EditorsMāris Kļaviņš Laimdota Kalniņa

THE UnivErsiTy of LaTvia prEss

UnivErsiTy of LaTviafaculty of Geography and Earth sciences

Bog and Lake

Latviaresearch in

Bog and Lake Research in Latvia/ Editors Māris Kļaviņš and Laimdota Kalniņa. – Rīga, University of Latvia Press, 2013 – p. 92.

The preparation and publication of this book is supported by project “Inovācija kūdras izpētē un jaunu to saturošu produktu izveidē” Projekta Vienošanās Nr.: 2010/0264/2DP2/2.1.1.1.0/10/APIA/VIAA/037

ISBN 978-9984-45-769-7

© University of Latvia, 2013

IEGULDĪJUMS TAVĀ NĀKOTNĒIEGULDĪJUMS TAVĀ NĀKOTNĒ

Technical Editor: Elīza Kušķe

Reviewers: Dr. geogr. Juris Soms (Daugavpils University), PhD, Professor Tom Frisk (Tampere University)

Cover Picture: Māris Kļaviņš

Layout by Baiba Lazdiņa

ContEnt

Ivans Cupruns, Guntars Eizembergs, Laimdota Kalniņa, Ilze OzolaRenaturalisation Measures in the Cut-Over Peatlands of Lielsalas Mire ................................................................................................. 6

Aija Dēliņa, Persijs ĢedertsEffect of Mire Restoration Measures on Their Hydrological Regime – Aklais Mire, Aizkraukle Mire, Rožu Mire and Melnais Lake Mire ............ 11

Mihails Čugunovs, Oļģerts NikodemusDevelopment of Scots Pine Pinus sylvestris Cover in Natural and Drained Raised Bogs in Latvia ....................................................................... 17

Linda Ansone, Māris Kļaviņš, Maruta JankēvicaThe use of Biosorbents for Metaloid Sorption ............................................ 21

Jānis Krūmiņš, Māris Kļaviņš, Valdis Segliņš, Elīza KušķeUse of Differential Thermal Analysis and Thermogravimetry in the Characterisation of Fen Peat Profile .................................................. 28

Jānis KarušsGround Penetrating Radar Signal Corelation with Peat Properties in Cenas tīrelis .................................................................................................... 32

Liene Ustupe, Aija Ceriņa, Karina Stankeviča, Laimdota Kalniņa, Māris Kļaviņš

Paleovegetation Changes in the Lake Pilvelis .............................................. 36

Anda Staškova, Aija Ceriņa, Agnese Pujāte Paleovegetation Changes According to Macrofossil Investigation Data During the Development of Lake Mazais Ungurs ............................ 45

Liene Ustupe, Laimdota Kalniņa, Agnese PujāteStudies of Modern Pollen “Rain” in Seda Mire ........................................... 51

Migle Stančikaitė, Vaida Šeirienė, Dalia Kisielienė, Julius Taminskas, Jonas Mažeika, Gražyna Gryguc

Mires and Lakes – Key Sites for the Postglacial Palaeoenvironmental Investigations in Lithuania: Old Questions and New Answers ............... 56

Alex Brown, Aleks PluskowskiThe Impact of the Teutonic Order on the Landscape of the Eastern Baltic: Preliminary Results of Investigations on Mire and Lake Sediments in Latvia ........................................................................................... 62

Aija Ceriņa, Laimdota Kalniņa, Valdis BērziņšChanges in the Level of Lake Sārnate and the Conditions for Settlement Along its Shore During the Holocene ...................................... 75

Ilze Ozola, Vita RatniecePalaeoenvironmental Changes and Geological Development of the Puikule Mire ............................................................................................ 81

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ForEword

Bogs and lakes are an essential element of our life, even if we living in our cities do not see them every day. They are an essential element of our landscape and places significantly affecting development of our country. However the real understanding of significance of bogs and lakes is coming only in XXI century and the key concepts to understand their significance includes: biogeochemical cycling of elements, reservoirs and storages of water and organic carbon, archives of the past and many others. In this respect it is of utmost importance to understand the processes affecting the development of bogs and lakes. Despite the significance of bogs and lakes in Baltic and especially Latvian environment these issues has not been much studied. Development of bogs and lakes in Latvia thus is an direction of research deserving detailed and in-depth studies, not only to gain new insights in these unique objects but also to develop better understanding of complex environmental objects.

Editors Māris Kļaviņš and Laimdota Kalniņa

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RenatuRalisation measuRes in the cut-oVeR peatlands of lielsalas miRe

1, 3a ivans cupRuns, 1 Guntars eizembeRGs, 2 laimdota KalniŅa, 2, 3 ilze ozola

1 SIA “Pindstrup Latvia”2 University of Latvia, Faculty of Geography and Earth Sciences

3 Latvian Peat Producers Associatione-mail: a ic@pindstrup.lv

IntroduCtIonRestoration or renaturalisation of mires and peatlands should be based

on the principles of Wise Use and should be commenced immediately after finishing peat extraction. After excavating peat fields, they have to be managed in accordance with the applicable laws and regulations. Accordingly, upon commencing any peat extraction activity, a project is developed, where one of the requirements is to specify the method of management to be applied to the peat field after excavation. However, in the long run (20–30 years), peat production companies that manage the relevant field often change. In addition, the initial project may become lost. Moreover, there is not always enough information for applying the best management and remediation measures, and the legislative requirements often change (Nusbaums un Silamiķele, 2012; Nusbaums et al., 2012).

On account of this, when peat extraction is finished in a given field, a thorough revaluation must be made as to what the most appropriate peatland management method would be, taking into account the given environmental as well as socio-economic conditions. It should be evaluated what types of management measures should be applied after peatland excavation. In Latvia, cut-over peat fields are usually left for renaturalisation, posing a threat to peatland habitats. Every peat excavation project should include measures of peatland management after peat cutting. However, in reality these measures are planned very formally and usually are forgotten after long years of peat cutting. Recultivation of cut-over peatlands became current in the late 1970s and then it was supported by the government. At that time, studies evaluating the potential of the use of excavated peat fields for agriculture, forestry and as water reservoirs were conducted, although the results of these studies were not implemented. Most commonly, peat fields are just left for renaturalisation, without making any additional measures and observations (Silamikele un Nusbaums, 2011; Nusbaums et al., 2012). Admittedly, such an approach does not always yield good results, and the process of renaturalisation is very slow. For these reasons, Pindstrup Latvia SIA has already for many years been carrying out targeted

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Fig. 1. location of cut – over fields (field a, field b, field no. 5) in lielsalas peatland

renaturalisation of the cut-over peat fields, looking for more effective methods for successful restoration of peatlands. During the last decades, restoration of excavated peat fields has been done by planting Sphagnum mosses. Such an experiment has also been done at Lielsalas Mire located in the Talsi region.

Study SItE dESCrIptIon Lielsalas Mire is located in the northern part of Curonian peninsula (Fig. 1),

north-eastern part of the Kursa Lowland, in the Ugāle Plain, in a depression of a plain of uneven accumulation, where formerly there was a bay of the Baltic Ice Lake. Geomorphologically it is part of the northern side of the Ventas–Usmas depression, mostly characterised by glaciolimnic deposits and a gently undulating topography. Accumulation of peat in the depression of Lielsalas Mire, like in the neighbouring Stiklu Mires, started already in the early Holocene, mainly by paludification of mineral soil in excessively wet conditions, while the origin of the mire is associated with the overgrowing of small pools of the shallow outliers of the Baltic Ice Lake, as indicated by the gyttja and fen peat deposits identified under the raised bog peat layers. A detailed study of the peat field of Lielsalas Mire was performed by the Leningrad State Institute of Peat Investigation in 1962 and 1977 (Peat Fund No. 175) (Kūdras fonds, 1980).

AIm And mEthodSThe aim of the study was to observe excavated peat fields (Field A, Field

B and Field No. 5, Fig. 1) that earlier had been left for renaturalisation and to introduce the Sphagnum moss planting method for their renaturalisation (Cupruns et al., 2013).

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Task No. 1: To restore the hydrological conditions of the mire in the excavated areas, promoting the restoration of wetland vegetation.

Renaturalisation of the excavated fields is based on a gradual restoration of their hydrological conditions. In the first 3 years after completing peat extraction, nothing is done in the peat field, just observing what kinds of changes occur there. After that, land tiles are removed from field ditches, while the ditches themselves are left as they are, without filling up or levelling.

Task No. 2: To plant Sphagnum mosses in the excavated fields, thereby facilitating faster restoration of peatland vegetation and accumulation of peat.

Sphagnum mosses were planted in an excavated peat field with a sufficiently level surface, using the milling technique. For planting, Sphagnum tufts about 10 cm in diameter were taken from a nearby wet mire area where the peat layer is not thick enough to be suitable for peat extraction. Sphagnum species were planted in shallow holes with a 15–20 cm diameter.

thE FIrSt rEnAturAlISAtIon mEASurES And ExpErImEntSPeat extraction in the Lielsalas Peat Field (still carried out by SIA “Pindstrup

Latvia”) was launched in 1964, in the north-western part of the area located relatively closer to the road, which is an important factor for both the preparation of the field for peat extraction and later for peat transportation (Cupruns et al., 2013). Consequently, peat extraction in these areas was started earlier. The milling method was used. Since the first peat extraction fields (about 200 ha) were located relatively close to the edge of the mire, they were shallower (~2 m); therefore, the extraction was completed there already in 1995–1997. The next group of fields is located to the south of the abovementioned first fields, and peat extraction there was completed in 2005. Since that time, renaturalisation processes have been taking place in these cut-over areas of the peat field. Given that each site is unique, renaturalisation there was managed using an experimental method developed by SIA “Pindstrup Latvia”.

rESultS And dISCuSSIonFor the first 3 years after the completion of peat extraction, no actions

were taken in the excavated peat fields, taking into account the experience that if hydrological conditions are sharply changed in an excavated peat field by rapidly increasing the groundwater level, pools and ponds are formed as a result, while the restoration of vegetation takes place very slowly. Since peat was extracted using the milling method, the field surface was level and neat. Field ditches and main ditches also remained intact during this period. It was observed that vegetation first appeared in the field ditches, which started to gradually overgrow. After 3 years, land tiles were removed from the field ditches. It was also observed that the groundwater level gradually began to rise in the excavated field areas after the removal of the land tiles, forming big and shallow pools, as the field surface was relatively flat.

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Furthermore, 2 years after the removal of the land tiles, tufted bulrush (Trichophorum cespitosum) tussocks and small birches started overgrowing the fields progressively from the sides of ditches as well as in the pool areas. Although birches grew rapidly at first, they began to wither away in about 9 to 10 years, while other plants gradually propagated. After 7–8 years since the beginning of the renaturalisation process, Sphagnum species began to grow in the shallow pools, gradually overgrowing them in 2–3 years.

The main ditches were not closed and still function, as they are needed for draining water from the peat fields where extraction still goes on. It was also noticed that the impact of main ditches has not changed since 1964.

One of the most recent peat field renaturalisation experiments in Lielsalas Mire was conducted in autumn 2012, when the first attempts of planting Sphagnum species were made. The planting material was taken from the areas adjacent to the cut-over fields, where the peat layer is not thick enough for extraction and mire vegetation, which consists mainly of Sphagnum species, has not therefore been affected. Due to such closeness, the acquisition and transportation of the planting material did not incur great expenses. The first preliminary results of this experiment could be verified during the survey performed at the newly planted Sphagnum fields in spring 2013, when it was found that about 60% of the planted Sphagnum mosses had already taken roots, and it is expected that the remaining plantings will do the same. In spite of point of view that currently it is not expedient to recultivate the cutover peat excavation sites, since natural processes have been taking place there for at least 40 years and these areas are bogging up again (Silamiķele et al., 2012) the first results of renaturalisation measures performed by Pindstrup Latvia SIA in Lielsalas Mire indicate that it is possible earlier to revert bog conditions in cut over peatlands. It should be taken into account that in nature transition from fen to bog can take even more time 200–600 years (Ozola, 2013).

ConCluSIonEven if the renaturalisation measures in the excavated peat fields of Pindstrup

Latvia SIA in Lielsalas Mire are at an early stage, the first results already show a successful propagation of mire vegetation and mire regeneration. These measures make it possible not only to consider mire regeneration theoretically but also to observe these processes really taking place on site. To acknowledge, Pindstrup Latvia SIA employees cannot explain all observations by themselves; therefore, the company is planning collaboration with researchers who could conduct studies in the area of mire restoration. Pindstrup Latvia SIA believes that such studies are indispensable: by wise management of peat fields, we have to give back to Mother Nature as much as possible of what we have taken from her.

