A dataset of soil microstructure features and physicochemical properties for 1968 and climate sequence for 1951-1992 in the Caspian lowland

Abstract

The soils of arid regions are sensitive to short-term climate changes, which are most quickly manifested in the saline state of alkaline and saline soils. Long-term climate changes are reflected in more stable soil characteristics, such as grain size distribution and microstructure. These properties can be used as indicators to assess the direction and degree of soil transformation under the influence of climate change in the longer term. This article presents data collected on the territory of the Caspian Depression near the Dzhanybek Research Station of the Institute of Forest Science RAS. The studied object is represented by microcatena of light chestnut soils with varying degrees of severity of the saline process which is located in the saline complex between the I and II belts of the Chapaevsk-Vladimirovka State Forest Wind Belt. The height range between the studied pits is 3.6 cm. The dataset includes data on soil grain size distribution, organic carbon content, the composition of exchangeable cations, the salt composition of soil-water extract and microphotographs of the state of the light chestnut soils in 1968. This year is the starting point for modelling soil properties and assessing soil changes in this area due to climatic changes. The weather data are collected at the Janybek weather station between May 1951 and December 1992. It includes daily, monthly and annual data on air and soil temperature, wind speed and direction, air moisture, precipitation, depth of soil freezing, snow density and thickness. Using the data presented in the article, it is possible to assess the nuances of global warming in the Caspian lowland and reconstruct changes in soil properties associated with it. In the future, such reconstructions will become a tool for making forecasts of both climatic and soil changes in this territory.

Specifications Table

Subject	Environmental Science
Specific subject area	Soil Science, Soil Evolution, Climate change
Type of data	Table Image
How the data were acquired	The weather parameters were measured at the Dzhanybek meteorological station (West Kazakhstan region, Kazakhstan; geographic coordinates are 49°25′26′' N, 46°50′21′' E). The analysis of the granulometric composition was carried out using a pipette method. The organic carbon content was determined by the method of I.V. Tyurin using phenylanthranilic acid. The composition of exchangeable cations was determined by the Pfeffer method. Soil-water extract of soil was analyzed according to the method described by E.V. Arinushkina. Soil thin sections were prepared with pine rosin as an impregnating compound and canadian balsam for gluing. Microphotographs of soil thin sections were obtained using an Olympus BX51 polarizing microscope with an Olympus DP26 digital camera and Stream basic software in plane-polarized and cross-polarized light (PPL and XPL).
Data format	Raw
Description of data collection	The soil cover of the study area located near the Dzhanybek Research Station of the Institute of Forest Science RAS is represented by a three-component complex (solonetz, light chestnut alkaline soil, meadow-chestnut soil). The location of soils in the complex is closely related to both the microrelief of the territory and plant cover. The studied soils are located on a microslope. Bulk soil samples were taken in layers from a depth of 0–5, 5–10 cm and then after 10 cm to a depth of 200 cm. Then the samples were dried and ground according to the methods of sample preparation for physico-chemical analyses. The undisturbed soil samples were collected from the horizons, dried and used for the preparing of soil thin sections.
Data source location	The soil sample site is located in Russian Federation (Volgograd region) near the Dzhanybek Research Station of the Institute of Forest Science RAS at a distance of 30 km north of Lake Elton between the I and II belts of the Chapaevsk-Vladimirovka State Forest Belt. The absolute height of the soil sample site is 23 m above sea level. Catena GPS coordinates: 49°23′12″ N 46°46′54″ E
Data accessibility	Repository name: Mendeley Data Data identification number: 10.17632/nht78v4mnk.1 Direct URL to data: https://data.mendeley.com/datasets/nht78v4mnk

Value of the Data

• •These data can be useful for climatic modelling and for reconstruction and prediction of micromorphological and physicochemical changes of arid soils due to the climate change.
• •This dataset is of interest to climatologists because it contains unique data on the climate sequence of the Janybek plain (Caspian lowland) in the period 1951–1992. In addition, these data will be useful to scientists studying the microstructure of soils of solonetz complexes.
• •These data contribute to the understanding of the state of the soils of the arid territory (Caspian Lowland) in the past and can be compared with modern data on the soils of this territory.

1. Objective

The dataset was created as part of a project aimed at creating a base for modeling the evolution of Russian soils under climate change and anthropogenic impact in the past and future based on processing large amounts of digital data when analyzing the main elements of micro and nanostructure and deep physical and mathematical analysis for the same soil thin sections. Data on the physico-chemical properties of soils will allow interpreting the results of mathematical analysis of digital photographs of thin sections from the point of view of the genesis and evolution of soils.

2. Data Description

Fig. 1 shows a 2.29 m long trench dug on a microslope. The figure shows the boundaries of the horizons assigned after generalization of field descriptions [4]. Horizon indexes are selected according to the Classification and diagnostics of soils of the USSR [3]. The trench demonstrates the microcatene of soils transitional between saline solonetz in microhill to meadow-chestnut in microdepression. The soils of the trench are solonetzic chestnut according to the Classification and diagnostics of soils of the USSR [3].

Fig. 1.

Distribution of soil horizons in the trench: A – humus horizon, B1 – solonetzic horizon, Bk1 – illuvial-carbonate horizon, Bk2 – accumulative-carbonate horizon, C – parent rock material. Black numbers mean numbers of soil pits. Transparent red numbers indicate the depths of horizons. Each block of the black-and-white ruler shows the size of 1 cm in the schematic layout.

