Journal of Paleolimnology 30: 415–426, 2003. # 2003 Kluwer Academic Publishers. Printed in the Netherlands.
415
Mid-Holocene palaeoclimatic and palaeohydrological conditions in northeastern European Russia: a multi-proxy study of Lake Vankavad Kaarina Sarmaja-Korjonen1,*, Seija Kultti1, Nadia Solovieva2 and Minna V€ aliranta1 1
Department of Geology, P.O. Box 64, FIN-00014 University of Helsinki, Helsinki, Finland; 2ECRC, University College London, Department of Geography, 26 Bedford Way, London WC1H OAP, UK; *Author for correspondence (e-mail:
[email protected])
Received 16 November 2002; accepted in revised form 19 April 2003
Key words: Diatoms, Holocene, Northern European Russia, Palaeoclimatology, Palaeohydrology, Plant macrofossils, Pollen, Subfossil Cladocera
Abstract Mid-Holocene changes in vegetation, palaeohydrology and climate were investigated from the sediments of Lake Vankavad in the northern taiga of the Usa Basin, NE European Russia, through the analysis of pollen, plant macrofossils, Cladocera and diatoms. Lake Vankavad was probably formed at ca. 5000 BP (ca. 5600 cal. BP) and initially it was shallow with a littoral cladoceran fauna. Macrofossil and pollen results suggest that dense Betula-Picea forests grew in the vicinity and the shore was close to the sampling point. At ca. 4600 BP (ca. 5400 cal. BP) the water level rose coincident with the decrease in the density and area of forests, probably caused by cooling climate and accelerated spread of mires. There was also a further rise in the water level at ca. 3500 BP (ca. 3800 cal. BP). The initiation of the lake, followed by two periods of rising waterlevel, as well as the increase in mire formation, was a consequence of a rise in groundwater level. This probably reflects lower evapotranspiration in a cooling mid-Holocene climate and/or higher precipitation in the lowland area. Also the decreased forest density and area may have contributed to the lower evapotranspiration. It is also possible that permafrost aggradation or changes in peat ecosystems might have affected the hydrological conditions in the area.
Introduction Our knowledge about Holocene climate, vegetation and hydrological changes in northeastern European Russia has increased during the last decade as new studies have been carried out. These have mainly concentrated on treeline ecotones which respond sensitively to environmental changes (Serebryanny et al. 1998; Kremenetski et al. 1999; Kaakinen and Eronen 2000; MacDonald et al. 2000; Paus 2000; Oksanen et al. 2001). This paper is a contribution to a larger multidisciplinary research project (TUNDRA) which assesses feedback processes from the Arctic region to the global climate system. The project focuses on
the Usa River Basin area (the main tributary of Pechora River) in northeastern European Russia (Figure 1). The vegetation zones vary from taiga in the southernmost part of the Usa Basin to foresttundra and tundra in the north. Mountain alpine taiga, tundra and barren ground prevail in the Ural Mountains to the east. The arctic tree line runs in a largely eastwest direction over a zone of discontinuous permafrost (Virtanen et al. 2002). The alpine tree line runs on the slopes of the Ural Mountains. In the southern part of the Usa Basin the altitude of the alpine tree line is ca. 600 m a.s.l. while in the northern part the arctic and alpine tree lines converge.
416 Inta, a local coal mining town. The lake lies ca. 10 km north from Kos’yu River, 50 m a.s.l. (Figure 2). The region is lowland and mires are abundant covering about half of the landscape. At present the forests are Norway spruce (Picea abies s.l.) dominated, often mixed with some birch (Betula pubescens) and grey alder (Alnus incana). Scots pine (Pinus sylvestris) only grows sporadically around the mires. Forest only occurs on the northern side of the lake, and the area is almost free from permafrost with only isolated patches (3–10%) (Oberman and Borozinetsh 1988).
Materials and methods
Figure 1. Location of Lake Vankavad, southeastern Usa Basin, northeastern European Russia.
We present results from Lake Vankavad which was chosen to represent the lowland taiga in the southeastern part of the Usa Basin, ca. 50 km northwest of the Ural Mountains. No previous palaeoenvironmental studies have been carried out in this lowland region. Lake Vankavad was studied for pollen, plant macrofossils, Cladocera and diatoms to investigate changes in vegetation, palaeohydrology and climate.
