Reconstruction of vegetation and climate of the past of the central Caucasus for materials from the Tarskoe swamp

Abstract

The reconstruction of vegetation changes of foothill zone in the central part of the North Caucasus based on the data of the Tarskoe swamp is presented. The swamp is the largest in this region of the Caucasus and is the most promising peat paleoarchive. It has been studied earlier, but the cores were poorly dated. The Tarskoe was re-drilled, the sediments were dated, and pollen and microcharcoal analysis were carried out. Twelve radiocarbon dates were obtained for the deposits, the age of the bottom sediments was about 4.6 cal. ka BP. Based on the data obtained, it was possible to establish that the of the bogging occurred against the background of more open landscapes, with a greater proportion of meadows than at present. Only after 4.4 cal ka BP broad-leaved forests become more closed, in their composition Fagus were dominant, with alternating admixture of Carpinus, Ulmus and Alnus. The increase of Alnus after Cyperaceae is most likely reflect local changes, since this tree species settled in the swamp at a late stage of its development. The dynamics of fire activity is interesting, it is most pronounced in the intervals between 4.4-3.3 cal. ka BP and than from 2.2 cal. ka BP until present. The frequency of fires is probably related not to climate, but to anthropogenic activities. In almost all cases, this coincides with the appearance of cultivated cereals pollen and with an increase in the diversity and quantity of grasses associated with humans (weeds). Thus, the obtained data for the first time give a possibility to construct a dated sequence of changes in the composition of broad-leaved forests of the belt of Caucasus piedmont and confirmed the appearance of cultivated cereals pollen about 4.3 cal. ka BP, which is probably associated with agriculture of the Maikop culture.

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Limnology and Freshwater Biology 2022 (4): 1615-1617 DOI:10.31951/2658-3518-2022-A-4-1615
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© Author(s) 2022. This work is distributed
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SI: «The 5th International Conference
Paleolimnology of Northern Eurasia»
1. Introduction
In the North Caucasus, very few Holocene natural
archives have been studied, and we can’t reconstruct
vegetation history or assess the long-term inuence of
agriculture and pastoralism on mountain ecosystems.
The Tarskoe swamp is one of the most promising
sites. It had been studied twice before 2019. The rst
study did not provide dating for the core (Neishtadt,
1955; 1957); at the second, the core did not contain
the upper sediments, they might have been removed
during peat harvesting (Knyazev et al., 1992). The new
drilling in 2019 xed these problems.
The Tarskoe swamp is one of the largest peat
bogs in the mid of North Caucasus, it occupies about 20
ha in the basin between the Lesisty and Pastbishchny
ranges (42°57’46”N, 44°43’32”E; 806 m a.s.l.). The
climate is temperate continental with warm and very
humid summer and medium cold, snowy winter. The
swamp is located to the low-mountain belt of broad-
leaved forests dominated by Fagus orientalis Lipsky
and Carpinus betulus L. with Quercus robur L., and an
admixture of Corylus avellana L., Ulmus glabra Huds.
and Pyrus caucasica Fed. Swamp vegetation is formed
by Carex sp. and Phragmites australis (Cav.) Trin. ex.
Stend with Matteuccia struthiopteris L. and Sphagnum
sp., with thickets of Alnus glutinosa L. in some places.
The swamp was drained for pasture and haymaking
in the mid-20th century. Traces of drains are still
visible. The new drilling was made between them in an
undisturbed area.
2. Materials and methods
2.1. Sediment description
A 327 cm core was collected using a Russian
corer with a 5 cm diameter, the Tarskoe core consists of
7 sections, 50 cm long each. The lithology of the core:
ABSTRACT. The reconstruction of vegetation changes of foothill zone in the central part of the North
Caucasus based on the data of the Tarskoe swamp is presented. The swamp is the largest in this region
of the Caucasus and is the most promising peat paleoarchive. It has been studied earlier, but the cores
were poorly dated. The Tarskoe was re-drilled, the sediments were dated, and pollen and microcharcoal
analysis were carried out. Twelve radiocarbon dates were obtained for the deposits, the age of the
bottom sediments was about 4.6 cal. ka BP. Based on the data obtained, it was possible to establish that
the of the bogging occurred against the background of more open landscapes, with a greater proportion
of meadows than at present. Only after 4.4 cal ka BP broad-leaved forests become more closed, in
their composition Fagus were dominant, with alternating admixture of Carpinus, Ulmus and Alnus. The
increase of Alnus after Cyperaceae is most likely reect local changes, since this tree species settled
in the swamp at a late stage of its development. The dynamics of re activity is interesting, it is most
pronounced in the intervals between 4.4-3.3 cal. ka BP and than from 2.2 cal. ka BP until present. The
frequency of res is probably related not to climate, but to anthropogenic activities. In almost all cases,
this coincides with the appearance of cultivated cereals pollen and with an increase in the diversity and
quantity of grasses associated with humans (weeds). Thus, the obtained data for the rst time give a
possibility to construct a dated sequence of changes in the composition of broad-leaved forests of the
belt of Caucasus piedmont and conrmed the appearance of cultivated cereals pollen about 4.3 cal. ka
BP, which is probably associated with agriculture of the Maikop culture.
Keywords: North Caucasus, Holocene, pollen analysis, paleoecology, microcharcoal
Yuzhanina E.D.1*, Ryabogina N.E.1, Borisov A.V.2, Idrisov I.A.3
1 Tyumen Scientic Centre of the Siberian Branch of the Russian Academy of Sciences, 86 Malygina str., Tyumen, 625026, Russia
2 Institute of Physicochemical and Biological Problems of Soil Science of the Pushchino Scientic Centre for Biological Research of the Russian
Academy of Sciences, 2 Institutskaya str., Pushchino, 142290, Russia
3 Institute of Geology of the Dagestan Scientic Centre of the Russian Academy of Sciences, 45 M. Gadzhieva str., Makhachkala, 367032, Russia
Reconstruction of vegetation and climate
of the past of the central Caucasus for
materials from the Tarskoe swamp
1615
Received: July 01, 2022; Accepted: August 13, 2022;
Available online: September 02, 2022
*Corresponding author.
E-mail address: el.yuzh@gmail.com (E.D. Yuzhanina)