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rEfErEncEsNusbaums, J., Silamiķele, I. 2012. Kūdras izstrādes lauku rekultivēšana: iespējas, problēmas,

rezultāti. Latvijas Universitāte 70. zinātniskā konference. Ģeogrāfija. Ģeoloģija. Vides zinātne. Referātu tēzes. http://www.geo.lu.lv/fileadmin/user_upload/lu_portal/projekti/gzzf/Konferences/Tezu_krajumi/70.pdf

Cupruns, I., Kalniņa, L., Ozola, I. 2013. Izztrādāto kūdras lauku rekultivācija Lielsalas purvā. Latvijas Universitāte 71. zinātniskā konference. Ģeogrāfija. Ģeoloģija. Vides zinātne. Referātu tēzes. Rīga, LU, 419–421.

Nusbaums, J., Silamiķele, I., Kušķe, I. 2012. Peat resources and renewable possibilities. Kūdras resursi un to atjaunošana. 5. starptautiskā konference “Vides zinātne un izglītība Latvijā un Eiropā: resursi un bioloģiskā daudzveidība. Konferences rakstu krājums. 33–34.

Ozola, I. 2013. Holocēna organogēnie nogulumi un to uzkrāšanās apstākļu izmaiņas purvos Ziemeļvidzemē: promocijas darba kopsavilkums doktora grāda iegūšanai ģeoloģijas nozarē. Rīga, LU Ģeogrāfijas un Zemes zinātņu fakultāte, Latvijas Universitāte.

Silamikele, I., Nusbaums, J., Cupruns, I., Ozola, I. 2012. Challenges of peatland recultivation in Latvia. 14th International Peat Congress. Peatlands in Balance. The Book of Abstracts, Extended abstract No. 90. Stokholm, Sweden, 160.

Silamikele, I., Nusbaums, J. 2011. Peatland recultivation problems in Latvia. 11. Baltijas kūdras ražotāju forums. The Book of Abstracts. Rīga, Latvija, 8–10.

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effect of miRe RestoRation measuRes on theiR hydRoloGical ReGime – aKlais miRe,

aizKRauKle miRe, Rožu miRe and melnais laKe miRe

a aija dēliŅa, b persijs ĢedeRts

University of Latvia, Faculty of Geography and Earth Sciencese-mails: a aija.delina@lu.lv; b persijsgederts.gmail.com

IntroduCtIonBogs and mires covers about 10% of Latvia, and many of them are raised

bogs or mires. The mires are significant natural habitats for protected and endangered species as well as an important source of peat. Due to the peat extraction activities (former, ongoing and planned ones) only about 5% of all mires are undisturbed (Pakalne, 2008). Thus, there is number of mires where natural habitats are disturbed and the water level in the mires is lowered applying ditch systems draining the mires. The result of the changed hydrological regime is degradation of bog habitats due to the overgrowth with trees. On the other hand, several of these mires today are Particularly Protected Nature Areas (PPNA), where no peat extraction my take place, although earlier the ditches were dug and the sites were prepared for peat extraction. These PPNA are the target sites for bog management and restoration measures.

The LIFE+ project No LIFE08 NAT/LV/000449 “Restoration of Raised Bog Habitats in the Especially Protected Nature Areas of Latvia” supports the restoration measures in four bogs in Latvia – Aklais mire, Aizkraukle mire, Rozu mire and Melnais Lake mire. The project measures are construction of dams on the main ditches draining the mires, thus maintaining higher water level in the mires. Groundwater level observations are integral part of the restoration measures, and based on these observations the effect of restoration activities could be assessed.

GroundwAtEr tAblE obSErvAtIon mEthodSGroundwater table observations are taken in several representative well

profiles, and there is at least one profile installed in each mire. The location of well profile was selected based on the following assumptions: (1) the ditch is located on the typical area of the mire, (2) the dams will be constructed on the ditch. Wells in the profile were located so that there is short distance between the wells closer to the ditch and longer distance further away from the ditch (Fig. 1). The total length of profile is 500 m, except some areas, where it is 250 m. The last well in the profile represents the natural, undisturbed hydrological regime in the mire.

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Totally there are nine profiles with 63 wells. Four profiles are installed in the PPNA “Aizkraukle mire and forests”: (I) perpendicular to the large ditch witch is dammed during the Project – 7 wells; (II) – near the small ditches, where dams are constructed – 7 wells; (III) – near the existing ditch along the operating peat fields, to observe the influence of the ditch – 7 wells; (IV) – in the wet forest and forest to observe the influence of management measures on adjacent forests – 5 wells. Two profiles are installed in the PPNA “Aklais mire”: (I) near the source of Girupe stream, where dams are constructed – 8 wells; (II) near the partially overgrown ditch, where dams are constructed – 8 wells. One profile and one group of the wells was installed in the PPNA “Melnais Lake mire”: (I) group of the wells around the former peat extraction field, where water is standing now – 6 wells; (II) near the ditch, where the dams are constructed – 7 wells. One profile was installed in the PPNA “Rožu mire” near the furthest ditch in the ditch system, where dams are constructed – 8 wells.

The wells are about 3 m deep, depending on the thickness of peat layer. The perforated PE pipe is installed in each location. The elevation and coordinates of the each well were measured using Leica GPS 900cCS.

Groundwater table observations were started 0.5–1 year before the construction of dams to provide data on disturbed hydrological regime. The observations are taken twice per month manually.

EFFECtS oF rEStorAtIon mEASurESThe groundwater table observations showed that the disturbing effect on

the hydrological regime of mire depends on the type of ditch. Several types of ditches could be recognized at the project sites: (1) deep ditches partially filled with water, (2) deep, wide ditches completely filled with water, (3) small, shallow ditches and (4) wide ditches, overgrown with Sphagnum species. Therefore the effect of restoration measures may depend on the type of the ditch as well.

Near the deep, partially filled ditches, like in Aizkraukle mire profile A3 or Melnais Lake mire profile M2 (Fig. 2) and wells M1-3 and M1-4 the groundwater table changes are more intensive, the difference between the lowest and the highest water table may reach 0.5–1.2 meters in the wells located

Fig. 1. schematic location of wells in the profile

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within 10 m from the ditch. The more distant wells show very slight impact of the ditch on the water level in the mire.

The effect of restoration measures is obvious in these cases. The groundwater table observations show that after the construction of dams the water table has risen in spring and is kept stable for the rest of the observation period. Comparing to the “pre-dam” period, when groundwater table fluctuation reached 0.5–1 m, the groundwater table fluctuations during the “after-dam” period is just 0.1–0.15 m. Besides, most intensive effects are observed closer to the ditch (distance 1–10 m), but the stabilization of groundwater table could be observed in the more distant wells, too. There the groundwater table fluctuations have minimized from around 20 cm to around 5 cm before and after the dam construction.

The deep wide ditches, which are completely filled with water like in Rozu mire, Aizkraukle mire profile A1, show similar effect on groundwater table fluctuations (Fig. 3) as the deep, partially filled ditches. The main difference there is that the range of groundwater table fluctuations is smaller – about 0.3–0.6 m before the construction of dams and around 0.1 m after the construction of dams.

Fig. 2. observed groundwater table in melnais lake mire profile m2, near the deep, draining ditch

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The more obvious effect in terms of groundwater table height also is observed in the wells 1–10 m from the ditch, but the stabilization of groundwater table is observed in all the wells of the profiles.

Rather surprising results are obtained from the profile A2 in Aizkraukle mire near the small, shallow ditches (depth about 0.5 m, width 0.2 m). Here the range of groundwater fluctuations is rather large in all the wells, also the ones, located further from the ditches (Fig. 4). Comparing to the other profiles, here the ditches causes sharper groundwater table changes in the nearby wells (A2-1, A2-2).

The groundwater table is still rising in this area after the construction of dams, but it is obvious that even such a small ditches may provide significant draining effect on the surrounding, and that construction of dams has immediate effect resulting in groundwater table rise in the closest wells.

The impact of wide, overgrown ditches, like in Aklais mire profile Ak2, on groundwater table fluctuations is not as sharp as in other cases. In the central part of the mire, where the profile is located, the groundwater table is rather stable before the construction of dams (Fig. 5). Here the range of groundwater fluctuations is 0.25–0.35 m in “pre-dam” period and just 2–3 cm in “after-dam” period, keeping the groundwater table even more stable. The observations show that even such overgrown ditches have impact on hydrological regime of the mire, but this effect is less intensive and not as obvious as in other cases.

Fig. 3. observed groundwater table in aizkraukle mire profile a1, near the deep ditch, filled with water

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Fig. 4. observed groundwater table in aizkraukle mire profile a2, near the small shallow ditches

Fig. 5. observed groundwater table in aklais mire profile ak2, near the wide, overgrown ditch

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ConCluSIonSThe restoration measures (construction of dams on ditches) taken in the

Aklais, Aizkraukle, Rozu and Melnais Lake mires have caused the anticipated effect. The groundwater table has risen and stabilized in all the bogs. The direct effect of the dams is observed in the nearby wells, located 1–10 m from the ditch, but the water table stabilization is observed also in the distance of 100–250 m from the ditch. Different patterns of the groundwater table fluctuations could be observed depending on the type of ditch.

rEfErEncEsPakalne, M. 2008. Mire habitats and their protection. In: Pakalna, M. (ed.) Mire conservation and

management in Especially Protected Nature Areas in Latvia. Latvia Nature Fund, 9–19.

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deVelopment of scots pine PINUS SYLVESTRIS coVeR in natuRal and dRained Raised boGs in latVia

a mihails ČuGunoVs, b oļģerts niKodemus

University of Latvia, Faculty of Geography and Earth Sciencese-mails: a michael.chugunov@inbox.lv; b olgerts.nikodemus@lu.lv

Mires in Latvia comprise approximately 6402 km2, which is 9.9% of the whole state area (Markots et al., 1989). In many of Latvian raised bogs the development of Scots pine cover is being observed lately. Similar processes have been documented in Northern Europe (Linderholm and Leine, 2004; Ohlson et al., 2001), Central Europe (Obidzinski et al., 2009) and Canada (Pellerin and Lavoie, 2003). Overgrowth of mires with pine is thought to be mostly negative process, because of it the moss layer is being disrupted, typical mire vegetation species are being lost and peat formation is hampered (Ohlson et al., 2001). Besides, open and wet bird habitats are being degraded (Petrins, 2008). Many of Latvian and foreign scientists and mire experts associate the development of Scots pine cover on raised bogs to drainage (Pakalne, 2008; Sarkkola et al., 2005). Simultaneously lately scientific publications stressing importance of the climate change to the development of bog pine cover (Linderholm and Leine, 2004) are being found. Studies have demonstrated that also atmospheric nutrient deposition (mainly nitrogen) can induce bog pine cover development (Gunnarsson, 2000), as well as that wildfires (Kucerova et al., 2008) can have an influence on these processess. The hypothesis of the current study is that drainage is not the only and the main factor driving pine cover development in raised bogs, other factors affect the process as well.

In this study the pine cover age spatial differentiation was ascertained in two raised bogs of Latvia – one drained and the other natural (undrained) bog. In the drained Cena bog, the study area was selected and established near the peat production area, lake Skaists and the nature trail (Fig. 1). In the undrained Ance Dizpurvs bog the area adjacent to Dumezers lake laying in the southwestern part of the bog was studied (Fig. 2). Using LGIA 3rd cycle aerial images, polygons with the same pine cover density were identified, and 1 to 3 sample plots were selected in each polygon for the collection of wood samples. In each sample plot wood from 3 or 4 trees was collected. Sometimes (for very large polygons) more than 3 sample plots were selected per polygon. Smaller trees were sawn and a disc was collected at the root collar, while larger trees were cored with Pressler’s increment borer as close to the root collar as possible. Sawn discs and boring cores were sanded with 3 sand-papers in the decreasing order of roughness and then tree-ring count (which corresponds to the tree age) was measured under the dissecting microscope for the wood

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samples. Finally, the corresponding pine cover age was mapped and compared to the historic data (drainage, climate change, eutrophication) of the occurence of possible driving factors.

In the Cena bog study area large territory is overgrown with pine of the 20–49 years age group (Fig. 1), and the highest recorded pine age was 147 years. In the vicinity of Skaists lake the average pine cover age is 110 to 120 years, however also older trees have been observed. Also to the west from Skaists lake, where drainage ditches are located, the age of pine cover is relatively higher, i.e., from 70 to 110 years and older . In turn, pine cover with age up to 49 years was documented across relatively vast territory from the bog edge near the contour-ditch to the places closer to the central part of the bog.

