Arid Ecosystems最新文献

A significant volume of research work carried out on the study of desertification processes and aridization of dry lands and continental deserts has created the basis for differentiating seasonal (temporary) changes that contribute to the change in the characteristics of arid soils and the corresponding components of ecosystems by elements of a regime with humid conditions. The radical change in the degree of soil and vegetation moisture by season is associated with the emerging differences in the provision of soils with moisture from atmospheric precipitation in different periods of the year. The natural stage of the processes of eliminating the deficiency of soil moisture in the autumn–winter and winter–spring periods in the zone of arid lands of semi-desert and steppe complexes leads to an increase in the drying of the soil profile, enriching the root-inhabited layer with moisture to the level of soil water supply characteristic of humid regions. The duration of the period of use of accumulated moisture by plants over the specified periods is 60–70 days, where the ratio of air temperature and soil moisture is determined in the range optimal for the growth and development of plants. Identification of a period with an optimal ratio of heat and moisture with a certain duration in zonal conditions of desertification, including the highest stage of desertification, provides a basis for developing a technology that differs from the generally accepted zonal one and takes into account the conditions characteristic of a semi-desert climatic regime (Akimtsev, 1957; Biarslanov et al., 2021).

The current study aims to comprehend the working processes of unique daya ecosystems by comparing the ecology of two Pistacia atlantica Desf. located in distinct geomorphological and bioclimatic contexts within the Djelfa province. We performed a floristic inventory of two sites by identifying the plant groups that characterize them individually using a correspondence factor analysis, and emphasizing the primary ecological gradients that control their distribution. Eighty phytoecological surveys have been conducted in order to achieve this goal. The 106 species found in our surveys exhibited a notable diversity of families and genera, with a prevalence of Asteraceae, Poaceae, Fabaceae, and Brassicaceae. Examining the biological spectrum showed that Therophytes were predominate, followed by Hemicryptophytes and Chamephytes, indicating that the environment is deteriorated. The primary ecological gradient identified by the correspondence factor analysis results is the geomorphological component. This would affect the moisture content of the soil and how plants are distributed. It is feasible to differentiate between the ecosystem of daya Bentoumi, which are less deteriorated, and the ones of Boucedraia, which are more degraded because of the gradient of anthropogenic disturbances.

The regional features of the wind regime in the northwestern part of the Caspian Sea are considered. The seasonal and annual dynamics of the main characteristics of the wind regime over a long-term period and in the current trends in their change are assessed. The analysis of time series of the average wind parameter values showed that easterly winds prevail in the northwestern part of the Caspian Sea, with the average long-term frequency being 26%. Despite their stability throughout the year, some seasonal variability can be observed. Among the winds of other directions, southeasterly, westerly, and northwesterly winds should be noted. Positive seasonal and annual dynamics are observed for the southeasterly wind. Characteristic features are also observed for the average wind speed; in the period 1991–2020, an increase in the climatic norms of 0.2–0.6 m/s is observed. Regional trend estimates obtained from the time series of the average annual air temperature and average wind speed show that the average wind speed increases along with an increase in the average annual air temperature. The main contribution of the trend to the change in wind speed by direction belongs to the spring and winter seasons. In the northwestern part of the Caspian Sea, weak winds prevail, most often in the gradation of 4–5 m/s. Average wind speeds of ≥15 m/s are observed in all seasons, with the highest frequency being noted in spring and autumn. The results obtained are of practical interest, since the need for marine climatological data arises when carrying out various activities.

The extent of distribution, the level of rise of groundwater, and the chemical composition depend mainly on the terrain and the quantitative and qualitative characteristics of precipitation. In conditions of increasing relief (middle of the slope), the GWL is lower relative to the lower part of the slope. On average, during this study, the difference in the occurrence of groundwater in a well from the middle of the field and a well in the lower part of the field is 4.4 times—343%. In conditions of increasing temperature in winter, precipitation is observed to have a liquid form, resulting in the increase in the subsurface runoff, which in turn affects the degree of mineralization of groundwater. The higher the concentration of salts in groundwater, the higher the degree of salinization of soil horizons. The predominant ions in the mineralization of natural waters also dominate among the ions of soil salts.