Yuzhanina E.D. et al. / Limnology and Freshwater Biology 2022 (4): 1615-1617
1616
0 – 276 cm: moss-herbs peat (Sphagnum, Bryidae,
Carex, Eriophorum) with interlayer of total sphagnum
peat from 140 cm to 153 cm.
276 – 290 cm: herbaceous decomposed peat
290 – 300 cm: clay with herbaceous detritus
300 – 315 cm: total sedge decomposed peat rich
in mineral matter
315 – 327 cm: clay
2.2. Dating
The chronology is based on twelve 14C dates
(Table). No suitable terrestrial remains were found, so
the main material was bulk. We use Bchron package in
the R for the age model (Haslett and Parnell, 2008; R:
The R Project for Statistical Computing). The average
sedimentation rate is 12 years/cm.
2.3. Microcharcoal analysis
Microcharcoal analysis was made on pollen
slides for the 78 samples of 6 ml volume, each sample
containing one tablet of Lycopodium at 15853 spores.
The diagram of the concentration of microcharcoal was
made in the Tilia-Tilia Graph (Grimm, 2004) (Fig.).
3. Results
The objectives of the study determined
subsampling from the core: sediments of the Bronze Age
and of the turn of the Eras were studied in detail (each
cm); the rest of the prole was subsampled with an
interval of 10 cm. We counted ca. 500 terrestrial pollen
in each of 78 samples and identied 185 palynological
taxa. The bottom sample had an unrepresentative
amount of pollen. Only terrestrial pollen (AP + NAP)
were used for the main percentage calculations. For the
Cyperaceae, aquatics, spores of mosses or pteridophytes
percentage were calculated from the total sum. Local
pollen zones (LPZs) were singled out by cluster analysis.
The AP/NAP ratio indicates the predominance of forest
vegetation. But large proportion of NAP (up to 65%) at
the base of the sequence is more typical of semi-open
landscapes.
LPZ1 (4.6-4.4 cal. ka BP) reects the beginning
of swamping; deciduous forests alternated with
meadow there (Fig.). The predominance of Pinus pollen
(up to 27%) is associated with an openness increase
and long distance wind transport, rather than with real
participation in the local forest. The composition of the
forests was formed by Fagus, with Carpinus, Corylus,
Tilia, a small amount of Acer and Prunus, in some places
with wild Vitis. Vast open spaces are identied by the
abundance of Asterаceae, Cichоriaceae and Poaceae,
many Caryophyllаceae, Apiaceae, Scabiosa, Centaurea
jacea. Hippоphae rhamnoides L. are associated with
forest edges. Weak human impact is suggested by the
presence of Arctium and Cardus.
In LPZ2 (4.4-3.2 cal. ka BP), the decreasing Pinus
and increasing Fagus (30-52%) mark this phase as start
of reforestation. The value of Tilia falls, but Carpinus,
Alnus, Ulmus, Quercus, Betula and Fraxinus excelsior L.
rise; Prunus, Pterocarya, and Juglans are occasionally
found. A lot of open and edge forest areas are identied
by the Hippоphae and Spiraea, even Daphne indicates
lightening of the forest. Artemisia increases; Poaceae,
Chenopodioideae are constantly present; Cichоriaceae,
Rosaceae, and Apiaceae have several peaks. An increase
in pastoral pressure is suggested by Plantago lanceolata
(max), Rumex acetosa, Urtica and Cаnnabis; Cerealia
pollen appears frequently.
Starting from LPZ3 (3.2-2.6 cal. ka BP), the stage
of the minerotrophic swamp ends and Sphagnum mosses
appear, it becomes more favorable for Alnus along the
swamp periphery. The forest becomes more closed:
Fagus reaches 57%, Carpinus 15%, Ulmus, Corylus and
Vitis increase, but Quercus decreases; Picea, Prunus,
Pterocarya, Juglans, Castanea are common. The NAP
composition has the same dominants, but the diversity
decreases. The anthropogenic markers are Plantago
lanceolata, Urtica, Brassicаceae, singly Cerealia.
In LPZ4 (2.6-2.1 cal. ka BP), Fagus predominates
(37-52%), Alnus reaches 30%, especially in Sphagnum
interlayer, but Carpinus gradually decreases, dark
conifers disappear, and the diversity of broad-
leaved trees declines. The NAP composition shows
insignicant changes, only Artemisia and Thalictrum
increase. Plantago media, P. lanceolata-type, and Urtica,
Table. Dating of Tarskoe swamp.
N Deth (cm) mean Lab nr. Ki Age BP Median Probability Age BP 2 σ
1 25 19688 1320 +/- 30 653-707
2 50 19689 1920 +/- 40 1835 1730 - 1939
3 75 19690 1880 +/- 80 1795 1687 - 1993
4 100 19691 2160 +/- 70 2152 1992 - 2335
5 125 19692 2329 +/- 40 2346 2302 - 2469
6 150 19693 2340 +/- 40 2356 2305 - 2491
7 175 19694 2750 +/- 50 2844 2759 - 2954
8 200 19695 2930 +/- 40 3081 2960 - 3183
9 225 19696 2980 +/- 40 3155 3003 - 3252
10 250 19697 2730 +/- 50 2827 2753 - 2939
11 275 19698 3490 +/- 50 3761 3631 - 3896
12 300 19699 4010 +/- 80 4492 4243 - 4656