Drainage in Cena bog was commenced in 1933, oblique drainage ditches towards Skaists lake were dug between 1933 and 1945, and a contour-ditch near the peat extraction field was set up in 1978 (Nusbaums, pers. comm., 2011). These periods are relevant to the timing of pine cover development in the corresponding zones, although contour-ditch, as the most influential part of the drainage system, was dug 31 years before the moment of study. Encountered 20–49 years old pine cover only partly corresponds chronologically to the timing of a contour-ditch excavation.

Fig. 1. pine cover age in the western part of cena bog (created by authors, using LGia 2008 aerial images)

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According to the observations of the “Riga-Universitate” meteorological station, in the precipitation distribution 5 dry periods can be identified (1851–1878, 1887–1903, 1931–1948, 1962–1977, 1993–2007). During the first dry period the oldest pines (around 147 years old) established in Cena mire study area, however during the second dry period – in 1887–1903, large part of pine cover – on average 110 to 120 years old – developed on the banks of Skaists lake (Fig. 1). The pine cover of 20–49 years age group, covering large territory in the Cena bog study area, corresponds to the dry period of 1962–1977.

It has been proved that the annual average temperature in Latvia increased steadily from 1913 until nowadays (Lizuma et al., 2007). Large part of pine cover in the Cena bog study area, including widely distributed 20–49 years old stands, chronologically corresponds to this trend.

A peak of the nitrogen deposition in Europe was observed during 1980–1990’s, after which deposition rates decreased due to collapse of the USSR and related economic changes, as well as because of introduction of stricter environmental regulations (Kopacek and Vesely, 2005). Nitrogen deposition influences sphagnum mosses and promotes pine cover development. The timing of the nitrogen deposition peak (20–30 years ago) corresponds to the timing of the development of a large part of pine cover in the Cena bog study area. Most probably even, nitrogen deposition could have influence on the pine

Fig. 2. pine coverage in the southwestern part of ance dizpurvs(created by authors, using LGia 2009 aerial images and LU GZZf WMs kartes.geo.lu.lv)

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cover development also up to 49 years before the study period, although the peak in deposition rates was not yet reached by that time.

In the Ance Dizpurvs bog study area (Fig. 2) bog pine cover of age between 30 and 49 years dominates, and only one stand is older than 50 years. The oldest documented tree is 62 years old. The documented pine cover age in Ances Dizpurvs bog (30–49 years) partly corresponds to the widely distributed 20–49 years old pine cover in Cena bog study area. As no drainage exists in Ance Dizpurvs bog, the remaining possible driving factors for the pine cover development there are climate change and eutrophication. This supports the evidence that drainage is not the only or main factor driving bog pine cover development.

rEfErEncEsGunnarsson, U. 2000. Vegetation changes on Swedish mires. Effects of raised temperature

and increased nitrogen and sulphur influx. Acta Universitatis Upsaliensis. Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 561, Uppsala, 25.

Kopacek, J., Vesely, J. 2005. Sulfur and nitrogen emissions in the Czech Republic and Slovakia from 1850 till 2000. Atmospheric Environment, 39, 2179–2188.

Kucerova, A., Rektoris, L., Stechova, T., Bastl, M. 2008. Disturbances on a wooded raised bog – how windthrow, bark beetle and fire affect vegetation and soil water quality? Folia Geobotanica, 43, 49–67.

Linderholm, H.V., Leine, M. 2004. An assessment of twentieth century tree-cover changes on a southern Swedish peatland combining dendrochronology and aerial photograph analysis. Wetlands, 24(2), 357–363.

Lizuma, L., Klavins, M., Briede, A., Radionovs, V. 2007. Long-term changes of air temperature in Latvia. In: Klavins, M. (ed.) Climate change in Latvia. Riga, University of Latvia, 11–19.

Markots, A., Zelca L., Zelcs, V. 1989. Augsto Purvu Fenomens. Zinatne un Tehnika, 11, 26–28.Obidzinski, A., Kloss, M., Cedro, A. 2009. Is spontaneous regeneration of raised mire vegetation

possible? A case study of the ‘Czarne Bagno’ mire in the Bystrzyckie Hills, southern Poland. The Holocene, 19(2), 229–239.

Ohlson, M., Okland, R.H., Nordbakken, J.F., Dahlberg, B. 2001. Fatal interactions between Scots pine and Sphagnum mosses in bog ecosystems. Oikos, 94, 425–432.

Pakalne, M. 2008. Purva biotopi un to aizsardziba. In: Pakalne, M. (ed.) Purvu aizsardziba un apsaimniekosana ipasi aizsargajamas dabas teritorijas Latvijā. Rīga, Latvijas Dabas Fonds, 8–19.

Pellerin, S., Lavoie, C. 2003. Recent expansion of jack pine in peatlands of southeastern Quebec: A paleoecological study. Ecoscience, 10(2), 247–257.

Petrins, A. 2008. Putni dabas lieguma “Cenas tirelis” In: Pakalne, M. (ed.) Purvu Aizsardziba un Apsaimniekosana Ipasi Aizsargajamas Dabas Teritorijas Latvijā. Riga, Latvijas Dabas Fonds, 42–46.

Sarkkola, S., Hökkä, H., Laiho, R., Päivänen, J., Penttilä, T. 2005. Stand structural dynamics on drained peatlands dominated by Scots pine. Forest Ecology and Management, 206, 135–152.

UnpUbLisHEd MaTEriaLNusbaums, J. 2011. Consultations on the timing of drainage in Cena bog, 27th July 2011.

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the use of biosoRbents foR metaloid soRption

1a linda ansone, 1 māris KļaViŅš, 2 maruta JanKēVica

1 University of Latvia, Faculty of Geography and Earth Sciences2 University of Latvia, Faculty of Chemistry

e-mail: a linda_ansone@inbox.lv

IntroduCtIonA large number of recent studies have been dedicated to the environment

pollution with metalloids (As, Sb, Te) located in the V and VI group in the periodic table of the elements. Due to wide distribution and toxicity, arsenic is the most studied metalloid in comparison to antimony and tellurium. However, it is important to study the fate of antimony and tellurium in environment, environmental pollution and possible solutions for environment remediation.

Arsenic enters natural water systems through the range of anthropogenic as well as natural sources. For example, mobilisation of natural arsenic-bearing deposits, biological activity and volcanic emission are some natural sources of arsenic. Anthropogenic sources of arsenic include discharges from various industries, such as smelting, petroleum refinery, glass manufacturing, fertiliser production and intensive application of arsenical insecticides and herbicides (Henke, 2009; Anirudhan and Unnithan, 2007).

Inorganic arsenic is the predominant form in polluted waters, and it exists in two oxidation states – As (III) and As (V), depending on pH and redox conditions (Ansari et al. 2006). Arsenite is predominant in reduced conditions, but arsenate prevails in an oxidising environment (Pokhrel and Viraraghavan, 2006). In the pH range 3–9, the dominant species of As (III) is the neutral H3AsO3, while those of As (V) are the negatively charged HAsO4

2– and H2AsO4

– (Nemade et al., 2009; Ko et al., 2004).Antimony as well as arsenic is present in the environment as a result of natural

and human activities. Natural antimony sources include rock weathering; soil runoff as well as geothermal waters. Antimony concentration in unpolluted waters is low – most frequently less than 1 µg/L, but in polluted areas – close by anthropogenic sources antimony concentration can be up to 100 times higher in comparison to natural levels (Filella et al., 2002).

Antimony is used in semiconductors for making infra-red detectors, also diodes. The presence of antimony enhances the hardness and mechanical strength of lead. It is used also in batteries, antifriction alloys, catalysts, small arms and tracer bullets as well as cable sheathing, brake lining, antiparasitic agents, polyethylene terephthalate plastics, as an additive in the tire vulcanization process and elsewhere (Filella et al., 2002; Ceriotti and Amarasiriwardena, 2009;

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Steely et al., 2007). In the past, antimony was mainly used in the production of alloys, but nowadays Sb is mostly used as a flame retarding additive.

Antimony similarly arsenic exists mainly as inorganic forms – Sb (III) and Sb (V) in the environment, but in a result of soil microbial activities organic forms of antimony, for example, trimethyl antimony ((CH3)3Sb) has been produced (Ceriotti and Amarasiriwardena, 2009).

Like arsenic antimony is metalloid and due to its position in periodic table of the elements its chemical and toxicological properties are similar to arsenic. Antimony and its compounds were considered as pollutants by Environmental Protection Agency of the United States (USEPA) as well as the European Union (Filella et al., 2002). The maximum admissible concentration of antimony in water is 5 µg/L recommended by EU (Council of the European Union, 1998). Antimony like arsenic is toxic and trivalent species are reported to be more toxic than pentavalent species (Filella et al., 2002; Ceriotti and Amarasiriwardena, 2009). Solubility of antimony compounds in bio fluids, Sb valence state and presence of complexing agents affects Sb toxicity (Ceriotti and Amarasiriwardena, 2009; Steely et al., 2007). It is suggested, that in the human body, antimony may interact with –SH groups in cellular components, particularly with enzymes, thus inhibiting enzymatic activity. Possibly therefore, toxic effect of Sb in high doses is observed (Ceriotti and Amarasiriwardena, 2009).

Although tellurium are found in low abundances in the Earth crust, its toxicity may induce local environmental problems. Up to now there are not much studies about tellurium and its compounds in the environment, mainly attention is focused on tellurium polution near main teilings and industrial areas. Tellurium is widely used in petrolium refining, electronic and photoelectric industries as well as glass, ceramics, ruber and alloy production, for example as an additive to steel and copper to provide machinability (Wang et al., 2011; Zhang et al., 2010).

Tellurium can exist in four oxidation states (–II, 0, IV and VI) in the environment. Like other metalloids toxicity of tellurium is dependent of its chemical form and oxidation state, for example Te (IV) is about 10 times more toxic than Te (VI) (Harada and Takahashi, 2009). Tellurim can be accumulated in kidney, heart, liver, spleen and it may induce the degeneration of kidney and liver, if Te content exceed 0.002 g/kg (Zhang et al., 2010).

Although up to now there are a lot of different sorbents that are used for metal and metalloid removal due to various efficiency and costs opportunities for finding new environmentaly friendly and cost effective sorbents are open. Recently great attention has been paid to the sorbents based on natural materials. There are a lot of sorbents that use unmodified natural materials, for example, naturaly available red soil (Nemade et al., 2009), and also sorbents based on natural materials, for example, iron modified sand, Fe (III) – orange juice industrial residue (Pokhrel and Viraraghavan, 2006).

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mAtErIAlS And mEthodS Analytical quality reagents (Merck Co., Sigma-Aldrich Co., Fluka Chemie

AG RdH Laborchemikalien GmbH Co.) were used without further purification. For the preparation of solutions, high purity water Millipore Elix 3 (Millipore Co.) 10–15 MΩ cm was used throughout.

Sodium arsenate heptahydrate (Na2HAsO4 × 7H2O from Sigma-Aldrich), potassium hexahydroxoantimonate (V) (KSb(OH)6 from Fluka), telluric acid (H6TeO6 from Aldrich) were analytical grade chemicals. Peat was obtained from Gagu Bog (Latvia) and modified chemically.

SYNThESIS mEThodSTo taking into account metalloid affinity to interact with Fe containing

compounds, Fe modified biomaterial sorbents were sythesized. Synthesis method is based on material impregnation with Fe oxohydroxide with following thermal treatment. 67.55 g (0.25 mol) FeCl3×6H2O were dissolved in 250 mL distilled water, adding 250 mL 3M NaOH and leaving for 4 hours. Then, the formed precipitates were rinsed and decanted in a 1 L vessel. The dispersion of Fe(OH)3 was mixed in 100 g of homogenised biomass (shingles, straw, sands, cane and moss). After filtration, the reaction product was rinsed with approximately 0.5 L deionized water, filtered, dried and heated for 4 hours at 60 °C. In a result Fe-modified peat, Fe-modified straw, Fe-modified shingles, Fe-modified sand, Fe-modified moss and Fe-modified canes were obtained.

