Архив метки: irrigated arable land

CHANGES IN ECOSYSTEM COMPONENTS OF REclaimed SOLONETZES IN THE PRIERGENINSKAYA PLAIN DURING THE GROWING PERIOD (REPUBLIC OF KALMYKIA)

Arid Ecosystems

UDC 581.5

Novikova N.M., Konyushkova M.V., Ulanova S.S., Volkova N.A., Chemidov M.M., Bembeeva O.G., Fedorova N.L. CHANGES IN ECOSYSTEM COMPONENTS OF RECLAIMED SOLONETZES IN THE PRIERGENINSKAYA PLAIN DURING THE GROWING PERIOD (REPUBLIC OF KALMYKIA) // Arid ecosystems. 2022. V.28. № 3 (92). P. 79-93. | PDF

During the growing season of 2021, in early May, late June and early September, observations were carried out on the functioning of the main components of ecosystems recovering after reclamation at 8 sites of the IV experiment of the Arshan-Zelmen hospital, where reclamation work that lasted 20 years was stopped almost 50 years ago. Currently, soils belong to one type of highly transformed soils, the deep-saline agrozems. Arable (0-45 cm) and sub-arable (50-60 cm) horizons have been preserved in the soil profile. In 2018 in most areas, the content of salts and, in particular, chlorine ion increased in the subsurface horizon. These changes have not been reflected in vegetation, and the formation of plant communities characteristic of the final stages of secondary succession of light chestnut soils, not saline, continues. Hydrothermal conditions in 2021 during the observation period (May-September) can be assessed as arid – the doubly increased value of the average temperature for each month turned out to be higher than the value of precipitation that fell that month. Precipitation fell every month except July. The precipitation that fell during this period (176 mm) exceeded the average annual amount for these months of 2011-2021 by 1.3 times, and the sum of temperatures only by 2°C. Therefore, the hydrothermal conditions of the growing season of 2021 can be assessed as more favorable for the functioning of ecosystem components than in other years.

Comparison of data characterizing the salt profile of soils during the growing season showed that the content of water-soluble salts (in % per 100 g of soil) in the horizons from September to May changed in the range from -1.42 to +0.36. At different periods of observations, both unidirectional changes  in the salt content and multidirectional changes were observed in the same soil horizons. In May, the upper horizons of all soils, including virgin soils, up to a depth of 30 cm were unsalted, they remained in the same category of salinity by September. In the profile of virgin soils, salinization began from a depth of 30-40 cm and intensified downwards, reaching values of strong salinization in the horizon of 70-100 cm (1.1-2%). By the end of the growing season, the salt content in these horizons decreased to an average (0.5-1%). In soils that had previously experienced forest reclamation, the lower horizons that were slightly saline in May (80-100 cm) moved to the category of non-saline by autumn. In previously reclaimed soils under the former arable land, on the contrary, previously unsalted lower horizons have moved into the category of slightly saline. The magnitude of the change in salinity of soil horizons has a high tightness of connection (r=0.89) with the chlorine ion.

The vegetation cover is relatively sparse; the total projective coverage ranges from 35% to 73%. The average values from May to June varied from 43% to 52% and by September decreased to 47%. Throughout the year, the communities are dominated by bulbous bluegrass (Poa bulbosa) and Lerch’s wormwood (Artemisia lerchiana). Chamomile (Tanacetum achilleifolium) is present in all areas, and in some, including virgin lands, acts as a codominant. In May, the volosnets (Leymus ramosus) aspect, in June and in September – annuals Anisantha tectorum and Atriplex tatarica, respectively. The aboveground phytomass of most plant communities increases from spring to autumn from 4-5 c/ha to 10-25 c/ha. In some areas, mainly previously forested and some virgin, the maximum values were reached at the end of June and decreased by autumn due to a significant decrease in the phytomass of perennial cereals. Plant communities by species composition and dominance during the entire growing season Artemisia lerchiana and Poa bulbosa should be attributed to the pasture variant of zonal semi-shrubby-tyrsikov (Stipa sareptana) plant communities characteristic of the desolate steppe on chestnut unsalted and slightly saline soils.

The novelty of this study is associated with new quantitative data on changes in the characteristics of the main components of the ecosystems of the desolate steppes during the vegetation period.

Keywords: Caspian lowland, virgin salt flats, land reclamation, irrigated afforestation with irrigation, irrigated arable land, hydrothermal conditions, vegetation period, salinization-desalinization of soils, species richness, plant communities, aboveground phytomass.

Financing. The work was carried out within the the State Task of the Water Problems Institute of the Russian Academy of Sciences, topic No. FMWZ-2022-0002,f «Research of geoecological processes in hydrological systems of land, formation of surface and groundwater quality, problems of water resources management and water use in conditions of climate change and anthropogenic impacts».

DOI: 10.24412/1993-3916-2022-3-79-93

CHANGE OF VEGETATION ON RECLAIMED SODIC SOILS ON THE PRIERGENINSKAYA PLAIN AFTER 10 YEARS (REPUBLIC OF KALMYKIA)

Arid Ecosystems

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.

Key words: Caspian lowland, sodic (solonetz) soils, reclamation, irrigated afforestation, irrigated arable land, soil salinization-desalinization, species richness, plant communities, stages of succession, aboveground phytomass.

DOI: 10.24411/1993-3916-2020-10104