Site Lake Vankavad (65 590 0800 N, 59 270 2300 E, 56 m. a.s.l.) is located at the northernmost taiga in NE European Russia (Figure 1), ca. 40 km west from
The fieldwork was carried out in spring 1998. The cores were collected from ice with a Russian peat corer. The cores were taken from the middle of the lake where the water depth was 5.6 m. The cores were packed in plastic and stored in a cold room. Loss-on-ignition analysis was carried out at 10 cm intervals to define the organic content in the sediment. Volumetric 5 cm3 samples of fresh sediment were ignited in 550 C for 4 h (cf. Heiri et al. 2001). The stratigraphy is: 220–200 cm silty/ sandy gyttja, 200–60 cm gyttja, 60–0 cm silty/sandy gyttja. The corer could not penetrate the sediment below a depth of 220 cm. Three conventional radiocarbon dates (Table 1) and two AMS dates were determined in the Dating Laboratory of the University of Helsinki. The AMS dates were determined from macrofossils (Picea needles, Betula catkin scales/seeds, Salix buds) found in vertically 10 cm thick samples (Table 1). The dates were corrected for isotope fractionation by normalisation on 13C ¼ 25ø and expressed with one standard deviation confidence intervals. The dates were calibrated using the Calib4.1-program (Stuiver and Reimer 1993). In the text the calibrated dates are denoted with ‘cal. BP’ and uncalibrated ages with ‘BP’. The cores were sampled at 10 cm intervals for microfossil analyses, except the topmost 6 cm for diatom analysis (see below). Preparation of pollen samples followed standard methods (Fægri and Iversen 1989). A known amount of exotic palynomorphs (Lycopodium) were added to 0.5 cm2 subsamples for concentration estimates (Stockmarr 1971). The samples were treated with KOH and
417
Figure 2. Location and the main vegetation types around Lake Vankavad, southeastern Usa Basin, northeastern European Russia. Vegetation classes are based on more detailed satellite image based vegetation and landuse classification of the Usa basin, produced by Tarmo Virtanen, Kari Mikkola and Ari Nikula, Finnish Forest Research Institute. Streams are indicated by continuous line.
Table 1. Conventional (Hel-) and AMS (Hela-) radiocarbon dates from Lake Vankavad and Lake Kharbei, northeastern European Russia. Lab. No. Lake Vankavad Hel-4329 Hel-4330 Hel-4162 Hela-610 Hela-609 Lake Kharbei Hela-428
Sample depth
Dated material
13C
14
14
110–125 cm 160–180 cm 200–210 cm 170–180 cm 210–220 cm
Bulk sediment Bulk sediment Bulk sediment Macrofossils Macrofossils
28.9 29.3 30.1 28.4 27.7
3370 ± 100 4680 ± 110 4780 ± 110 4640 ± 85 4935 ± 75
3620 5380 5510 5430 5650
215–217 cm
Wood
27.4
5085 ± 75
5790
acetolysis, mounted in glycerol and stained with safranine. A minimum of 500 terrestrial pollen grains was counted. The total sum of terrestrial pollen was used as the basal sum for percentage calculations. The pollen percentages for the spores and the aquatics were calculated from the basal sum plus the sum of the spores or the sum of aquatic pollen. Pollen accumulation rates were calculated using calibrated 14C dates.
C Age BP
C Age cal. BP
After the subsamples for loss-on-ignition, pollen, Cladocera and diatom analyses were taken, the core was cut into 10 cm sections and from each section 30 cm3 of sediment was taken for macrofossil analysis. The volume of sediment was measured by displacement of water in a glass beaker. The sections 0–10 cm, 120–130 cm and 170–180 cm could not be analysed. The sections 120–130 cm and 170–180 cm were used for dating. The
418 sediment was soaked overnight, or longer if needed, in sodiumpyrophosphate (Na4P2O7 H2O) solution. The sediment was then sieved through a 125 m mesh and the material left on the sieve was analysed using both a stereomicroscope and a compound microscope. Volumetric subsamples (2 cm3) for cladoceran analysis were heated in 10% KOH for 30 minutes using a magnetic stirrer and sieved through a 100 m mesh. The samples were mounted with glycerol jelly stained with safranine. About 250–300 cladoceran remains were counted from each sample, when possible. Since there were large variations between the quantities of planktonic and littoral Cladocera, representing different habitats, the percentages for littoral forms were calculated of the basic sum of total littoral Cladocera. Thus a more reliable general picture of their succession within the littoral zone was obtained. The shares for planktonic forms were calculated of the basic sum of total Cladocera remains. The nomenclature follows Flo¨ssner (1972). Eurycercus head pores were round (different from head pores of E. lamellatus). It is possible that it is Eurycercus glacialis (Frey 1973) but until the identification is sure the taxon is called Eurycercus sp. At least two types of Chydorus carapaces and headshields could be distinguished (not calculated separately) and are called here Chydorus sphaericus s. l. Numerous unidentified medium-size Alona type carapaces and headshields were found (Alona sp.). Diatoms were analysed at 10 cm intervals, except the topmost 6 cm, which was studied with a highresolution analysis [every 0.5 cm (0–4.5 cm) and 1 cm (5–6 cm)]. Diatom slide preparation followed standard methods (Battarbee 1986) using the water-bath method (Renberg 1990). Slides were mounted using Naphrax1 medium. Diatom concentration was determined using microsphere markers (Battarbee and Kneen 1982). Between 300 and 400 valves were counted at most levels. Diatom nomenclature follows Krammer and LangeBertalot (1986, 1988, 1991a, b)) and AL : PE guidelines (Cameron et al. 1999). Total diatom concentration was calculated using program TILIA. pH was reconstructed using the AL : PE model (Cameron et al. 1999). Epilimnetic total phosphorus concentration [TP] was reconstructed using the CALIBRATE 0.85 software of Juggins and ter Braak (1997–1999, unpublished software)
Figure 3. Loss-on-ignition and sedimentation rates from Lake Vankavad, northeastern European Russia.