SoRPTIoN ExPERImENTSSorption experiments were conducted using batch system. Na2HAsO4 ×

7H2O was used for As stock solution preparation at concentrations from 5 to 300 mg/L, KSb(OH)6 and H6TeO6 were used for Sb and Te stock solution preparation accordingly (10–800 mg/L). 40 mL of metalloid solution was added in each 100 mL glass bottle with 0.5 g sorbent. Bottles were shaken for 24 h at room temperature. Suspension was then filtered, and arsenic in the filtrate was analysed using Perkin-Elmer atomic absorption spectrophotometer AAnalyst 600 with graphite furnace (ETAAS – Electrothermal Atomic Absorption Spectrometry). Sb and Te were analyzed using atomic absorption spectrophotometer PerkinElmer AAnalyst 200 with flame atomisation.

rESultS And dISCuSSIonSorption isotherms characterise the equilibrium partitioning between

sorbed and desorbed phases, providing information about the sorption process. Biosorption has been demonstrated to be a useful alternative to conventional treatment methods for the removal of metalloids and metals from aqueous solution. Biomaterials are usually pre-treated and modified in order to enhance their sorption capacity. A wide variety of different materials are used to remove metalloids from water with various efficiencies. In this study sorption

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experiments were carried out using unmodified materials (peat, humic acid) as well as iron-modified biomass sorbents.

We have found that metalloid (As (V), Sb (V) and Te (VI)) sorption capacity depends on the biomass sorbent used, although reaction conditions were similar. The highest sorption capacity of As (V) was observed for Fe-modified peat (peat from Gagu Bog) sorbents, whereas Fe-modified moss, Fe-modified shingles and Fe-modified straw showed similar but not as high results. The sorption capacities of Fe-modified sand (results not shown) and Fe-modified canes were less than 2 mg/g (Fig. 1). Natural materials that are not modified with iron – such as raw peat material and humic acid – are not useful for arsenic removal, but their impregnation with Fe compounds significantly enhance sorption capacity.

For better understanding the sorbed amounts of arsenic were calculated to percentage. Iron-modified peat can sorb 98% at the initial concentration of 100 mg/L, and the sorbed amount of arsenic decreases to 70% if the initial arsenic concentration reaches 270 mg/L. The sorbed amounts of modified shingles, modified moss and modified straw exceed 95%, 97% and 99% accordingly if the initial arsenic concentration is 45 mg/L, whereas less effective sorbents, such as modified canes and modified sand, may be used effectively at lower arsenic concentrations. Fe-modified canes sorb more than 97% of As (V) if the initial concentration arsenic does not exceed 40 mg/L, and modified sand can sorb 94% if the initial arsenic concentration does not exceed 10 mg/L.

To sum up, iron-modified peat was the most effective sorbent for arsenic removal and it is possible to use this sorbent for waters severely polluted with arsenic. We also propose that Fe-modified moss, Fe-modified shingles and Fe-modified straw can be applied when arsenic concentrations are lower.

Fig. 1. arsenic removal using iron-modified biomass, sorption time 24 h, room temperature

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Fe-modified peat is very effective for antimony (V) removal (Fig. 2). Sorption capacity of Fe-modified peat exceeds 40 mg/g at the initial antimony concentration of 730 mg/L. Fe-modified peat may sorb up to 95% of Sb (V) at the initial concentration of 370 mg/L and it decreases to 75% at the initial concentration of 730 mg/L. Fe-modified moss as well as Fe-modified shingles show similar sorption capacity, although the results are not as high as using Fe-modified peat. The sorbed amount of modified moss and modified shingles exceed 95% at the initial concentration of 90 mg/L and it decreases to 48% and 41% at initial concentrations of 556 and 580 mg/L for modified moss and modified shingles accordingly. Less effective sorbent – Fe-modified straw can be used in the areas with lower antimony concentration. Modified straw may sorb up to 57% of Sb (V), if initial antimony concentration is 92 mg/L.

To sum up, in this study used biosorbents are very effective in antimony removal. Although As and Sb have similar chemical properties, sorption capacity of modified peat is almost 3 times higher to compare Sb and As.

Fe-modified peat, Fe-modified moss, Fe-modified cane as well as Fe-modified shingles and Fe-modified straw show similar sorption ability for Te (VI) (Fig. 3). Fe-modified peat has the highest sorption capacity – it may sorb more than 98% of Te (VI) at initial concentration of 50 mg/L, and Te (VI) removal efficiency decreases to 55% if initial concentration reaches 400 mg/L. Similar trend was observed also for modified shingles and modified canes. Fe-modified sand was the less effective sorbent for Te (VI) in comparison to other sorbents used in this study. It may sorb up to 70% at initial concentration of 25 mg/L.

To sum up, Fe-modified peat, modified moss and canes is able to use this sorbent for waters severely polluted with tellurium, but the others sorbents are able to use when tellurium concentration is lower.

Fig. 2. antimony removal using iron-modified biomass, sorption time 24 h, room temperature

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ConCluSIonSFe-modified peat is the best sorbent for arsenic, antimony as well as tellurium.

However, sorption capacity for arsenic and tellurium are similar, much higher it is for antimony. Modified moss and modified shingles are in this study used sorbents that effectively may sorb all metalloids (As, Sb, Te). The sorption capacities of the sorbents synthesised in this study are comparable with those of other biomaterials. For example, the study of Thirunavukkarasu et al. (2001) found that the sorption capacity of Fe oxide-coated sand and ferrihydrite used for arsenic removal from natural water was 18.3 µg/g and 285 µg/g respectively, a comparatively high sorption capacity of As (V) was obtained using modified biomasses (P. chrysogenum) – 37.85 mg/g for HDTMA-Br-modified Mycan biomass, 56.07 mg/g for Magnafloc-modified biomass and 33.31 mg/g for Dodecylamine-modified biomass (Loukidou et al. 2003). However, the conditions – such as the amount of sorbent used, metalloid concentration, pH and others – are crucial, as they noticeably influence sorption capacity and these conditions also complicate comparing the efficiency of different sorbents.

rEfErEncEsAnirudhan, T.S., Unnithan, M.R. 2007. Arsenic (V) removal from aqueous solutions using an

anion exchanger from coconut coir pith and its recovery. Chemosphere, 66, 60–66.Ceriotti, G., Amarasiriwardena, D. 2009. A study of antimony complexed to soil-derived humic

acids and inorganic antimony species along a Massachusetts highway. Microchemical Journal, 91, 85–93.

Council of the European Union. 1998. Council Directive 98/83/EC on the quality of water intented for human consumption. Adopted by the Council, on 3 November 1998. http://www.lenntech.com/applications/drinking/standards/eu-s-drinking-water-standards.htm#ixzz2HMxCY4bF

Fig. 3. tellurium removal using iron-modified biomass, sorption time 24 h, room temperature

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Filella, M., Belzile, N., Chen, Y. 2002. Antimony in the environment: a review focused on natural waters I. Occurrence. Eart-Science Reviews, 57, 125–176.

Harada, T., Takahashi, Y. 2009. Origin of the difference in the distribution behavior of tellurium and selenium in a soil-water system. Geochimica et Cosmochimica Acta, 72, 1281–1294.

Henke, K.R. 2009. Arsenic: environmental chemistry, health threats, and waste treatment. Wiltshire, John Wiley and Sons.

Ko, I., Kim, J., Kim, K. 2004. Arsenic speciation and sorption kinetics in the As-hematite-humic acid system. Colloids Surf A: Physicochem. Eng. Aspects, 234, 43–50.

Loukidou, M.X., Matis, K.A., Zouboulis, A.I., Liakopoulou-Kyriakidou, M. 2003. Removal of As (V) from wastewaters by chemically modified fungal biomass. Water Res., 37, 4544–4552.

Nemade, P.D., Kadam, A.M., Shankar, H.S. 2009. Adsorption of arsenic from aqueous solution on naturally available red soil. Journal of Environmental Biology, 30(4), 499–504.

Pokhrel, D., Viraraghavan, T. 2006. Arsenic removal from an aqueous solution by a modified fungal biomass. Water Research, 40, 549–552.

Steely, S., Amarasiriwardena, D., Xing, B. 2007. An investigation of inorganic antimony species and antimony associated with soil humic acid molar mass fractions in contaminated soils. Environmental Pollution, 148, 590–598.

Thirunavukkarasu, O.S. Viraraghavan, T., Subramanian, K.S. 2001. Removal of arsenic in drinking water by iron oxide-coated sand and ferrihydrite – batch studies. Water Qual. Res. J., 36(1), 55–70.

Wang, X., Liu, G., Zhou, J., Wang, J., Jin, R., Lv, H. 2011. Quinone-mediated reduction of selenite and telurite by Echerichia coli. Bioresource Technology, 102, 3268–3271.

Zhang, L., Zhang, M., Guo, X., Liu, X., Kang, P., Chen, X. 2010. Sorption characteristics and seperation of tellurium ions from aqueous solutions using nano-TiO2. Talanta, 83, 344–350.

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use of diffeRential theRmal analysis and theRmoGRaVimetRy in the chaRacteRisation

of fen peat pRofile

a Jānis KRŪmiŅš, māris KļaViŅš, Valdis seGliŅš, elīza KušĶe

University of Latvia, Faculty of Geography and Earth Sciencese-mail: a krumins.janis@lu.lv

Wide range of thermal analyses, performed in a controlled environment, makes possible observation of any changes in chemical or physical properties of peat sample in relation with time or temperature. One of the most perspective methods is a combination of differential thermal analysis (DTA) and thermogravimetry (TG) which significantly increases the accuracy of results. The DTA represents the data about temperature ranges with the most pronounced changes in peat samples, in most cases; it coincides with the most significant weight loss. In turn, the TG allows monitoring of sample weight loss which is dependent on a heat input. The DTA/TG allows monitoring of both endothermic and exothermic reactions thus it is possible to trace the sequence of physical and chemical processes in a peat sample. For instance, this method allows monitoring of time, temperature and weight loss in which sample collapses in the event of gas release etc. The illustration of an early diagenesis is one of the most significant results represented by this method; results give representation of a transformation of organic matter into peat deposits and further into coal.

The analysis was performed using derivatograph SII Exstar 6300 TG/DTA. As an optimal mass for the analysis was used 20 mg of an air dried, grinded peat. The heating process was performed in a nitrogen atmosphere at the temperature range from 25 °C to 550 °C. The initial temperature (25 °C) was variable and corresponded to a room temperature at the moment of analysis. The temperature was automatically increased by 10 °C every minute.

Both DTA and TG analysis of fen peat points to a more complex composition (Fig. 1–3) in comparison with raised bog peat. The character of DTA curves (thermogramms) indicates more frequent changes in fen peat due to a heat input than in raised bog peat, although, there are similarities. An important factor causing these differences is botanical composition of fen peat which consists of simple, but variable plant remains. In the vegetation of fens is a high content of lignin, variety of its derivatives and high content of cellulose. The vegetation of raised bogs is more primitively and, in general, peat consists of sphagnum remains (with admixture of dwarf, shrub or wood remains). Therefore, botanical composition of raised bog peat is less complex – changes, dependent on thermal exposure, are not as pronounced as in fen peat.

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Temperature ranges with significant changes in peat a sample differs also among fen peat types (Fig. 1–3). They are affected not only by the botanical composition, but also by the deposit depth and decomposition degree. In the thermogramms of fen peat are two to seven expressed peaks; while of raised bog peat are not more than three peaks. DTA curve usually is similar to DTG curve (Fig. 1–3), however, as exception is temperature range approximately from 90–120 °C. In this range is characteristic DTG peak, while in the DTA curve at this range is slope (Fig. 3). This appearance can be explained with fact that in the temperature range from 100 to 120 °C occurs (Fig. 1–3), highly expressed, endothermic processes – loss of the hydroscopic moisture (Almendros et al. 1982; Francioso et al. 2005).

As the result of an endothermic reaction, due to a gas release, the input heat is absorbed. It is represented as an expressive curve slope on the thermogramms; this situation was observed in all analyzed peat samples. With 120 °C exothermal reactions begins to take place and begins collapse of the sample itself; although, this process interchange with less expressed endothermic reactions, as well. As the result of an exothermic reaction, due to a burning, the input heat is released. It is represented as an expressive peak. An important factor is that the highest weight loss occurs during exothermic processes; the loss during endothermic processes is negligible.

