Arid Ecosystems最新文献

The results of studies on the species diversity and ecology of oribatid mites (Acari, Oribatida) living in the Repetek Biosphere Reserve located in the Eastern part of the Karakum Desert are presented. The species composition and abundance of oribatid mites in the main phytocenoses of the Karakum deserts were revealed. In particular, 36 species of oribatid mites were found on the litter and in the soil under trees and shrubs, including ten new ones for the fauna of Turkmenistan. This study established the formation of mass accumulations of the dominant species Epilohmannia cylindrica and subdominants Oribatula skrjabini, Psammogalumna thysanura, Scheloribates turkmenistaniensis, and Hemileius turanica penetrating into the inner layers of plant residues. Their numbers reach 50–400 specimens in each 1 m². This paper provides a comparative analysis of the seasonal dynamics of the number of the dominant species Epilohmannia cylindrica in the upper layer (1–10 cm) of sandy soils. Observations have established the prevalence of species diversity and abundance of oribatids in the Karakum Desert, compared to other groups of soil mites. Data on the importance of oribatid mites in the destruction of litter as well as plant waste formed as a result of covering plant residues with sand are presented.

Changes in the frequency, intensity, and duration of severe soil droughts in the upper soil layers in May and June in the European part of Russia (EPR) south of 55° N in the period 1981–2020 were studied based on soil moisture observations in the arable layer at 19 hydrometeorological stations, as well as in a 10-cm-deep layer according to the GLEAM model using satellite measurements. A close relationship was revealed between soil moisture in May–June according to satellite data and atmospheric moistening in April–June. The analysis of the results obtained indicates an increase in the frequency of droughts in the surface soil layer, caused by extremely low moisture, at the beginning of the growing season in most of the area studied in the first twenty years of the 21st century compared to the previous twenty years. Moreover, the largest statistically significant increase in the frequency of droughts by four events in May–June was observed in the Central Black Earth Region, the Volga Region, the Trans-Volga Region, the Azov Region, and the Black Sea coast. The increase in the frequency of droughts occurred against the background of the most noticeable decrease in moisture in the surface soil layer in the period 2001–2010. At the same time, the increase in the duration of such droughts in the same regions was the greatest and ranged from 15 to 30 days. The increase in the frequency of droughts in the Volga and Trans-Volga regions was accompanied by a significant decrease in soil moisture, the greatest in the study area. It was found that the majority of the most severe extensive droughts in the surface soil layer in May and June have been observed since the beginning of the current century. Differences in the frequency of soil droughts in the arable layer based on in-situ data were shown depending on the chosen definition.

Surface carbonate soils were identified and mapped in the dry steppe zone of Volgograd oblast on the territory of the Volga–Don irrigation system, stretching along the Volga–Don Canal. The study site is the Oroshaemaya experimental station in the center of the irrigation system. Field no. 28 of the station is used as an example to show all the stages of creating a digital vector map based on high-resolution space images (0.5–0.7 m) from the Pleiades satellite (April 25, 2020) and field studies in 2022–2023. Field studies included route work to determine the presence of carbonates in the surface horizon of soils (by effervescence from the interaction of soil with a 10% HCl solution). The degree (class) of soil effervescence was also assessed visually. The first stage of mapping included the classification of the space image of this field and the construction of a vector layer of the field boundary. The second stage included the creation of a vector file of the map consisting of polygons of different classes in the field (according to the prevailing degree of soil effervescence) and the calculation of the share of different classes within the vectorized polygons. Modern programs (Random Forest, QGIS) were used to classify and vectorize polygons of surface carbonate soils. The sequence of technological stages of map creation, the algorithms, and the functions used are shown. In the future, it is expected to find a relationship between the degree of soil effervescence and the amount of carbonates in the surface horizon of soils. As a result of solving this problem, space materials and a simple, fairly prompt method for field identification of surface carbonate soils will make it possible to obtain quantitative indicators of the content of carbonates in the arable horizon. The map created reflects the scale of anthropogenic impact on soils and helps to determine the necessary reclamation measures to improve their condition.

