ISSN 00124966, Doklady Biological Sciences, 2014, Vol. 457, pp. 248–251. © Pleiades Publishing, Ltd., 2014. Original Russian Text © K.E. Vershinin, D.Yu. Rogozin, 2014, published in Doklady Akademii Nauk, 2014, Vol. 457, No. 6, pp. 732–735.
GENERAL BIOLOGY
The 1300Year Dynamics of Vegetation Cover in the Lake Shira Depression (Khakassia, Siberia, Russia) Reconstructed on the Basis of Bottom Sediments K. E. Vershinin and D. Yu. Rogozin Presented by Academician A.G. Degermendzhi March 18, 2014 Received April 1, 2014
DOI: 10.1134/S0012496614040140
The Late Holocene bottom sediments of Lake Shira (Khakassia, Southern Siberia, Russia) have been for the first time analyzed by quantitative spore–pol len analysis in order to assess the vertical distribution of a wide range of plant species. Five pollen zones have been distinguished in the examined time span of 1300 years with the help of factor analysis. The major arboreal components of the spore–pollen spectrum (SPS) over the entire examined section are the pollen of Pinus sylvestris and Betula sect. Albae in the arboreal group and representatives of the families Astereaceae and Poaceae in the nonarboreal group. In the arboreal group, the prevalence of B. sect. Albae during the time period studied (1300 years) has been gradually replaced by the prevalence of P. sylvestris, reflecting an increas ing aridization of Siberian area in the Middle–Late Holocene. This is also confirmed by elimination of fir and spruce pollen from SPS approximately 600 years ago and almost complete disappearance of Juniperus s.l., B. sect. Nanae, and Salix pollen by the 1600s. According to the obtained chronicle, the overall vegeta tion cover surrounding the lake belongs to a boreal– steppe type, with its steppe ecotope increasing over the past 600 years. These results suggest climate aridization in the area of the Northern Minusinsk Depression dur ing the last millennium. Further studies of deeper bot tom sediment layers will allow the reconstruction of the vegetation dynamics (and, correspondingly, climate dynamics) over a more extended period. Forecasting of the changes in ecosystems caused by possible climatic changes requires the information about the corresponding changes in the past; there fore, paleoreconstructions of the specific dynamic fea Limnological Institute, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia Institute of Biophysics, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk, Russia email: [email protected]
tures in vegetation development are topical for all regions of the world, including Siberia. Analysis of the composition of various paleoindicators in the dated bottom sediment layers of lakes allows the reconstruc tion of landscape and climate changes in the adjacent area. Fossil plant pollen and spores represent one of the most important data sources on the changes in vegetation cover. Lake Shira (54°30′ N, 90°11′ E) lies in the steppe zone of the Northern Minusinsk Depression (Repub lic of Khakassia), 15 km from the village Shira. The water surface area is 35.9 km2 and the maximal depth is 24 m (2007–2012). Currently, this lake is meromic tic, with hydrogen sulfide in its monimolimnion [1]. The lake belongs to the Altai–Yenisei Floristic Prov ince [2] and is surrounded by small (oat grass) and large sod grass steppes [3]. The current climate there is semiarid with an average annual precipitation over the past 50 years of 300 mm/year (according to the data of the Shira station of the weather service of the Russian Federation), whereas the potential evapora tion amounts to approximately 600 mm/year [4]. A distinct layered structure of the Lake Shira bottom sediments makes the lake an appropriate object for paleoreconstructions [5]. In this study, the pollen and spore compositions in the upper layers of the bottom sed iments (10–100 cm), which cover the last 1300 years, have been analyzed for the first time. The core sample of bottom sediments with a length of 2.8 m was drilled in the June of 2011 in the central part of Lake Shira (54°30′025′′ N, 90°12′122′′ E) with the help of a gravity tube (diameter, 100 mm). The rate of sediment accumulation in Lake Shira was assessed by 137Cs and 210Pb datings and confirmed by counting annual layers [5]. The age of deposits housing plant fossils is estimated based on the average sedimentation rate ranging from 2 mm/year in the upper part of the core sample to 0.5 mm/year in deeper layers. Palyno morphs were distinguished using the standard tech
