Arid Ecosystems最新文献

This article presents data on the distribution of the steppe marmot Marmota bobak Müll, 1776 in the Burtinskaya Steppe Site of the Orenburg State Nature Reserve (Orenburg Region, Belyaevsky District), from its inception to the present. The research was carried out by the author in 1998–2001 and 2021–2022; information on the number of steppe marmots from the archive of the reserve was also used. Mapping of all residential colonies of the steppe marmot and families in them was carried out, and the area of family plots was calculated. Statistical processing of the results of observations was carried out using the STATISTICA 10.0.1011 computer program. The spatial structure of the population, which had developed even before the establishment of the reserve, has been preserved with minor changes for more than 30 years. In the first years (1989–1990), eight relatively small settlements were noted on the territory of the site. Since 1996, ten colonies have been identified, and in 1999, 75 residential family plots were noted on them. By 2003, the territories of the colonies were completely developed, the marmots occupied old abandoned burrows within the colonies, and the number of families on the site increased to 106. Over the next 9 years, the number of families remained stable, after which their number began to decline: by 2017, only 55 families remained. Currently, there is a gradual increase in the number of families in the Burtinskaya Steppe Site; according to the results of mapping in 2022, 74 families were noted.

An unfavorable hydrological regime has contributed in recent years to negative changes in the species and age structure of the ichthyofauna in the northern part of the Agrakhan Bay of the Caspian Sea. The article presents the data on the species composition, age categories and morphometric indicators of semi-anadromous and freshwater fish species in detail based on the results of studies in 2019–2021. A comparative analysis of the obtained results with the data of previous years was carried out; negative dynamics of changes in the studied indicators under modern conditions were established. There has been a reduction in the species composition of semi-anadromous fish from 14 to 9 species, the commercially valuable kutum Rutilus kutum (Kamensky, 1901), catfish Silurus glanis (Linnaeus, 1758), vimba Vimba vimba (Linnaeus, 1758), tench Tinca tinca (Linnaeus, 1758) and asp Aspius aspius (Linnaeus, 1758) have disappeared, the share of the remaining surviving species has significantly decreased. The average age has increased, the proportion of fish of older age categories has grown, and, accordingly, the number of younger groups of fish has decreased, which indicates a decrease in growth potential. At the same time, freshwater low-value fish species such as crucian carp Carassius gibelio (Bloch, 1782), rudd Scardinius erythrophthalmus (Linnaeus, 1758), white bream Blicca bjoerkna (Linnaeus, 1758), and others have growth trends in terms of age and morphometric parameters.

Bivalve mollusks are an important component of the ecosystems of many natural and artificial reservoirs. However, the ecological role of some of them is very ambiguous, especially if we talk about invasive species that have spread widely beyond their natural habitats over the past 100 years. The present study aims to obtain quantitative estimates of the distribution of a southern invasive species, the zebra mussel bivalve mollusk, over the water area of the Ivankovo reservoir and to assess the contribution of its filtration capacity to water self-purification.

The study of the state and economic value of pasture ecosystems in Mongolia in the context of their progressive degradation continues to be very relevant. The existing methods of forage assessment of pastures are either laborious (the zootechnical method) or do not reflect the real situation (assessment of overall productivity) in the formation of low-species or monodominant degraded communities. To determine the nutritional value and productivity of pasture ecosystems in Mongolia, the palatability coefficient (PC) is proposed, which is determined on the basis of data on the nutritional usefulness of plant species that make up the community, as well as the diversity of eaten species. The PC was calculated as the ratio of the phytomass eaten to the total aboveground phytomass, multiplied by the number of eaten species included in the composition of dominants and codominants. The PC was determined for 158 communities of meadow and steppe pasture ecosystems. These were ranked in four categories. It has been established that a significant part of the studied communities have a high PC. Although these communities are characterized by varying degrees of anthropogenic disturbance, including severe ones, the high PC is due to the fact that some of the digressively active species have satisfactory or good palatability. This fact probably supports the potential for an increase in the number of livestock in Mongolia, which have a wide range of food preferences. At the same time, there is a high proportion of pastures with low and very low PCs. To a greater extent, such pastures are formed by communities of real and dry steppes, which experience the greatest pasture load in Mongolia.

