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Biogeographic status of the steppe plains and
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lowland
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Ninth International Symposium "Steppes of Northern Eurasia"
IOP Conf. Series: Earth and Environmental Science 817 (2021) 012106
IOP Publishing
doi:10.1088/1755-1315/817/1/012106
1
Biogeographic status of the steppe plains and foothills of
the northern and western Caspian lowland
AATishkov1,2ORCID 0000-0001-8887-7226, EABelonovskaya1ORCID 0000-0002-8354-4606,
NASobolev1ORCID 0000-0003-3413-1458
1Institute of Geogarphy, RAS, Moscow, Russia
2Belgorod National Research University, Belgorod, Russia
E-mail: tishkov@igras.ru
Abstract.The discussion focuses on the zonal nature of the Caspian steppe and the status of the
local biota, which in its spatial-temporal organization and regional succession system has
preserved the pool of biodiversity of dry-steppe and desert complexes. Each of them represents
a set of ancient systematic groups of organisms that migrated here along both the Eastern
(Turan) and Western (Caucasus, Mediterranean) coasts of the Caspian Sea, forming "young"
lowland ecosystems. There is a weak significance in the Genesis of the biota of the xerophilic
foothills of the Eastern Caucasus (Daghestan) and the southern Urals, which, apparently, only
at the early stages of formation during periods of major sea transgressions served as refugia.
The phylocenogenetically determined polyclimax and the predominance of pasqual and
climatogenic subclimaxes in the region are manifested due to constant impact of cyclical short-
term (hundreds of years) destabilizing factors.
1. Introduction
The zonal-provincial character of the biogeographic zoning of the European part of Russia is to some
extent violated by the allocation of the Caspian region, which has well-defined boundaries, but not
quite a definite biogeographic status [1, 2]. On one side, it is the prolongation of the Russian plain by
geomorphological and geological features. So one would expect that there should be formed the “East-
European” zonality in the biota distribution along the climatic gradient. So one would expect that there
should be formed the “East-European” type of zonality in the biota distribution along the climatic
gradient. But, on the other side, fluctuations of the Caspian Sea’s level, climate and depth of the saline
waters’ occurence in the Later Pleistocene and Holocene led to the development of the massive of
original arid ecosystems, biogeographical status of which needs, to our opinion, clarification. In
addition, dominance of the anthropogenic modifications of arid ecosystems in this area in the last
millennia and the relatively recent inclusion of their biota in the phylocenogenetic (evolutionary) and
successional (modern digressive-demutational) system operating in the region are also an important
distinctive feature of the local ecosystems.
2. Factors of evolutional and successional dynamic of biome of the Caspian lowland
Before the start of these phylocoenogenetic transformations among external factors of biota dynamic
were only climate, fire and selective hunting for the big animals of the ancient people. As a rule, all
these was accompanying with the self-restoration of biota. With the including of the Caspian lowland
to the single “Eurasian steppe pastoral system” cyclic climatic and hydrologic changes in synergism of
the grazing began influence reversible or irreversible on the regional biota status. By the Early
Ninth International Symposium "Steppes of Northern Eurasia"
IOP Conf. Series: Earth and Environmental Science 817 (2021) 012106
IOP Publishing
doi:10.1088/1755-1315/817/1/012106
2
Holocene the Caspian ecosystem lost the major of the components of the “Mammoth’s fauna” and
with the development of the cattle breeding it lost big herbivorous animals (Onager, Steppe tarpan,
Persian gazelle) and then predators (Guepard, Manulcat, etc.). As a pastoral one, a dry-steppe,
replaced the entire zonal steppe natural complex and desert digressive-demutational complex was
formed here, which demonstrated and continues demonstrate cyclical biogeographic rearrangements in
accordance with climate changes, fluctuations in the Caspian Sea level and grazing loads.