The results of studies on the growth and development of black saxaul (Haloxylon aphyllum (Minkw.) Iljin.) of various geographical origins and its relationship to the main environmental factors in order to identify the most promising climatypes for the creation of a seed base are provided. By testing 19 climatic ecotypes of saxaul, it was established that, in the first year after planting in the experimental plot, they suffered from frost, which was due to insufficient lignification of the annual growths of the southern climatic types. The preliminary permissible boundaries for zoning of saxaul seed material for the arid zone have been identified. The main growth indicators of saxaul during the growing season were analyzed, which made it possible to identify the earliest swelling of buds in Zaisan saxaul (Mongolian ecotype), as well as in saxauls introduced from Kazakhstan, Baskunchak, and Kharabali (Astrakhan oblast). The growth processes of saxaul continue throughout the summer period, but in the hottest years, growth is also observed in September. It has been established that the growth energy of saxaul increases with increasing air temperature, which is especially noticeable in southern climatic types. The dependence of shoot growth energy on the amount of precipitation in representatives of this species has not been noted. The highest water regime indicators were noted in saxaul introduced from Dosang (Astrakhan oblast), which characterizes them as the most drought-resistant biotypes. The crops created from northern reproduction seeds showed the highest frost resistance. The adaptation of saxaul to new growing conditions is demonstrated by its good fruiting, growth in height, increase in the diameter of the trunk and crown, and high biomass indicators. Damage to experimental plants by pests and diseases was noted by the authors only during dry and hot periods, mainly in saxaul climatypes from Kazakhstan and introduced species; no damage was noted in southern climatypes. Observations of the state of the saxaul in the conditions of the Astrakhan Trans-Volga region showed the prospects of creating its seed base in geographical cultures.

In the mountain steppes of Altai, Sayan, Tuva, and the Baikal region, large-bush wormwoods with a powerfully developed lignified caudex, a bunch of branched shoots from the base, are of the utmost importance. These are subshrub wormwoods: Artemisia obtusiloba, Artemisia altaica, Artemisia martjanovii, and Artemisia subviscosa. In the Altai Mountains and southwestern Tuva, Artemisia obtusiloba and Artemisia altaica are typical. Artemisia martjanovii is known from the foothills of the Sayan Mountains: in the steppes of the Minusinsk Basin and the Abakan forest–steppe. A. subviscosa is found in the northeastern part of the Baikal region: its largest massif is located in the central and upper sections of the Barguzin valley. The ecological and cenotic features of these related wormwoods, belonging to the Absinthium section of the subgenus of true wormwoods, in the contrasting conditions of the mountains of Southern Siberia have noticeable differences in morphology and ecology from the cryoxerophytic Altai–West Tuvan A. obtusiloba and A. altaica, the mesoxerophytic A. martjanovii in Khakassia, and the xerophytic A. subviscosa in the Baikal region. In addition to the classical morphological diagnostic features in the structure of leaves and inflorescences, which are variable and complicate the diagnosis of taxa, the phytochemical criterion was taken into account with the identification of the component composition of essential oil using modern methods of spectral analysis. As a result, the greatest degree of similarity of the composition of compounds in the metabolites of Artemisia obtusa and Artemisia altaisis was established, thereby confirming the subspecies status of Artemisia altaisis from A. obtusiloba, which was first substantiated by I.M. Krasnoborov (1997). At the level of independent species, taking into account both morphological characteristics, especially in the structure of the inflorescence (involucres and receptacle), and phytochemical indicators, Artemisia martjanovii and Artemisia subviscosa are substantiated. Wormwoods have important resource value as medicinal plants. A wide variety of components has been found in the essential oil of the studied wormwoods, many of which are pharmacologically very valuable. For example, detailed analysis and pharmacognostic studies of A. subviscosa yielded positive results on the richness and diversity of biologically active substances; in addition to turpentines, the content of flavonoids, coumarins, and tannins was found.