and a 61-lake training set collected from Southern Finland (Kauppila et al. 2002). Diatom species richness at a constant sample count was estimated by rarefaction using programme RAREPOLL version 1.0 (Birks and Line, unpubl. programme) with a base count of 300 (Birks and Line 1992). Results The loss-on-ignition (Figure 3) was low (below 20%) in the lowermost sample but rose sharply towards 205 cm (80%). The organic content remained high in the lowermost core up to ca. 120 cm where it declined to below 20% in the topmost 60 cm. The sedimentation rate (Figure 3) was rather high (ca. 1.8 mm yr1) between 220 and 180 cm and subsequently decreased to ca. 0.3 mm yr1. The pollen percentage abundances (Figure 4) were relatively stable during the history of the lake. Betula dominated and Picea and Pinus were
419
Figure 4. Relative pollen diagram from Lake Vankavad, northeastern European Russia. Sediment symbols are shown in Figure 3.
abundant. Pinus started to increase from the VanP1/VanP2 zone boundary towards 90 cm (ca. 2600 BP, ca. 2800 cal. BP). Alnus was present at low proportions. Abies and Larix were found sporadically throughout the core. Cyperaceae was most abundant at 220–210 and above that steadily present. The pollen record also showed a rich herb pollen flora with e.g., Artemisia, Apiaceae, Filipendula, Ranunculaceae, Chenopodiaceae, Rumex and Thalictrum. Polypodiaceae had high proportions in the lowermost samples. Also Equisetum, Menyanthes and Nuphar characterized the core below 165 cm. After sporadic finds in the lowermost core, Sphagnum reappeared at 80 cm and increased towards 35 cm. Total pollen accumulation rate (Figure 5) is high at 220–180 cm (ca. 20 000 grains cm2 yr1) and subsequently stays relatively steady (ca. 5000 grains cm2 yr1). The plant macrofossil results (Figure 6) showed abundant tree and non-arboreal plant remains in the lowermost 40 cm (VanM1, 220–180 cm). Tree Betula seeds and catkin scales were the most common tree remains. Picea needles and conifer bark and other tissues were also relatively abundant, although sporadic finds were made throughout the core. Carex and Menyanthes trifoliata seeds were the dominant non-arboreal remains. Poaceae, Potentilla palustris and Cicuta virosa also occurred. Equisetum tissues were common
Figure 5. Pollen accumulation rates for the main tree species and the total pollen accumulation rates from Lake Vankavad, northeastern European Russia. Sediment symbols are shown in Figure 3.
and Nuphar tissues were found in two samples. A clear change occurred at the VanM1/VanM2 zone boundary (ca. 4600 BP, ca. 5400 cal. BP), with most species disappearing or becoming rare. 180–140 cm
420
Figure 6. Plant macrofossils from Lake Vankavad, northeastern European Russia. The results are expressed as absolute abundance of plant remains or relative abundance in 30 cm3 of sediment. Andromeda polifolia s.=A. polifolia seed, V. vitis-idaea=Vaccinium vitis-idaea. Sediment symbols are shown in Figure 3.
