine sand (0.02–0.25 mm) was highest at Kling Cot Aroun, Kuta Kruen and in the “yellow horizon” at Udjong Blang Mesjid, making them more prone to hardsetting and compaction after intensive tillage. Soil compaction was present in all sites with that in the “yellow horizon” at Udjong Blang Mesjid being highest. The relatively low porosity in this layer may be beneficial, as it is likely to reduce the high rates of water drainage and nutrient leaching in this sandy soil. The more compacted soils were characterised by higher numbers of micropores (r, pore radius < 4.3 μm), lower water retention at saturation, smaller numbers of macropores (r > 14.3 μm), lower hydraulic conductivity and intensive gleying, indicating frequent waterlogging. The soils in all depths from Kling Cot Aroun and the “yellow horizon” at Udjong Blang Mesjid were very dispersive, that at Meue moderately dispersive in the 0.3–0.5 m depth but stable in the 0–0.1 m depth, and at Kuta Kruen very stable in all depths. Soil physical degradation was a feature of the soils examined, and its amelioration will be the key to improving and sustaining crop yields in these soils. Possible management interventions include organic amendments such as compost or manure, and minimum tillage options such permanent beds or zero tillage with retention of crop residues as in situ mulch together with suitable cover crops.     

The humus status of modern and buried volcanic soils in Mexico and its role in the paleogeographic interpretation of tephra-paleosol sequences

Chemical and optical characteristics of soil humus have been analyzed as “memory” components of the Pleistocene volcanic paleosols in Mexico. We have studied the A1 horizons of buried Andosols of the Nevado de Toluca series and of the modern Andosols formed under different bioclimatic conditions. Data on the organic matter of buried paleosols suggest that Andosols of the Nevado de Toluca series were formed in humid forest ecosystems. Optical characteristics of the humic acids and data on the molecular-mass distribution of the humus make it possible to assume that these soils were formed under pine forests rather than under fir forests.