The influence of the Chirkei Reservoir and of its hydrodynamic regime that causes negative exogenous processes associated with the activation of landslides and water spills is considered. For example, one of the landslide massifs located 1 km from the high dam of the hydroelectric power station is capable of causing a wave ten meters or more high, and a breakthrough of the Tishiklinskaya earthen dam 1 km long, which is located in the eastern part of the reservoir, could lead to the flooding of a large area of agricultural lands and settlements. The Chirkei reservoir is geographically located in Dagestan, at the coordinates 42°58′00″ N, 46°53′00″ E. Considering the small percentage of land suitable for agricultural activity in the mountainous part of Dagestan, the preservation and prevention of flooding of fertile lands is an important national economic task. In the Republic of Dagestan, there are seven hydroelectric power stations with dams from 40 to 232 m high. Services on them are limited to monitoring the condition of the dams. However, monitoring of hazardous geological processes in reservoir areas has not been given due attention. The results of geophysical monitoring that allows detecting landslide body deformation under the influence of seasonal changes in the reservoir level are presented.

The ecological and phytocenotic characteristics of the Medicago sativa type of pastures, common in the Eastern Cliff of the Karakalpak Ustyurt (Uzbekistan) are presented. The species composition, productivity of pasture varieties, soil type, vegetation cover, and landscape types are characterized; the recommended seasonality of use is determined. According to geobotanical zoning, the Medicago sativa type of pastures covers small areas concentrated in inter-hump depressions with close standing of groundwater, noted in the Kabanbai, Aktumsuk, Kassarma, Karakuduk, and Akbulak massifs. It is distributed from the first to the second terraces of the Cliff and occupies a territory of about 202 ha between the Urga and Baygubekmurun capes. This type consists of three pasture varieties: Medicago sativa + Agropyron fragile – Artemisia diffusa, Medicago sativa + Agropyron fragile and Medicago sativa + Cynoglossum viridiflorum, common on loamy and gray–brown soils. The seasonal yield of the forage mass fluctuates from 0.4 to 1.3 c/ha. According to the results of this study, the studied pasture varieties are recommended for use as year-round pastures.

The current state of a rare medicinal species, the “green-flowered” hound’s tongue (Cynoglossum viridiflorum Pall. ex Lehm.), of Uzbekistan growing in the Karakalpak part of the Ustyurt Plateau, based on the structure of its cenopopulations is examined. New data is reported with respect to the ontogeny and ontogenetic structure of cenotic populations of this rare endemic, and plant communities with its participation are characterized. In the Ustyurt conditions, the vegetation cycle of C. viridiflorum spans approximately eight months from March to October. The studied populations were shown to be normal and full-membered. The left-sided ontogenetic spectrum is characteristic of C. viridiflorum due to the high seed productivity and germination capacity. Altogether, this reflects the biological characteristics of C. viridiflorum and points to a stable state of the species population in the Ustyurt conditions.

The plant communities of the sandy massifs of the Northern Gobi Desert on the territory of the Bulgan Omnogovi aimag are considered. The classification of vegetation by the Braun–Blanquet method, first carried out for vegetation of the flat part of the Bulgan soum, revealed six vegetation associations belonging to three unions of three orders of the class Stipetea glareosae-gobicae Hilbig 2000. The flora of sandy massifs includes 108 species from 73 genera and 28 families. The species structure of genera and families reflects the specifics of the flora of this desert–steppe region within the Bulgan soum. In the spectrum of life forms of plants in sandy communities, perennial and annual and biennial grasses predominate, although in terms of participation in the structure of plant communities, the dominant phytocenotic role belongs most of all to woody plants. Dominant types of vegetation of the sandy massifs (Krascheninnikovia ceratoides, Caragana korshinskii, Haloxylon ammodendron, Psammochloa villosa, Nitraria sibirica, Brachanthemum gobicum, etc.) are natural sand fixers. At the same time, these species are for the most part well-eaten food for livestock. Consequently, grazing in such habitats must be strictly regulated.

Soil cover as a systemic formation is characterized by the formation of properties of different taxonomic levels and signs of structural organization with hierarchical subordination. As an integral natural formation, soils have resource potential, subject to the active influence of factors of the physical and geographical environment. Individual soil properties and their overall functional purpose may differ in time and space. Such properties are formed in different regions, reflecting the influence of local conditions. Typical representatives of soils with signs of salinity, excluding the implementation of production processes, are formed in arid conditions (Caspian lowland, Volga delta). The difference in the target functioning of soils in the region is expressed in the presence of a special natural combination of properties that the components of a typical soil profile do not possess (Neustruev, 1915). This is due to the fact that, when determining the classification characteristics of saline soils, processes that occur between individual horizons and are reversible in nature remain unaccounted for to date. The possibility of reversibility and restoration of physicochemical properties to the level of indicators characteristic of the climatic regime with the duration of geological periods of time remains in the shadows for many types of soils to this day (the water-soluble part of carbonates, silicates, and organic matter). We consider it appropriate to use a systematic approach when analyzing the temporal and seasonal functions of various types of soils (especially saline ones) under conditions of desertification and arid degradation.