248
THE 1300YEAR DYNAMICS OF VEGETATION COVER
nique for processing palynological samples of lake sediments elaborated using commonly accepted methods [6, 8]. The step of assay was 5 cm. At least 450 pollen grains of tree species were counted in each horizon. The spore and pollen concentrations were calculated relative to 100% of the contained spores and pollen grains and amounted to no less than 222 000 spores/pollen grains per 1000 µL of the final sediment aliquot. We observed a good preservation of the spore–pollen specimens throughout the length of the core sample. The boundaries of the local palynozones (sh 1–5) were determined with the help of factor analysis [9], by initially extracting the factors using principal compo nent analysis and further redistribution by varimax rotation; STATISTICA 8 software package (StatSoft) was used for computations. The steppe–forest index (SFI) was used to demonstrate the interactions between boreal and steppe elements within the vegeta tion cover as indicators of the changes in atmospheric precipitation [6]. SFI was calculated as (Artemisia + Chenopodiaceae (AC)/(AC + arboreal pollen (AP)) × 100. The identified taxa in Fig. 1 follow the systematic order [2]. The major SPS components over the entire section are the pollen of P. sylvestris and B. sect. Albae in the arboreal group and the pollen of Astereaceae and Poaceae among the herbs. Taking into account that the sediments housing SPS are rather recent, applica tion of the actualism principle [10] allowed us to esti mate the changes in the vegetation composition in the Shira Lake depression over the past 1300 years. In gen eral, the vegetation cover of the area surrounding the lake is boreal–steppe with an increase in the steppe ecotope over the past 600 years. In palynozone sh 5 (100–95 cm; see Fig. 2), the pollen of B. sect. Albae is the major component. Char acteristic of this palynozone are birch and pine forests with shrubs and forbs about 1300 years ago and the lowest SFI values. Palynozone sh 4 (95–85 cm) displays a decreased proportion of birch pollen. For the period of 1300– 1100 years ago, polydominant mixed smallleaved– light and dark coniferous forests with a developed forb layer are typical. In palynozone sh 3 (85–65 cm), the birch pollen content continues to decrease and small amounts of fir and Pinus sibirica–type pollen are observed. Charac teristic of this palynozone is expansion of the areas of coniferous forests with undergrowth. For the period of 1100–800 years ago, the data suggests development of hydrophilic vegetation in the lower layers, as well as increase in the areas of bogged sites and semiaquatic vegetation. As for palynozone sh 2 (65–45 cm), the horizon of 60 cm contains the highest concentrations of spores DOKLADY BIOLOGICAL SCIENCES
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2014
249
and pollens (up to 290 000 per 1 mL of sediment). This coincides with the reduction in the area covered with forests. Characteristic of palynozone sh 1 (45–10 cm) are the highest SFI values and prevalence of steppe land scapes over the past 500 years. The SPS contains the taxa that characterize development of farming (land plowing and cattle breeding) as well as raising of fruit crops. In the group of arboreal plant species, the preva lence of B. sect. Albae pollen over the 1300year time period is gradually replaced by the prevalence of P. sylvestris (Fig. 1), thereby reflecting an increasing aridization in Siberian region during the Middle–Late Holocene [11, 12]. This is also confirmed by elimina tion of fir and spruce pollen in SPS approximately 600 year ago and almost complete disappearance of the pollen of Juniperus s.l., B. sect. Nanae, and Salix representatives by the 1600s. This is also favored by rather considerable (up to 2%) content