This study aimed at determination of main stand characteristics and estimate the aboveground tree biomass allocation by biomass component in Larix sibirica Ledeb. plantations in Mongolia. The study was carried out in 20-year-old Larch plantations established in the Shiliyn Bogd mountains of Sukhbaatar aimag, Mongolia using 2-yr-old seedlings. The results of our assessments showed the mean diameter and height amount for 8.8 cm and 5.76 m, and therefore the stem density and volume were 2400 ind. ha^–1 and 47.33 m³ ha^–1, respectively. Our findings revealed that mean values of stand characteristics were quite similar to mean values at the natural young larch stands growing in the northern part of the country. Aboveground biomass in the study area was averaged 29.68 T ha^–1. We found a strong correlation (R² = 0.99) between stem diameter at breast height (DBH) and aboveground biomass. The polynomial equation P_kg = 0.228(D_{{1.3}}^{2}) – 0.6944D_1.3 + 0.8223 was selected as a most optimal equation to estimate aboveground biomass of larch trees in the plantation. Our results revealed a relatively higher proportion of water content (69.9%) in aboveground biomass than absolute dry biomass (30.1%). Moreover, biomass component analyses indicated that the dominant part of aboveground biomass belongs to only stem wood (55.5%), and followed by branch (20.0%), bark (15.1%) and needles (9.4%). Based on our assessments we concluded that the establishment of larch tree plantation in the dry-steppe is possible via transplanting of 2-year-old containerized seedlings in Mongolia. The introduction of this afforestation technology plays important contribution to mitigation of land degradation in Central Asia. Therefore, the initial high planting density positively affected to tree survival post-planting period and creation of better microclimate in plantation area. We found that the predominant tree biomass belonged to stem biomass which exceed 55.5% in total aboveground biomass, and the water content amounted for 64% in fresh biomass. The polynomial equation P_kg = 0.228(D_{{1.3}}^{2}) – 0.6944D_1.3 + 0.8223 was selected most optimal equation to estimate the total aboveground mass. This planting method, planting design and outputs play an important contribution in development of dry steppe afforestation in Central Asia.

Arid regions have received little attention in carbon management studies so far. The results of assessment and comparison of organic carbon stocks in arid soils with different degrees of degradation in the arid zone of southern Russia (Astrakhan oblast) are provided. Based on the analysis of data characterizing 263 soil profiles, it was found that carbon stocks decrease with an increase in the degree of degradation. Significant spatial variability is observed both between and within biogeocenoses. The results showed that automorphic soils have a lower capacity for organic carbon deposition compared to hydromorphic soils. In automorphic soils, carbon stocks are 9.37 ± 1.02 t ha^–1, which is four times lower than in hydromorphic soils at 37.01 ± 2.34 t ha^–1. It was found that hydromorphic solonchaks in the coastal areas of crustal solonchaks of a very strong degree of degradation in the complete absence of vegetation have organic carbon stocks at the level of automorphic zonal soils.

The results of the study of plant communities of Mountainous Dagestan with the rare endemic species goat’s-wheat (Atraphaxis daghestanica (Lovelius) Lovelius) are given. The taxonomic structure of communities is considered, geo-elements are analyzed, and endemic species of the Caucasus are identified. We have described 79 plant species assigned to 65 genera and 31 families in communities with A. daghestanica. The analysis of the flora shows the domination of the Caucasian xerophilic element of the boreal group of species, which testifies to the great autochthony of the development of communities with the participation of the rare species A. daghestanica in the arid part of the Eastern Caucasus and to the high proportion of endemics: among 18 species, there are 11 (61%) endemics of the Caucasus, two endemics of the Greater Caucasus, and five endemics of the Eastern Caucasus. The results of the study of these communities are presented for the first time and may be used for monitoring rare endemic species growing in arid conditions of the Eastern Caucasus.

To study in depth the functions of soil as a component of the biosphere and to promote sustainable and effective management of vineyards, comprehensive studies were conducted, including biogeochemical, biological, and mineralogical analyses of soils on the territory of one of the regions of grape cultivation known since ancient times, the Derbent region, located in the Primorskii strip in the southern part of the Western Caspian. The territory is represented by light chestnut carbonate soils with a full-profile structure of vertical profile horizons. For the first time, the obtained data on the mineralogical composition included calcinite, quartz, feldspar, and a clay component (ferrous chlorite, layered silicate, colite, hydromica), the presence of which is due to the residual part of sedimentary rocks. The revealed salt composition of genetic horizons illustrated the predominant role of Na and K, where HCO₃ is 0.33 mg-eq. This is a characteristic indicator of arid soils, indicating the ecological adaptability of grape crops to extremely dry climatic conditions. The discriminatory model of the regional cluster structure of mineral elements in wine was constructed using the following predictors: K > Mg > Na > Ca > Fe > Mn > Zn > Cu > Ni > Co, which is typical for regional wine in Dagestan. It was established that the samples of experimental wines had high tasting characteristics and a biologically valuable component composition of mineral and aromatic substances. The data obtained reveal the potential resources of light chestnut soils and can be used by producers when choosing sites for growing vineyards in areas where arid land degradation is occurring.