Arid Ecosystems最新文献

The problem of desertification is one of the most pressing modern environmental problems in the world. In the context of increasing changes in climatic conditions and the progressive expansion of the desert areas of the arid zone, the depletion of fresh artesian water reserves, the deterioration of their quality, the drop in pressure in aquifers, flooding, salinization, and pollution of artesian lands cause significant damage to the geoecology of the Caspian basin. There is no alternative to the use of fresh groundwater in arid deserts and semi-deserts where there are no reserves of surface water. The relevance of the research conducted in the conditions of the arid ecosystems of the region is beyond doubt. The long-term intensive exploitation of the North Dagestan artesian basin in the last century and the increase in uncontrolled extraction of groundwater from wells abandoned in the post-Soviet period and newly drilled in an “ownerless” manner worsens the environmental situation in the region. Under these conditions, the study of the groundwater regime and its potential for the purposes of irrigation of soils of arid ecosystems of the region acquires particular importance. This paper provides an overview of the results of previous studies, an analysis of newly obtained results, and recommendations for the implementation of further research on the stated topic. The analysis of the conducted studies of hydrogeological conditions and the assessment of the potential of groundwater in the region can become the basis for conducting an inventory of groundwater resources, extracting artesian water and establishing water consumption standards for populated areas of the region and for the purposes of irrigating the soils of arid ecosystems, as well as the creation and rational placement of a network of stationary reference observation points in the study area and the organization of regional monitoring of the groundwater regime.

A brief review of the current status and prospects of aquatic research using various DNA analysis techniques (aDNA—ancient DNA, eDNA—environmental DNA, hDNA—historical DNA) in the post-Soviet space, with the emphasis on modern Russia, is presented. It is shown that, despite the rapid development of the use of DNA analysis to investigate fundamental and applied problems in various aquatic studies worldwide, research in this area in Russia is at an initial stage. Similar situations exist in countries that were part of the former USSR, as well as in other developing countries. The information presented on the Russian Federation may be relevant to other countries where aquatic research using DNA analysis is at an early stage.

The Volga River Delta, as one of the largest deltas in the world, has a wide variety of hydrological features, which creates a wide range of conditions for the development of diatoms. The aim of this work is to study the species composition of diatom assemblages of the surface layer of bottom sediments in modern watercourses of the delta of the Volga River and to identify the characteristics of the distribution of species depending on the habitat and the main indicator species of these habitats. This work will serve as a basis for the creation of a diatom database and its further application in paleoecological reconstructions. The diatom analysis method was used to study 24 samples of the surface layer of bottom sediments collected using a bottom grab from water bodies of various hydrological characteristics on the territory of the Damchik section of the Astrakhan Biosphere Reserve. The most common species in the studied objects are: Aulacoseira granulata, Aulacoseira ambigua, Stephanodiscus minutulus, typical for the phytoplankton of the Volga River. One object, the Gryaznukha channel, is distinguished by the composition of dominant species—Cocconeis placentula, Cocconeis pediculus—and a high proportion of the benthos (77–99%). Analysis of samples collected in watercourses along the profiles showed a difference in the ratio of plankton and the benthos depending on the depth: in deeper areas, an increase in the proportion of planktonic species was found. The results of diatom analysis were also studied using the principal component method. The most significant factor in the formation of diatom complexes in the studied samples is the depth of the watercourses. The principal component method reliably identifies a cluster of samples from the deepest sections of the Bystraya River and one sample from Sazanii Bay, collected near the Bystraya River, as the characteristic species Aulacoseira ambigua and Stephanodiscus minutulus.

A number of physically justified and complementary characteristics of agrocenoses are proposed, allowing for a quantitative assessment of their condition from the point of view of water resource availability and including the indicator of security of the agroecosystem, the risk of a deficit in its moisture supply, and the risk of crop failure caused by deviation of the dynamics of the water regime from the optimal, as well as the efficiency of the consumption of natural water resources by the ecosystem. A methodology for assessing the specified characteristics has been developed based on the use of the land surface model SWAP, standard meteorological information, and data on the hydrophysical parameters of the soil. This method was tested using the example of winter wheat crops under rainfed conditions at nine agrometeorological stations located in the steppe and forest–steppe regions within the grain belt of the European territory of Russia, Western and Eastern Siberia. The results of the assessment of the above characteristics for the historical period are presented, demonstrating the varying degrees of tension in the situation with water security of crops in the specified regions and the existing potential for increasing their water supply.