of the larch pollen in samples of the upper horizons, as well as a gradual increase (to 28.8% in 40cm horizon) in the content of Asteraceae pollen. A considerable content of the cereal pollen in SPS (up to 7.8%) is explainable by that Phragmites australis grows in the lake. A potential evidence of the small ice period (500– 600 years ago) in the examined area is peak concentra tions of the pollen of the taxa, such as Juniperus s.l., B. sect. Nanae, and Salix (Fig. 1, palynozone sh 2), which suggests increased moistening and cooling at that time. Such changes took place in the Eastern Siberia and Central Asia [13–15]. The maximum con tents of pollen of Chenopodiaceae, Asteraceae, Eri cales, Cyperaceae, and Gramineae are also observed during this period as well as of the spores of some cryp togamic plants (club mosses and ferns). Note that palynozone sh 1 (45–10 cm) suggests the presence of landscapes close to the modern forest–steppes, dis playing the highest SFI values. As for the group of dwarf shrubs and herbs, an increase in the proportion of xerophilic components, such as Chenopodiaceae and Caryophyllaceae, in SPS, as well as synanthropic indicators, such as Can nabis, Plantago, and Urtica, is also observed for the period of 200–300 years ago. The presence of this last group suggests that the land around the lake was plowed. Solitary pollen grains of Populus, Ulmus, and Acer were observed in horizons of 20–40 cm, which were presumably brought there with the flow of the Son River, running into the lake. Despite that the pol len grains are well preserved, we believe that the untyp ical pollen is resedimented. The upper horizon of palynozone sh 1 (10 cm) contains the pollen of Hip pophae, resulting from planting of this culture in the neighborhood of Lake Shira in 1976–1980. The dynamics of total content of the spore plants falling out of SPS in 30cm horizon (approximately 300 years
Depth, cm
Age of sediments 40
60
Dwarf shrubs and herbs
Spore plants
Fig. 1. Spore–pollen diagram of Lake Shira bottom sediments.
35 0.5 0.5 5 2 1.5 5 0.3 0.3 0.3 0.2 0.5 5 0.3 0.5 0.6 0.5 0.5 0.5
25 0.3
1
0.5 2 0.3 50 8 1 0.5 1.5
sh 4 sh 5
Arboreal
% 100
Spores
Nonarboreal
sh 3
sh 2
sh 1
sa ico ae e ae ae t e a s ea ace ace ea id b nt fru an c l e e a iac iops оны a e ll d i la m a N a l l s i e a s l y a e e p e e .s A . i u o o u k u e d d з Total e h c s h s a a a a c e er he la s lu s op n op op le ab a ce ce ce tag ac ce ra ea tic gn les in po o но la pu lmucer unip usc etu alix ipp anu ary hen rica ann rtic osa aba pia lan ster ilia ype oac qua pha rya elag yco olypали composition tu e o B P U A J D B S L C P A S B S L P п H R C C E C U R F A P A ae
Shrubs
100
90
80
70
60
50
40
30
20
10
Depth, cm
1960−1955 10 1917−1902 1846−1831 20 1775−1760 1704−1690 30 1634−1620 40 1562−1550 1493−1478 50 1422−1408 1351−1337 60 1280−1266 1208−1194 70 1137−1122 1065−1051 80 993−979 922−907 90 778−764 100 707−687 0 1 2.5 4 4
pe ty ris a c st ir i v e es arix cea sib syl i Ab L Pi P. P.
Arboreal
250 VERSHININ, ROGOZIN
DOKLADY BIOLOGICAL SCIENCES
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THE 1300YEAR DYNAMICS OF VEGETATION COVER
251
This study was supported by the Russian Founda tion for Basic Research, project no. 130500429.
Concentration, spores/pollens per 1 mL 220000 240000 260000 280000 Forest
REFERENCES 20 sh 1
Depth, cm
40
sh 2 60
sh 3 80 sh 4 Steppe 100
16
20
sh 5 24 SFI
28
32
Fig. 2. Concentrations of spore–pollen material (gray line) and steppe–forest index.
ago) also suggests an increase in the degree of aridiza tion in the sampled area over the past 1300 years. Thus, our study has demonstrated the trend of cli mate aridization in the Northern Minusinsk Depres sion over the past millennium. Further studies of the deeper bottom sediment layers will make it possible to reconstruct the dynamics of vegetation (and, conse quently, of climate) over a more extended period. ACKNOWLEDGMENTS We are grateful to I.A. Kalugin and A.V. Dar’in (Sobolev Institute of Geology and Mineralogy, Sibe rian Branch, Russian Academy of Sciences) for their major contribution to selection of bottom sediments and their dating.
