Arid Ecosystems最新文献

The regularities of biomorphological, ecological, and species differentiation of phytocenoses in the most arid southeastern sector of the Altai Republic reflect a tendency towards the local formation of a complete type of arid vertical zoning. This is typical for arid mountains of Central Asia and includes the following belts (from bottom to top): (1) dwarf shrub deserts, (2) communities of thorn cushion plants (mountain xerophytes), (3) high-mountain steppes, and (4) cryophyte cushion plant formations. The relatively wide spread of this zoning type (in areas with sufficient height of the mountains), including belts of thorn cushion plants and cryophyte cushion plant formations, requires the revision of traditional botanical–geographical concepts in order to increase the diversity of higher vegetation syntaxa and orobiomes both in the Southeastern Altai and in the mountains of South Siberia in general.

According to the data of 1995–2020 surveys conducted in the Sulakskaya and Turalinskaya lagoons on the western coast of the Caspian Sea in Dagestan, as well as according to information about the returns of bands obtained from the banding center of the Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, the geographic dispersion of migrating wader populations was determined, for ten species of which population trends were established. Of the ten model taxa, the abundance decreased in four, increased in two, and remained at the same level in four. There is a correlation between changes in air temperature in the Primorskaya lowland of Dagestan with average annual fluctuations in the abundance of the model group of birds. The dynamics of the number of migrating shorebird populations is determined by hydroclimate cycles, anthropogenic factors, and foraging. It is recommended to introduce a temporary ban on the hunting withdrawal of lapwing, herbalist, snipe and black-tailed godwit until their populations recover steadily.

In 2015–2018, a study was made of the species composition, productivity of the vegetation cover and the composition of the diet of midday gerbil in the arid zone of the Northwestern Caspian Sea region. Midday gerbils use all types of available food in their diet, but the food can vary significantly in percentage in different seasons of the year. Using the method of cuticular–scatological analysis, it was shown that in the spring the largest share in the diet of gerbils is made up by Lapulla squarrosa (K = 15.97), Hordéum vulgáre (K = 9.5), and Medicago sativa (K = 5.4) and in summer by Poa bulbosa (K = 12.3), Amaranthus albus (K = 3.5), and Agropyron sibiricum (K = 4.3). In autumn, high rates of selectivity are characteristic of Poa bulbosa (K = 13.2). In winter, midday gerbils feed mainly on the seeds of Amaranthus albus (K = 11.2) and Agropyron sibiricum (K = 2.5), as well as Poa bulbosa (K = 14.3). In winter, there is almost no selectivity in the diet of midday gerbils and they use all the food available at this time of the year. Basically, the diet of the gerbil is made up by xerophytic vegetation species.

The characteristics of climatic, lithological and geomorphological conditions of formation of sandy soils of Transbaikalia (Barguzin basin) is given. It has been established that the main soil-forming processes are cryo- and light-humus, accumulative-carbonate and pale-metamorphic. In the soils of deposits, the processes of stratification and abrasion are expressed. Moving sands are not affected by soil formation, but with partial fixation of herbaceous and/or shrub vegetation on them, embryonic underdeveloped soils (layered-eolian, humus psammozems) begin to develop. For the first time, the results of the material composition of the rocks of the Angara-Vitim batholith, soil-forming sand, as well as the composition of minerals of fractions <1.1–5 and >5 µm of cryohumus and light humus soils are presented. It has been determined that the regional features of soil-forming sands are carbonation, alkalinity, and polymineral content, which is inherited from calc-alkaline rocks. The sandy and silty soil fractions have a similar mineralogical composition, which are characterized by a high content of plagioclases and K-feldspars and a low content of quartz. The composition of the silty fraction consists of a mixed-layer phase of illite-smectites interbedded with single chlorite packets, di-trioctadridic illite, ferruginous chlorite, and kaolinite. Modern soil formation is characterized by a low degree of chemical weathering (CWC, CWI, and GM) and weak profile differentiation. A feature of the material composition of sandy soils is an increased content of potassium and sodium. According to the values of total alkalinity, the studied soils are highly alkaline soils. There is a clearly pronounced division of the soil profile according to biological activity. It was revealed that during arable use, sandy soils are potential centers of desertification: in the studied area, all arable lands and fallows located on them are deflated to varying degrees. At the same time, it was found that more than 70% belong to very strongly deflated and strongly deflated types. In such areas, humus soil layers are blown out and carbonate horizons and even soil-forming sands are exposed. The exposed middle horizons and sands do not possess elements of effective fertility. The yield of agricultural crops on such arable lands is very low, the process of natural restoration of vegetation cover on fallow lands is extremely difficult, and deflation ulcers practically do not overgrow. The inhibition of the processes of restoration of natural cenoses is largely due to the alkalinity and carbonation of soil-forming sands.