was characterized by finds of Ericales, e.g., Andromeda polifolia and Vaccinium spp. The lowermost part of the cladoceran stratigraphy (VanC1, 210–180 cm) (Figure 7) was characterized by low proportions of planktonic taxa and a rich and diverse chydorid fauna. Chydorus sphaericus s.l., Alona affinis, Camptocercus fennicus, Acroperus harpae, Alonella excisa and Alona sp. were the dominants. Also e.g., Alona affinis dentata, Pleuroxus laevis, Pleuroxus trigonellus and Kurzia latissima occurred. Daphnia and Bosmina (Eubosmina) were rare in the lowermost samples but increased in zone VanC2 (180–125 cm). Chaoborus mandibles were found in this zone. At the beginning of zone VanC3 (125–2.5 cm) (125 cm; ca. 3500 BP, ca. 3900 cal. BP) a dramatic change took place. Daphnia almost disappeared and Bosmina (Eubosmina) suddenly increased from ca. 5% to ca. 90%. The latter was found at the same high proportions for the rest of the sequence. Therefore the proportion of chydorids of the counted remains was small and the results probably did not show a complete picture of the
chydorid fauna but sporadic findings. However, the chydorid composition was different from the lower core. Chydorus sphaericus s.l. and Alona affinis still were the dominants but Eurycercus sp. and Alona quadrangularis were also abundant. At 130 cm Camptocercus rectirostris replaced Camptocercus fennicus. A total number of 141 diatom taxa were identified in the core. In zone VanD1 (200–140 cm) (Figure 8) small benthic Fragilaria taxa (mainly Fragilaria construens v. venter and F. brevistriata) together with Tabellaria flocculosa were dominant. Both the reconstructed pH and TP slightly increased towards 140 cm (ca. 3900 BP, ca. 4400 cal. BP). The total diatom concentration was very low within zones VanD1 and VanD2 (140– 100 cm). The abundance of Aulacoseira lirata v. lirata, A. perglabra and A. lirata v. alpegina increased at the end of zone VanD1. Tabellaria flocculosa almost totally disappeared at VanD1/ VanD2 transition. The total diatom concentration started to increase. Zone VanD3 (100–4 cm) was dominated by Fragilaria brevistriata v. brevistriata,
421
Figure 7. Cladoceran diagram from Lake Vankavad, northeastern European Russia. Since there were large variations between the quantities of planktonic and littoral Cladocera, representing different habitats, the percentages for littoral forms were calculated of the basic sum of total littoral Cladocera. Thus a more reliable general picture of their succession within the littoral zone was obtained. The shares for planktonic forms were calculated of the basic sum of total Cladocera remains. Anchistropus emarg. ¼ A. emarginatus. Chaoborus curve shows the percentage abundance of Chaoborus mandibles calculated from the sum of total Cladocera remains. Sediment symbols are shown in Figure 3.
Figure 8. Percentage abundances of selected diatom taxa, diatom-inferred TP (Total Phosphorus) and pH from Lake Vankavad, northeastern European Russia. Only diatom taxa occurring at abundance >3% were included. Sediment symbols are shown in Figure 3.
F. construens v. venter and F. pinnata v. pinnata. Aulacoseira spp. stayed relatively abundant. The planktonic taxon Asterionella formosa appeared within zone VanD4 (4–0 cm). Aulacoseira lirata v. lirata and A. perlabra totally disappeared and Tabellaria flocculosa increased within this zone.
Discussion Vegetation development According to the radiocarbon dates the lake was probably initiated at ca. 5000 BP (ca. 5600 cal. BP).
422 The pollen evidence (Figure 4) shows that the forest composition has been approximately the same as today since the lake was formed (Betula-Picea forests with some Pinus on mires, Alnus and possibly Larix sporadically). Tree immigration and succession took place earlier in the Holocene (Kultti et al. 2003) and therefore are not visible in the Vankavad stratigraphy. The presence of macrofossils of the rich fen herbs Menyanthes, Potentilla palustris, Cicuta virosa, Stellaria borealis, together with Poaceae (Figure 6), suggests a nutrient-rich moist shore meadow during the initial stage of the lake. The very high proportions of Polypodiaceae spores in the lowermost pollen samples (Figure 4) indicate that ferns were also abundant near the sampling point but did not preserve as macrofossil remains in Vankavad. Betula seeds and catkin scales, as well as Picea needles were concentrated in the lowermost 40 cm (Figure 6), which coincides with the highest accumulation rates of Picea and Betula pollen (Figure 5). It suggests a period of high forest density near the initial pond/wetland. The subsequent rapid decrease in Picea and Betula macrofossils and pollen therefore may derive from a decline in forest density and perhaps also forest area ca. 4600 BP (ca. 5400 cal. BP). An approximately contemporaneous withdrawal of the mixed forest has been suggested from the arctic treeline at Ortino, ca. 350 km northwest (V€ aliranta et al. 2003) and the alpine treeline at Lake Mezhgornoe, 80 km south (Kultti et al. 2003). Although the accumulation rates of Betula and Picea fall, their percentage abundances stay the same (Figure 4), which suggests that the forest composition itself had not changed. Since Pinus presently grows only around mires, the increase in Pinus pollen towards 90 cm, together with reappearance of Sphagnum (Figure 4), may be due to an increasing area of Sphagnumcovered mires near the lake. Another explanation could be that the proportion of long-distance transported Pinus pollen rose because of more open forests or a decline in the pollen production of other trees as a result of cooling climate (see below). However, there is no clear change in the pollen accumulation rates of Picea and Betula, while only Pinus (Figure 5) slightly rises, which is in agreement with the increase in mires. The plant macrofossil