DOKLADY BIOLOGICAL SCIENCES
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2014
1. Rogozin, D.Y., Genova, S.V., Gulati, R.D., and Deger mendzhy, A.G., Aquat. Ecol., 2010, vol. 44, no. 3, pp. 485–496. 2. Konspekt flory Sibiri: sosudistye rasteniya (Synopsis of Siberian Flora: Vascular Plants), Baikov, K.S., Ed., Novosibirsk: Nauka, 2005. 3. Prirodnyi kompleks i bioraznoobrazie uchastka “Ozero Shira” zapovednika “Khakasskii” (The Ecosystem and Biodiversity of the Ozero Shira Station of the Kha kasskii Reserve) Nepomnyashchii, V.V., Ed., Abakan: Khakasskoe Knizhn. Izd., 2011. 4. Aivazyan, S.A., Enyukov, I.S., and Meshalkin, L.D., Prikladnaya statistika. Osnovy modelirovaniya i pervich naya obrabotka dannykh (Applied Statistics: Principles of Simulation and Primary Data Processing), Moscow: Finansy i Statistika, 1983. 5. Kalugin, I.A., Darin, A.V., Rogozin, D.Y., and Tretyakov, G.A., Quat. Int., 2013, vol. 290/291, pp. 245–252. 6. Traverse, A., Paleopalynology, Sydney: Allen and Unwin, 2011. 7. Fagri, K. and Iversen, J., Textbook of Pollen Analysis, Chichester: Wiley, 1989, 4th edition. 8. Moore, P.D., Webb, J.A., and Collinson, M., Pollen Analysis, London: Blackwell, 1991. 9. Parnachev, V.P. and Degermendzhy, A.G., Aquat. Ecol., 2002, vol. 36, no. 2, pp. 107–122. 10. Slavin, V.I. and Yasamanov, N.A., Metody paleo geograficheskikh issledovanii (Methods of Paleogeo graphic Studies), Moscow: Nedra, 1982. 11. Blyakharchu, T.A., J. Sib. Fed. Univ. I. Biol., 2009, no. 2, pp. 4–12. 12. Levi, K.G., Zadonina, N.V., and Yazev, S.A., Radiou glerodnaya khronologiya prirodnykh i sotsial’nykh fenomenov Severnogo polushariya (Radiocarbon Chro nology of Natural and Social Phenomena of the North ern Hemisphere), Irkutsk: Irkutsk. Gos. Univ., 2010, vol. 1. 13. Zadonina, N.V. and Levi, K.G., Khronologiya prirod nykh i sotsial’nykh fenomenov v Sibiri i Mongolii (Chro nology of Natural and Social Phenomena in Siberia and Mongolia), Irkutsk: Irkutsk. Gos. Univ., 2008. 14. Wang, W., Ma, Yu., Feng, Z.D., Meng, H.W., Sang, Y.L., and Zhai, X.W., Chin. Sci. Bull., 2009, vol. 54, pp. 1579–1589. 15. ChengBagn An, Yanbin Lu, Jiaju Zhao, Shichen Tao, Weinmiao Dong, Hu Li, Ming Jin, and Zongli Wang, Holocene, 2012, vol. 22, no. 1, pp. 43–52.