Fig. 1. thermogramm of a sedge fen peat sample, svetupe mire, depth: 2.30–2.35 m.a: dtG – speed of weight loss (%/min); b: dta – heat input (cel);

c: tG – amount of weight loss (%)

a

b

c

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Fig. 2. thermogramm of a grass fen peat sample, Viki mire, depth: 0.30–0.35 m.a: dtG – speed of weight loss (%/min); b: dta – heat input (cel);

c: tG – amount of weight loss (%)

Fig. 3. thermogramm of a wood-sphagnum fen peat sample, Viki mire, depth: 0.45–0.50 m.a: dtG – speed of weight loss (%/min); b: dta – heat input (cel);

c: tG – amount of weight loss (%)

a

b

c

a

bc

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There is an inherent appearance that most significant part of sample weight losses at the 300 °C (Fig. 1–3), the highest amount of sample weight (60%) losses at the temperature range from 250 to 400 °C which means that chemical compounds, which collapses at this temperature range, dominates in peat samples (Almendros et al., 1982; Rustschev and Atanasov, 1983). This appearance is observable also in raised bog peat samples thus it can be concluded that in composition of raised bog peat dominates similar chemical compounds. At the temperature of 300 °C to 350 °C (Fig. 1–3) frequently occurs collapse of polysaccharides and degradation of humic functional groups, carboxyl-, methyl-, methylene groups, cellulose and aliphatic chains, decarboxylation of acidic groups and dehydration of aliphatic structures. Intensity of peaks and area, at this temperature range, usually are inversely proportional to peat decomposition degree and directly proportional to content of plant biomass (Sheppard and Forgeron, 1987). Not less important is the range from 400 to 450 °C, in this range (Fig. 1–3) the highest intensity of DTG and DTA peak occurs. At these temperatures occurs oxidation of last carbon remains, pyrolysis of aromatic lignin components, degradation of lignin aromatic skeleton and humic substances, collapse of aromatic structures and cleavage of C-C bond (Sheppard and Forgeron, 1987).

It is characteristic that by the increase of depth on DTG and DTA curves occur more peaks thus changes in samples are more frequently. However, curves become less expressed and peak ranges wider.

rEfErEncEsAlmedros, G., Polo, A., Vizcagno, C. 1982. Application of thermal analysis to the study of several

Spanish peats. Journal of Thermal Analysis, 24, 175–180.Francioso, O., Montecchio, D., Gioacchini, P., Ciavatta, C. 2005. Thermal analysis (TG–DTA)

and isotopic characterization (13C–15N) of humic acids from different origins. Applied Geochemistry, 20, 537–544.

Rustschev, D., Atanasov, O. 1983. Thermal and group analysis of peat. Journal of Thermal Analysis, 27, 439–442.

Sheppard, J.D., Forgeron, D.W. 1987. Differential thermogravimetry of peat fractions. Fuel, 66, 232–236.

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GRound penetRatinG RadaR siGnal coRelation With peat pRopeRties in cenas tĪRelis

Jānis KaRušs

University of Latvia, Faculty of Geography and Earth Sciencese-mail: janis.karuss@inbox.lv

IntroduCtIonGround penetrating radar for investigation of various deposits, inter alia

bog deposits, is applied relatively recently. Already in the seventies of previous century was verified, that ground penetrating radar can be used for peat resources estimation in bogs (Bogorobckij i Trepov, 1979). Ground penetrating radar signals were detected and correlated with characteristic surfaces of the geological sections. That was considered to be appropriate for general peat evaluation.

Although several researches in past years were done, the reasons of ground penetrating radar reflections are not sufficiently explained till now. In these studies for the most part correlations of ground penetrating radar signals and determined properties of peat are searched. Thus the opinion is expressed frequently, that acquired ground penetrating radar signals are related to variations of density and moisture content of deposits within geological section (Oliveira et al., 2012; Plado et al., 2011; Slater and Reeve, 2002). In the same way it is noted, that ground penetrating radar signals may be related to changes of peat type and degree of decomposition within geological section (Comas et al., 2005; Hänninen, 1992). So it must to conclude, that there is not found generally accepted and sufficiently mathematically well-grounded statement of reasons for ground penetrating radar reflections in bogs.

mAtErIAlS And mEthodSIn Cena Tīrelis in autumn of the year 2012 geophysical measurements

using ground penetrating radar “Zond-12e” of SIA “Radar Systems” were done. Ground penetrating radar profiling was done with 300 MHz antenna system. Profile lenght measurements were done using measuring-tape. Location of the research area was determined wit GPS device “Magellan Explorist”. Several ground penetrating radar profiles with overall length about 3 km were recorded. For detailed studies ground penetrating radar profile cena-2 (x – 489430; y – 6301463) was chosen (Fig. 1).

For to be possible to correlate ground penetrating radar signals with physical properties of the deposits, in research area boreholes were done and samples for laboratory analysis were taken. Boreholes were done in places where at least several with changes of bog deposit properties related ground penetrating radar signals (except reflection from the bed surface of the bog) were recognized.

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Considering into account that ground penetrating radar signals rather frequently are explained with changes of moisture or ash content in geological section, for taken samples moisture content and ash content analysis were done. Moisture content was determined by weight loss within the samples after drying at 105 °C (Krūmiņš u.c., 2012). Ash content was determined by weight loss within the samples after burning them at 800 °C (Krūmiņš u.c., 2012). Laboratory analyses were done by the author of the paper in Rock investigation laboratory and in Environmental chemistry laboratory in Faculty of Geography and Earth Sciences of University of Latvia.

Accuracy of the obtained results of analysis was determined by using method of fractional uncertainties ( Jansons u.c., 1979). Measurement errors were calculated by equation 1.

(1)f – function;x – variable; n – count of variables.

Calculated moisture content errors vary between 0.005 and 0.02 mass percents. In their turn calculated ash content errors vary between 0.05 and 0.43 mass percents.

rESultSIn achieved ground penetrating radar profile it is possible to recognize

unambiguous signal, which is related to bed surface of the bog. It is possible also to detect five signals, which are related to bog deposit layers with different electromagnetic properties (Fig. 1).

Till now samples from borehole 2–1 (Fig. 1) are analyzed in laboratory. Within this borehole four layers of bog deposits are recognized. In dept to 0.6 m lies undecomposed plant layer. In dept interval from 0.6 m to 2.6 m lies brown peat of low degree of decomposition. In this peat layer also separate plant remains are recognizable. In dept interval from 2.6 m to 3.25 m lies dark-brown peat of low degree of decomposition. This peat is more dense than overlying peat, but also there separate plant remains are recognizable. In dept interval from 3.25 m to 4.42 m lies dark-brown peat of average degree of decomposition. Peat in this layer is dense, in places with black-coloured interlayers and plant remains are rarely recognizable there.

Moisture content in vertical section of borehole 2–1 varies between 87 and 95 mass percents. In the section rather high moisture content layers interchanges with considerably lower moisture content layers (Fig. 2). In general natural moisture content of deposits decreases in section downward direction.

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Fig. 1. in cena tīrelis obtained ground penetrating radar profile (vertical line indicates location of the borehole 2–1)

Fig. 2. moisture content changes in borehole 2–1

Fig. 3. ash content changes in borehole 2–1 (error bars indicate calculated ash content errors)

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Ash content in vertical section of borehole 2–1 varies between 0.43 and 7.3 mass percents. In general ash content is increasing downward in section, however it is also possible to recognize a layer with rather high ash content in depth interval from 80 to 90 cm (Fig. 3).

In the geological section there are several intervals identified (150–170 cm, 200–230 cm, 260–270 cm, 370–390 cm) with relatively large moisture content varieties, which can not be unambiguously related with ground penetrating radar signals nonetheless (Fig. 2). Since ash content in the section downward direction gradually increases, ground penetrating radar signals can not be related also with ash content changes.

ConCluSIonSIn view of till now achieved results in Cena Tīrelis it is concluded that

ground penetrating radar signals in geological section can not be explained by moisture content changes or ash content changes alone, as well as combination of these two parameters. For searching the reasons of ground penetrating radar reflectations, in further such peat properties like degree of humification and botanical content need to determine. However up to now done researches there are no recognized well-founded relations with above mentioned peat properties and ground penetrating radar signals. Thereby attention should be paid on theoretical models developing which at least in some cases could offer explanation of acquired ground penetrating radar signals.

In general it is concluded that both moisture content and ash content are determined with relatively high precision, so the acquired date are usable for high accuracy calculus.

rEfErEncEsBogorobckij, V.V., Trepov, G.V. 1979. Radiolokatsionnuie izmereniya tolshchinui zalezheĭ torfa i

sapropelya. Zhurnal tekhnicheskoĭ fiziki, 49(3), 670–673.Comas, X., Slater, L., Reeve, A. 2005. Stratigraphic controls on pool formation in a domed bog

inferred from ground penetrating radar (GPR). Journal of Hydrology, 315, 40–51.Hänninen, P. 1992. Application of ground penetrating radar techniques to peatland investigation.

Geophysical Survey of Finland, 16, 217–221.Krūmiņš, J., Silamiķele, I., Purmalis, O., Stankeviča, K., Kušķe, E., Pujāte, A., Ozola, I., Ceriņa, A.,

Rūtiņa, L., Stivriņš, N. 2012. Kūdras un sapropeļa pētījumu metodes. Rīga, Latgales druka, 80.Jansons, L., Zambrāns, A., Badūns, A., Ginters, M., Jansone, A. 1979. Fizikas praktikums. Rīga,

Zvaigzne, 504.Oliveira, M., Porsani, J., Lima, G., Jeske-Pieruschka, V., Behling, H. 2012. Upper Pleistocene

and Holocene peatland evolution in Southern Brazilian highlands as depicted by radar stratigraphy, sedimentology and palynology. Quaternary Research, 77, 397–407.

Plado, J., Sibul, I., Mustasaar, M., Joeleht, A. 2011. Ground – penetrating radar study of the Rahivere peat bog, eastern Estonia. Estonian journal of earth sciences, 60(1), 31–42.

Slater, L.D., Reeve, A. 2002. Case history: investigating peatland stratigraphy and hydrogeology using integrated electrical geophysics. Geophysics, 67, 365–378.

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paleoVeGetation chanGes in the laKe pilVelis

a liene ustupe, aija ceRiŅa, b Karina stanKeViČa, laimdota KalniŅa, māris KļaViŅš

University of Latvia, Faculty of Geography and Earth Sciencese-mails: a l.ustupe@gmail.com; b karina.stankevica@lu.lv

AbStrACt Spore – pollen analysis of lake sediments is significant because it results gives

insight in the vegetation changes around the lake, allows to reconstruct past vegetation dynamics, past climate change and anthropogenic impact on vegetation.

If the spore – pollen analysis, mainly reflects the regional vegetation then the plant macrofossil analysis provides information about local vegetation and allows to determine the environmental conditions in basin where the macrofossil complex was found.

The study aim is to investigate the paleovegetation changes in the Lake Pilvelis during the development of the lake, using the paleobotanical sediment analysis and radiocarbon dating (14C).

Key words: spores, pollen, plant macrofossils, lake sediments

IntroduCtIonThe Lake Pilvelis, also known as Lake Kaupinka, is located in the south-

western part of Raznavas hilly area of Latgale Upland (Markots, 1997).Pilvelis Lake is located in the small interhill depression which is partly

bogged up and over time part of the lake shallows were overgrowing formed biogenous deposits – peat (bQ 4) and gyttja (lQ 4). Interhill depression formed during the last glacier activities between the moraine hills, which consists mainly of glacigenic sediments moraine sandy loam and clay loam (gQ3ltv).

For this study was used sediments from 4 m thick sediment core was made 50 m from the lake north-west coast. From the core were taken samples for spore-pollen, plant macrofossil analysis and sediment dating with the 14C method.

During spore-pollen analysis were made two percentage pollen diagrams with six subdivided pollen zones. Climate warming observed in the three zones, in which dominate broad-leaved pollen, as well as noted increasing proportion of herbaceous pollen.

After the plant macrofossil analysis is possible to distribute six zones. The results deduce that plant diversity in the Lake Pilvelis begins to increase before 2700 calendar years. This is related with rising water level and increasing nutrient inputs into the lake as a result of human impact increase.

37

mAtErIAlS And mEthodSIn this study was used 4 m thick sediment profile from Lake Pilvelis.

Sampling point (56°39’45.21” N lat., 27°17’31.40” E long.) was selected according earlier investigations and after lake sounding and getting information about gyttja layer.

Coring was done at the western part of lake (Rutina et al., 2012).The lake sediment section from bottom to top up consists of limnic clay (3.9

to 4.0 m), organic gyttja (3.9 to 2.0 m), sandy gyttja (2.0 to 1.30), peat (1.30–1.20 m) and organic gyttja (1.35–0.0 m).