The unprecedented anomalies of the annual runoff of the Volga and the Northern Dvina rivers in 1920–1940s are considered in the context of global warming in the mid-twentieth century and climate extremes of recent decades. The analysis of climate characteristics demonstrates that the global temperature rise during a given period manifested itself in the long-term drought in 1934–1940s on the Eastern European Plain, which, according to Palmer’s classification, has no analogues in the region in terms of intensity and duration and caused extreme hydrological events. The results of the spectral analysis of the river runoff variability, as well as the analysis of empirical orthogonal functions of atmospheric pressure anomalies, suggest that the droughts of 1972 and 2010 can be considered as the closest similar phenomena, but significantly inferior in their impact on the natural environment.

Our knowledge about soil properties and soil organic carbon stock under arid ecosystems is crucial if we are to optimize soil organic carbon sequestration to mitigate climate changes. This study aims at investigating soil properties, soil organic carbon (SOC) pools, and stocks in soil under arid ecosystem oasis. Soil samples were randomly collected from 0–5 and 0–30 cm depths in 17 sites (34 samples). The bulk density, pH, electrical conductivity EC, calcium carbonate and gypsum were measured in soil samples. Total SOC, particulate organic carbon (POC), SOC associated with the fine mineral fraction concentrations and stocks were also determined. Results showed that soils under oasis are characterized by high pH and EC values. Similarly we recorded great amount of CaCO₃ and gypsum among sites and depths. However bulk density values ranged from 1.23 to 1.30 and 1.18 to 1.35 g cm^–3 respectively in 0–5 and 0–30 cm layer depths. The total SOC concentrations range on average between 8.47 to 13.25 g kg^–1 and between 9.27 to 11.06 g kg^–1 in 0–5 and in 0–30 cm layers respectively. In all samples the SOCff represents the major organic pools of SOC (>60%). Among sites the SOCs in 0–5 cm layer depth were between 0.4 and 0.8 kg C m^–2 and reach 4 kg C m^–2 (40 t ha^–1) in 0–30 cm. The POCs constitute only between 21 and 34%. The correlation matrix established between soil properties shows significant negative correlation (p = 0.05) between POC and EC. However, SOCs are largely positively correlated (p = 0.01) with different SOC pools. It can be said that soils under oasis store relatively high amount of organic carbon. Therefore, this study confirms that arid soils can be considered as a potential sink in North Africa to sequester SOC.

Mathematical methods for description of the processes of evaporation from the soil surface under conditions of the sub-arid zone of the south of Russia are discussed. Theoretical studies in this area and the results of their practical application have been analyzed. Natural observations are explained using mathematical modeling. Mathematical models of evaporation from the soil surface are divided into two types: physico-mathematical, which are based on the interaction between the water and the soil carcass, and phenomenological, which are based on balance ratios. The data on the evaporation from the surfaces of light soils have been analyzed with allowance for the diffusive and film transfer of moisture within the pore space. The cumulative evaporation from extended areas has been analyzed using a semi-empirical model, which connected evaporation intensity with the precipitation and the hydrophysical state of the soil moisture in the aeration zone. Good agreement between the theory of the capillary transfer of moisture and the data on the evaporation from the surface of open sandy soils has been revealed. A nonlinear relationship between the evaporation rate and the depth of the underlying surface, as well as the capillary-sorption pressure, has been revealed. The amount of annual precipitation in the south of Russia and the cumulative evaporation are associated with each other via a power dependence indicating the capillary-sorption nature of the evaporation.