evidence does not show any major changes during the late Holocene. Palaeohydrological implications The fact that most of the plant macrofossil remains are concentrated in the lowermost 40 cm (Figure 6) suggests that their source was nearby. The high sedimentation rate at 180–220 cm (Figure 3) also indicates littoral conditions. Thus, the shore appears to have been very close to the sampling point in the beginning of the lake history. Also the cladoceran results (Figure 7) suggest that in the beginning the basin was very shallow with a rich littoral chydorid fauna, with only a very small portion of planktonic Cladocera (cf. Alhonen (1970); Sarmaja-Korjonen and Alhonen (1999); Sarmaja-Korjonen (2001)). The shape of the lake (Figure 2) and its location ca. 10 km from Kos’yu River suggest that originally it may have been an ox-bow lake. However, no geomorphological evidence of palaeochannels has been found from the area (Margriet Huisink, pers. comm.). Neither do the palaeoecological results from the lowermost sample show any evidence pointing to river sediments. If there are such sediments, they are located beneath the lowermost silt and could not be penetrated with the Russian corer. Even if the origin of the basin cannot be ascertained, the fact remains that ca. 5000 BP (ca. 5600 cal. BP) a very shallow pond or lake was formed and at this time the coring point was near the shore and the sedimentation rates were high. The water level rose ca. 4600 BP (ca. 5400 cal. BP) as shown by increasing proportions of planktonic Daphnia and Bosmina (Eubosmina) (Figure 7). The area of the lake increased until the coring point was so far from the shore that fewer plant macrofossils were deposited. The remains of shore meadow plants disappeared and the subsequent appearance of Ericales (e.g. Andromeda and Vaccinium) at 180 cm (Figure 6) indicates a different kind of biotope. There is a slight increase in the diatom-inferred pH and TP (Figure 8) in the lowermost core towards 140 cm, probably reflecting a slight rise in the trophic state. At 140 cm there is a change in the diatom flora. The increase in meroplanktonic Aulacoseira spp. probably also reflects the increase in water level. The rising water-level is also shown
423 by the increasing proportions of planktonic Cladocera Daphnia and Bosmina (Eubosmina) (Figure 7). At 125 cm (ca. 3500 BP, ca. 3900 cal. BP) planktonic Bosmina (Eubosmina) dramatically increased (Figure 7). This suggests a considerable further rise in the water level but it is possible that the subfossil Cladocera record also reflects changes in the predator–prey relationships. The mandibles of Chaoborus, a midge larva preying on planktonic Cladocera, disappear, and there is a sharp decrease in Daphnia, commonly eaten by fish. This suggests that fish predation may have increased and invertebrate predation decreased. The opposite reaction was observed in a small Finnish lake (SarmajaKorjonen 2002) where Chaoborus and Daphnia increased following a fish kill caused by a decline in pH. This resulted in an abrupt increase in invertebrate predators, including Chaoborus. However, the increase of large Eurycercus spp., a common prey for fish, above 100 cm (Figure 7) does not support the increased fish predation, at least in the littoral area. It is also possible that the prominent increase in Bosmina (Eubosmina) is a result not only from a rise in water level but also from the excellent preservation of Bosmina remains. Other planktonic Cladocera leave only a few body parts or none at all. For example, only postabdominal claws and ephippia are preserved in Daphnia. Therefore, it is possible that prior to the dramatic rise in Bosmina (Eubosmina) other planktonic Cladocera taxa dominated but their remains were not preserved. A change then took place, possibly in predator assemblages (e.g. increase in fish predation), and Bosmina (Eubosmina) was able to become dominant and because of the good preservation of its remains the increase appears to be very dramatic. The rise in water level is also suggested by the prominent decrease of LOI (Figure 3) as the shore, where more organic debris accumulated, was even further away. The diatom-inferred total phosphorus (TP) (Kauppila et al. 2002) stayed relatively stable (Figure 8), ca. 20 g l1, after the initial slight rise, suggesting mesothrophic conditions. At 60 cm LOI (Figure 3) further decreased so low that the increase of minerogenic matter is visually seen in the sediment. Here also the diatom concentration rose, suggesting that erosion increased in the
catchment and this resulted in accelerated leaching and an input of nutrients, also seen as a slight rise in TP. The considerable change of the diatom flora at 4 cm (Figure 8) may be a reflection of either recent climatic changes and/or anthropogenic impact. These changes did not lead to a rise in the trophic state as the diatom-inferred TP decreases. There is no response in the cladoceran record in the topmost 4 cm, probably because no high-resolution cladoceran analysis was made from the topmost sediment.
