“BIOLOGICHESKAYA BALKA” OF BIOSPHERE RESERVE “LAKE ELTON”, A BOTANICAL PHENOMENON IN THE SALINE PLAINS OF THE NORTHERN ELTON REGION Текст научной статьи по специальности «Биологические науки»

====== STRUCTURAL ORGANIZATION OF ECOSYSTEMS =====

AND PATTERNS OF THEIR DISTRIBUTION

UDC 581.524

"BIOLOGICHESKAYA BALKA" OF BIOSPHERE RESERVE "LAKE ELTON", A BOTANICAL PHENOMENON IN THE SALINE PLAINS OF THE NORTHERN ELTON REGION

© 2022. Yu.D. Nukhimovskaya*, A.V. Bykov**, A.V. Kolesnikov**, N.Yu. Stepanova***

*A.N. Severtsov Institute of Ecology and Evolution of the Russian Academy of Sciences Russia, 119071, Moscow, Leninskiy Avenue 33. E-mail: Dr.Nukhimovskaya@yandex.ru **Forestry Institute of the Russian Academy of Sciences Russia, 143030, Moscow Region, Odintsovo Urban District, Uspenskoye, Sovetskaya Str. 21

E-mail: wheelwrights@mail.ru ***N.V. Tsitsin Main Botanical Garden of the Russian Academy of Sciences Russia, 27276, Moscow, Botanicheskaya Str. 4. E-mail: ny_stepanova@mail.ru

Received Februar 18, 2021. Revised Februar 28, 2021. Accepted March 01, 2022.

In this article we present detailed results of our study of the vegetation cover of the "Biologicheckaya Balka" or "Biological" dry valley, where the largest derivative of a ravine forest of the desert-steppe Trans-Volga region is located. The data on tree-shrub vegetation, soils and groundwater, taken from the stationary drill wells, was collected in different seasons of 2008-2021. The floristic observations were carried out by routing, with trees and shrubs studied along the way during the growing seasons of 2014 and 2018-2021. "Biological" dry valley (length - 850 m, elevation difference - 17 m) differs distinctly from the surrounding saline plains that are formed by the zonal semi-dwarf shrub-bunch grasses desert steppes. Its extremely small territory has intrazonal and extrazonal mesophilic vegetation, an unusually high floristic abundance and phytocenotic diversity. At the valley mouth there are halophytic annual saltwort plants, thickets of reeds, followed by the grass-forb communities with Phragmites australis further above, with meadow and forb-grass communities, and with a specific tarragon and couch grass meadow at the very top. Most of the area is occupied by a tree-shrub massif, located in the middle part of the valley bottom, and by the shrubs-forb-grass steppes on its right slope. In the catchment areas and on the left slope various types of desert and dry steppes are common, close to the vegetation of the flat interfluves. Their vegetation is heterogeneous and mosaic. We also explain what role the most important environmental factors, such as the level and salinity of groundwater, surface runoff, slope orientation, pyrogenic factor, livestock grazing and erosions, play in the spatial organization and vegetation dynamics. Over the past 50 years the upper border of the closed tree-shrub massif has moved along the bottom of the valley almost 50 m up. The local flora consists of 201 vascular plants species from 44 families, which is about 30% of species and 80% of families of the total number in the Elton Region; including 4 species from the "Red Data Book of the Russian Federation" (2008), and 5 from the "Red Data Book of the Volgograd Region" (2018). There are also 30 or 15% ruderal species.

The materials of this study contribute and help to achieve the main strategic goals of the UNESCO biosphere reserve "Lake Elton", such as the protection and restoration of natural ecosystems, development of scientific researches, ecological monitoring, ecological education, enlightenment and education. They prove there is a need of a protection regime in the "Biologicheksya Balka", as well as of fire-preventing and graze-prohibiting measures.

Keywords: Volga-Ural interfluve, Caspian lowland, Elton region, Lake Elton Biosphere Reserve, Eltonsky Nature Park, Khara River, Biologicheskaya Balka, Biological dry valley, tree-shrub vegetation, shrub vegetation, meadow vegetation, steppe vegetation, halophyte vegetation, soils, wildfires, livestock grazing, flora, vascular plants, Red Data Book of the Russian Federation, Red Data Book of the Volgograd Region, monitoring DOI: 10.24412/2542-2006-2022-1-53-99

In the farthest southeast of the European Russia, in the Volga-Ural interfluve of the Caspian Region, the dry and desert steppes are dominant in the natural vegetation cover, and the vegetation cover is quite complex (Lavrenko et al., 1991; Safronova, 2006). The species composition and horizontal structure of the vegetation cover of the desert steppes in the Caspian Region within Russian territory are poor (Safronova, 2007, 2014). The mesophilic forest and meadow vegetation, although way richer, still has extremely limited opportunities for growth due to the salinity level of clay plains, severe air aridity and lack of water in the territory. In the XVIII and early XIX centuries the ravine forests in this region were widespread, covering the valleys of drainless salty rivers, with accessible groundwaters (Dinesman, 1960). Nowadays the natural tree and shrub vegetation is very disturbed and remains only in a few fitting habitats, located in the hollows of salt lakes and deep depressions (Dinesman, 1960; Bykov, Bukhareva, 2016). There are numerous valleys of various depths and lengths, leading into the valleys of salty rivers that run into the Elton region or directly into Elton Lake, with preserved fragments of tree-shrub phytocenoses or biological groups of shrubs. However, the "Biologicheskaya Balka" or "Biological" dry valley has the largest area and shows the best preservation of the tree-shrub massif (Bykov, Bukhareva, 2016; Bykov et al., 2021). Specific flora and diverse herbaceous vegetation, concentrated in a very small area and never described before, also add to its uniqueness.

A primal description and further monitoring of composition and growth conditions of such communities, particularly in the specially protected natural areas, are necessary to assess the state of protective measures, predict their fate, and develop recommendations for ecosystems maintenance or restoration.

The aim of this article is to reveal the spatial organization of the "Biological" dry valley vegetation, to describe its uniqueness, its floristic and phytocenotic features that differ a lot from the surrounding territories, the ecological factors of its vegetation cover formation process, and its role in the preservation of phytodiversity of the biosphere reserve "Lake Elton" and the region itself.

Objects and Methods

The studies were carried out at the Dzhanybek Station of Forestry Institute of the Russian Academy of Sciences, in the Volgograd Region, Pallasovsky District (Fig. 1). "Biologicheskaya Balka" is located in the east of the Volgograd Region, in the Eltonsky Natural Park that surrounds Elton, the largest salt lake in Europe. In 2019 the park and the adjacent territories were granted a status of a UNESCO Biosphere Reserve "Lake Elton". The Elton Region is located in the northwestern of the Caspian Lowland, on the Volga-Ural interfluve.

According to the climatic indices, acquired from the Dzhanybek meteorological station, the study area belongs to the droughty arid territories. Its average annual (1952-2013) precipitation is 291 mm, and the average annual moisture coefficient (ratio of precipitation to evaporation) is 0.32 (fluctuating between 0.28 and 0.37; Sizemskaya, Sapanov, 2010; Sapanov, Sizemskaya, 2015). Territories with similar hydrothermal parameters are classified as semi-deserts and dry steppes (Grebenshchikov, 1986). Since 2005, when the Elton station was established, a significant and reliable increase of winter precipitation is registered there. Just like in the entire territory of the Lower Volga Basin, a significant increase in the absolute minimal air temperatures was noted there as well, both in the warm half of the year and during the entire year (i.e., its cold half). However, the very strong summer droughts, common for the Lower Volga, was not observed by the Elton station. The further warming, expected in the region, and the increasing winter precipitation do not apply to the Elton weather station (Kuzmina, Treshkin, 2014).

The light chestnut, usually solonetzic soils with light and clay loam prevail in the catchment areas. The lake terraces are formed by the alkaline and steppified solonetzs (Nikolayev et al., 1998; Andreyeva et al., 2009). Unlike the complex soil cover that is common for the most of the

Caspian Lowland, the Elton Region is characterized by the non-complex soil combinations, with highly developed fine surface deposits (Konyushkova, 2014). Botanically and geographically, the Elton region is located in the Southern subzone of the dwarf semishrub-bunch grasses (desert) steppes of Yergeni-Volga Province of Volga-Kazakhstan Province of the Eurasian steppe region. For the Elton region those steppes are considered zonal. Their main feature is complexity, caused by the heterogeneous relief and the salinity of the territory (Lavrenko, 1991; Safronova, 2006; Safronova et al., 2018).

The studies of tree-shrub vegetation of the "Biological" dry valley were initiated by L.G. Dinesman in the 1950s. From the 1980s they were continued by the Dzhanybek Station employees of Forestry Institute of the Russian Academy of Sciences. A theodolite survey of the profile of the lower and middle valley was carried out, including its lower meadow and middle afforested areas and, partially, its treeless top (670 m). The elevation difference there is 17 m. In July 2018 the entire valley was affected by a severe wildfire, which made it possible for us to identify and examine the old trees and bushes, previously hidden by the thickets, as well as to make and describe some soil profiles. Once the data on the history of the tree and shrub vegetation development for the past 100 years was generalized, along with the data on soils and groundwater from the stationary wells that were drilled in 2013, it was revealed that the tree-shrub vegetation exists there due to the accessible fresh groundwaters (Bykov et al., 2020, 2021).

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Fig. 1. Scheme of the study region and satellite imagery (Google.Earth) of the "Biological" dry valley running into the Khara River.

Geobotanical descriptions of these communities have been carried out since 1980, according to the accepted methodology, and by routing (Field Geobotany, 1964). Floristic observations were carried out by routing as well (Yurtsev, Kamelin, 1987), during the various growing seasons of 2014 and 2018-2021. We took into account the vegetation of the valley bottom, slopes, edge and the strips along its watershed, i.e. the transitive strip that stretched from the landscapes of the actual catchment areas of the landscapes of flat interfluve to the ones of slopes (Milkov, 1974). The size of the area is about 25 hectares. Unfortunately, we could not study the slopes before the fire of 2018.