Animals have a significant impact on the territory where they live by the process of their lives. The studied objects are located in the zone of dry steppes, where climatic conditions limit the development of vegetation and contribute to changes in soil characteristics, which, in combination with the impact of animals, enhances the effect. The purpose of the work was to assess the impacts of animals on the ecological state of the soils of the enclosures of the Wildlife of the Steppe Association. In the course of the study, the main indicators of the ecological state of soils in enclosures with animals on the territory of the enclosures of the Wildlife of the Steppe Association in the arid regions of the Rostov region were determined. We explored enclosures of different sizes, with African ostriches (Struthio camelus), emu (Dromaius novaehollandiae), goats (Capra sp.), Przewalski’s horses (Equus ferus przevwalskii) and saigas (Saiga tatarica), and on the territory with semi-free grazing of ungulates, that is, horses (Equus caballus), camels (camelus bactrianus), buffaloes (Bubalus arnee), yaks (Bos mutus), and lamas (Lama ganicoe). The studied areas differed in the intensity of soil degradation. To assess the physical condition the moisture, temperature, density, and structure of the soil were determined; pH, the gross chemical composition of soils, humus content, and biological activity were also assessed, and plots were ranked according to the degree of pasture digression. In the course of the study, the enclosure with African ostriches had the maximum degree of degradation of ten, which is characterized by severe inhibition of vegetation and soil degradation. As well, the soil density in the enclosure with African ostriches was the highest, 1.49 g/cm³, and the percentage of structure was the smallest, 37%. These parameters had a close negative correlation with the pressure of the animals' hooves and paws on the ground (–0.9). The humidity level in the studied areas did not rise above 11%; despite this, the enzymatic activity of the soils no longer depended on hydrothermal conditions, but on the influence of excretions of animal waste products. In enclosures with ungulates, in particular in the enclosure with goats, the activities of catalase and urease were always higher than in other areas. A high content of humus, 10.3%, was also noted there, which is uncharacteristic for chestnut soils and confirms the influence of animal life on them. According to the research results, the lowest quality of the structure, humus, and biological activity, as well as increased soil density, occurred in the enclosure with the African ostrich. The data we obtained explain the decrease in the growth and development of vegetation in the area where animals kept in crowded conditions live.

The unreclaimed dumps of the Moscow coal basin are a long-term spontaneous experiment reflecting the transformation of soils and toxic technogenic material under the influence of acid mine drainage with compounds of heavy metals and metalloids. In the Tula region, the particle size distribution, pH value, the electrical conductivity of a water extract, the concentration of total organic carbon and three mobile fractions, as well as the total content of Al, Ca, Fe, Mn, and S were obtained to analyze the transformation of the fractional composition of compounds of six elements in the soils of sulfuric acid geocomplexes at 11 key sites (a total of 57 samples). Heavy loamy chernozems that were not exposed to the waste heap contain up to 9% total organic carbon, have a near-neutral environment, and low electrical conductivity. In these, the average mobility of elements (in %) decreases in the series: Ca (62) > Mn (35) > Al, Fe (14) > S (3). Among the mobile compounds of Ca, exchangeable ones predominate, while Al, Fe, and Mn are extractable in 1 N HNO₃ at close levels of the S concentration of the three studied mobile fractions. Medium-heavy loamy toxylithostrats of the bare surface of the waste heap with a predominantly very acidic environment often have sulfate salinity. In these, the average mobility of elements decreases in the series Ca (80) > Fe (36) > S (15) > Al, Mn (3). Among the mobile compounds of Ca, Mn, and S, exchangeable compounds predominate, that is, Al and Fe, extracted with 1 N HNO₃. Acid mine drainage and solid matter from the waste heap form toeslope talus that bury highly productive chernozems. In terms of the fractional composition of the Al, Ca, Fe, Mg, Mn, and S compounds, the bare soils of the talus are close to the toxic substrates of the waste heap and the grass-covered soils of the toeslope talus are close to the background chernozems. Relative to the waste heap material, the content of mobile compounds and total Ca and S is reduced in the displaced substrate from toeslope talus. Presumably, due to the influence of vegetation in the grass-covered substrate, the contents of mobile Mn compounds and the mobility of Al are significantly increased, while due to the lower supply of substances from the body of the waste heap, the mobility of Fe is reduced. The AUx horizon of chernozems has increases in the content of mobile compounds and total S, as well as water-soluble Ca²⁺ and Mg²⁺ with a decrease in the content of mobile compounds and total Mn.