The dataset consists of 41 soil microstructure images in plane-polarized light (PPL) and 43 soil microstructure images in cross-polarized light (XPL). All images are sorted into 3 folders named after number of soil pit (pit 3, pit 4, pit 5). Pit 3 is located in the lower part of microslope, pit 5 is located in the higher part of microslope, pit 4 occupies an intermediate position between pits 3 and 5. The images are marked according to the following general principle: the pit number comes first, – then the sampling depth, – then the number of the field of vision, - then the type of light (plane-polarized light (PPL), cross-polarized light (XPL). Usually for describe the horizon more than one pair of microphotos are required so the photo marking contains numbers of the field of vision. Fig. 2 represents small part of microphotos from the dataset. This image dataset reflect variability of micropedofeatures in the trench at Dzhanybek Research Station in 1968, which is initial moment for investigation of soil evolution in last 55 years under changing climate conditions. The literature claims that climate change accelerated in the XX century [5], and the territories of southern and arid regions are very sensitive to climate change [6].

Fig. 2.

Microstructure of soil horizon of the trench: a – pit3_2–15cm_3_XPL; b – pit4_14–22cm_3_XPL; c – pit5_2–15cm_1_PPL; d – pit3_100–120cm_2_PPL; e – pit4_110–120cm_3_XPL; f – pit5_12–19cm_3_XPL.

The dataset contains data on weather conditions that affected soils of microcathena for 17 years predated to soil sampling in 1968 (1951–1992). Here is the list of weather conditions in the dataset: relative daily mean air temperature; relative daily mean air humidity; soil surface temperature; daily mean soil temperature at a depth of 5 cm; daily mean soil temperature at a depth of 10 cm; daily mean soil temperature at a depth of 15 cm; daily mean soil temperature at a depth of 20 cm; daily mean soil temperature at a depth of 40 cm; max. (maximum) wind speed; wind direction; precipitation; snow cover thickness on a fixed stake; mean snow cover density; soil freezing depth. Data is placed in an Excel file named «Zhanybek-day-month-year-1951–1992». Fig. 3 shows an example of data arrangement in the dataset. The dataset uses standard designations of wind directions, comma means that there were two main wind directions on that day, «VARIABLE» means that there were more than two wind directions on that day. Some parts of these data were published in the papers of G.S. Bazykina (for example, data on precipitation, air temperature and humidity in April, May, June 1954–1980) [2].

Fig. 3.

Distribution of the weather parameters in the Excel file across three Excel sheets: 1 – daily data; 2 – average monthly data; 3 – average annual data. «NA» (not available) means «the researchers did not take measurements during this period». «NONE» means that there was no wind on that day.

The dataset also includes data of chemical and physical properties of studied soils: grain size distribution and organic carbon content of soil pit 4, content of exchangeable cations and soluble salts of soil pits 3, 4, 5. Data is placed in an Excel file named «Physicochemical data pits 3,4,5». The data are presented in layers, not according to the horizons marked in the field description. These data can be used to verify models of changes in soil properties associated with climate change.

3. Experimental Design, Materials and Methods

Soil thin sections were prepared at the V.V. Dokuchaev Soil Science Institute by E.F. Mochalova [9] with pine rosin as an impregnating compound and canadian balsam for gluing. Microphotographs of soil thin sections were obtained using an Olympus BX51 polarizing microscope with an Olympus DP26 digital camera and Stream basic software (equipment of the FRC V.V. Dokuchaev Soil Science Institute Collective Center «Functions and properties of soils and soil cover») in plane-polarized and cross-polarized light.

The analysis of the granulometric composition was carried out using a pipette method [7], the preparation of the soil for analysis was carried out according to the method of N.A. Kachinsky. The soil is washed on a filter sequentially 0.05 n. HCl until the displacement of the Ca ion and water — until there is no reaction to Cl. The carbonate soil is pretreated with a solution of 0.2 n. HCl until the release of CO₂ bubbles ceases. The treated suspension is boiled for 1 hour with the addition of 1 n. NaOH [7]. The organic carbon content was determined by the method of I.V. Tyurin modified by V.N. Simakov [10]. The modification consists in the use of phenylanthranilic acid as an indicator during the titration of potassium bichromate with a solution of More salt. The composition of exchangeable cations (old term used in the dataset – absorbed bases) was determined by the Pfeffer method [8]. Soil-water extract of soil was analyzed according to the method described by E.V. Arinushkina [1].

Air temperature was measured using mercury thermometer TM (measuring range from -35°C to +50 °С with an accuracy of 0.1 °С). The relative air humidity was determined using an M-19 hygrometer with an accuracy of 1%. Soil surface temperature was measured using a surface mercury thermometer TM whose reservoirs and covers were half submerged into the soil (measuring range from -35°C to +50 °С with an accuracy of 0.1 °С). The temperature of the deep layers of the soil was measured using a Savinov thermometer with an accuracy of 0.1° С. The wind speed was measured using an anemometer with accuracy of 1 m/s. The wind direction was measured using a compass. The amount of precipitation was determined using the O-1 rain gauge with an accuracy of 0.1 mm. The snow cover thickness was measured on a fixed stake with accuracy of 1 cm. The snow cover density was measured by volume-weight method with accuracy of 0.01 g/cm3. The depth of soil freezing was measured using a Ratomsky permafrost meter with accuracy of 1 cm.

Ethics Statements

The work did not involve the use of human subjects, animal experiments and data collected from social media platforms.

CRediT authorship contribution statement

O.O. Plotnikova: Writing – original draft, Visualization, Investigation. M.P. Lebedeva: Investigation, Writing – original draft. P.R. Tsymbarovich: Validation, Resources. V.A. Devyatykh: Data curation.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data Availability

• A dataset of soil microstructure features and physicochemical properties for 1968 and climate sequence for 1951-1992 in the Caspian lowland (Original data) (Mendeley Data).