Yuzhanina E.D. et al. / Limnology and Freshwater Biology 2022 (4): 1615-1617
1617
infrequent Cerealia, Brassicаceae, Аrctium and Rumex
acetosa are associated with humans.
LPZ5 (2.1-1.8 cal. ka BP) reects the initial
gradual increase in open areas. Fagus and Carpinus
decrease, but shares of Pinus, Betula, dark coniferous,
shrubs, and lianes rise. The Poaceae and diversity of
meadow grasses increase; the Secale curve appears.
In LPZ6 (1.8 cal. ka BP – present), forest area
continues decreasing or becomes sparser. Fagus
noticeably reduces up to 15%, and then Alnus to 18%,
with a slight rise in Carpinus, Corylus, and Quеrcus.
Besides, value of distant pollen (Pinus, Picea, and
Abies) increases. Open areas increase, as demonstrated
by Poaceae (max), Cichоriaceae and Asteraceae. The
pasture indicators include Plantago lanceolata, Rumex
acetosa, and Cardus; and the agricultural ones - Cerealia
and Secale.
The maximum concentration of microcharcoal
in the section is noted in LPZ2(1500 units), the next
highest value is observed in LPZ6 a little more than
1000 units. LPZ3 and LPZ4 has a very low concentration
of microcharcoal.
4. Discussion and сonclusions
At the beginning of the formation of the swamp
about 4.6 cal. ka BP, the landscape of the foothills of
the central part of the North Caucasus was semiopen,
with a large proportion of meadows than today,
perhaps this kind of landscape was under the inuence
of previous human activity, precisely of agriculture
Maikop culture in the Bronze Age. This short-term
episode is gradually replaced by broad-leaved forests,
with a predominance of beech. Among the local
transformations the replacement of Cyperaceae to
Alnus and the appearance of Sphagnum, indicates
a change in the type of water supply of the swamp.
The greatest value of microchrcoal is most likely
associated with anthropogenic activity, and is almost
always synchronous with the appearance of cultivated
cereals pollen. The rst peak of microcharcoal (LPZ2) is
associated with an increase in diversity among a group
of human-related grasses and appearance of cultivated
cereals pollen about 4.3 cal. ka BP; the second peak
(LPZ6) realeted with the increases of quantity of weeds
and signicantly increases the proportion of cultivated
cereals pollen.
Acknowledgments
Radiocarbon dating of sediments by the Russian
Science Foundation, grant nr.19-18-00406, pollen
analysis by the Russian Foundation for Basic Research,
grant nr. 20-35-90014.
Conict of interest
The authors declare no conict of interest.
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Fig. Pollen and microcharcoal diagram of Tarskoe swamp.