3. Contemporary biogeographic trends as reflection of biom’s “youth”
As we see it, contemporary biogeographic trends in the region are tied with the beginning of the
Anthropogen. They should be looked for not only and not so much in comparing the compositions of
regional floras and faunas, but in phylocenogenesis in the whole biota and in those displays that are
determined by the anthropogenic transformation of the regional succession systems. During very rapid
and deep climate changes, the ecosystem first changes its position on the relief. Then it whether
migrates following the movement of climatic regions (geographic changes), or, if migration is
impossible, it died, making space for new ecosystems, which develops as a result of phylocoenogenes.
Both used to appear in the different periods of biome’s developing, following the catastrophic (rapid)
impacts of sea transgressions and regressions, humidization and aridation, cyclicity of grazing loads.
Caspian region, which in comparing with neighboring plain and low mountain areas (steppes of
Volga and Transvolga region, steppes of Terek-Sulak lowland, seashore foothills of the Eastern
Caucasus, Stavropol highland, Ust-Yurt plateau, Mugodzhary), exists for a relatively short period of
time in conditions close to modern conditions. Therefore, we can speak about the “youth” of the
natural complex that has developed here. The last large transgressions and regressions of Caspian Sea
had significant biogeographic effect not only for the maritime biota, but also for the land biota of the
Caspian region. Sea level fluctuations, in fact, were an important factor in the spread of animals and
plants, the development of microevolutionary processes in them in connection with periodically
occurring geographical isolation of organisms and, conversely, due to biotic translatitudinal and
transmeridional flora and fauna exchange with areas featuring more ancient biota, and also in
connection with processes of new reclamation of surfaces freed from flooding.
4. Effects of “island biogeography” and biota’s isolation in the Caspian lowland
These processes were influenced also by effects of “island’s biogeography” for the region’s territories
with various elevation above the sea level both on the plain and in the foothills of the Eastern
Caucasus. In addition, the processes of "narrowing" and "expansion" of the space of development of
biota, associated with transgressions and regressions of the Caspian sea, were influenced by the quite
contrasting conditions of the regional climate, fluctuations in the level of salty groundwater and the
thermal regime of the sea itself - from cold-water in the final period of the Valdai glaciation to warm-
water in Holocene (contemporary). It is known [3], that on the end of the Atlantic time (nearly 5,000
ago) in the period of the Makhachkalinian sea regression the transition from arid warm conditions to
the modern one (more humid and colder) was carried out. The regression, which lasted for about 2,000
years, formed “land bridges” both in the west and east of the Caspian region, which, against the
background of the advancing transgression, directed streams of “steppe” biota onto arid (in fact,
desert) complexes of the lowland.
Earlier, as can be understood when analyzing the Holocene chronology of the region,
biogeographic status on the plain and low mountain parts of the northern Caspian region was changing
considerably.The reason was in the oscillations of the sea level, which were not be synchronized with
dynamic of zonal vegetation (ecosystems) of the adjacent land. It “disjuncted” during the period of the
Khvalynskaya transgression’s maximum, when the natural biotic exchange between the eastern
(“Turanian”) and western (“Pontic”) elements of the terrestrial biota was disrupted, then it created
wide corridors of transmeridian exchange of flora and fauna, when the Caspian lowland, in fact, united
into a single whole with the Tersko-Kumskaya lowland. At the same time, the eastern regions of the
Caucasus - foothills and mountains - were periodically separated from the plain by water barriers. On
Ninth International Symposium "Steppes of Northern Eurasia"
IOP Conf. Series: Earth and Environmental Science 817 (2021) 012106
IOP Publishing
doi:10.1088/1755-1315/817/1/012106
3
the one hand, it stimulated evolutionary processes, and on the other, did not allow the mountains to be
traditional refugia for zonal vegetation and fauna of the steppes (and moreover, deserts) during periods
warming and / or aridization of the climate in the Caspian region. Rather, on the contrary, in the
foothill part of the Western Caspian Sea, according to S.V. Kirikov [4], herds of kulans, tarpans,
saigas against the background of a relatively high pasture use by nomads and sedentary populations up
to the 19th century were common. L.G. Dinesman [5] writes about the same, however, paying
attention to the dry steppe complex of the fauna of small mammals and birds, which is quite dynamic
in relation to anthropogenic impact, which, with an increase of grazing and aridity, changes more
intensively towards desertification. Truth to be told, the weakening and disappearance of grazing in
the region unambiguously led to the emergence of both early spring and autumn burns, which in turn
stimulated the development of degradation processes here up to the formation of deserts.