The Latin species names are given according to the "Flora of the Lower Volga Region" (2006, 2018), while the rest that are absent in the first two volumes of the "Flora" are given according to the work of P.F. Mayevsky (2014), with the synonyms, when necessary, added in the brackets. The authors' names are dropped if the taxa were mentioned in the text before. Most of the photos were taken by Yu.D. Nukhimovskaya, otherwise the author is given in the brackets.

Results and Discussion

The studied region is a flat accumulative marine plain, with the early Khvalynian loams on its surface and almost none surface and ground runoff (Doskach, 1979). Lake Elton is located inside the Botkul-Baskunchak depression, where the absolute elevation of the interfluve plains is about 0 meters, and the mouths of small salty rivers is at a negative height of -15 m above sea level. Elton has a meadow-solonchak floodplain and 2 terraces above it, a low solonchak-solonetzic one and an upland solonetzic one, both dissected by ravines and gullies (Nikolaev et al., 1998). "Biological" dry valley runs into the second terrace of Lake Elton, covering an area of 9.4 ha (catchment areas of flat interfluves are not included). It opens into the large Kharu River on its right, next to where it runs into the lake itself on the northern coast. It stretches from the northwest to the southeast (Fig. 1, Photo 1), with its total length being 850 m. Its upper part is located on the watershed of the saline rivers Khara and Lantsug. The upper reaches of the valley begin with a vertical 1.6-meter-high ledge (its geographical coordinates in 2018: N49° 13' 54.5", E46° 38' 45.0"; Bykov et al., 2020, 2021). Higher above it merges into a gap, formed by erosions and shaped like a shallow ravine or a narrow gully in some areas, less than 1 m of which tears into the interfluve, with the rest of it stretching for about 1500 m.

Photo 1. On the left - "Biological" dry valley in April (photo by A.V. Kolesnikov), 26/04/2016, on the right - same in May, 12/05/2014.

Soils and water regime. The sides and bottom of the valley are formed of homogeneous loess-loamy sedimentary rocks. Their soil cover is represented by sections of synlithogenic soils: gray humus water-accumulative stratozems, formed mostly on a mineral substrate and partially on an alluvial drift band. The soil material transported along the bottom with the flowing waters form burdens of various depth and assortment. The dynamic development of soils on a mineral substrate, associated with a cyclic and repeated deposition-redeposition, is common mainly to the zone of active growth of the top and middle parts of the dry valley. The soils at the base of the valley form under the prevailing soil-forming processes, with intensive involvement of the material of the newly

incoming solid runoff into the local formation process. This causes formation of specific soils with a low biological productivity and weakly pronounced genetic horizons (Bykov et al., 2020).

The growth of mesophilic vegetation on the bottom, primarily trees and shrubs, is largely due to the rainwater that flows from the catchment areas to the slopes, as well as to the annual and stable snow cover, which is formed when the snow is blown off the adjacent territories, and, most importantly, due to the available fresh and slightly saline groundwaters. From the bottom to top the groundwater depth increases from 0.9-1.2 m at the valley mouth to more than 4.5 m in its upper reaches, while their mineralization decreases (Bykov et al., 2020).

The vegetation type on the valley slopes is determined primarily by incloming moisture, which depends on the size of the relevant catchment area and exposition. The right slope of the northeastern exposition is high and sloping. It receives a significant amount of moisture that flows from the large catchment areas of the Khara and Lantsug rivers. The left slope of the southwestern exposition merges into a low, compared to the right bank, part of the plateau that borders the Khara River, and receives a limited amount of moisture.

These slopes are cut through by several short channels gullies and washouts. On the left slope there are only gullies, formed instead of the former and now collapsed badger holes, the tops of which do not reach the middle of the valley slopes, and the ground keeps crumbling there. Four large washouts on the right bank tear through the entire slope, up to where it bends onto the interfluve plain. They have obviously formed on the site of the former livestock trails of different age; the landslides are common for this territory (Bykov et al., 2021).

Environmental management. The plant communities of the Elton Region and, in particular, the "Biological" dry valley have a history of suffering under the impact of wildfires and livestock grazing. Since the late 1970s grazing has been virtually non-existent there, but has resumed in the early 1990s. An analysis of the century-long history of the development of the local mesophilic ravine-valley community showed that its modern tree-shrub communities are the result of anthropogenic transformation of the ravine forest. The most noticeable changes in the last century are a result of pasture impacts (Bykov et al., 2021). In July 2018 the entire dry valley, along with a protected patch of its ravine forest, the valley of the Khara River and the catchment area were affected by a strong wildfire in a total area of about 500 ha (Photo 2).

Photo 2. Dry valley 10 days after a wildfire, view at its upper part, 14/07/2018

(photo by A.V. Kolesnikov).

Botanical Study of the Elton Region and the "Biologicheskaya Balka". The literature sources about the flora of vascular plants and vegetation of the Elton Region are scarce and lacking. The most well-known major work was written by M.M. Ilyin (1927), although it has no information about the dry valleys vegetation. Among the later smaller publications that shed some light on the characteristics of the vegetation cover of the Pallasovsky and Elton regions, worth mentioning are the following: an article of V.A. Brylev and V.A. Sagalaev (2000), written on the problem of creating the Elton Nature Reserve, as well as the ones of I.N. Safronova (2006), T.V. Balyuk and A.V. Kutuzov (2006), V.A. Sagalaev (2008), with a brief description of the current state of the flora and vegetation of the Elton Region. However, they all lack any information about the vegetation of the "Biological" dry valley.

Some publications characterize the halophyte vegetation of the Elton region, its classification, relationship with the relief, soils, and its indicator role (Svet, 1939; Grebenyuk, 1979, 1984; Boltova et al., 1987; Freitag et al., 2001; Lysenko, 2008, 2013; Lysenko et al., 2010, 2012; Lysenko, Mitroshenkova, 2011; Kanishchev, 2014). According to V.A. Sagalaev (2008), the flora of Lake Elton and adjacent areas consists of 562 species. For the "Eltonsky" area, 62% of which belongs to the territory of the Natural Park of the same name, the "Emerald Book of the Russian Federation" (2013) lists 11 vascular species, al included in the "Red Data Book of the Russian Federation" (2008). The valley complexes have 36% of plant habitats, listed in the Red Data Books or subject to international conventions of various ranks (Kalyuzhnaya, 2017).

Despite the fact that the "Biological" dry valley was visited by many researchers, there are none complete descriptions of its herbaceous vegetation. The trees of this and other valleys of the Elton region are of bigger research interest, connected to numerous soil and zoological studies. Since 1980 the ravine forests of the Elton region, including the "Biological" valley, have been studied by employees of Forestry Institute of the Russian Academy of Sciences, who work on its Dzhanybek station (Bykov, Bukhareva, 2016; Bykov et al., 2020; Bykov, 2021). The authors analyzed the dynamics and identified the development stages of the local tree and shrub vegetation under the influence of livestock grazing and wildfires over the past 100 years. We considered the mechanisms of communities' resistance to those factors, as well as the conditions for the conservation and reproduction of such communities (Bykov et al., 2021).

Vegetation Cover of the Valley Bottom

The vegetation cover of the bottom of the dry valley is heterogeneous and various. A narrow strip of halophyte vegetation, where the valley runs into the Khara River, merges into the reed thickets, which then give way to the forb-grass meadow communities, which, in their turn, abruptly change into a shrub massif, merging into a yet sparse forming community of buckthorn, blackthorn and Spiraea, then into an almond forest, a tarragon phytocenosis and, finally, into a grass (couch grass) meadow (Fig. 2). We will describe this vegetation, following the same direction from the valley mouth to its top.

Meadow Vegetation of the Lower Valley

The "Biological" dry valley opens into the Khara River floodplain with a gently sloping mouth. The soil cover is represented by a hydrometamorphosed gray humus stratozem on a buried light solonetz, with the signs of gleization are found 100-centimeter-deep into the profile, which indicates that there are hydromorphism and anaerobic conditions in the lower layers of the soil-ground stratum.

In its lowest part a 10-meter-long, highly saline creek runs from a salty spring, and the groundwater with sodium-chloride salt composition is close to the surface. Both these factors led to

the growth of reed thickets (Phragmites australis (Cav.) Trin. ex Steud.) there. A small and narrow sloping area in the mouth, free of reeds, and the shallow waters of about 10-15 m2 are covered with an annual-saltwort halophytic on a meadow saline land, where the species common for the humid saline habitats grow: Salicornia perennans Willd., Spergularia salina J. et C. Presl. and Suaeda salsa (L.) Pallas (Photo 3).

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Fig. 2. Ecological levelling profile of the "Biologicheskaya" dry valley and its vegetation cover. Legend: 1 - Rhamnus cathartica, 2 - Prunus spinosa, 3 - Malus domestica, 4 - forming community of trees and shrubs, 5 - Prunus tenella and Spiraea hypericifolia, 6 - reeds, 7 - meadow vegetation, 8 - relief of the valley bottom, 9 - relief of the valley edge (right slope), 10 - groundwater level, 11 - drill wells, 12 - Khara River, 13 - groundwater depth (m, numerator) and mineralization (g/l, denominator); A - halophytic meadow with annual plants and saltwort, E - reeds thickets, forb-reeds meadow, grass-forb meadow, B - meadow community with trees and reeds, r - trees and shrubs of the valley bottom, ^ - forming polydominant community of trees and shrubs, E - Prunus tenella thickets with the sods of Spiraea and tarragon, K - forb-tarragon community, H - couch grass meadow.

Photo 3. Salicornia perennans-Suaeda salsa community, located where the dry valley runs into the Khara River, 09/06/2018.

Among the reeds there are found such species as Tripolium pannonicum (Jacq.) Dobrocz. and Atriplexprostrata Boucher ex DC. Higher above, in the small margins between the reeds Plantago cornuti Gouan. is abundant, although P. uliginosa F.W. Schmidt is more rare, growing on a 7-8-meter-wide strip along the channel of the Khara River; Juncus gerardii Loisel. and Saussurea salsa (Pall.) Spreng. are also found there (Photo 4, 5). The reed stretches far above the water edge and can be found throughout the entire lower valley, up to where the compact tree-shrub massif begins, However, its height and density decrease where the ground keeps elevating. There are Atriplex tatarica L., Oxybasis chenopodioides (L.) S. Fuentes, Uotila & Borsch (Chenopodium chenopodioides (L.) Aellen) in the more bared elevated areas.