This article presents the results of a study of the state of the cenopopulation of a rare species, Allium praemixtum Vved. in the Nurata and Turkestan ranges. The ontogenetic structure of the cenopopulation was studied by the generally accepted methods (Uranov, 1975; Tsenopopulyatsiya rastenii…, 1976). Cenopopulations were characterized according to the classifications of A.A. Uranov and O.V. Smirnova (1969) and “delta–omega” (Zhivotovsky, 2001). The ecological density was determined by the method of W. Odum (1986). Geobotanical descriptions were made according to the standard methodology on sites of 100 m² (Field geobotany, 1964). The characteristic ontogenetic spectrum is left-sided, with an absolute maximum in one of the pregenerative groups (Cheremushkina, 2004). Cenopopulations (CP) 1, 5, 6 correspond to the characteristic left-sided ontogenetic spectrum with a maximum peak in the virginal state of the species. The centered ontogenetic spectrum does not coincide with the characteristics, culminating in middle age. The bimodal ontogenetic spectrum is then considered as a temporary left-sided variant with an equal peak in the medium generative and virginal states. The density of individuals in the studied cenopopulations varied from 1.1 to 9.7 ind./m², and the ecological density is from 2.3 to 17.63 ind./m². According to the “delta-omega” classification Allium praemixtum cenopopulation CP 1 is maturing, CP 5 and 6 are young, CP 2 and 4 are transitional, and CP 3 is mature. Existing cenopopulations are mainly located on unprotected territory, with the exception of CP 3 (near Mazhrumsay) and 4 (near Gurdarasay). The only solution to this problem can be the strict protection of cenopopulations.

This article presents the results of a comprehensive hydrochemical and hydrobiological study of 13 different types of lakes in Transbaikalia conducted in July 2022. Based on factor analysis of hydrochemical and hydrobiological indicators, the lakes were divided into three groups: 1) brackish soda; 2) chloride and sulfate, as well as one salty soda lake, Shvartsivskoe; and 3) brine soda. It has been established that the number of species of different groups of aquatic organisms decreases as the salinity level increases, regardless of the chemical type of water. It has been shown that the dominant composition of primary producers in lakes of different types differs. Two new species of macroalgae for Transbaikalia have been identified (Stigeoclonium flagelliferum Kütz. and Rhizoclonium riparium: (Roth.) Harv.). In the flora of aquatic plants of Baikal Siberia, after more than a 100-year hiatus, Ruppia maritima L is present. The zooplankton of lakes is dominated by halotolerant species. The dominant structure of zoobenthos in brine and salt lakes is dominated by Artemia crustaceans and Ephydridae flies. In deeper brackish lakes, Chironomidae mosquitoes are always the dominant species. Quantitative indicators of phytoplankton and zooplankton communities are characterized by an inverse relationship. With the massive development of cryptophyte algae in brine reservoirs, the abundance and biomass of zooplankton are minimal. No significant fluctuations in the biomass of zoobenthos and phytomass of aquatic plants were detected. In sulfate and chloride lakes, the trophic structure of heterotrophs is represented in zooplankton by a grazing chain, and in zoobenthos by detritivores.

The aim of this study is a modern assessment of the agro-climatic resources of the semi-desert and desert landscapes of the North Caucasus. The methods of mathematical statistics used in agroclimatology have been used to analyze the changes in average monthly and annual air temperatures, the growing season, the amount of precipitation, and the hydrothermal coefficient according to the data of five weather stations with a long series of observations. Within the semi-desert and desert landscapes of the North Caucasus, there is an increase in annual air temperature over the period under review by an average of 0.86°С compared to the previous period. The sum of active temperatures increased by 9–11%. The duration of the period increased when passing through 0°C for 17 days, 5°C for 15 days, 10°C for 10 days, and 15°C for 8 days. An increase in precipitation is noted at all meteorological stations except Makhachkala. On average, precipitation increased by 36 mm. The hydrothermal coefficient of Selyaninov varies from 0.5 to 0.7 and is within the limits of natural fluctuation. Modern agro-climatic changes within the semi-desert and desert landscapes of the North Caucasus are characterized by an improvement in the conditions for heat and moisture supply to the territory. These conditions are favorable for the cultivation of melons and all types of grape varieties, with the exception of very late ones.

The species diversity of the entire meta-community is made up of local pools of species of individual communities, including both the totality of actually observed taxonomic groups and species of “dark” diversity, which, by their ecological properties, are theoretically suitable for living in existing conditions and are potentially found during repeated studies. To assess the dark diversity, quantitative indices of suitability of the surveyed areas of the study area are calculated in relation to various taxa of the community under consideration. The study of the species composition of benthic communities was carried out on small and medium lowland rivers, tributaries of the Kuibyshev, Saratov and Volgograd reservoirs, including the rivers of the arid region of the Lake Elton basin. A total of 132 local communities were surveyed, from which 147 taxa of macrozoobenthos were selected for calculations. To highlight the dark diversity, an analysis of the joint occurrence of species was carried out and, using hypergeometric distribution formulas, estimates of the conditional probabilities of the statistical relationship of each of these species with individual sections of the rivers were calculated. Relationships between observed species richness and dark diversity are considered; the occurrence of latent species was tested in sections of rivers of a similar type. The concept of “gray” diversity is introduced, i.e., a subset of observed species, in which the indices of correspondence to the focal area are less than a given threshold.

The extreme weather conditions of Transbaikalia cause phytostress in plants. This results in the formation of protective systems and mobilization that involves certain metabolic changes acting as survival means, including an increase in the content of lipids and lignin. Metabolism undergoes modifications determined by the pace and depth of changes that can occur in it without disturbing the balance between individual functions; as a result, the unity of the plant and the environment is not disturbed. Cryoarid conditions cause specific morphological and chemical adaptations in plants. It was found that the total content of lipids and lignin in the studied soils of Transbaikalia is higher, while the content of proteins is lower compared to similar soils in European Russia. It was also established that virgin chestnut soils contain more lipids, lignin, and proteins compared to fallow and arable soils.