Climatic implications There are no inlets or outlets in Vankavad (Figure 2) and probably the ground water has sensitively controlled the water level during the lake history. It is probable that the initiation of the lake reflects reduced evapotranspiration or/and increasing precipitation from ca. 5000 BP (ca. 5600 cal. BP) onwards in the lowland area of the Usa Basin. There is evidence of a rising water level also from Kharbei Lake, in northeastern Usa Basin (Figure 1). A piece of tree found from the lowermost sediment was dated to 5085 BP (5790 cal. BP) (Table 1) (S. Kultti, unpublished data). Apparently the original Kharbei Lake was smaller prior to 5000 BP (ca. 5600 cal. BP) and expanded due to a rising water level. Kultti et al. (2003) found evidence of a warm and moist early Holocene from Lake Mezhgornoe on the western slopes of the Ural Mountains, ca. 80 km south from Vankavad. There is increasing evidence of the warm early Holocene also from other parts of northern Russia (Serebryanny et al. 1998; Kremenetski et al. 1999; MacDonald et al. 2000; Paus 2000; Porinchu and Cwynar 2002; V€aliranta et al. 2003). According to Tarasov et al. (1999) at 6000 BP (ca. 6800 cal. BP) dryer conditions than presently occurred in the Usa Basin area. A middle Holocene dry period has also been detected in northern Fennoscandia where the driest conditions prevailed around 6000 BP (ca. 6800 cal. BP) (Hyv€arinen and Alhonen 1994; Barnekow 1999, 2000; Eronen et al. 1999; Sarmaja-Korjonen and Hyv€arinen 1999; Korhola et al. 2000; Sepp€a and Birks 2001; Sepp€ a et al. 2002).
424 The rising water level in Vankavad and Kharbei in the middle Holocene occurs at the onset of cooling climate and possibly marks the end of the dry Mid-Holocene period. Also the decrease in forest density ca. 4600 BP (ca. 5400 cal. BP), inferred from Vankavad, coincides with the mid-Holocene cooling of climate found at many sites in Russia (Kremenetski et al. 1999; MacDonald et al. 2000; Snyder et al. 2000; Oksanen et al. 2001; Solovieva and Jones 2002; Kultti et al. 2003; V€ aliranta et al. 2003). The further rise of lake level, shown by Cladocera data, ca. 3500 BP (ca. 3800 cal. BP) approximately coincides with a rise in Bosmina (Eubosmina) in Mezhgornoe Lake (Kultti et al. 2003). Apparently there was a further cooling of climate ca. 3000 BP in northern European Russia which resulted in rising water levels. The same cooling has been detected in the initiation of permafrost aggradation in the Rogovaya River peat plateau (Oksanen et al. 2001) and in the change of vegetation towards tundra in the Pechora lowland (Kaakinen and Eronen 2000). There was also a further decrease of vegetation towards treeless tundra-like conditions ca. 3000 BP at Tumbulovaty Lake, at the arctic treeline in the Nenets Region, ca 90 km north of Vankavad (S. Kultti et al. unpublished data).
Conclusions We propose that the following development probably took place at Vankavad. The lake was initiated at ca. 5000 BP and the first, low-water phase was short in duration, with the lowermost 40 cm of sediment deposited in only a few hundreds of years. The initiation of the pond resulted from the beginning of the mid-Holocene climate cooling which decreased evapotranspiration. The cooling climate also decreased the density and area of the Picea-Betula forests at approximately 4600 BP (ca. 5400 cal. BP) and the water level in Vankavad rose higher at this time. The decline of forest density and area decreased the evapotranspiration even further. The topography of the lowland where Vankavad is located is noticeably flat and presently mixed Picea-Betula forests are found only on highest ground that is not covered by peat. The decrease in evapotranspiration resulted in a rise of ground-
water level that also accelerated the spread of peat bogs which again further decreased the forest area. Apparently the lake level also rose at ca. 3500 BP (ca. 3800 cal. BP) and this probably resulted from a further cooling and decreased evapotranspiration/ increased precipitation. Permafrost aggradation or changes in peat ecosystems might also have affected the hydrological conditions in the area. Acknowledgements We would like to express our sincere thanks to the following persons. Matti Eronen and Philippa Noon for participating in the field work, Anu Eskelinen for laboratory work, Tarmo Virtanen for the present vegetation classification and maps, Hilary Birks for helping MV with macrofossils, Tommi Kauppila for TP calculations and Peter Kuhry for helpful comments. Vivienne Jones kindly improved the English. We also want to thank Hilary Birks and an anonymous reviewer for valuable comments which improved the text. References Alhonen P. 1970. On the significance of the planktonic/littoral ratio in the cladoceran stratigraphy of lake sediments. Soc. Sci. Fenn., Comm. Biol. 35: 1–9. Barnekow L. 1999. Holocene tree-line dynamics and inferred climatic changes in the Abisko area, northern Sweden, based on macrofossil and pollen records. The Holocene 9: 243–265. Barnekow L. 2000. Holocene regional and local vegetation history and lake-level changes in the Tornetr€ask area, northern Sweden. J. Paleolim. 23: 399–420. Battarbee R.W. 1986. Diatom analysis. In: Berglund B. (ed.), Handbook of Holocene Palaeoecology and Palaeohydrology, John Wiley & Sons, Chichester, USA, pp. 527–570. Battarbee R.W. and Kneen M. 1982. The use of electronically counted microspheres in absolute diatom analysis. Limnol. Oceanogr. 27: 182–188. Birks H.J.B. and Line J.M. 1992. The use of rarefaction analysis for estimating palynological richness from Quaternary pollenanalytical data. The Holocene 2: 1–10. Cameron N.G., Birks H.J.B., Jones V.J., Berge F., Catalan J., Flower R.J., et al. 1999. Surface-sediment and epilithic diatom calibration set for remote European mountain lakes (AL:PE Project) and their comparison with the Surface Waters Acidification Programme (SWAP) calibration set. J. Paleolim. 22: 291–317. Eronen M., Hyv€arinen H. and Zetterberg P. 1999. Holocene humidity changes in northern Finnish Lapland inferred from lake sediments and submerged Scots pines dated by tree-rings. The Holocene 9: 569–580.