Photo 4. Plantago cornuti among the reeds, 04/10/2018.

Trachomitum sarmatiense Woodson is one of the most common species of the lower valley. Along with reeds and other species, it forms a forb-reeds meadow there, above the densest thickets of reeds (Photo 6). These communities consist of plants that form a meadow of tall grasses, including several species of Apiaceae family: Cenolophium denudatum (Hornem.) Tutin, Seseli libanotis (L.) W.D.J. Koch, Heracleum sibiricum L. and Chaerophyllum prescottii DC. that can be found almost throughout the entire valley. Chartolepis glastifolia (L.) Cass. (C. intermedia Boiss.) is abundant among the grasses there, along with Althaea officinalis L., Echinops sphaerocephalus L. and other species (Photo 7, 8). The lower layer is formed by Galium aparine L. and G. humifusum Bieb., with Cynanchum acutum L. growing outside any layers. Artemisia santonica L. and Limonium gmelinii (Willd.) O. Kuntze can be found in the solonetzic, more open areas. The general projective cover of the area is 100%.

On a small grass-forb meadow, relatively free of reeds, aside from the aforementioned species there are many 40-50-centimeter-high plants of Galatella biflora (L.) Nees, Tanacetum vulgare L., Artemisia abrotanum L. (in the more humid habitats) and A. pontica L., rare encounters of Lithospermum officinale L., Medicago x varia T. Martyn, Geranium collinum Stephan ex Willd., Lactuca tatarica (L.) C.A. Mey., Linaria biebersteinii Bess., Taraxacum officinale Wigg. s.l. and

other species. Tanacetum vulgare can be found everywhere in the lower part of the valley. Grasses of this meadow community are represented by Bromopsis inermis (Leyss.) Holub, Elytrigia repens (L.) Nevski, Calamagrostis epigeios (L.) Roth and Poa angustifolia L. Its general projective cover is 100% as well (Photo 9, 10).

Photo 5. Saussurea salsa, 06/06/2019.

Photo 6. Phragmites australis and blooming Trachomitum sarmatiense near the valley mouth, 19/06/2019.

Photo 7. Budding Chartolepis intermedia, 06/06/2019.

Photo 8. Althaea officinalis, 05/07/2020.

Meadow Community with Trees and Reeds

The meadow grass-forb community with reeds stretches along the valley bottom up to the lower border of the tree-shrub massif. However, its composition changes, and 30-35 m away from the

Khara River, on the flat divide with a road, there are some bushes, such as Rubus caesius L., Rosa cinnamomea L. (Rosa majalis Herrm.), growing up to 1 m, and another plant, very common for the valley, Artemisia dracunculus L. that grows up to 1 m as well. Among the forb of the meadow, along the washouts, there are several separate 2-meter-high and larger trees of Malus domestica (Suchkow) Borkh (M. praecox (Pall.) Borkh.), Pyrus communis L. and Rhamnus cathartica L. Although single encounters of honeysuckle bushes and dog-rose were registered even within the valley mouth, on the elevated part of the bank (Photo 11, 12).

Photo 9. Tall herbaceous vegetation in the Photo 10. Blooming Galatella biflora in the valley mouth, 06/06/2019. lower valley, autumn after the wildfire,

04/10/2018.

Photo 11. Lonicera tatarica on the Khara River bank in the valley mouth, 13/06/2021.

The grass cover is dense (general projective cover is 100%), dominated with reed and dogbane (the latter is not as abundant 70-73 m away from the Khara River, where it moves to the foot of the slopes), as well as Tanacetum vulgare, Chaerophyllum prescottii, Galatella biflora, Seseli libanotis and Chartolepis glastifolia (Photo 13, 14). Asparagus officinalis L., Euphorbia virgata Waldst. et Kit., Allium caeruleum Pall., Rumex crispus L., Veronica spicata L., Xanthoselinum alsaticum (L.)

Schur, Convolvulus arvensis L., and Althaea officinalis, Lavatera thuringiaca L. from Malvaceae family can also be found there.

Further above tarragon is encountered much less, moving to the foot of the slopes. Next to the washouts and channel gullies Agropyron cristatum (L.) P. Beauv., Bromopsis inermis, Calamagrostis epigeios, Galium aparine and Glycyrrhiza glabra L. grow (Photo 16).

Photo 12. View from the meadow part of the valley (meadow community with trees and reeds) on the tree-shrub massif, 09/06/2018.

Photo 13. Lower part of the dry valley and the Khara River with a belt of blooming Trachomitum sarmatiense at the foot of the left slope, 05/07/2020.

Photo 14. Seseli libanotis, 06/06/2019.

Reeds can be found there locally, Chartolepis glastifolia grows in patches, as well as Melandrium album (Mill.) Garcke (Silene alba (Mill.) E. Krause), Potentilla bifurca L. and

ECOSYSTEMS: ECOLOGY AND DYNAMICS, 2022, Vol. 6, No. 1

P. supina L. Further along the bottom center there is a lot of tarragon, the reeds are still present, and the number of species increases along with the shrubs density.

Along the left slope of the dry valley, 5-6 m away from the lower border of the dense tree-shrub massif, a group of apple trees remained that developed from the stumps, where a lonely tree previously grew in 1960s (its diameter was about 40 cm). In 2018 along the lower part of the right slope, below the massif, there were separate groups of buckthorns and several bushes of spindle tree. That area has formed on the debris cone of a short ravine of the high right slope, which developed there in the 1990s, where a livestock trail was, opposite the lower part of the massif. Further above the ravine a landslide occurred. As a result, a platform about 25-meter-long and 10-centimeter-high was formed by the relocated earth, which now stops the surface runoff.

There, on a forb-loosebunch grass meadow the dominant species are as follows: Bromopsis inermis, Calamagrostis epigeios, Tanacetum vulgare, Artemisia dracunculus, Chaerophyllum prescottii, Onopordum acanthium L., Chorispora tenella (Pallas) DC. and sometimes Phragmites australis. Steppe species are encountered there as well, mostly abundant at the foot of the slopes: Krascheninnikovia ceratoides (L.) Gueldenst. (Eurotia ceratoides (L.) C.A. Mey), Agropyron cristatum, with forb formed by Falcaria vulgaris Bernh., Phlomoides tuberosa L., Salvia nemorosa L. (S. tesquicola Klokov et Pobed.), Galium verum L. (including G. ruthenicum Willd.), Geranium linearilobum DC. (G. tuberosum auct. non L.p.p.) and Scabiosa ochroleuca L. below the right slope.

Photo 15. Meadow with trees in front of the Photo 16. Meadow with trees, and with trees and shrubs massif, with Chaerophyllum Glycyrrhiza glabra and Bromopsis inermis in the prescottii and Artemisia dracunculus in the grass canopy, 06/06/2019. grass canopy, 06/06/2019.

Tree-shrub Vegetation on the Valley Bottom and its Differentiation from the Lowest to the Highest

Dense tree communities of the valley appear at about 140 m along the thalweg from the coast of the Khara River. Before the wildfire of 2018 their area was approximately 3,500 m2 (Bykov, Bukhareva, 2016). The bottom width there ranges from 10 to 19 m. The organogenic-accumulative soils of a homogeneous loamy granulometric composition formed under the tree-shrub communities, which determine the even and deep level of humidity, provided by the melt water that stream down to 120-230 cm, washing the easily soluble salts from the profile. The low mineralization level of groundwater provides a direct water source for the trees and shrubs, while its great depth (about 3 m, i.e. hydromorphic conditions) fills the entire profile with capillary moisture.

The lower border of tree communities is determined by high sodium-chloride salinization of groundwater proximity, and by the anaerobic conditions that develop in the root layer. And vice versa, the upper border is determined by the groundwater inaccessibility, since it is located below 450 cm (i.e. semi-hydromorphic conditions), and the dry or "dead" horizon at a depth of 240-410 cm (Bykov et al., 2020).

By 2018 the tree-shrub communities on the bottom of the "Biologicheskaya Balka" were a closed, almost impassable massif. Nowadays it became discontinuous. By its species composition and the approximate age of the local trees we can divide it into 6 zones (1-6), from the lowest to the highest (Bykov et al., 2021).

(1) Even-aged decaying thickets of Prunus spinosa L. with Rhamnus cathartica L. Its length up the thalweg is 47 m. Before the 1990s this area had a dead cover with blackthorn thickets, the density of which was 1. The maximal trees height was 3.5 m, 8 cm in diameter. In the 1990s the thickets started to decay, and their density decreased down to 0.7, while the herbaceous vegetation appeared underneath the trees. The decay of the blackthorn thickets that are over 60 years old matches the period of intense livestock grazing in the area and the moment when the drain was blocked with a scree. Near the right slope there are 5 old dense bushes of Rhamnus cathartica with a lot of almost vertical stems. Heracleum sibiricum, Chaerophyllum prescotti, Echinops sphaerocephalus, Galium aparine and Thalictrum minus L. were found there, with many plants of Allium caeruleum, the bulbs of which are carried down the valley by the flowing water, so some of them can be found even in the lowest areas. Moreover, it even reaches up to the plateau next to the left slope (Photo 17, 18).

Photo 17. On the left - Allium caeruleum among the high grasses in the lower part of the tree-shrub massif, 06/06/2019, on the right - on the edge of the left slope of the upper valley, 07/06/2019.

The ruderal plants and weeds are abundant there: Onopordum acanthium, Amaranthus albus L., Blitum hybridum L. (T.A. Theodorova) (Chenopodium hybridum L.), Ceratocarpus arenarius L., Chenopodium album L., Arctium lappa L., Artemisia absinthium L., Erigeron canadensis L. (Conyza canadensis (L.) Cronq.), Leonurus glaucescens Bunge, Sisymbrium altissimum L. and single plants of Salsola tragus L. Many of them can be also found further above. Their abundance can be explained by the livestock gathering at the watering hole and entering the area nowadays as well. After the wildfire of 2018 they became widespread. In the autumn of 2019 along the entire length of the bushy part of the valley a lot of young sprouts of Ceratocarpus arenarius were found, since its fruiting individuals rolled down there from the catchment areas.

