Pugacheva A.M. The Climatic Fluctuations in Dry Steppes and Their Role in the Process of Regeneration // Arid ecosystems. 2020. V. 26. № 3 (84). P. 14-22. | PDF
For the first time a research paper presents the results of the analyses of moisture-providing during the active growing seasons in dry steppes. The climatic fluctuations were examined together with the defining their characteristics. Contrary to the common opinion, that the steppe zone receives the highest rainfall in summer and that fact becomes its special feature including subzones, the analyses of 64 years show that the dry steppes of Lower Volga region received the highest rainfall in summer only in 39 % of years, in spring – in 27% of years and in autumn – in 34% of years. The time-series analysis during the seasons of moisture-providing for more than 50 years identified the general trend of decrease in summer rainfall and the increase of spring and autumn rainfall. The processing of time-series by exponential smoothing and the regression analysis points to the rate of humidity increase in spring after the critical years of 1990 and 1991, which is proved by Student’s t-test (probability 0,00005) together with the humidity decrease in autumn (probability 0,01). These features characterize the regeneration processes of secondary phytocenoses on fallow lands in the form of domination of loose bunch cereaks and dense cereals in them because the moisture-providing in late spring (May) and early summer (June) has the primary importance for their development. In addition, the characteristics of moisture-providing show a tendency towards aridization. The number of species of Poaceae family in the examined phytocenoses is 28 with 24.5% of representation. Moreover, this fact characterizes the existence of ephemeral plants and ephemeroids in the plant community, because their vital activity mainly depends on the spring rainfall. The number of their species is 8% of the total.
Novikova N.M., Volkova N.A., Ulanova S.S., Chemidov M.M. Change of Vegetation on Reclaimed Sodic Soils on the Priergeninskaya Plain After 10 Years (Repablic of Kalmykia) // Arid ecosystems. 2020. V. 26. № 3 (84). P. 30-39. | PDF
After 10 years the new observations of natural vegetation restoration were made. As 10 years ago at the same time (end of May) same methods of data collecting on 9 sites at the Arshan-Zelmen scientific station were used. Almost 50 years ago reclamation works that lasted for 20 years were stopped at the scientific station. Comparison of data obtained during field work for two observation periods (2008 and 2018) shows that changes in the salt profile of soils caused by reclamation remain unchanged. All these soils are of the same type of strongly transformed soils – deeply-saline agrozems. In the soil profile, the plowed layer (45 cm) and below lying horizon down to 50-60 cm, free from salts, identified in the 2008 descriptions were preserved in 2018. But in soil samples taken in 2018, the content of salts and, in particular, the chlorine ion increased in most areas under layer 50-60 cm. These changes were not reflected in the vegetation and the formation of plant communities that are typical for the final stages of secondary succession on light-chestnut soils rather than on solonetz continues. The total number of species recorded on geobotanical sites decreased from 70 to 62. From the list of species in 2008 almost half (35 species) fell out, and by 2018, 27 species had been introduced. This occurred mainly in groups of perennial and annual herbage species. Tree and shrub species (Populus album, Quercus robur, Ulmus pumila, Acer tatarica, Cotinus coggygria) continue to shrink and fall out, and only pear (Pyrus communis) and golden currant (Ribes aureum) have regeneration. Despite the decrease of total number of species, the species abundance of communities on all geobotanical sites increased significantly — by 1.5-2.5 times. During last 10 years representative species of zonal communities became widely spread: Artemisia lerchiana, Tanacetum achilleifolium, Poa bulbosa, Stipa lessingiana, Leymus ramosus, Artemisia austriaca. This fact contributed to the flattering of the species composition of plant communities on observation sites and caused an increase of species composition similarity between these communities up to 56-77%, which is significant compared with similarity 37-57% calculated in 2008. Similar changes were detected in the aboveground phytomass: not only the increase (average phytomass in 2008 and 2018 was respectively 734 and 849 C/ha), but also some flattering of the values on different sites. In 2018 in the virgin sodic soils the upper layer of 20 cm remain unsalted, and the above-ground phytomass in 2018 became more than twice higher than in 2008.