Violation of nomadic forms of pasture use leads to vegetation degradation, periodic large-scale outbreaks of deflation and desertification, and transformation of the physicochemical properties of sandy soils in the arid zone. Practice has shown that an effective means of restoring their production potential is the creation of multi-tiered vegetation cover—forest and pasture lands. The purpose of this study is to assess the current state, feed productivity, attractiveness, and sustainability of forest pastures and to develop proposals for their optimization. This research was carried out through a comprehensive study of natural objects on temporary trial plots using standard methods of agroforestry, geobotanical and soil research, and statistical data processing. It has been established that on the thick blown sands of the Nogai steppe in forest pastures with a tree layer of Robinia pseudoacacia and Ulmus pumila, the forage yield increases to 2–3 t/ha (in terms of hay) and, depending on the seasons of the year, is 1.5–3.5 times higher than that on natural pastures. On the fine sands of the Black Lands, there are forest pastures formed by plantings of Krascheninnikovia ceratoides and Calligonum aphyllum. At the age of 30–40 years, they produce 1.5–3 t/ha of dry food, which is 1.4–2 times higher than in the surrounding steppe. On weakly and unwinnowed sands of the Astrakhan Trans-Volga region, in 20- to 60-year-old forest–pastures with protective fodder plantings of Haloxylon aphyllum, C. aphyllum, and K. ceratoides, the consumed mass of shrubs is 0.1–4 t/ha, while the grass stand is 0.3–1 t/ha, which is 20% more than in the open steppe. Pastures with tree and shrub layers attract animals and are more resistant to deflation. The functional durability of silvopastures depends on the technology of their creation, maintenance, and operation regime. The most important measures are fire protection and rationing of the pasture load.

This work is devoted to assessing the features of the distribution of spatiotemporal changes in the characteristics of the minimum 30-day winter flow of rivers in the basin of Lake Sevan. The problem of spatiotemporal changes in the minimum river flow is especially relevant for regions with insufficient and unstable moisture, like the basin of Lake Sevan, most of which is located within the steppe zone. The purpose of this work is to summarize modern ideas about the impact of climate change on the characteristics of the minimum 30-day winter river flow based on the authors’ own research, to analyze and evaluate the spatiotemporal variability of long-term fluctuations, and to identify nonstationarity in the series of minimum winter flow. The characteristics of the minimum flow have been determined, their spatiotemporal changes have been studied, and the dates of violations of homogeneity in the series of long-term runoff observations have been discovered. Using statistical parameters and difference integral curves, we assessed the representativeness of time series of minimum 30-day winter water flows at 12 sites during the period of instrumental observations. Nonstationarity in the series of minimum winter runoff in the basin of Lake Sevan has been revealed, and the dates for changes in stationary regimes have been determined. For most of the watersheds analyzed, the changes are statistically significant. Maps of the date of violation of the stationarity of the series under consideration based on information up to 2021 are presented, including a map of the distribution of the module of the minimum 30-day runoff for the winter period and maps on the nature of changes in the minimum 30-day winter flow. It is shown that changes in the minimum 30-day winter flow have a multidirectional nature, but mainly for the minimum 30-day winter flow, on average, over the territory of the lake basin. In recent decades, Lake Sevan has shown an increasing trend associated with rising air and soil surface temperatures. For some of the watersheds analyzed, the changes are statistically insignificant. On the territory of the Vardenis, Lichk, and Bakhtak river basins, on average, the minimum 30-day winter flow decreases by 20–30%, which will lead to an increase in environmental risk, requiring the adoption of appropriate measures. The obtained statistical materials will serve as the basis for scientific generalizations of research on the territory under consideration and can also be used for practical purposes in hydraulic engineering design and assessment of natural hazards and in making appropriate preventive decisions.