(2) All-aged shrub community of Rhamnus cathartica, Prunus spinosa with Lonicera tatarica L. Its length is 113 m. Blackthorn and buckthorn grew on the bottom and sometimes in the lower parts of the slopes before the wildfire of 2018. Honeysuckle was found only along the

thalweg. Canipy density there was 0.9-1. Most blackthorns and buckthorns were about 3.5-meter-high and 8 cm in diameter. There were also 3 apple threes that died eventually, 30-40 cm in diameter and 6.5-meter-high. Before the wildfire there could be found such species as Rubus caesius, Cynoglossum officinale L., Solanum dulcamara L., Nepeta cataria L. under the canopy or at the foot of the slopes. Lavatera thuringiaca, Blitum hybridum, Chenopodium album are abundant there, as well as in the next areas (Photo 19, 20).

Photo 18. Echinops sphaerocephalus, 05/07/2020.

Photo 19. Lavatera thuringiaca, 06/06/2019. ECOSYSTEMS: ECOLOGY AND DYNAMICS, 2022, Vol. 6, No. 1

(3) Prunus spinosa thickets with single Rhamnus cathartica plants. The length of this area along the thalweg is 39 m. In the early 1970s the dense massif ended on its upper border, with 5 bushes of spindle trees growing there up to 2-2.5 m. They vanished by the end of the 1980s.

(4) Young Prunus spinosa thickets with single plants of Rhamnus cathartica and Spiraea hypericifolia L. The length of this area is 50 m. Its canopy density was reached 1 by 2018, the stem diameter was up to 3 cm, the plants height was up to 2 m. From the second half of the 1970s to the early 1980s the layer of trees and bushes had only begun to form there. Several sods of Spiraea grew along the thalweg, and single blackthorn bushes, as well as groups of Prunus tenella Batsch (Amygdalus nana L.), were scattered around the entire area; 2-3 buckthorn plants grew at the foot of the right slope. By the 1980s its density was just about 0.5-0.6. By the early 1990s the layer of trees and shrubs finally closed. No Spiraea were found along the thalweg, however it is possible that single weakened bushes remained inside the massif. There are 2 wide margins in the middle of the area, 6-meter and 4-meter-wide, which are a result of horses' intense grazing in the mid-1990s.

(5) Young thickets of Prunus spinosa. The length of this area is 14 m; the upper border is located at the N 49° 13' 46.4'', W 46° 39' 00.5'' (Photo 21). This is the youngest part of the dense massif. Blackthorn is dominant. Along the edges of the bottom, sometimes spreading onto the lower part of the slopes, single buckthorn plants can be found. Their stem diameter is 2-4 cm, plants height is up to 2.5 m. Their canopy density reached 1 by 2018. In the late 1980s the sods of blackthorn and Spiraea were scattered all over the valley bottom, with 2-3 buckthorns, several sods of Prunus tenella and low, down to 0.5 m, bushes of dog-rose. The entire area was covered with blackberry.

(6) Sparse forming polydominant community of grass-forb with Rhamnus cathartica, Prunus spinosa, Spiraea hypericifolia and Prunus tenella, with Rosa cinnamomea, located above the dense massif (1-5). Its length is 110 m. Single bushes of buckthorn and blackthorn are lower than 1 m, their canopy density is 0.2-0.3. Sparse and burnt buckthorns of average height (160 cm), with the undergrowth of Spiraea and of Prunus tenella , recovering after the wildfire, can be found on the bottom. Sods of Prunus tenella and Rosa cinnamomea, as well as bushes of Spiraea hypericifolia stretch along the washouts (Photo 22).

Photo 20. Solanum dulcamara, 06/06/2019.

Next autumn, a year after the wildfire of 2018, some blackthorns seedlings were found in the area. Presumably, 10-15 years later a dense patch of polydominant tree-shrub community will form

there with the help of their vegetative and seed reproduction. In 2021 the bushes were covered with Cuscuta monogyna Vahl. and Fallopia convolvulus (L.) A. Love. The herbaceous layer includes Agropyron cristatum, Artemisia absinthium, A. dracunculus, Carex melanostachya Bieb. ex Willd., Chaerophyllum prescottii, Elaeosticta lutea (Hoffm.) Kljuykov (Muretia lutea (Hoffm.) Boiss.) Pimenov et V. Tikhomirov, Elytrigia repens, Galium verum, Linaria biebersteinii, Medicago falcata L. s.l., M. sativa L., Melandrium album, Melilotus albus Medik., Phlomoides tuberosa, Poa angustifolia, Salvia nemorosa, Seseli libanotis, Tanacetum vulgare, Verbascum chaixii Vill. (V marschallianum Ivanina et Tzvel.), V. phoeniceum L., Veronica spicata (with blue-violet and pink flowers), V. longifolia L. Above the landslide, next to a small burnt group of high buckthorn plants, there are also Cynoglossum officinale, Lavatera thuringiaca, Scabiosa ochroleuca, Taraxacum erythrospermum Andrz., with Onopordum acanthium and Leonurus glaucescens Bunge found mostly at the foot of the right slope (Photo 23-27). The growth of the burnt buckthorns and diversity of the meadow-steppe herbaceous plants in that relatively wide area can possibly be caused by the high humidity of the valley, which, in its turn, is a result of an extreme snow accumulation. In the lower part this community is interrupted by the thickets of tarragon; in the area before the young blackthorn (5) some grasses, such as Agropyron cristatum and Elytrigia repens, are quite abundant.

Photo 21. Edge of the area with young blackthorn (5) and the forming polydominant grass-forb community (6) of Rhamnus cathartica, Prunus spinosa, Spiraea hypericifolia and Prunus tenella, with Rosa cinnamomea, 30/04/2019.

Bushes of the valley bottom consist of Prunus tenella patches with the sods of Spiraea hypericifolia and abundant bushes of Artemisia dracunculus (140 m). In the spring of 2019, a year after the wildfire, Prunus tenella was blooming mostly on the right slope, while the older plants of Spiraea were still burnt, although growing anew (Photo 28). Spiraea stretch down along the right slope, sometimes dominating on the bottom. There the grass composition is similar to the previous community.

Meadow Vegetation on the Valley Bottom above the Bushes

It occupies about 200 m, 60 of which covered with a peculiar forb-tarragon (Artemisia dracunculus) community on the gray humic, water accumulative stratozems on loess. Since this area is close to the one of the active growth, the soils of insignificant depth form there due to the

cyclic and multiple deposition/re-deposition of the mineral substratum. Small single bushes of buckthorn can be found there only in the lower part of the community, at the foot of the right slope. The herbaceous layer is overall dominated by Artemisia dracunculus, also Artemisia absinthium, Elaeosticta lutea, Elytrigia repens, Galium verum, Geranium linearilobum, Phlomoides tuberosa and Tanacetum vulgare occur (Photo 29).

Photo 22. Forming polydominant community of trees and shrubs (6) on the valley bottom, view of the left slope, 10/06/2019.

Photo 23. Carex melanostachya, 09/06/2019.

It is interesting to note that Artemisia dracunculus formation is widespread in Central Asia, on the Pamir-Alay mountain system. There it belongs to a group of types of semi-humid vegetation or a xerocryophytic "meadow-steppe" florocenotype1, or, specifically, to a high mountain-forb steppes. This florocenotype is formed by the temperate and mountain warm-temperate floras that

1 Florocenotype is a complex of vegetation formations, which edificators have undergone a general adaptive evolution under the specific, long-term physical and geographical conditions. Practically speaking, florocenotype combines "flora" and "vegetation" (Safarov, 2018).

are based on the Arctic flora and have developed during Pliocene and Post-Pleistocene, after the mountains grew higher (Safarov, 2016, 2018). Moreover, tarragon thickets can be found on the slopes with fine-grained, which were affected by intense grazing in the past (Hushnazarov, 2008).

The highest part of the dry valley stretches for 140 m, covered with a meadow community of Elytrigia repens that clearly replaces the tarragon thickets (its geographical coordinates are N 49° 13' 52.7'', W 46° 38' 49.0'').

Photo 24. Verbascum chaixii, 07/06/2019. Photo 25. Veronica longifolia, 07/06/2019.

Photo 26. On the left - violet Veronica spicata, 07/06/2019, on the right - a pink one, 10/06/2019. ECOSYSTEMS: ECOLOGY AND DYNAMICS, 2022, Vol. 6, No. 1

In the lower part the valley is relatively narrow (5-meter-wide, stretching for 53 m), growing even thinner further above. The 6-8-meter-long area on the bottom of its top, as well as some slopes, is covered with lumps of bare ground and earth monoliths due to erosion and landslides, and occasionally with sods of Tanacetum achilleifolium (Bieb.) Sch. Bip. and other plants that have slid down. There is an obvious runoff gully on the bottom, washed out with rains and, therefore, reappearing occasionally. The active growth of the valley forms thin stratozems; the gully contains washed-off loess.

Photo 28. On the left - Prunus tenella with sods of Spiraea hypericifolia and Artemisia dracunculus, blooming, 29/04/2019, on the right - same spot after the wildfire (photo by A.V. Kolesnikov), 07/10/2018.

Growing in thick bushes, couch grass covers the bottom and the foot of the slopes, especially the right one, interrupted here and there with more bared areas that were formed by the landslides of

the left slope. There are patches of Phlomoides tuberosa andPhlomis pungens, Tanacetum vulgare, Convolvulus arvensis, Euphorbia undulata Bieb., Serratula erucifolia (L.) Boriss., Galium verum, Chorispora tenella, Lappula patula (Lehm.) Menyharth, as well as even smaller ones of Falcaria vulgaris, single bushes of Agropyron cristatum, Limonium sareptanum (A.R. Becker) Gams, Artemisia lerchiana Weber ex Stechm. Carex sp. and Medicago falcata L. s.l. (Photo 30).

Photo 29. Thickets of Artemisia dracunculus and forb, 07/06/2019.

Photo 30. Elytrigia repens, 13/06/2021.