Pollen samples were prepared based on standard KOH and acetolysis methods. Stained with fuchsine and mounted in glycerine for the microscope slide preparation. For each sample were identified at least 400 terrestrial pollen grains. The pollen data were expressed as percentages of the total pollen sum (Moore and Web, 1978).

Samples for macrofossils analyses (approximately 50 cm3) were washed through sieves with a gentle spray of water. The residue was washed gently off the sieve into a container and kept cold until analyse. Small quantities of the residue were suspended in 2–3 mm of water in a shallow dish (e.g., Petri dish) and examined systematically under a stereomicroscope at about 40 magnifications until the whole sample had been examined. Remains of interest were picked out and sorted, identified (Velichkevich and Zastawniak, 2006; Velichkevich and Zastawniak, 2008), counted, and tabulated (Birks, 1980). Pollen and macrofossil diagrams were compiled using Tilia 1.17.6. and TGView 2.0.2. program.

Several samples containing material suitable for radiocarbon dating were selected and packed separately directly in the field. The bulk samples of sediments were sent to the Institute of Geology at Tallinn University of Technology, Estonia. In total, 9 horizons were dated. Calibrated 14C years were transformed and an age-depth model was built with using the programs CLAM 2.1. (Blaauw, 2010) and R 2.15.2. (R Core Team, 2012).

rESultS And IntErprEtAtIonSampling point in the Lake Pilvelis was located 50 m from north western

coast, which has been overgrown and formation of fen took place. In the result of these preconditions small amounts of coastal and terrestrial plant remains have been found in the sampled lake sediments.

RESULTS of SPoRE – PoLLEN aNaLYSISLocal pollen zones have been defined based on the claster analysis and

changes in dominant pollen curves – highs, lows, peaks. There were divided six local pollen zones.

The 1st pollen zone Betula–Pinus distributed from 4.00 to 3.61 m depth, before 10 200 to 9280 calendar years. The depth interval from 4.00 to 3.90 m consists of limnic clay, 3.90 to 3.61 m depth interval consists of organic gyttja.

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In this zone dominate birch Betula (Fig. 1), reaches 66% from all pollen amount, found hazel Corylus average 5%. Shrubs represent willow Salix, average 1–3%, pollen. Coniferous are dominated by pine Pinus, an average of 20%. Herb pollen (Fig. 2) mainly represented by grass Poaceae pollen, reaching 6.4% and 1.3% Cyperaceae from all pollen amounts. The aquatic pollen is found mostly 0.2% cattail Typha, water lily family Nymphaea and pondweed Potamogeton pollen. Birch, pine, grass dominance and low diversity of herbaceous indicate cool conditions that limited the spread of the plants.

2nd pollen zone Pinus–Ulmus distributed from 3.61 to 3.09 m, before 9280 to 8090 calendar years. The depth interval from 3.61 to 3.09 m consists of organic gyttja.

Observed percentage increase of pine Pinus pollen, reaching a high of 29.2%. While the spruce Picea pollen retains a stable incidence, ranging from 1.3% to 6%. Also increase of broad-leaved elm Ulmus pollen percentage from 3.3% to 9%. Alder Alnus and hazel Corylus pollen percentages is growing, respectively, from 1.5% to 4.7% and from 7% to 17.7%. Appears dwarf shrubs heather Ericaceae pollen and from cultivated plants flax family Linaceae pollen. From herbs dominate sedge family Cyperaceae, above 3%, and grasses Poaceae, over 1.7% of all pollen sums, maintaining a constant curve. Ruderal herbs represent – mugwort Artemisia, an average of 2.4%, plantain Plantago average of 0.5%. The spores are represented by ferns Polypodiaceae, Sphagnum, horsetail Equisetum.

Fig. 1. tree and shrub pollen percentage diagram of the lake pilvelis

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3rd pollen zone Betula–Corylus–Tilia is subdivided in section depth interval from 3.09 to 2.31 m, represented organic gyttja in the depth interval from 3.09 to 2.31 m, formed before 8090 to 6340 calendar years.

Values of birch Betula pollen reaches 27%, as well as, hazel Corylus pollen reaches high values above 18.5%. Increasing of linden tree Tilia and oak Quercus pollen ranging from 1.2% to 6.2%, Alnus and Ulmus, above 5.8% from total pollen amount has been observed. Increasing of broad leaved tree pollen indicates the climate warming. Spruce Picea pollen amount remains in range of 2.4–5.3%, while the pine Pinus values is reduced by 9%, comparing with 2nd zone. The number of Salix pollen is increasing. Observed decrease in the values of herb pollen, although in small amounts appear carnation Caryophyllaceae, madder Rubiaceae and Umbelliferae although known as Apiaceae family’s pollen. The number of aquatic plants decreases in the interval of zone, but increase the percentage of spores.

4th pollen zone Corylus–Alnus–Picea subdivided in depth interval from 2.31 to 1.60 m, before about 6340 to 4800 calendar years. The depth interval from 2.31 to 1.99 consists of organic gyttja, from 1.99 to 1. 60 m depth interval composition of gyttja has been changed due to increase of ash values (up to 40%) (Stankevica et al., 2012).

Continues dominance of broadleaf – hazel Corylus the average incidence in all zone is 17.8% of the total amount of pollen. Alder Alnus and ash Fraxinus pollen increase at the end of the zone, but decrease amount of Betula pollen. Constant values retain linden Tilia and oak Quercus pollen in range from 4–7.3%. Number of Ulmus pollen varies from 10.6% to 14.1%. Appears small amount of hornbeam Carpinus pollen. Increase percentage of spruce Picea pollen, reaching 15.6% from total amount of pollen. Throughout zone interval shrub willow Salix pollen decreased, but pollen amount of Ericaceae Increased. At the end of zone decreased grass family Poaceae and sedge family Cyperaceae, but increased percentage amount of aquatic plants pondweed Potamogeton pollen. It is observed that number of spore plants – horsetail Equisetum and Sphagnum increase in zone. Broad leaved tree pollen dominance refers to the warm and favourable climate for growing.

5th pollen zone Betula–Alnus is subdivided from 1.60–0.80 m depth (before 4800 to 2550 calendar years). 1.60 to 1.42 m depth interval consists of silicate gyttja with high amount of ash up to 40% (Stankevica et al., 2012), from 1.42 to 1.30 m depth interval consists of Hypnum peat and the depth interval between 1.30 to 0.80 m consists of organic gyttja.

The Betula reaching 34.1% of the total pollen amount dominates, alder Alnus pollen, reaching 29.4%. About 3–5% observed decline of hazel Corylus, elm Ulmus and linden tree Tilia pollen percentages. In the middle of zone beech Fagus pollen appear reaching up to 0.5% of the total amount of pollen. At the end of zone hazel Corylus decreased, but increased hornbeam Carpinus pollen values. A slight increase of pine Pinus, but decrease in spruce Picea pollen has

40

been observed. Decrease in grasses Poaceae amount, but about 0.4% increased of sedge family Cyperaceae pollen has been noted. Pollen dispersal of mugwort Artemisia, buttercups Ranunculus and carrot family Apiaceae have been increased. Number of the aquatic plants – water lily family Nymphaceae and pondweed Potamogeton pollen, as well as, value of spores – horsetail Equisetum and Sphagnum decreased.

6th pollen zone Betula–Pinus–Poaceae is subdivided in the upper part of Lake Pilvelis sediment section from 0.80 to 0.00 m (before 2550 calendar years till nowadays – 1950). The depth interval from 0.80 to 0.00 m represented by organic gyttja.

In the zone birch Betula pollen varies from 29 to 42.2%, Pinus reached 26.3% of the total amount of pollen. In the zone increased pollen amount of birch Betula and conifers – pine Pinus and spruce Picea pollen, but amount of broad-leaved pollen decreased because the climate conditions become more favourable to the spread of conifers not broad-leaved trees. Increase the prevalence of grass family Poaceae, reaching 2.6% of total pollen amount and decrease the pollen amount of sedge family Cyperaceae. At the end of the period increase herbaceous – aster family Asteraceae, nightshade family Solanaceae, and carrot family Apiaceae pollen amount. Cultivated plants, rye

Fig. 2. herb pollen percentage diagram of the lake pilvelis

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Secale cereale, values in zone reach about 1.5% of the total pollen amount. It can be explained by influence from agricultural areas increase near the lake or in the banks of river which inflow into the lake. In zone is observed decrease in number of aquatic plant pollen, but at the end of period increase amount of algae Pediastrum sp., which is an indicator to eutrophication process in the lake. Increase of Sphagnum spores and decrease in amount of fern Polypodiaceae spores is noted.

RESULTS of PLaNT macRofoSSIL aNaLYSISSix plant macrofossil zones have been subdivided in diagram based on the

macrofossil composition and their changes in the sediment core of the Lake Pilvelis (Fig. 3):

I PM zone – Carex, subdivided in the plant macrofossil diagram in the depth interval 4–3.9 m. Zone is poor in macroremains. There have been found rare Carex nutlets and Characeae oospores. Betula sect. Albae nutlets washed from lake shores were found. Chitin fragments of zooplankton and several Hypnum moss leaves and culms occurred. Hence, it was suggested that during accumulation of clay in the bottom part of section there were small amount of aquatic plants in the lake.

II PM zone – Najas marina-Najas flexilis-Typha-Carex subdivided in the depth interval 3.9–3.2 m represented by organic gyttja. Sediments in zone

Fig. 3. plant macrofossil distribution in sediment section of the lake pilvelis

42

contain remains of N. marina, N. flexilis and Typha, Carex and Characeae oogonia. Regular presence of bryozoans Cristatella mucedo (Cuvier, 1798) statoblasts was observed. Detritus consisted of washed in fragments of tree-plant leaves and twigs, aquatic plant vegetative remains were found in small numbers.

III PM zone – Najas flexilis-Characeae-Potamogeton pussillus subdivided in the depth interval 3.2–2.4 m of organic gyttja. Interval is rich in Characeae oogonia, P. pusillus and especially N. flexilis seeds. This kind of coexistence of N. flexilis and P. pusillus was established in sediments of climatic optimum of the Holocene and Subboreal chronozone in Poland (Galka et al., 2012). In some layers bryozoa statoblasts occurred in significant amounts. Bryozoa C. mucedo indicated relatively high water temperature, small wave action, medium or high levels of calcium, medium level of magnesium, slightly acidic water and medium water colour (Okland and Okland, 2000). Seeds of coastal plants were not found, probably indicating some water level rising since the II PM zone.

IV PM zone – Betula subdivided in the depth interval 2.4–1.8 m. Zone is very poor in plant remains – almost no aquatic and telmatic plants. Small fragments of zooplankton chitin and Daphnia ephippia remains were found, as well as, few bryozoa C. mucedo statoblasts occurred. Hypnum moss leaves were found more than in III PM zone. Washed in Betula nutlets were dominant. Lack of aquatic plant remains can be explaned by lake water level rise. Disappearance of terrestrial plant and limnophyte remains suggest deep water and a remote location from the shoreline (Birks and Birks, 1980). Presence of Hypnum moss remains give evidence about bogging-up surrounding areas.

V PM zone – Betula-Picea-Characeae subdivided in the depth interval 1.8–0.9 m represented by silicate in lower part and organic gyttja in upper part of zone. Characeae oogonia and seeds of P. pusillus, Typha sp. occurred in small amounts. Remains of Daphnia rapidly increased and reach maximum values. Daphnia are considered to be particularly useful for answering questions regarding the effects of climatic warming on both plankton communities and whole ecosystems, as they represent a major link in the energy flow between primary producers and secondary consumers in food webs (Wojtal-Frankiewicz, 2012).

Washed in spruce needles and seeds indicate that spruce was growing in surrounding areas. Increasing number of aquatic plant remains may indicate water level decreasing but growth of Hypnum moss leaves especially from 1.3 m till 1.1 m – about reducing of open water areas of lake. Lower part of zone interval, represented by silicate gyttja is characterised by significant increase in remains of aquatic fauna, mainly represented by Daphnia ephippia.

VI PM zone – Potamogetons natans-Nymphaea alba-Characeae subdivided in the top interval of lake sediment section from 0.9–0 m represented by organic gyttja. Dominant species were P. natans, N. alba, Characeae. Daphnia and bryozoa occurred in small amounts. P. natans and N. alba indicate, that in this

43

period floating-leaved plants were more common. Increasing number of aquatic macrophytes species and total amount of aquatic plants remains were suggested that water level was slightly raising and water was enriched with nutrients. From 0.2 m to top of sediments sphagnum moss leaves were found indicating about transition mire development in the lake shore.

