The Change in the Components of the Ecosystems of Reclaimed Solonetz Soils on the Yergeni Plain during the Vegetation Period (the Republic of Kalmykia)

The functioning of the main components of ecosystems that are recovering after reclamation at eight plots of the Arshan’-Zel’men experimental station, where reclamation works that lasted for 20 years were terminated almost 50 years ago, was monitored in the 2021 vegetation period in early May, at the end of June, and in early September. The soils belong to one type of highly transformed soils: deeply saline agrozems. The soil profile has preserved the ploughed (0–45 cm) and subsurface (50–60 cm) horizons. In 2018, the content of salts, in particular, chlorine ion, increased in the subsurface horizon at most of the plots. These changes did not affect the vegetation; the typical plant communities for the final stages of secondary succession for light-chestnut soils, rather than for solonetz soils, continued to form. The 2021 hydrothermal conditions during the observation period (May–September) can be regarded as arid. The monthly mean temperature was recorded to increase twice as much each month. Precipitation fell each month except for July. The past precipitation (176 mm) in this period exceeded the long-term mean annual precipitation over these months in 2011–2021 by a factor of 1.3, while the sum of temperatures exceeded the long-term mean annual temperature only by 2°С. Therefore, the hydrothermal conditions of the 2021 vegetation period can be rated as more favorable for the functioning of the ecosystem components than in the past years. The comparison of the data that characterizes the soil salt profile in the vegetation period showed that the content of water-soluble salts (in % per 100 g of soil) varied in the horizons from September to May in the range from –1.42 to +0.36. In different observation periods, the same soil horizons were recorded to have both unidirectional changes (only an increase) in salt content and oppositely directed changes. In May, the upper horizons of all soils, including the virgin soils, were nonsaline to a depth of 30 cm and remained in such a state until September. In the profile of virgin soils, salinization began from a depth of 30–40 cm and intensified downward, reaching the values of high salinity in the horizon of 70–100 cm (1.1–2%). At the end of the vegetation period, the salt content in these horizons decreased to the moderate level (0.5–1%). In the soils that underwent afforestation earlier, the lower horizons (80–100 cm), which were weakly saline in May, passed to the category of nonsaline soil in the fall season. In the soils that were previously reclaimed beneath the former plowed field, on the contrary, the lower horizons that were nonsaline passed to the category of weakly saline. The value of the change in salinity of soil horizons has a highly reliable correlation ratio (r = 0.89) with the chlorine ion. The vegetation cover is relatively sparse, the total projective cover (TPC) varies from 35 to 73%. The average values varied from 43 to 52% in May–June and decreased to 47% by September. The communities were dominated by bulbous bluegrass (Poa bulbosa) and Lerch’s wormwood (Artemisia lerchiana) during the entire year. Pyrethrum (Tanacetum achelliefolium) was present at all plots and at some plots, including the virgin soil, it acted as a codominant. Wild rye (Leymus ramosus) aspected in May; annuals Anisantha tectorum and Atriplex tatarica aspected in June and September, respectively. The aboveground phytomass of most phytocenoses increased from the spring to the fall, from 4–5 c/ha to 10–25 c/ha. At some plots that underwent afforestation earlier and in some virgin segments, its maximum values were reached at the end of June and decreased by the fall due to a significant decrease in phytomass of perennial grasses. In terms of species composition and domination during the entire vegetation period, Artemisia lerchiana and Poa bulbosa were referred to a pasture variant of zonal dwarf-semishrub-fаeather grass (Stipa sareptana) phytocenoses, which are typical of a semidesert steppe on chestnut nonsaline and weakly saline soils. The novelty of this study is related to the recent quantitative information on the change in the characteristics of the main components in the ecosystems of the semidesert steppes during the entire vegetation period.