Approximately 10 m away from the top the thickets of couch grass grow much sparser, interrupted with long, up to 10-12 m, patches of Lactuca tatarica (L.) C.A. Mey, while the aforementioned species become even more infrequent. Instead the single ruderal plants are common

there: Cynanchum acutum, Ceratocarpus arenarius, Chenopodium album L. s.l., Cyclachaena xanthiifolia (Nutt.) Fresen., Lamium amplexicaule (L. paczoskianum Worosch.), Xanthium albinum (Widder) H. Scholz. During autumn dry plants littered the upper part of the valley, especially its top, rolling down from the flat interfluve, including such specis as Amaranthus albus, Atriplex sphaeromorpha Iljin, Ceratocarpus arenarius, Petrosimonia triandra (Pallas) Simonk., Phlomis pungens, etc. Inside the crater of the upper valley near the catchment area a Tanacetum achilleifolium community grows.

Steppes with Shrubs and Other Steppes of the Right Slope

The right slope is covered with steppe and bushy vegetation. Its geomorphological features, landslides and water erosion, digging activities of earth-dwelling animals, rainfalls and aftermath of the wildfire created diverse micro-conditions and, therefore, formed a mosaic vegetation. Communities of the lower valley formed parallel and undulated (zigzag) belts. The soils up the slope are represented by various types, from the gray humic stratozems in the lower part to the light chestnut solonetz stratozems, with different stages of erosion, in the upper part and at the valley edge.

In the wide lower part of the valley, at the foot of the long right macro-slope there are patches of forb-grass meadow-steppe vegetation with dominant Agropyron cristatum, Elytrigia repens, Festuca valesiaca Gaudin, Elaeosticta lutea, Artemisia austriaca Jacq., Limonium sareptanum, Salvia nemorosa (covered with Cuscuta approximata Bab.). Among them there are Artemisia pontica, Asparagus officinalis, Astragalus brachylobus Fisch, Dianthus andrzejowskianus (Zapal.) Kulcz., Medicago falcata, Phlomoides puberula (Kryl. et Serg.) Adyl., R. Kam. et Machmedov, Poa bulbosa L., Potentilla bifurca, Thesium arvense Horv., Tragopogon dasyrhynchus Artemcz. (rarely encountered) and Veronica spicata (Photo 31, 32).

Photo 31. Right slope in the lower valley, 13/06/2021.

Photo 32. Patch of forb and grasses in the meadow-steppe phytocenosis in the lower part of the right slope of the lower valley, 10/06/2019.

The middle part of the slope in the lower valley with solonetz soils is covered with the communities of forbs and firm-bunch grasses (Agropyron desertorum, Festuca valesiaca, Tanacetum achilleifolium). Such species as Krascheninnikovia ceratoides, Limonium sareptanum, Gypsophila paniculata L., Elaeosticta lutea, Filago arvensis L., Serratula erucifolia are also common there, with sparse Atriplex aucheri Moq. and Poa bulbosa (Photo 33).

The territory near the catchment area of the right slope in the lower valley is covered with

sparse wormwood-fescue-feather grass community (Stipa sareptana A. Beck., Festuca valesiaca, Artemisia lerchiana), wormwood (Artemisia lerchiana), grass (Leymus ramosus (Trin.) Tzvel.) and other variations of desert-steppe communities. Its general projective cover is about 50%. These communities have occasional patches of dwarf semishrub-wormwood (Artemisia lerchiana, Bassia prostrata (L.) A.J. Scott (Kochia prostrata (L.) Schrad.), feathergrass (Stipa sareptana A.K. Becker), grass-feather grass (S. sareptana, Agropyron desertorum) and other phytocenoses. They sometimes include Tanacetum achilleifolium, Prangos odontalgica (Pall.) Herrnst. et Heyn, Atriplex aucheri, Sterigmostemum tomentosum (Willd.) Bieb., Stipa lessingiana Trin. et Rupr., Iris scariosa Willd. ex Link. L, Serratula erucifolia, Tulipa biebersteiniana Schult. et Schult.fil., T. biflora Pall., T. gesneriana L. (T. schrenkii Regel) and other species (Photo 34, 35).

Photo 33. Agropyron desertorum-Tanacetum Photo 34. Steppe of Artemisia and bunch achilleifolium belt in the middle of the right grasses on the right slope near the catchment slope of the lower valley, 10/06/2019. area in the lower valley, 10/06/2019.

Photo 35. Community of Artemisia lerchiana on the right slope near the catchment area of the lower valley, 10/06/2019.

Single bushes of Spiraea are spotted on the right slope of the lower valley, way before the massif of trees and shrubs begins on its bottom. Further they merge into steppes of Spiraea hypericifolia and forb-grass steppes, which are constantly disturbed by landslides and were affected by the wildfire in 2018 (Photo 36, 37). The burnt and recovering bushes spread very unevenly, interrupted occasionally with herbaceous steppe phytocenoses or groups of ruderal species. The herbaceous layer is dominated with Agropyron cristatum, Artemisia austriaca and Elytrigia repens. The forb include Allium inaequale Janka, A. lineare L., A. tulipifolium Ledeb., Amaranthus retroflexus L., Astragalus brachylobus, Camelina sylvestris Wallr., Capsella bursapastoris (L.) Medik., Chenopodium album, Dracocephalum thymiflorum L. and, occasionally, Ephedra distachya L., as well as Erysimum leucanthemum (Steph.) B. Fedtsch. subsp. versicolor (Bieb.) Schanzer, Galium aparine, G. verum, Geranium linearilobum, Holosteum glutinosum (M. Bieb.) Fisch. et C.A. Mey., Limonium sareptanum, Medicago sativa, M. x varia, Polygonum aviculare L., Potentilla recta L., Phlomis pungens Willd., Phlomoides tuberosa, Silene viscosa (L.) Pers., Sedobassia sedoides (Pallas) Freitag et G. Kadereit (Bassia sedoides (Pall.) Aschers.), Valeriana tuberosa L., Verbascum phoeniceum L. and Veronica longifolia L., Artemisia marschalliana Spreng. (Photo 38, 39).

Photo 36. View of the middle and upper valley, shrubs of the right slope, desert steppes of the left slope, catchment area and the lower border of the tree-shrub massif, 13/06/2021.

Photo 38. Geranium linearilobum, 30/04/2019.

Photo 37. Spiraea steppe of the right slope and desert steppes of the left slope in the middle valley, 27/04/2021.

Photo 39. Valeriana tuberosa, 02/05/2019.

Among the Apiaceae family Elaeosticta lutea is abundant there, as well as Chaerophyllum prescottii and Falcaria vulgaris, with occasionally found Eriosinaphe longifolia (Fisch. ex Spreng.) DC. Elaeosticta lutea is common for every herbaceous communities of the valley, except for its upper part with couch grass, and creates a yellow aspect in the early summer.

The vegetation cover of Spiraea steppe, including the large margins in the middle and upper parts of the valley, has such dominant species as Agropyron cristatum, Artemisia austriaca, Elytrigia repens and other aforementioned species. It also includes Achillea nobilis L. (patches), Alyssum desertorum Stapf, Artemisia absinthium, Artemisia pontica, Dianthus andrzejowskianus, Ferula caspica M. Bieb., Gagea bulbifera (Pall.) Salisb., Galatella tatarica (Less.) Novopokr., G. villosa (L.) Reichenb.fil., Hieracium virosum Pall., Prangos odontalgica, Sedum maximum (L.) Hoffm. (Hylotelephium stepposum (Boriss.) Tzvel.), Otites wolgensis (Hornem.) Grossh. (Silene wolgensis (Hornem.) Otth.), Taraxacum erythrospermum and Veronica spicata (Photo 40-42).

Photo 40. Steppe with Spiraea hypericifolia on the right slope, opposite the thickets of Prunus tenella on the bottom, 10/06/2019.

Photo 41. Hieracium virosum at the foot of the Photo 42. Prangos odontalgica among the right slope, 05/07/2020. thickets of Spiraea hypericifolia, 10/06/2019.

Vegetation of the two largest landslides of the right slope is sparser, with a relatively poor species composition, lower general projective cover and bigger areas of bare ground. The latter is the most common to have such annual species as Blitum hybridum, Camelina sylvestris, Ceratocarpus arenarius, Chenopodium album, Consolida paniculata (Host) Schur, Erigeron canadensis, Galium aparine, Lamium amplexicaule, Polygonum aviculare, Sedobassia sedoides, Veronica sp. and Viola kitaibeliana Schult. (Photo 1, 43).

There are about 5 washouts on the right slope, which some bushes grow in, reaching from the bottom: Prunus tenella, Rosa cinnamomea and some herbaceous plants, such as Lavatera thuringiaca, Asparagus officinalis, etc., with Artemisia dracunculus in the upper part of the dry valley. These bushes can sometimes be found in the species composition of Spiraea communities.

Photo 43. A wide landslide with a small ravine in the middle of the dry valley, with sliding bushes of Spiraea and a group of burnt buckthorn at the foot of the right slope, 30/04/2019.

Through almost the entire valley Carduus uncinatus Bieb. can be found on its bottom and each slope, along with the groups of Onopordum acanthium (mostly on the right slope) that sometimes almost spread onto the plateau. After the wildfire Ceratocarpus arenarius and Chenopodium album are abundant both on the bottom and the slopes.

Thickets of Spiraea on the right slope end, where tarragon on the bottom changes by couch grass. The height and width of the valley decrease down there, as the right slope grows shorter and steeper, covered with collapsed earth monoliths. Communities of Agropyron cristatum and Tanacetum achilleifolium and communities of Tanacetum achilleifolium and Agropyron cristatum are spread there, but their species composition is poor and consists of Dianthus andrzejowskianus, Festuca valesiaca, Phlomis pungens, Phlomoides tuberosa, Limonium sareptanum, Koeleria cristata (L.) Pers., Artemisia pontica, Otites wolgensis, Gagea podolica Schult. et Schult. fil., Poa bulbosa and some other species along the slope ledges (Photo 44, 45).