Translated by G. Chirikova
GENERAL BIOLOGY
The 1300Year Dynamics of Vegetation Cover in the Lake Shira Depression (Khakassia, Siberia, Russia) Reconstructed on the Basis of Bottom Sediments K. E. Vershinin and D. Yu. Rogozin Presented by Academician A.G. Degermendzhi March 18, 2014 Received April 1, 2014
DOI: 10.1134/S0012496614040140
The Late Holocene bottom sediments of Lake Shira (Khakassia, Southern Siberia, Russia) have been for the first time analyzed by quantitative spore–pol len analysis in order to assess the vertical distribution of a wide range of plant species. Five pollen zones have been distinguished in the examined time span of 1300 years with the help of factor analysis. The major arboreal components of the spore–pollen spectrum (SPS) over the entire examined section are the pollen of Pinus sylvestris and Betula sect. Albae in the arboreal group and representatives of the families Astereaceae and Poaceae in the nonarboreal group. In the arboreal group, the prevalence of B. sect. Albae during the time period studied (1300 years) has been gradually replaced by the prevalence of P. sylvestris, reflecting an increas ing aridization of Siberian area in the Middle–Late Holocene. This is also confirmed by elimination of fir and spruce pollen from SPS approximately 600 years ago and almost complete disappearance of Juniperus s.l., B. sect. Nanae, and Salix pollen by the 1600s. According to the obtained chronicle, the overall vegeta tion cover surrounding the lake belongs to a boreal– steppe type, with its steppe ecotope increasing over the past 600 years. These results suggest climate aridization in the area of the Northern Minusinsk Depression dur ing the last millennium. Further studies of deeper bot tom sediment layers will allow the reconstruction of the vegetation dynamics (and, correspondingly, climate dynamics) over a more extended period. Forecasting of the changes in ecosystems caused by possible climatic changes requires the information about the corresponding changes in the past; there fore, paleoreconstructions of the specific dynamic fea Limnological Institute, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia Institute of Biophysics, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk, Russia email: [email protected]
tures in vegetation development are topical for all regions of the world, including Siberia. Analysis of the composition of various paleoindicators in the dated bottom sediment layers of lakes allows the reconstruc tion of landscape and climate changes in the adjacent area. Fossil plant pollen and spores represent one of the most important data sources on the changes in vegetation cover. Lake Shira (54°30′ N, 90°11′ E) lies in the steppe zone of the Northern Minusinsk Depression (Repub lic of Khakassia), 15 km from the village Shira. The water surface area is 35.9 km2 and the maximal depth is 24 m (2007–2012). Currently, this lake is meromic tic, with hydrogen sulfide in its monimolimnion [1]. The lake belongs to the Altai–Yenisei Floristic Prov ince [2] and is surrounded by small (oat grass) and large sod grass steppes [3]. The current climate there is semiarid with an average annual precipitation over the past 50 years of 300 mm/year (according to the data of the Shira station of the weather service of the Russian Federation), whereas the potential evapora tion amounts to approximately 600 mm/year [4]. A distinct layered structure of the Lake Shira bottom sediments makes the lake an appropriate object for paleoreconstructions [5]. In this study, the pollen and spore compositions in the upper layers of the bottom sed iments (10–100 cm), which cover the last 1300 years, have been analyzed for the first time. The core sample of bottom sediments with a length of 2.8 m was drilled in the June of 2011 in the central part of Lake Shira (54°30′025′′ N, 90°12′122′′ E) with the help of a gravity tube (diameter, 100 mm). The rate of sediment accumulation in Lake Shira was assessed by 137Cs and 210Pb datings and confirmed by counting annual layers [5]. The age of deposits housing plant fossils is estimated based on the average sedimentation rate ranging from 2 mm/year in the upper part of the core sample to 0.5 mm/year in deeper layers. Palyno morphs were distinguished using the standard tech
248
THE 1300YEAR DYNAMICS OF VEGETATION COVER