5. Biogeographic status of Caspian region
There appear to be not finish the Discussion on the nature zonality of the Caspian region for more than
100 years [6-10]. This fact has not allow to solve the main question about the status of the local biota,
which saved in its spatial-temporal organization and, above all, in the regional successional system the
pool of the biodiversity, providing development and coexistent of the biotic systems of the dry steppes
and deserts. Each of them represent the group of sufficiently ancient organisms [11-12], which
migrated here along both the eastern (Turan) and western (Caucasus, Mediterranean) seashore of the
Caspian Sea and formed the “youth” ecosystems. During the last millennia, the huge sea
transgressions was not being here and exponiration of the surface of the lowland allows finishing the
primary succession with development of light chestnut and brown desert soils, sands, solonetzs and
solonchaks. In addition, it is safe to conclude that the main result of evolution of the Caspian
ecosystems under the cyclic short-terms (hundreds of years) destabilizing factors, that is
phylocoenogenetic policlimaxs and anthropogenic modifications domination (pastures and
climatogenic subclimax).
From a biogeographic point of view, one can confirm, that two biotic areas – Eurasian steppe area
and African-Asian one – give floristic and faunistic pool for formation development of the
ecosystems’ terminal stages in the Caspian Region. According species richness of the leading families
and biggest genera the flora of the concerned region closer to the deserts of Turan, but not to the Black
Sea (Pontic) steppes. So, representatives of Rubiaceae occupy the leading positions here, and genera
of Artemisia (12), Atriplex (11), Salsola (10), Suaeda (9), Petrosimonia (7), Astragalus (6), Allium (6),
Lepidium (5), Chenopodium (5), Climacoptera (5), Leymus (5), Limonium (5) dominate by the number
of species.
Endemism of Caspian region’s flora is near to that in the northern deserts of Turan (2-3%). For
example, there are practically no endemics in the plain steppes of Daghestan, contrary to the
mountains areas of the region, where endemism reach 15-20% (similar value of the endemism of the
Caucasus at whole) [13].
"Eastern relation" also demonstrates phytocenotic diversity: the desert wormwood-fescue-feather
grass steppes are represented mainly by the Trans-Volga-Kazakhstanian variants and are common on
the northern and western outskirts of the Caspian Sea (Ergeni), in the Southern Ural-Ilek Syrt and the
Obshchiy Syrt. Gramineous Festuca valesiaca, Stipa sareptana, S. lessingiana, S. capillata,
Agropyron desertorum, Koeleria macrantha and Leymus ramosus dominate here. Desert dwarf shrubs
Artemisia lercheana, Tanacetum achilleifolium, Artemisia austriaca, Bassia prostrata, Salsola
laricina, Artemisia taurica (in the Ergeni), Artemisia pauciflora, Bassia prostrata, Camphorosma
monspeliaca ssp. monspeliaca (on the solonets) are sodominants. The border between steppe and
desert zones corresponds approximately to that between areas of light chestnut and brown soils. The
deserts of the Caspian Sea region are also North Turanian in terms of their botanical and geographical
relation, area and diversity. The question on the existence of the “eastern deserts of the Black Sea
region” in the Kuma-Manych depression and the South-West of the Volga-Ural watershed as nature
phenomena could be discussed, but in whole it demonstrates the anthropogenic modification of the dry
Ninth International Symposium "Steppes of Northern Eurasia"
IOP Conf. Series: Earth and Environmental Science 817 (2021) 012106
IOP Publishing
doi:10.1088/1755-1315/817/1/012106
4
and desert steppes. In vegetation cover of the desert ecosystems grasses give way to xerophilous
suffrutices Artemisia lercheana, A. pauciflora, A. taurica, A. terrae-albae, etc., shrubs and dwarf
shrubs of Tamarix, Salsola, Ephedra, Calligonum, Nitraria, etc. and species of Anabasis, Salsola,
Kalidium genera.