Sloping areas near the catchment areas on the right of the middle and upper valley are covered with communities of Agropyron cristatum and Tanacetum achilleifolium and communities of Tanacetum achilleifolium and Agropyron cristatum, of Festuca valesiaca and Tanacetum achilleifolium communities, feather grass (Stipa sareptana), wheatgrass-feather grass (Stipa sareptana, Agropyron desertorum), wormwood (Artemisia lerchiana), grass (Leymus ramosus)

communities and other phytocenoses. These plant communities also consist of Artemisia taurica Willd., Atriplex aucheri, Ceratocephala testiculata (Crantz) Roth, Euphorbia undulata, Filago arvensis, Gagea bulbifera, Goniolimon rubellum (S.G.Gmel.) Klokov, Bassia prostrata, Lappula patula, Limonium sareptanum, Phlomis tuberosa, Prangos odontalgica, Serratula erucifolia, Sterigmostemum tomentosum; ephemeral plants and ephemeroids, such as Allium tulipifolium Ledeb., Alyssum desertorum, Eremopyron orientale (Gaertn.) Nevski, E. triticeum (Jaub.) et Spach, Iris scariosa, Meniocus linifolius (Steph.) DC., Ornithogalum fischerianum Krasch., Poa bulbosa, and Tulipa spp. Extremely sparse groups of Atriplex aucheri, Ceratocarpus arenarius and Tragopogon dubius Scop. can be found occasionally in what seems to be the burnt-out thickets of Poa bulbosa (Photo 47, 48).

Photo 44. Koeleria cristata on a ledge of the right slope, 10/06/2019.

Photo 46. View of the Tanacetum achilleifolium-Agropyron desertorum

community near the catchment area of the right slope, opposite the tarragon thickets on the bottom, as well as the left slope, 10/06/2019.

Photo 45. Patch of vegetation on the actively collapsing right slope in the upper valley, 10/06/2019.

Photo 47. Patch with Stipa sareptana on the steppe of the catchment area, adjacent to the right watershed, in the upper valley, 10/06/2019.

In the upper part of the dry valley, on the catchment areas, adjacent to the right slope, there are mosaics Agropyron cristatum, A. desertorum and Tanacetum achilleifolium communities and

communities of Artemisia austriaca with Limonium sareptanum, Phlomoides tuberosa, Leymus ramosus, Serratula erucifolia, with additional ruderal and pasture species, such as Ceratocarpus arenarius, Chenopodium album, Lappula patula, Pyankovia brachiata (Pallas) Akhani et E.R. Roalson (Salsola brachiata Pallas, Climacoptera brachiata (Pallas) Botsch.), etc. Further up the slope they merge into the steppes of feather grass and pasture variations.

Steppes of the Left Slope

The left slope is mainly covered with sparse dry-steppe and desert-steppe vegetation on the washed-off light chestnut soils and stratozems at the subslope part. The bushes are represented by the occasional plants of Spiraea hypericifolia, Atraphaxis frutescens (L.) C. Koch. (Photo 48) and Krascheninnikovia ceratoides. In the lower part of the dry valley Krascheninnikovia forms a narrow transitive belt between meadow vegetation of the valley bottom (strip of Phragmites australis and Trachomitum sarmatiense at the subslope) and steppe vegetation of the slope (Photo 13). Further above there are communities of Artemisia lerchiana, Festuca valesiaca, Stipa lessingiana, Agropyron desertorum and Bassia prostrata, in different proportions (Photo 49), followed by wormwood-fescue-feather grass (Artemisia lerchiana, Festuca valesiaca, Stipa sareptana A.K. Becker, S. lessingiana, S. ucrainica P. Smirn.) communities. They are mixed with Ephedra distachya, Falcaria vulgaris, Gypsophila paniculata, Phlomis pungens, Galium ruthenicum, Poa bulbosa, Atriplex aucheri and other species (Photo 50-52). Along the hollows of the channel such species of shrubs and herbaceous plants, as Prunus tenella, Artemisia dracunculus, Eleoasticta lutea, Phlomis pungens, Phlomoides tuberosa, Salvia nemorosa, Medicago falcata s.l., Allium caeruleum stretch up from the bottom, as well as Phragmites australis in the lower valley.

Photo 48. Atraphaxis frutescens, 09/06/2019. Photo 49. Patch of Bassia prostrata and

Ephedra distachya community, 09/06/2019.

On rare occasions Artemisia marschalliana can be found on the edge of the middle valley. Jurinea multiflora (L.) B. Fedtsch., Galatella villosa, Galium ruthenicum, Medicago sativa, Astragalus brachylobus grow locally, where the moisture is relatively higher in the depressed areas of the valley edge. The area near the catchment area is occupied with the feather grass (Stipa sareptana), wormwood-feather grass and wormwood (Artemisia lerchiana) communities. Also, Orobanche lanuginosa (C.A. Mey) Greuter (Orobanche caesia Reichb.), a plant that parasitizes on Artemisia lerchiana, was found there. The ruderal species play a significant role as well: Capsella bursa-pastoris, Ceratocephala testiculata, Descurainia sophia, Erigeron canadensis, Lappula caspia (Fisch. & C.A. Mey.) Popov ex Dobrocz. (L. semiglabra (Ledeb.) Gurke), L. patula, Lepidium perfoliatum L, as well as Pyankovia brachiata.

During the spring and early summer, on the edge of the left slope and in the catchment area Camelina sylvestris, Erysimum hieracifolium L., Sterigmostemum tomentosum bloom, along with the ephemeral plants and ephemeroids, such as Allium lineare, A. tulipifolium, Iris scariosa, Adonis aestivalis L., Alyssum desertorum, Androsace maxima L., Chorispera tenella, Eremopyron orientale, Euphorbia undulata, Gagea bulbifera, Holosteum glutinosum, Meniocus linifolius, Ornithogalum fischerianum, T. gesneriana L. (Tulipa schrenkii Regel), T. biebersteiniana, T. biflora Pall., etc. Their general projective cover is just about 30-50%. (Photo 53, 54).

Photo 50. Grass-feather grass-wormwood Photo 51. Stipa sareptana and Allium lineare on community along the left slope, 09/06/2019. the edge of the left slope in the lower valley,

view upwards along the slope, 09/06/2019.

Photo 52. Wormwood-firm-bunch grass community with Stipa ucrainica, 13/06/2021.

Near the catchment area, in the middle valley (opposite its afforested part), the fescue-wormwood communities and the sparse dry-steppe groups sometimes include Astragalus biebersteinii Bunge, A. ucrainicus M. Pop. et Klokov and A. dolichophyllus Pallas, and even less often Ferula caspica Bieb. and Atraphaxis frutescens (Photo 55, 56). In the wide micro-hollows Galatella tatarica grows, forming local communities (Photo 57). In the bare convex areas Ephedra distachya L. can be found, with a few concomitant species and a low (20%) projective cover. In the more even areas it is accompanied by other species.

In the middle and upper valley, tarragon sometimes climbes quite high along the crumbling slope; in the bare areas of the left slope Lactuca tatarica, Cynanchum acutum and Falcaria vulgaris grow locally. Leymus ramosus grows higher up the slope, while Atriplex aucheri can be found everywhere.

Approximately, starting next to the dead vegetation cover of the young blackthorn thickets (5) and the forming polydominant community of buckthorn, blackthorn and Spiraea (6) that grows on the bottom, the vegetation of the edge of the left slope and its part of the catchment area becomes thinner. Meanwhile, the species diversity and especially the amount of feather grass declines, but the amount of Tanacetum achilleifolium, Leymus ramosus and Ceratocarpus arenarius increases. On strip near the watershed, in the upper third of the dry valley, the sparse groups (general projective cover is 20-40%) of, mainly, Agropyron desertorum, Tanacetum achilleifolium, Leymus ramosus, Artemisia lerchiana, A. taurica Willd., Bassia prostrata, Serratula erucifolia are dominant. The following species are very sparse: Prangos odontalgica, Phlomis pungens, Phlomoides tuberosa, Limonium sareptanum (on the edge of the valley), Ornithogalum fischerianum, Goniolimon rubellum, Carduus uncinatus, Poa bulbosa, however, Atriplex aucheri, Ceratocarpus arenarius, Tulipa spp., Lappula squarrosa (Retz.) Dumort., Descurainia sophia are abundant (Photo 58, 59).

Photo 53. Iris scariosa, 30/06/2019. Photo 54. Sterigmostemum tomentosum,

12/05/2014.

Photo 55. Astragalus biebersteinii, 30/04/2019. Photo 56. Astragalus ucrainicus, 12/05/2014.

The height of the left slope decreases down to 2-2.5 m upon reaching the upper valley. Elytrigia repens is common there on the bottom. Leymus ramosus is dominant higher up the slope, along with Elytrigia repens. On the low crumbling left slopes of the upper valley Artemisia ausrtriaca, A. pontica, Adonis aestivalis, Euphorbia leptocaula Boiss., E. virgata, Falcaria vulgaris, Fumaria vaillantii Loisel., Goniolimon rubellum, Lactuca tatarica, Limonium sareptanum, Phlomis pungens, Phlomoides tuberosa, Tragopogon dubius can be found (Photo 60, 61).

Photo 57. Galatella tatarica community, 13/06/2021.

Photo 58. The amount of feather grass is insignificant in the upper valley, on the slope near the catchment area; Bassiaprostrata can be seen in the foreground, 09/06/2019.

Photo 59. Community of Leymus ramosus, Tanaceum achilleifolium and Saussurea erucifolia near the catchment area of the left slope of the upper valley, 09/06/2019.

In a big area along the catchment area in the upper part of the dry valley very sparse halophyte communities can be found as well, consisting of semi-shrub and dwarf semishrub halophytes: Anabasis aphylla L., Suaeda physophora Pallas, Nitrosalsola laricina (Pallas) T.A. Teodorova (Salsola laricina Pallas), Bassia prostrata, along with long-vegetating annual species, such as Pyankovia brachiata, Salsola tamariscina Pall., Soda foliosa (L.) Schrad. (Neocaspia foliosa (L.) Tzvel.), Petrosimonia brachiata (Pallas) Bunge, P. oppositifolia (Pallas) Litv., P. triandra (Pallas) Simonk., Sedobassia sedoides (Photo 62-65). In the upper valley large patches of extremely sparse

groups reach from the left plateau onto the strip near the catchment area. They are formed with Anabasis aphylla and Prangos odontalgica, perhaps, accompanied previously by Poa bulbosa before the wildfire (Photo 66).

Photo 60. Fumaria vaillantii on the left slope Photo 61. Goniolimon rubellum, 09/06/2019. in the upper valley, 29/04/2019.

Photo 62. Community of Pyankovia brachiata with occasionally encountered Anabasis aphylla in the left catchment area and the nearby left slope, 07/07/2020.