425 Fægri K. and Iversen J. 1989. Textbook of Pollen Analysis. John Wiley & Sons, Chichester, USA, 382 pp. Flo¨ssner D. 1972. Krebstiere, Crustacea. Kiemen- und Blattf€ ußer, Branchiopoda Fischl€ause, Branchiura. Die Tierwelt Deutschlands 60. Gustav Fischer Verlag, Jena, East Germany, 499 pp. Frey D.G. 1973. Comparative morphology and biology of three species of Eurycercus (Chydoridae. Cladocera) with a description of Eurycercus macracanthus sp. nov. Int. Rev. ges. Hydrobiol. 58: 221–267. Heiri O., Lotter A.F. and Lemcke G. 2001. Loss on ignition as a method for estimating organic and carbonate content in sediments: reproducibility and comparability of results. J. Paleolim. 25: 101–110. Hyv€ arinen H. and Alhonen P. 1994. Holocene lake-level changes in the Fennoscandian tree-line region, western Finnish Lapland: diatom and cladoceran evidence. The Holocene 4: 251–258. Kaakinen A. and Eronen M. 2000. Holocene pollen stratigraphy indicating climatic and tree line changes derived from a peat section at Ortino, in the Pechora lowland, northern Russia. The Holocene 10: 611–620. Kauppila T., Moisio T. and Salonen V.-P. 2002. A diatom-based inference model for autumn epilimnetic total phosphorus concentration and its application to a presently eutrophic boreal lake. J. Paleolim. 27: 261–273. Korhola A., Weckstro¨m J., Holmstro¨m L. and Er€asto¨ P. 2000. A quantitative Holocene climatic record from diatoms in northern Fennoscandia. Quat. Res. 54: 284–294. Krammer K. and Lange-Bertalot H. 1986. S€ ußwasserflora von Mitteleuropa. Bacillariophyceae. 1. Teil: Naviculaceae. Gustav Fischer Verlag, Stuttgart, Germany, 876 pp. Krammer K. and Lange-Bertalot H. 1988. S€ ußwasserflora von Mitteleuropa. Bacillariophyceae. 2. Teil: Bacillariaceae, Epithemiaceae, Surirellaceae. Gustav Fischer Verlag, Stuttgart, Germany, 596 pp. Krammer K. and Lange-Bertalot H. (with H. Ha˚kansson and M. No¨rpel) 1991a. S€ ußwasserflora von Mitteleuropa. Bacillariophyceae. 3. Teil: Centrales, Fragilariaceae, Eunotiaceae. Gustav Fischer Verlag, Stuttgart, Germany, 576 pp. Krammer K. and Lange-Bertalot H. 1991b. S€ ußwasserflora von Mitteleuropa. Bacillariophyceae. 4. Teil: Achnanthaceae, Kritische Erg€anzungen zu Navicula (Lineolatae) und Gomphonema Gesamtliteraturverzeichnis Teil 1-4. Gustav Fischer Verlag, Stuttgart, Germany, 436 pp. Kremenetski C., Vaschalova T. and Sulerzhitsky L. 1999. The Holocene vegetation history of the Khibiny Mountains: implications for the post-glacial expansion of spruce and alder on the Kola Peninsula, northwestern Russia. J. Quat. Sci. 14: 29–43. Kultti S., V€ aliranta M., Sarmaja-Korjonen K., Solovieva N., Virtanen T., Kauppila T. and Eronen M. 2003. Palaeoecological evidence of changes in vegetation and climate during the Holocene in the pre-Polar Urals, northeast European Russia. J. Quat. Sci. 18: 503–520. MacDonald G.M., Gervais B.R., Snyder J.A., Tarasov G.A. and Borisova O.K. 2000. Radiocarbon dated Pinus sylvestris L. wood beyond tree-line on the Kola Peninsula. Russia. The Holocene 10: 143–147.