Doubtless, the comparison of the representativeness and systematic diversity of the different groups
of fauna can give additional arguments to clarify the biogeographic status of the Northern Caspian
region. So, quite contrasting differences are observed when comparing the representativeness of
different groups of flora and fauna of dry steppes and deserts of the Northern Caspian region and
steppes, xerophytic communities and forests of the foothills and mountains of Daghestan (table 1). The
difference is just emphasized by the generally "desert" and "Turanian" image of the plain biome with
an impoverished fauna of mammals, amphibians, vascular plants, and an exceedingly high diversity of
reptiles.
Table 1. Representativeness (number of species) of flora and fauna groups in the dry
steppes and deserts of the Northern Caspian region and Daghestanian foothills and
mountains.
Biome
Mam-
mals
Birds
Reptiles
Amphi-
bias
Vascular
plants
Bryophy-
tes
Lichens
Steppes and
xerophytic
communities of
the
Daghestanian
foothills
70
180
15
12
3000
200
350
Dry steppes,
deserts and
flood lands of
the Caspian
region
40
150
25
5
1200
130
120
6. Conclusions
Caspian steppe is one of the youngest biomes in European part of Russia, which is experiencing in the
last millennia, the cyclic action of sea oscillations, deflation-denudation processes, high pasture load
(at first wild, and then mixed - both wild and domestic, and at the present stage - home ungulates).
The formation of its biota proceeded mainly due to the migration of species along the coasts of the
Caspian Sea in the regression period, which went almost evenly over the east and west coasts, but at
the present stage more due to "Turanian" way. To some extent, this is also confirmed by the
predominance of Central Asian species in the “adventive” part of the flora, rather than European ones.
The xerophilic foothills and low mountains of the Eastern Caucasus (Dagestan) and the Southern
Urals, as well as xero-mesophilic steppes along the northern border of the biome, which, apparently,
only at early stages, during periods of large transgressions, played the role of refugia, are of relatively
low importance in the genesis of the biota.
Under the conditions of constant action of cyclical short-term (hundreds of years) destabilizing
factors (natural and anthropogenic) in the region and due to phylocenogenesis, polyclimaxity of plant
communities and the dominance of their anthropogenic modifications (pasqual) and climatogenic
subclimaxes, included in the modern successional system of the region, are become obvious in the
region.
With this paper, we mark directions of the future researches in the region, which will allow not
only clarify the biogeographic status of the Caspian region but also reveal here the key biogeographic
landmarks, coincide or not coincide with the zonal or climatic borders. The whole block of researches
is planned to devote to evaluating of the role of biota of xerophilic foothills and low-mountains of the
Ninth International Symposium "Steppes of Northern Eurasia"
IOP Conf. Series: Earth and Environmental Science 817 (2021) 012106
IOP Publishing
doi:10.1088/1755-1315/817/1/012106
5
Eastern Caucasus and of the Southern Ural and northern deserts of Turan in formation of the Caspian
biome's original composition. All this will help to solve important fundamental problems – genesis,
successional dynamic, originality of the floristic and faunistic complexes of the region, and various
applied problems of the territorial nature conservation and biota’s renewal.
Acknowledgments
The article was prepared on the state assignment theme of the Institute of geography of the RAS No.
0148-2019-0007.
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