Photo 63. Suaeda physophora on the edge of the left slope, 13/06/2021.

Dynamics of the Dry Valley Vegetation

The aforementioned description of vegetation is based on observations that took place in different years and growing seasons, and, therefore, it is generalized. The composition, structure, height, seasonal and yearly condition of the local communities, as well as the entire valley, are very dynamic, changing beyond recognition under the natural and anthropogenic factors.

The formation of its polydominant tree-shrub community is a result of a succession. It started when the constantly bare substrate overgrowing with a pioneer community of Elytrigia repens, then with tarragon, then with a steppe shrub Prunus tenella that was later replaced by dog-rose, blackthorn and, finally, buckthorn. In the subslope areas of the formed tree-shrub communities (14), the dog-rose and almonds create small margins. After the wildfire, the rose began to grow

intensively in some areas of the bottom, but in the 1950s it was less common there (Nasimovich, 1960; Photo 66-68).

After the dynamics of the 100-year-long development of "Biologicheskaya Balka" natural tree and shrub complex, unique for the Trans-Volga semi-desert, was assessed (Bykov et al., 2020, 2021), it became possible to identify trends of the complex's development under different anthropogenic pressure.

In 50 years this closed community has moved up by about 50-60 m due to the active growth of the ravine part of the dry valley and the decreasing erosion basis. A significant role in the linear erosion is played by the funnel-shaped configuration of the ravine catchment area, which forms a channel hollow down there (Photo 69-72).

Photo 64. Neocaspia foliosa in the thickets of Leymus ramosus near the catchment area of the left slope of the upper valley, 10/06/2019.

Photo 65. Sparse community of Anabasis aphylla with Prangos odontalgica in the catchment area of the left slope of the upper valley, 09/06/2019.

Photo 66. Margin of Rosa cinnamomea at the foot of the left slope, 27/04/2021.

Photo 67. Margin of Prunus tenella at the foot of the left slope (photo by A.V. Kolesnikov).

Before the wildfire that took place in the early July of 2018, the polydominant tree and shrub vegetation of the bottom was a uniform and basically closed massif. It was observed after the fire

that the soil cover was not burned too deep and the renewal buds were well-preserved inside it, which indicated that the recovery of the local vegetation was possible. In the autumn the process of intensive renewal began through the tillers that grew from the dormant buds of the underground and surface parts of every tree and shrub species. We found the sprouts of Artemisia lerchiana on the left slope in the lover valley (Photo 73-75). Meanwhile the recovery of Poa bulbosa and Festuca valesiaca is significantly worse on the slopes near the catchment area.

Photo 68. Thickets of Rosa cinnamomea, 07/06/2019.

Photo 69. A 1.6-meter-high ledge in the upper Photo 70. A forming washout above the valley valley, 07/06/2019. ledge, 09/06/2019.

L.G. Dinesman (1960) showed that the assumption about climate being the reason for the forest vegetation disappearance in the Caspian Region in the second half of the 19th - early 20th centuries had no actual proofs. The only obstacle to its restoration is anthropogenic and zoogenic activities, especially animals' grazing, which causes soil washout and irreversible disturbance of the soil-vegetation habitat conditions and succession processes. The almost 10-year-long observations of the seasonal dynamics of the groundwater level and its chemical composition confirm that full-fledged

tree-shrub vegetation can develop there with the help of the preserved tree species under the regime of a nature reserve. However, from the 1930s (we have no data on the earlier period) a mass recovery of buckthorn, blackthorn, honeysuckle, almond and dog-rose from the seeds was recorded only for 1952, which was exceptionally humid (Dinesman, 1960). Since then the remaining polydominant communities spread only using a vegetative way, which made the area of the Elton Region they grow in decrease twice over the past 30 years (Bykov, Bukhareva, 2016), which, in its turn, threatens the very existence of these communities. After 2010, albeit still destroyed by livestock, the single self-seeding plants started to appear, the young sprouts of which are eaten during the snowy winters by European hares and mouse-like rodents (Bykov et al., 2020). Trees and shrubs restoration from the seeds in the already existing and newly forming habitats, the soil-vegetation conditions of which are suitable for the growth, is difficult due to their competition for the area with herbaceous vegetation and the lack of water. It is possible only on in the areas of bare earth and occurs mostly along the washouts on the valley bottom, where buckthorn regrows again, since it cannot compete with grasses (Knight et al., 2007).

Photo 71. A washout filled with water 2 years after in the ravine of the valley, 27/04/2021.

Photo 73. Growing tillers of Malus domestica in the autumn after the wildfire, 30/09/2018 (photo by A.V. Kolesnikov).

Photo 72. A furrow of erosion further down from the water-filled washout, view at the valley, 27/04/2021.

Photo 74. Growing Prunus spinosa in the autumn after the wildfire, 30/09/2018 (photo by A.V. Kolesnikov).

Photo 75. Artemisia lerchiana regrowing from the seeds on the left slope of the lower valley, with 80 juvenile plants per 1 m2, 13/06/2021.

Fluctuation of vegetation cover mostly depends on the pyrogenic factor, amount of precipitation and their annual distribution, as well as constant animals' grazing in the dry valley. Thus, in 2019 near the catchment areas the round plants of Serratula erucifolia were visually dominant, while in 2021 it was Atriplex aucheri and other ruderal species.

In the autumn of 2018, after the wildfire that took place in July, the yellow aspect was prevailing in the lower valley due to the overgrowing and blooming Tanacetum vulgare. In the autumn of 2021 it was overgrown with 2.3-meter-high Atriplex aucheri, which completely suppressed the growth of Tanacetum vulgare and other high plants (Photo 76, 77).

Photo 76. On the left - blooming thickets of Tanacetum vulgare during the autumn after the wildfire, view at the valley mouth, 04/10/2018, on the right - view at the tree-shrub massif, 04/10/2018.

A combination of several negative factors has a very noticeable effect on the development of vegetation. For example, in the winter of 2020-2021 the livestock distributed in the lower valley, destroying and trampling reeds and other plants, and eating tree branches (Photo 78). By the autumn of 2021 reeds of the lower valley was completely trampled, the aforementioned tall herbaceous vegetation disappeared and empty margins formed near the valley mouth (Photo 79). During the

drought of the second half of the summer in 2021, when the grazing was intense as well, the even-aged decaying blackthorn thickets (1) were trampled by the animals that sought shelter from the sun so hard they left nothing but bare earth (Photo 80), while the patches between the bushes above the area were covered with high grasses, such as Chenopodium album s.l. and Blitum hybridum, and the pathways to the valley top were made.

Photo 77. On the left - a meadow near the valley mouth, formerly covered with various species of high grasses, and overgrown by autumn with high thickets of Atriplex aucheri after a very dry summer of 2021, 09/09/.2021, on the right - view from the meadow at the tree-shrub massif, 09/09/.2021.

Flora Analysis and State of Rare Species Protection

Species composition of the "Biologicheskaya Balka" flora consists of 201 species (44 families) of vascular plants. This unusually high taxonomic abundance of such a small area is due to the fact that, according to V.A. Sagalaev (2008), the flora of Lake Elton itself and its adjacent territories includes 562 species (54 families). Therefore, the local flora contains about 30% of the species and 80% of the families of the Elton Region total number.

Both the valley and the lake (Sagalaev, 2008) have the same four dominant families, although with different positions (Table). The Chenopodiaceae family is on the 2nd place due to, apparently, the determining influence of the arid and quite extreme conditions, as well as to the presence of various saline habitats in such a limited area.

Populations of many plant species of the dry valley are very small, which makes the remaining phytodiversity highly vulnerable.

The "Red Data Book of the Russian Federation" (2008) lists Eriosynaphe longifolia (2a rank), Iris scariosa (2a), Stipa ucrainica2 (3r), Tulipa gesneriana (2a, b; Photo 53, 54). Iris scariosa is a subendemic species of the Volga River basin (Vasyukov et al., 2015).

The "Red Data Book of the Volgograd Region" (2017) also lists Allium caeruleum (3r), Megacarpaea megalocarpa (Fisch. ex DC.) B. Fedtsch. (3g), Saussurea salsa. (3v; Photo 5, 17, 81) aside from the aforementioned species. Seven more species are included into the "Appendix 2" (2017), into a "List of Plant Species and Other Organisms that are Being Monitored in the Volgograd Region": Allium tulipifolium, Atraphaxis frutescens, Ornithogalum fischerianum, Sterigmostemum tomentosum, Stipa sareptana, Suaeda physophora, Tulipa biflora (Photo 47, 48, 51, 52, 54, 63).

The nature park is the only territory of the Volgograd Region, where two species from the

2 In the "Red Data Book of the Russian Federation" (2008) Stipa ucrainica P. Smirn. is included into another species, such as Stipa zalesskii Wilensky (incl. S. ucrainica P. Smirn., S. rubens P. Smirn. S. glabrata P. Smirn.).

Red Data Book (2017) can be found: Megacarpaea megalocarpa, which can suffer from frequent steppe wildfires, and Allium caeruleum, the habitat of which can be easily destroyed due to its small size, especially by erosion, caused by the grazing livestock that ruins the vegetation cover (Popov, 2017a, b). These exact factors affected the valley in 2018-2021. The habitat area of some rare species is extremely small there. The only exemplar of Megacarpaea megalocarpa was found there just once, near the catchment area of the left slope, in September 2018, soon after the wildfire (Photo 81). The area of Saussurea salsa, a rare halophilic species, is also very small; by the autumn of 2019 and in the spring of 2021 the grazing livestock completely destroyed its habitat in the valley mouth, along with the reeds and the entire community of annual halophilic plants.

Photo 78. Destroyed and trampled vegetation after livestock's grazing in the lower valley during the winter of 2020-2021, 27/04/2021.

Photo 79. Vegetation that was trampled by the livestock in the valley mouth, where the thickets of reeds grew before the dry summer of 2021, 30/08/2021.

Photo 80. On the left - the lower border of vegetation before the livestock's grazing, 09/06/2018, on the right - same spot after the summer grazing, 09/09/2021.

40 species are the wild relatives of the cultivated ones, therefore being of great interest for selectionists. Along with the cultivated plants they belong to the genetic vegetation resources, which must be protected as a national natural legacy (Smekalova, Chukhina, 2005). 13 species are the pharmacopoeial medicinal plants of Russia (Atlas ..., 2006).