Presence of N. flexilis, N. marina and Characeae in sediments at depth interval 4.0–2.4 m indicate that lake’s water reaction was alkaline or near neutral (Feldmann and Noges, 2007).

Further bogging-up process caused water acidification. This circumstance determinate N. flexilis extinction. Eutrophication and acidification of lakes are the main threats to N. flexilis. Acidification appears to reduce the ability of N. flexilis to produce seeds (potentially fatal for an annual). On the other hand, eutrophication leads to conditions where N. flexilis, an obligate carbon dioxide utiliser, cannot photosynthesise due to the predominance of bicarbonate rather than dissolved carbon dioxide in lake water (Wingfield et al., 2006).

ConCluSIonSSince approximately before 2500 years till the present day the Lake Pilvelis

is eutrophic lake because of increase of aquatic plant macrofossil remains and diversity of species, as well as, it is proved by pollen data, showing increase in reed, sedge, horsetail and aquatic plant pollen, which indicates lake fill-in processes and fen development at the lake shore.

Traces of man agricultural activities can be determined approximately before 1500 calendar years, indicated by finds of rue Secale cereale pollen in lake sediments at depth of 40 cm.

Obtained results show that the organogenic lake sediments begun to accumulate at the depth 3.9 m before 9900 calendar years.

rEfErEncEsBirks, H.H. 1980. Plant macrofossils in Quaternary lake sediments. Archiv fur Hydrobiologie, 15.

1–60.Birks, H.J.B. and Birks, H.H. 1980. Quaternary Palaeoecology. Edward Arnold, London, 66–84.Blaauw, M. 2010. Methods and code for “classical” age-modelling of radiocarbon sequences.

Quaternary Geochronology, 5, 512–518.Feldmann, T., Noges, P. 2007. Factors controlling macrophyte distribution in large shallow Lake

Vortsjarv. Aquatic Botany, 87: 15–21.Galka, M., Tobolski, K., Kolaczek, P. 2012. The Holocene decline of slender naiad (Najas flexilis

(Willd.) Rostk. and W. L. E. Schmidt) in NE Poland in the light of new palaeobotanical data. Acta Palaeobotanica, 52(1): 127–138.

Markots, A. 1997. Rāznavas pauguraine [Rāznavas hilly]. In: Kavacs, G. (ed.) Latvijas dabas enciklopēdija, 4. sējums. Preses nams, Rīga, 226–288.

Moore, P. D., and Webb, J. A. 1978. An Illustrated Guide to Pollen Analysis. Hodder and Stoughton, London. 133 p.

R Core Team. 2012. Writing R Extensions. Version 2.15.2. 167 p.

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Økland, K., Økland, J. 2000. Freshwater bryozoans (Bryozoa) of Norway: Distribution and ecology of Cristatella mucedo and Paludicella articulate. Hydrobiologia, 421: 1–24.

Rūtiņa, L., Ceriņa, A., Stankeviča, K., Kļaviņš, M. 2012. Character of paleovegetation change in lakes Pilcines, Pilveļu and Padēlis. Acta Biologica. University of Daugavpils, Suppl. 3, 94–107.

Stankevica, K., Klavins, M., Rutina, L., Cerina, A. 2012. Lake sapropel: a valuable resource and indicator of lake development. Advances in Environment, computational chemistry and bioscience. WSEAS Press: Montreux, 247–262.

Velichkevich, F. Y., Zastawniak, E. 2006. Atlas of the Pleistocene Vascular Plant Macrofossils of Central and Eastern Europe. Part 1 – Pteridophytes and Monocotyledons. Krakow, W.Szafer Institute of Botany, Polish Academy of Sciences.

Velichkevich, F. Y., Zastawniak, E. 2008. Atlas of the Pleistocene Vascular Plant Macrofossils of Central and Eastern Europe. Part 2 – Herbaceous Dicotyledons. Krakow, W.Szafer Institute of Botany, Polish Academy of Sciences.

Wingfield, R., Murphy, K. J., Gaywood, M. 2006. Assessing and Predicting the Success of Najas flexilis (Willd.) Rostk. & Schmidt, a Rare European Aquatic Macrophyte, in Relation to Lake Environmental Conditions. Biology and Environmental Studies: Journal Articles (Peer-Reviewed), 1: 10–26.

Wojtal-Frankiewicz, A. 2012. The effects of global warming on Daphnia spp. population dynamics: a review. Aquatic Ecology, 46: 37–53.

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paleoVeGetation chanGes accoRdinG to macRofossil inVestiGation data

duRinG the deVelopment of laKe mazais unGuRs

a anda stašKoVa, b aija ceRiŅa, c agnese puJāte

University of Latvia, Faculty of Geography and Earth Sciencese-mails: a anda.staskova@inbox.lv; b aija.cerina@lu.lv; c agnese.pujate@gmail.com

AbStrACtThe results of the study provide information of the paleovegetation changes

according to macrofossil investigation data during the development of Lake Mazais Ungurs and Isoëtes lacustris (lake quillwort) occurrence in relation to sediment chemical parameters.

Results allow to conclude that changes of aquatic plant macrofossil composition in Lake Mazais Ungurs sediment, is directly affected by swamp Ungurs impact on the Lakes water pH. Aquatic plant and wet meadow plant community changes indicate the water level fluctuations in Lake Mazais Ungurs.

Key words: plant macrofossil analysis, Isoëtes lacustris, chemical analysi

IntroduCtIonLake Mazais Ungurs is a glacial type lake, which is endangered because of

anthropogenic impact, therefore, it is necessary to research the development of the Lake to find the best method how to protect it and some very rare aquatic plant species. Especially important is Isoëtes lacustris (lake quillwort), which reproduction and population amount is mainly determined by the lakes location, water and sediment chemistry (Smolders et al., 2002). The study results, including fieldwork (coring, sediment description), plant macrofossil analysis and sediment chemical analysis, allows to conclude that changes of aquatic plant macrofossil composition in Lake Mazais Ungurs sediment, is directly affected by swamp Ungurs impact on the Lakes water pH and the appearance of Isoëtes lacustris in lakes sediment coincides with the appearance of wood coal, which may be a reflection of the impact human activities have on species development.

Study ArEALake Mazais Ungurs (also known as a lake Rustēgs) is located in the eastern

Latvia (Fig. 1) (57o19´58´´N 25o03´54´´E) at an elevation of 69 m. Depth of the lake bed is about 5 m. Third of the lake bed is filled by gyttja, which consists of organogenic – siliceous gyttja (Alksnītis, 1997). Mean January temperature is –6.2 °C and mean July temperature is +16.7 °C (Kavacs, 1994).

46

mEthodSA 5.55 m-long sediment core was collected from Lake Mazais Ungurs in

March 2012. The upper layer (50 cm) of sediments, including an undisturbed sediment water interface, was collected with a modified piston sampler. Other part of Mazais Ungurs sediments section was sampled with Russian type corer with 1 m long camera.

PLaNT macRofoSSIL aNaLYSISThe sampling interval was 5 cm. The volume of each subsample was

approximately 50 mL. Altogether 120 samples from sediment core were prepared for macrofossil analysis following standard techniques (Warner, 1990). Identification of plant macrofossil was based on available reference materials (Cappers et al., 2006; Katz et al., 1965).

chEmIcaL aNaLYSISSediment chemical analysis determined the total nitrogen concentration

(g kg–1) using a modified Kjeldahl method according to ISO 11261 (1995) standard; phosphorus pentoxide (g kg–1) concentrations (Tan, 2005) and sediment pHKCl value method according to ISO 10390 (2005) standard.

rESultSPlant macrofossil

Five plant macrofossil assemblages (PMA) were determined (Fig. 3):PMA-I (5.55–4.95 m).A small number of coastal plant remains (Scirpus lacustris and Carex). The

dominance of different insect remains, maximum at the depth of 5.0 m. Bryozoa (Fig. 2c) appearance in this PMA. Macroremains of birch are prevailing in this PMA, which probably were transported in by a wind.

Fig. 1. lake mazais ungurs are located at the augstroze hilly area of the idumeja highland

47

Fig. 2. a – isoëtes lacustris megaspores; b – charcoal; c – bryozoa statoblast

a b c

Fig. 3. plant macrofossil diagram of lake mazais ungurs

PMA-II (4.95–3.45 m)Characeae oogonia were found in the lake sediments in a depth of 4.95 m.

A few macroremains of Pinus sylvestris determined at the depth of 3.75 m and 4.90 m. At the depth of 4.10 m Hydroptildae remains were found.

PMA-III (3.45–2.60 m)The dominance of remains of aquatic plants – Nuphar lutea, maximum at the

depth of 3.15 m and Characeae oogonia also were found.

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PMA-IV (2.60–2.05 m)Only a few plant remains were found in this depth interval. A charcoal

(Fig. 2b) appearance in this PMA may be a reflection of the impact of human activities around the lake.

PMA-V (2.05–0 m)Dominate seeds of aquatic plants (Isoëtes lacustris, Typha, Nuphar lutea).

Isoëtes lacustris was found at the depth of 2.05–0 m that suggests that it has not been in Lake from its beginning. The quantity of charcoal is in its maximum. Macroremains of plants from wet meadows and fens (Carex, Lycopus europaeus, and Comarum palustris) were found in this depth interval.

SEdImENT chEmIcaL aNaLYSISThe chemical analysis data of the specially protected aquatic species Isoëtes

lacustris (Fig. 4), shows that in the places where the species are growing, the concentrations of the total nitrogen (g kg–1), phosphorus pentoxide (g kg–1) and total carbon (%) content are bigger than the places were Isoëtes lacustris are not growing. But the sediment pHKCl value was bigger where the species are not growing.

dISCuSSIonThe annual influx of allochthonous mineral matter (sediment yield and

the dominant grain-size) into the Lake Mazais Ungurs is determined by the rate of catchment erosion and ease of material transportation during

Fig. 4. the chemical analysis data of the specially protected aquatic species Isoëtes lacustris

49

the spring snowmelt runoff. Changes in the catchment, such as forest fires and anthropogenic activities like forest clearance and agriculture, typically increase and amplify the general rate of erosion and sediment transportation into the Lake. Charcoal in lakes sediment may be a reflection of the impact of human activities on I. lacustris development, because in the north of the lake is located national protected archaeological monuments – Ureles hillfort and ancient burial ground Zaļkalni (Sprūds, 2006). In the plant macrofossil data a remarkable increase in I. lacustris megaspores values is likely to be connected to increased mineral matter input into the lake. Studies from southern Finland suggests that increasing erosion and the consequent accumulation of mineral mater on the lake bottom makes conditions more favourable for the growth of Isoëtes (Ojala and Alenius, 2005).

In the southeast of Lake Mazais Ungurs, there lies bog Lielais Ungurs, from which humus substances are flowing into the lake, because of this, water transparency is decreasing as well as pH (Sprūds, 2006). In the deeper parts of the sediment, interval from 3.50–3.30 m, were found Potamogeton natans seeds, for which an optimal water pH value for development is from 6.7 until 7.2 (Barr and Roelofs, 2002). Now that the area of swamp Ungurs is increasing, even more humus substances are being streamed into the lake. Perhaps because of this P. natans and Characeae are disappearing, but Nuphar lutea which are more resilient to fluctuations in pH (5.9–8.2) are appearing (Barr and Roelofs, 2002). The continuous decline of water pH contributes to the disappearance of Nuphar lutea and the appearance of I. lacustris, which appear in Lake Mazais Ungurs at the depth of 2.50 metres. Optimal water pH value for I. lacustris development is 5.6–5.8 (Barr and Roelofs, 2002), but they could grow also to pH 4.5 (Husak et al., 2000).

ConCluSIonSChanges of aquatic plant macrofossil composition in Lake Mazais Ungurs

sediment is directly affected by bog Lielais Ungurs impact on the Lakes water pH: seeds found in the deeper parts of the sediment (Nuphar lutea, Potamogeton natans, Characeae) indicates towards basic Lake water pH, but the upper parts of sediment (Isoëtes lacustris, Typha) suggest acidic water pH value. Aquatic plant (Nuphar lutea, Isoëtes lacustris, Potamogeton natans, Scirpus lacustris, Typha) and wet meadow plant (Carex, Lycopus europaeus, Comarum palustris) community changes indicate the water level fluctuations in Lake Mazais Ungurs. Isoëtes lacustris development in Lake Mazais Ungurs coincides with the appearance of charcoal appearance in sediments, which may be a reflection of the human impact on the development of Isoëtes lacustris.