Oberman N.G. and Borozinetsh B.E. 1988. Geocryological description of the European Territories of the USSR. Urals. In: Ershov, E.D. (ed.), Geocryology of the USSR, European Territories. Nedra, Moscow, USSR, 301–324. Oksanen P., Kuhry P. and Alekseeva R. 2001. Holocene development of the Rogovaya River peat plateau. European Russian Arctic. The Holocene 11: 25–40. Paus A. 2000. Interpretative problems and sources of error related to pollen-analytical studies of the Holocene on the Timan ridge, western Pechora Basin, northern Russia. AmSSkrifter 16: 111–126. Porinchu D.F. and Cwynar L.C. 2002. Late-Quaternary history of midge communities and climate from a tundra site near the lower Lena River. Northeast Siberia. J. Paleolim. 27: 59–69. Renberg I. 1990. A procedure for preparing large sets of diatom slides from sediment cores. J. Paleolim. 4: 87–90. Sarmaja-Korjonen K. 2001. Correlation of fluctuations in cladoceran planktonic/littoral ratio between three cores from a small lake in S. Finland - Holocene water-level changes. The Holocene 11: 53–63. Sarmaja-Korjonen K. 2002. Multi-proxy data from Kaksoislammi Lake in Finland: dramatic changes in the late Holocene cladoceran assemblages. J. Paleolim. 28: 287–296. Sarmaja-Korjonen K. and Alhonen P. 1999. Cladoceran and diatom evidence of lake-level fluctuations from a Finnish lake and the effect of aquatic moss layers on microfossil assemblages. J. Paleolim. 22: 277–290. Sarmaja-Korjonen K. and Hyv€arinen H. 1999. Cladoceran and diatom stratigraphy of calcareous lake sediments from Kuusamo. NE Finland. Indications of Holocene lake-level changes. Fennia 177: 55–70. Sepp€a H. and Birks H.J.B. 2001. July mean temperature and annual precipitation trends during the Holocene in the Fennoscandian tree-line area: pollen-based climate reconstructions. The Holocene 11: 527–539. Sepp€a H., Nyman M., Korhola A. and Weckstro¨m J. 2002. Changes of treeline and alpine vegetation in relation to post-glacial climate dynamics in northern Fennoscandia based on pollen and chironomid records. J. Quat. Sci. 17: 287–301. Serebryanny L., Andreev A., Malyasova E., Tarasov P. and Romanenko F. 1998. Lateglacial and early Holocene environments of Novaya Zemlya and the Kara Sea Region of the Russian Arctic. The Holocene 8: 323–330. Snyder J.A., MacDonald G.M., Forman S.L., Tarasov G.A. and Mode W.N. 2000. Postglacial climate and vegetation history, north-central Kola Peninsula, Russia: pollen and diatom records from Lake Yarnyshnoe-3. Boreas 29: 261–271. Solovieva N. and Jones V.J. 2002. A multiproxy record of Holocene environmental changes in the central Kola Peninsula, northwest Russia. J. Quat. Sci. 17: 303–318. Stockmarr J. 1971. Tablets with spores used in absolute pollen analysis. Pollen et Spores 13: 615–621. Stuiver M. and Reimer P.J. 1993. Extended 14C data base and revised CALIB 3.0 14C age calibration program. Radiocarbon 35: 215–230. Tarasov P.E., Guiot J., Cheddadi R., Andreev A.A., Bezusko L.G., Blyakharchuk T.A., Dorofeyuk N.I., Filimonova L.V.,
426 Volkova V.S. and Zernitskaya V.P. 1999. Climate in northern Eurasia 6000 years ago reconstructed from pollen data. Earth Plan. Sci. Lett. 171: 635–645. V€ aliranta M., Kaakinen A. and Kuhry P. 2003. Holocene climate and landscape evolution in the Ortino region, East-European Russian Arctic. Quat. Res. 59: 335–344.
Virtanen T., Mikkola K. and Nikula A. 2002. Spatial structure of the timberline landscape and its relation to climate and permafrost in the Usa Basin, NW Russia. In: Kankaanp€a€ a, S., M€ uller-Wille, L., Susiluoto, P. and Sutinen. M.L. (eds), Northern timberline forests: environmental and socioeconomic issues and concerns. Research Papers of the Finnish Forest Research Institute 862, 91–95.