Anthropogenic process and erosion by wind and water increase the invasive rate of the plant communities, the introduction and distribution of weeds and ruderal species. There are 30 of those species in the valley, or 15% of the total number of species, similar to the Elton Region (Sagalaev, 2008).

Table. Richness of pecies of the main flora families on the "Biologicheskaya Balka" of the Elton Region.

"Biologicheskaya Balka" Elton Region (Sagalaev, 2008)

No. Families Number of % of the total Families

species number of species

1 Asteraceae 35 17.6 Poaceae

2 Chenopodiaceae 23 11.0 Asteraceae

3 Poaceae 17 8.5 Chenopodiaceae

4 Brassicaceae 13 6.5 Brassicaceae

5 Rosaceae 10 4.5 Fabaceae

6 Fabaceae 9 4.5 -

Photo 81. Megacarpaea megalocarpa near the catchment area along the left slope, autumn after the summer wildfire, 04/10/2018.

The natural park "Biologicheskaya Balka", which is of exceptional scientific, environmental and educational interest in the Elton Region, is located in the main natural zone of the zonal scheme - the nature protection zone. Preservation of its natural complexes and some other elements is one of the goals of the park creation (Regulations ..., 2015). In order to achieve this goal, it is necessary to create conditions for the restoration of a closed and continuous tree-shrub layer, which will strengthen the fire resistance of the park. The data, presented in our article, provides the basis for further floristic and phytocenotic monitoring, which, among other things, will allow us to assess the efficiency of nature protection measures, carried out in the park.

Conclusions

1. The vegetation cover of the "Biologicheskay Balka" or "Biological" dry valley of the "Elton Lake" Biosphere Reserve is described in detail, including its extra- and intrazonal mesophilic vegetation, which differs distinctly from the surrounding saline plains with zonal desert steppes.

2. The valley depth, which is significant for the Elton region (elevation difference is 17 m), the variety of relief, slope expositions, the mosaic soil-ground conditions and, therefore, mosaic moisture and salinity, as well as other factors, have determined the distribution of acutely different plant communities on a very limited area, where extrazonal tree-shrub, intrazonal meadow, dry-steppe and zonal desert steppe communities with edaphic variations coexist.

3. More than half of the current area of the tree-shrub massif is covered with a derivative ravine forest, where the species that are most resistant to intense grazing and wildfires are preserved. The tree-shrub communities of the bottom of the middle valley are formed exclusively by zoochory species, the absolute majority of which are able to spread vegetatively.

4. The formation of the local ravine polydominant tree-shrub community is a result of a succession. It starts with the overgrowing bare substrate with a pioneer community of Elytrigia repens, then with Artemisia dracunculus, then with the steppe shrubs of Prunus tenella, replaced then by Rosa cinnamomea, Prunus spinosa and, finally, Rhamnus cathartica. The closed massif of trees and shrubs on the bottom has traveled up the slope over the past 50 years for at least 50-60 m.

5. The limiting growth factor for the tree-shrub communities is the availability of fresh groundwater. According to the results of well drilling, the level of fresh groundwater that is available for trees (1.6-2.8 m, i.e. hydromorphic conditions) stretches down for 160 m, with a plot above it (about 100 m) where the soil is regularly soaked down to 2.4-4.5 m (semi-hydromorphic conditions) with melt water, providing water charge. Therefore, the valley has those conditions fitting for restoration of tree-shrub vegetation.

6. The valley flora is highly rich. It consists of 201 plant species from 44 families. This unusually high taxonomic abundance of such a small area is due to the proximity of the flora of Lake Elton and the adjacent territories, which, according to V.A. Sagalaev (2008), include 562 species from 54 families.

7. The valley flora includes many rare and valuable plants. The "Red Data Book of the Russian Federation" (2008) lists Eriosynaphe longifolia, Iris scariosa, Stipa ucrainica (as part of Stipa zalesskii), Tulipa gesneriana (T. schrenkii). The "Red Data Book of the Volgograd Region" (2017) also lists Allium caeruleum, Saussurea salsa. Seven more species are included into the "Appendix 2" (2017), into a "List of Plant Species and Other Organisms that are Being Monitored in the Volgograd Region"; 40 species are wild relatives of cultivated plants, and 13 more are pharmacopoeial medicinal plants of Russia.

8. The materials, mentioned in the work, prove there is a need of a protection regime in the "Biologicheksya Balka", as well as of fire-preventing and graze-prohibiting measures.

Acknowledgments. The authors express their gratitude to the leaders of the State Budgetary Institution of the Volgograd Region "Natural Park 'Eltonsky'" for their assistance in this study.

Funding. The work was carried out as part of the research work of A.N. Severtsov Institute of Ecology and Evolution Problems of the Russian Academy of Sciences "Ecology and Biodiversity of Terrestrial Communities" (No. 0109-2019-0006), of Forestry Institute of the Russian Academy of Sciences "Factors and Mechanisms of Sustainability of Natural and Artificial Forest Biogeocenoses of the Forest-Steppe Zone and Arid Regions of European Territory of Russia under the Natural and Anthropogenic Transformations" (Government Task No. 0121-2019-0003). It was also carried out in accordance with the Agreement on Scientific Cooperation between Forestry Institute and the Eltonsky Nature Park.

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УДК 581.524

БОТАНИЧЕСКИЙ ФЕНОМЕН НА ЗАСОЛЕННЫХ РАВНИНАХ СЕВЕРНОГО ПРИКАСПИЯ - «БИОЛОГИЧЕСКАЯ БАЛКА» БИОСФЕРНОГО РЕЗЕРВАТА «ОЗЕРО ЭЛЬТОН»

© 2022 г. Ю.Д. Нухимовская*, А.В. Быков**, А.В. Колесников**, Н.Ю. Степанова***

*Институт проблем экологии и эволюции РАН им. А.Н. Северцова Россия, 119071, г. Москва, Ленинский просп., д. 33. E-mail: Dr.Nukhimovskaya@yandex.ru

**Институт лесоведения РАН Россия, 143030, Московская обл., Одинцовский ГО, с. Успенское, ул. Советская, д. 21

E-mail: wheelwrights@mail.ru ***Главный ботанический сад им. Н.В. Цицина РАН Россия, 27276 г. Москва, ул. Ботаническая, д. 4. E-mail: ny_stepanova@mail.ru

Поступила в редакцию 18.02.2022. После доработки 28.02.2022. Принята к публикации 01.03.2022.

Приведены подробные результаты изучения растительного покрова «Биологической балки» с крупнейшим в пустынно-степном Заволжье дериватом байрачного леса. Материал по древесно-кустарниковой растительности, почвам и грунтовым водам из стационарных буровых скважин собран в разные сезоны 2008-2021 годов. Флористические наблюдения проведены маршрутным методом попутно с изучением древесно-кустарниковой растительности в различные вегетационные периоды 2014, 2018-2021 годов. Балка «Биологическая» (протяженность -850 м, перепад высот - 17 м) резко отличается от окружающих ее засоленных равнин с зональными полукустарничково-дерновиннозлаковыми опустыненными степями наличием интразональной и экстразональной мезофильной растительности, необычайно высокой флористической насыщенностью и фитоценотическим разнообразием на очень ограниченной территории. В устье имеются галофитные однолетнесолянковые сообщества, заросли тростника, выше - злаково-богаторазнотравные с тростником луговые, разнотравно-злаковые луговые сообщества, в вершине балки - своеобразные эстрагоновые и пырейные луговые. Большую площадь занимает древесно-кустарниковый массив в средней части днища и кустарниковые разнотравно-злаковые сообщества на склоне правого борта балки. В приводосборных частях и левом склоне распространены варианты опустыненных степей,

Stewart J.R., Reich P.B. 2007. Ecology and ecosystem impacts of common buckthorn (Rhamnus cathartica): A Review // Biological Invasions. Vol. 9. P. 925-937.

приближающихся к растительности плакоров. Растительность носит неоднородный и мозаичный характер. Показана роль важнейших экологических факторов (уровень грунтовых вод и ее соленость, поступление поверхностного стока, ориентация склонов, пирогенный фактор, выпас, эрозионные процессы) в пространственной организации и динамике растительности. За последние 50 лет верхняя граница сомкнутого древесно-кустарникового массива продвинулась вверх по днищу балки приблизительно на 50 м. Во флоре отмечен 201 вид сосудистых растений из 44 семейств (около 30% видов и 80% семейств от их числа в Приэльтонье), в том числе 4 вида, включенных в Красную книгу РФ (2008) и 5 - в Красную книгу Волгоградской области (2018). В составе флоры - 30 сорных видов (15%). Полученные материалы вносят вклад в достижение основных стратегических целей биосферного резервата ЮНЕСКО «Озеро Эльтон»: охрану и восстановление природных экосистем, развитие научных исследований, экологического мониторинга, экологического воспитания, просвещения и образования. Приведенные данные свидетельствуют о необходимости соблюдения в «Биологической балке» режима охраны, предотвращения пожаров и выпаса скота. Ключевые слова: Волго-Уральское междуречье, Прикаспийская низменность, Приэльтонье, биосферный резерват «Озеро Эльтон», Biosphere Reserve «LakeElton», природный парк «Эльтонский», река Хара, «Биологическая балка», растительность древесно-кустарниковая, кустарниковая, луговая, степная, галофитная, почвы, пожары, выпас, флора, сосудистые растения, Красная книга РФ, Красная книга Волгоградской области, мониторинг. Благодарности. Авторы выражают благодарность руководству ГБУ Волгоградской области "Природный парк «Эльтонский» за содействие в работе.

Финансирование. Работа выполнена по теме НИР Института проблем экологии и эволюции РАН «Экология и биоразнообразие наземных сообществ» (№ 0109-2019-0006), Института лесоведения РАН «Факторы и механизмы устойчивости естественных и искусственных лесных биогеоценозов лесостепной зоны и аридных регионов Европейской России в условиях природно-антропогенных трансформаций» (Госзадание № 0121-2019-0003), а также в соответствии с Договором о научном сотрудничестве Института лесоведения РАН и природного парка «Эльтонский». DOI: 10.24412/2542-2006-2022-1-53-99