Thanks to theoretical works on the use of low-pressure underground fresh water, it has become advisable to build artificial storage reservoirs for efficient use of water resources in the irrigation of arid lands. Problems arise in the construction of reservoirs with regard to the external and internal waterproofing of the structures. The most widely recognized materials for this purpose are the waterproofing materials based on bitumen, synthetic resin polymers, and mineral binders. They are distinguished by their water impermeability, water resistance, durability, and mechanical strength due to their chemical composition. Today, there is a particular need for new, more durable materials that meet these requirements and are affordable. With these features in mind, we conducted studies on a highly effective composite waterproofing material made from bentonite clays. We present the results of laboratory tests on the chemical and mineralogical composition and thermal analysis of bentonite clay from the Levashi deposit in the mountains of Dagestan. Experimental studies have established the optimal compositions based on bentonite clay and Portland cement clinker with the addition of a modifier, nanodispersed sodium polysilicate, ground together in a ball mill to a specific surface area of 2500–3000 g/cm². The technological and physicomechanical properties of the composite paste and the composition as a whole after hardening have been determined both under natural conditions and under optimal heat and moisture conditions of the arid regions in southern Russia.

The size diversity of algal communities in the plankton of saline tributaries of the hyperhaline Elton Lake was studied based on the volume and linear parameters of alga cells. The size structure of these communities includes nanoplankton (51–68%), microplankton (16–41%), and picoplankton (7–16%). The ratio of size groups in the phytoplankton was characterized by temporal and spatial heterogeneity. Long-term observations revealed an increase in the picoplankton fraction in polyhaline rivers compared to mesohaline ones, as well as the same increase along the longitudinal river profile: from the upstream water to the mouth reach (“river–lake” contact). In spite of differences in the species composition of algal communities in different rivers, the average coenotic cell volume represents a stable and sensitive morphological parameter of these communities. A significant reduction in the coenotic volume was observed in the lower reaches and mouths of the studied rivers during periods of extreme salinity caused by the inflow of saline water from the lake. An association between the size characteristics and the content of biogenic nutrients was observed for certain species. Correlation coefficients between the size diversity indices and mineralization were higher for polyhaline rivers (0.59–0.78, p ≤ 0.05) compared to mesohaline ones (0.50–0.58, p ≤ 0.05). Thus, in the saline rivers of the basin of Elton Lake, the average coenotic volume and the ratio of size fractions can serve as informative morphological indicators of how phytoplankton communities respond to changes in mineralization.

The paper presents the results of a comparative geographical and hydrological analysis of long-term fluctuations in air temperature, atmospheric precipitation, annual river runoff, and maximum and minimum monthly runoff in the Don and Ural river basins. It has been shown that, with relatively little change in precipitation, the main factor in hydrological variations over the last few decades (since the 1990s) has been the rise in air temperature during the cold season leading to reduced surface runoff and flood flow. As a result, despite increased runoff during the winter and summer-autumn low water periods, annual river flow in the basins of these rivers decreased significantly between 1992 and 2021, by 31 and 27% relative to the norm at the beginning of the 1960s and by 30 and 15% relative to the 1980 norm, respectively.

The paper examines the influence of the Indo-Asian collision on the formation of arid ecosystems covering a vast territory in the subtropics. It has been shown that the rise of the Tibetan Plateau to more than 4000 m above sea level and the rain shadow produced by the Himalayas, Karakoram, and Hindu Kush are the main reason for the lack of moisture over most of Tibet. To characterize the natural zonation of the Qinghai-Tibet Plateau, we used the classification of vegetation zones proposed by D.H.S. Chang (1981). The Indo-Asian collision is seen as an ecological factor (megafactor) primary to the factors generated by collision processes.

Rice and wheat straw are among the most common types of field residues. Earlier studies have shown that some soil detritophages, such as enchytraeids and woodlice, are able to utilize these residues at varying efficiency rates even under arid conditions, in which organic matter degradation is very slow. We have evaluated the decomposition of oak, birch, raspberry, linden, willow, wheat, rice, and corn residues by the Porcellio scaber, Porcellionides pruinosus, and Porcellio laevis woodlice. Ten woodlice belonging to each of the studied species were placed in containers, where they could choose from 1 g of each type of plant feed, for 21 days. The woodlice preferred linden, willow, birch, and corn residues, these being mostly feeds with a low silicon concentration. Porcellio laevis showed a wide range of food preferences and high survival rates on different feeds. Thus, when the structure of plant food resources in southern Russia changes, the studied species of woodlice are able to change their diet and switch to more accessible food sources. From the industrial point of view, P. laevis may be efficiently used for processing corn stover, including because of the low silicon content in its leaves.