nique for processing palynological samples of lake sediments elaborated using commonly accepted methods [6, 8]. The step of assay was 5 cm. At least 450 pollen grains of tree species were counted in each horizon. The spore and pollen concentrations were calculated relative to 100% of the contained spores and pollen grains and amounted to no less than 222 000 spores/pollen grains per 1000 µL of the final sediment aliquot. We observed a good preservation of the spore–pollen specimens throughout the length of the core sample. The boundaries of the local palynozones (sh 1–5) were determined with the help of factor analysis [9], by initially extracting the factors using principal compo nent analysis and further redistribution by varimax rotation; STATISTICA 8 software package (StatSoft) was used for computations. The steppe–forest index (SFI) was used to demonstrate the interactions between boreal and steppe elements within the vegeta tion cover as indicators of the changes in atmospheric precipitation [6]. SFI was calculated as (Artemisia + Chenopodiaceae (AC)/(AC + arboreal pollen (AP)) × 100. The identified taxa in Fig. 1 follow the systematic order [2]. The major SPS components over the entire section are the pollen of P. sylvestris and B. sect. Albae in the arboreal group and the pollen of Astereaceae and Poaceae among the herbs. Taking into account that the sediments housing SPS are rather recent, applica tion of the actualism principle [10] allowed us to esti mate the changes in the vegetation composition in the Shira Lake depression over the past 1300 years. In gen eral, the vegetation cover of the area surrounding the lake is boreal–steppe with an increase in the steppe ecotope over the past 600 years. In palynozone sh 5 (100–95 cm; see Fig. 2), the pollen of B. sect. Albae is the major component. Char acteristic of this palynozone are birch and pine forests with shrubs and forbs about 1300 years ago and the lowest SFI values. Palynozone sh 4 (95–85 cm) displays a decreased proportion of birch pollen. For the period of 1300– 1100 years ago, polydominant mixed smallleaved– light and dark coniferous forests with a developed forb layer are typical. In palynozone sh 3 (85–65 cm), the birch pollen content continues to decrease and small amounts of fir and Pinus sibirica–type pollen are observed. Charac teristic of this palynozone is expansion of the areas of coniferous forests with undergrowth. For the period of 1100–800 years ago, the data suggests development of hydrophilic vegetation in the lower layers, as well as increase in the areas of bogged sites and semiaquatic vegetation. As for palynozone sh 2 (65–45 cm), the horizon of 60 cm contains the highest concentrations of spores DOKLADY BIOLOGICAL SCIENCES
Vol. 457
2014
249
and pollens (up to 290 000 per 1 mL of sediment). This coincides with the reduction in the area covered with forests. Characteristic of palynozone sh 1 (45–10 cm) are the highest SFI values and prevalence of steppe land scapes over the past 500 years. The SPS contains the taxa that characterize development of farming (land plowing and cattle breeding) as well as raising of fruit crops. In the group of arboreal plant species, the preva lence of B. sect. Albae pollen over the 1300year time period is gradually replaced by the prevalence of P. sylvestris (Fig. 1), thereby reflecting an increasing aridization in Siberian region during the Middle–Late Holocene [11, 12]. This is also confirmed by elimina tion of fir and spruce pollen in SPS approximately 600 year ago and almost complete disappearance of the pollen of Juniperus s.l., B. sect. Nanae, and Salix representatives by the 1600s. This is also favored by rather considerable (up to 2%) content of the larch pollen in samples of the upper horizons, as well as a gradual increase (to 28.8% in 40cm horizon) in the content of Asteraceae pollen. A considerable content of the cereal pollen in SPS (up to 7.8%) is explainable by that Phragmites australis grows in the lake. A potential evidence of the small ice period (500– 600 years ago) in the examined area is peak concentra tions of the pollen of the taxa, such as Juniperus s.l., B. sect. Nanae, and Salix (Fig. 1, palynozone sh 2), which suggests increased moistening and cooling at that time. Such changes took place in the Eastern Siberia and Central Asia [13–15]. The maximum con tents of pollen of Chenopodiaceae, Asteraceae, Eri cales, Cyperaceae, and Gramineae are also observed during this period as well as of the spores of some cryp togamic plants (club mosses and ferns). Note that palynozone sh 1 (45–10 cm) suggests the presence of landscapes close to the modern forest–steppes, dis playing the highest SFI values. As for the group of dwarf shrubs and herbs, an increase in the proportion of xerophilic components, such as Chenopodiaceae and Caryophyllaceae, in SPS, as well as synanthropic indicators, such as Can nabis, Plantago, and Urtica, is also observed for the period of 200–300 years ago. The presence of this last group suggests that the land around the lake was plowed. Solitary pollen grains of Populus, Ulmus, and Acer were observed in horizons of 20–40 cm, which were presumably brought there with the flow of the Son River, running into the lake. Despite that the pol len grains are well preserved, we believe that the untyp ical pollen is resedimented. The upper horizon of palynozone sh 1 (10 cm) contains the pollen of Hip pophae, resulting from planting of this culture in the neighborhood of Lake Shira in 1976–1980. The dynamics of total content of the spore plants falling out of SPS in 30cm horizon (approximately 300 years
Depth, cm
Age of sediments 40
60
Dwarf shrubs and herbs
Spore plants
Fig. 1. Spore–pollen diagram of Lake Shira bottom sediments.
35 0.5 0.5 5 2 1.5 5 0.3 0.3 0.3 0.2 0.5 5 0.3 0.5 0.6 0.5 0.5 0.5
25 0.3
1
0.5 2 0.3 50 8 1 0.5 1.5
sh 4 sh 5
Arboreal
% 100
Spores
Nonarboreal
sh 3
sh 2
sh 1
sa ico ae e ae ae t e a s ea ace ace ea id b nt fru an c l e e a iac iops оны a e ll d i la m a N a l l s i e a s l y a e e p e e .s A . i u o o u k u e d d з Total e h c s h s a a a a c e er he la s lu s op n op op le ab a ce ce ce tag ac ce ra ea tic gn les in po o но la pu lmucer unip usc etu alix ipp anu ary hen rica ann rtic osa aba pia lan ster ilia ype oac qua pha rya elag yco olypали composition tu e o B P U A J D B S L C P A S B S L P п H R C C E C U R F A P A ae
Shrubs
100
90
80
70
60
50
40
30
20
10
Depth, cm
1960−1955 10 1917−1902 1846−1831 20 1775−1760 1704−1690 30 1634−1620 40 1562−1550 1493−1478 50 1422−1408 1351−1337 60 1280−1266 1208−1194 70 1137−1122 1065−1051 80 993−979 922−907 90 778−764 100 707−687 0 1 2.5 4 4
pe ty ris a c st ir i v e es arix cea sib syl i Ab L Pi P. P.
Arboreal
250 VERSHININ, ROGOZIN
DOKLADY BIOLOGICAL SCIENCES
Vol. 457
2014
THE 1300YEAR DYNAMICS OF VEGETATION COVER
251
This study was supported by the Russian Founda tion for Basic Research, project no. 130500429.
Concentration, spores/pollens per 1 mL 220000 240000 260000 280000 Forest
REFERENCES 20 sh 1
Depth, cm
40
sh 2 60
sh 3 80 sh 4 Steppe 100
16
20
sh 5 24 SFI
28
32
Fig. 2. Concentrations of spore–pollen material (gray line) and steppe–forest index.
ago) also suggests an increase in the degree of aridiza tion in the sampled area over the past 1300 years. Thus, our study has demonstrated the trend of cli mate aridization in the Northern Minusinsk Depres sion over the past millennium. Further studies of the deeper bottom sediment layers will make it possible to reconstruct the dynamics of vegetation (and, conse quently, of climate) over a more extended period. ACKNOWLEDGMENTS We are grateful to I.A. Kalugin and A.V. Dar’in (Sobolev Institute of Geology and Mineralogy, Sibe rian Branch, Russian Academy of Sciences) for their major contribution to selection of bottom sediments and their dating.
DOKLADY BIOLOGICAL SCIENCES
Vol. 457
2014
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Translated by G. Chirikova