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rEfErEncEsBarr, J., Roelofs, J.G.M. 2002. Distribution of Plant Species in Relation to pH of Soil and Water.

In: Rengel, Z. (ed.) Handbook of Plant Growth. pH as the Master Variable. Perth, University of Western Australia, 384–386.

Cappers, R.T.J., Bekker, R.M., Jans, J.E.A. 2006. Digital seed atlas of the Netherlands. Groningen, Barkhuis publishing & Groningen University library.

Husak, Š., Voge, M., Weilner, C. 2000. Isoëtes echionospora and I. lacustris in the Bohemian Forest lakes in comparison with other european sites. Silva Gabreta, 4, 245–252.

Kavacs, G. 1994. Augstrozes paugurvalnis. Grām.: Kavacs, G. (red.) Latvijas daba: enciklopēdija. 1. sēj. Rīga, Latvijas enciklopēdija, 85–86.

Katz, J.A., Katz, S.V., Kipiani, M.G. 1965. Atlas and keys of fruits and seeds occuring in the quaternary deposits of the USSR. Moscow, Publishing house Nauka.

Ojala, A.E.K., Alenius, T. 2005. 10 000 years of interannual sedimentation recorded in the Lake Nautajarvi (Finland) clastic – organic varves. Palaeogeography, Palaeoclimatology, Palaeoecology, 219, 285–302.

Smolders, A.J.P., Lucassen, E.C.H., Roelofs, J.G.M. 2002. The isoetid environment: biogeochemistry and threats. Aquatic Botany, 73, 325–350.

Sprūds, J. 2006. Ungura dabas aizsardzības plāns. Latvijas ezeri. www.ezeri.lv/blog/DownloadAttachment?id=743

Tan, K., H. 2005. Soil sampling, preparation, and analysis. Second edition. Taylor& Francis Group, Boca Raton, 623.

Warner, B.G. 1990. Plant Macrofossils. Methods in Quaternary Ecology. Geoscience, 53–63. ISO 10390. 2005. Soil Quality – Determination of pH. International Organization for Stan-

dardization. Geneva, Switzerland, 5.ISO 11261. 1995. Soil Quality – Determination of total nitrogen – Modified Kjeldahl method.

International Organization for Standardization. Geneva, Switzerland, 4.

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studies of modeRn pollen “Rain” in seda miRe

a liene ustupe, laimdota KalniŅa, agnese puJāte

University of Latvia, Faculty of Geography and Earth Sciences e-mail: a l.ustupe@gmail.com

IntroduCtIonVegetation has been changed during the mire development in result of both

nature factors and human impact. It is essential to forecast vegetation further development based on the knowledge of its character in the past.

Pollen monitoring in Seda Mire is carried out in two sites. One Tauber trap is settled in semi – natural forested mire, where human impact is insignificant, but the second trap is located in extracted peatland, where human impact is very strong. Pollen monitoring in Seda Mire was started in 1998 (Kalnina et al., 2009), but in 2003 location of traps were changed because of damages and overflowing. Since 2003 new sites traps are settled.

Seda Mire is the fourth largest mire (7582 ha) in Latvia located in North Vidzeme Biosphere Reserve and nowadays is partly extracted peatland. The aim of investigation is to analyse the modern pollen “rain” monitoring data, to compare them with surrounding vegetation and to assess the changes of the Seda Mire vegetation. In this research is analysed data from 2007 till 2011 year.

mEthodSAccording to Pollen Monitoring Program guidelines (Hicks et al., 1996,

1999) in Seda Mire were placed two modified Tauber traps and surround the traps was made vegetation mapping.

Moss polster samples for pollen analysis have been taken next to the each trap (Cundill, 1991; Pardoe et al., 2010; Prentice, 1986).

The results of pollen counting were to process by computer program Tilia 2.0. and the pollen diagram was created.

rESultSInfluence of the dominating the south winds in the spring (April, May)

during blossoming of the Pinus, Betula, Picea, Alnus has been noted both in data from traps as well that from moss pollster. The best agreement has been found between values of the different forest tree species. Pollen composition from mosses pollsters show more differences, which can be explained by wash-out pollen and spores from very upper layer. In moss samples dominate spores, for example, Pteridophyta.

Pollen monitoring in Seda Mire is carried out in two sites – SE3 and SE4. SE3 Tauber trap is settled in semi – natural forested mire, where human impact

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is insignificant, but the second trap SE4 is located in extracted peatland, where human impact is very strong. Comparison of composition of pollen spectra with that of the tree species in the surrounding forests of trap reflects influence of the south, south-western winds.

Around the pollen trap SE3 in vegetation dominate Urtica dioica, Rubus idaeus, Pteridophyta, Betula, Picea (Fig. 1). The second pollen trap SE4 is located in extracted peatland therefore dominate Betula and Calamagrostis epigeios and other herbs are common in some samples (Fig. 2). Around the trap SE4 Pinus and Picea are spreading. Although at changes in surrounding vegetation during monitoring has not recognized. Pollen data and vegetation mapping results reflect that last 5 year, since 2007 till 2011, in both pollen traps increase herbs pollen diversity.

Pollen percentage data from SE3 pollen trap (Fig. 3) reflect dominance of Betula, Pinus, Urtica, Poaceae and Pteridophyta. Pollen spectra in 2008 represent increase of herb pollen and decrease of tree pollen which indicate secondary succession because of complete deforestation in 2007 not far from SE3 pollen trap. SE4 pollen trap data reflect dominance of Betula, Alnus, Poaceae, Asteraceae (Fig. 4). Betula and Pinus pollen dominated in both pollen traps.

Fig. 1. tree mapping around the se3 Fig. 2. tree mapping around the se4

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Fig. 3. pollen percentage diagram from seda mire, site se3

Fig. 4. pollen percentage diagram from seda mire, site se3

dISCuSSIonTree pollen spectra characterize the composition of regional vegetation,

which changes may in turn be associated with climate change and human activity. Regional vegetation is considered of plants, mostly trees, located at least 100 m away from the Tauber trap.

Sedas Mire is one of recent pollen “rain” monitoring sites in Latvia, where Tauber type pollen trap is operated since 1998 to 2012.

Data obtained during years 2007–2011 have been compared with that from earlier years. It was found that it is very complicated to compare these data because during years 2003–2005 more attention was given to the tree pollen data, which reflects regional vegetation (Kalniņa et al., 2007). Influx values from monitoring data from 2003–2005 is different from latest monitoring period, however the main tendencies in pollen volume and diversity can be comparable.

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Herb pollen in trap SE3 mainly represented by Urtica and Poaceae, which high influx values from 2007–2011 can be explained by that Urtica and Poaceae are anemophylous plants, which produce large amount of pollen. Vegetation mapping prove that Urtica is growing close to the trap, just in distance 0.5 m. Increase in herb pollen diversity can be observed since year 2008, just 1 year after complete deforestation nearby.

Poaceae pollen is dominating in trap SE4 during 2007–2011 years is observed decrease of Artemisia pollen and increase in Pteridophyta spores. The largest diversity in pollen composition has been found in 2011.

Althrough during vegetation mapping presence of spruce Picea abies, in surrounding of traps SE3 and SE4 was stated, still pine pollen is dominating in pollen composition of traps.The results are contrary to data from earlier investigations both in terms of pollen “rain” monitoring and in fossil pollen record and probably are caused by local factors, including meteorological factors. Part of non-arboreal pollen is represented by Ericaceae, Poaceae, Cyperaceae and Chenopodiaceae. In general investigation results show increase in pine pollen and decline in spruce pollen. In all analysed 12th years of pollen “rain” is dominated by pine and birch. Pollen data reflect some changes in Seda Mire vegetation, which is less expressed than that reflected by Tauber traps from Teiči Mire during last 10 years (Namateva and Kalnina, 2009). Pollen analysis from traps generally shows decrease of pine and significant increase of birch pollen proportion in composition.

ConCluSIonS Betula is dominating in Seda Mire – in vegetation and pollen “rain” samples

because it is a pioneer species in extracted peatland in Seda Mire. Research in Seda Mire has shown relationships between local pollen and

vegetation and development of vegetation from closed to open area. There some differences in traps located in forest and that from open areas. In

composition of local vegetation e.g. herbs and dwarf shrubs from open area of Seda Mire are find out decrease of Poaceae and Cyperaceae pollen and some increase of Calluna vulgaris and Ledum palustre, as well as Sphagnum spores.

rEfErEncEsCundill, P. R. 1991. Comparisons of moss polster and pollen trap data: a pilot study. Grana, 30,

301–308.Hicks, S., Latalowa, M., Ammann, B., Pardoe, H., Tinsly, H. 1996. European Pollen Monitoring

programme. Project description and guidelines, 3–5; 7; 9–1; 13.Hicks, S., Tinsley, H., Pardoe, H., Cundill, P., 1999. European Pollen Monitoring Programme,

Supplement to the Guidlines. Oulu University Press, Oulu, p. 24.Namateva, A., Kalnina, L. 2009. Microlandscapes, vegetation and pollen composition changes

in Teici Bog, Eastern Latvia. In: Panajiotidis, S., Syropoulou (eds.) Pollen Monitoring

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Programme, 7th Internatioanl meeting. Volume of abstracts. Poster presentations. Taxiachis – Chalkidiki, Greece, 22–27 April, 2009, 62–63.

Kalnina, L., Nikodemus, O., Ritenberga, O., Silamikele, I. 2009. Comparison of pollen composition from Burkard and Tauber traps monitoring data and surrounding vegetation. In: Panajiotidis, S., Syropoulou (eds.) Pollen Monitoring Programme, 7th Internatioanl meeting. . Volume of abstracts. Section 5. Pollen monitoring by different means. Taxiachis – Chalkidiki, Greece 22–27 April, 2009, 38–39.

Pardoe, H.S., Giesecke, T., van der Knaap, W.O., Svitavska-Svobodova, H., Kvavadze, E.V., Panajiotidis, S., Gerasimidis, A., Pidek, I. A., Zimny, M., Swieta-Musznicka, J., Latalowa, M., Noryskiewicz, A.M., Bozilova, E., Tonkov, S., Filipova-Marinova, M.V., van Leeuwen, J.F.N., Kalnina, L. 2010. Comparing pollen spectra from modified Tauber traps and moss samples: examples from a selection of woodlands across Europe. Vegetation History and Archaeobotany, 19, 271–285.

Prentice, I.C. 1986. Forest – composition calibration of pollen data. In: Berglund, B.E. (eds) Handbook of Holocene Paleoecology and Paleohydrology. Chichester [etc.], John Willey & Sons, 799–816.

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miRes and laKes – Key sites foR the postGlacial palaeoenViRonmental inVestiGations in lithuania:

old questions and neW ansWeRs

a migle stanČiKaitė, Vaida šeiRienė, dalia Kisielienė, Julius taminsKas, Jonas mažeiKa, Gražyna GRyGuc

Nature Research Center, Institute of Geology and GeographyT. Ševčenkos Str. 13, LT03223, Vilnius, Lithuania

e-mail: a stancikaite@geo.lt

Being important component of the today’s ecosystem, mires and lakes play the leading role in palaeoenvironmental investigations also. Natural achieves have attracted attention of numerous scientists since the survey of the postglacial started.

Transition from XIX to XX century can be described as a time of the initial investigations of the lateglacial and Holocene environmental history in the territory of the present Lithuania. Concentrated in the western and southwestern parts of the country territory these earliest works have recovered botanical composition of Aukštumala peat bog (Weber, 1902), geological-geomorphological structure and history of Samba peninsula and Kuršių Nerija (Curonian Spit), delta of Nemunas River and neighboring areas (Wichdorff, 1919). Especially prominent investigations were carried out by P. W. Thomson who had firstly described Holocene forest history based on the results of pollen data obtained from two bogs laying in the SW Lithuania (Thomson, 1931). There was the first attempt to apply pollen survey in our country. Later, Lithuanian palinologist K. Brundza and his Colleagues from Academy of Agriculture sciences published works describing Holocene forest history, development of Kamanos and Šepeta peat bogs situated in northern Lithuania (Brundza, 1934, 1936, 1940). Being of rather descriptive character these publications based the further survey of the postglacial environmental history in the region.

Consistent studies of the lakes and mires started during the second half of the XX century in Lithuania. Simultaneously extended survey of the sediment sequences laying in these basins became of particular interest as well. Beside of that, scientists have increasingly recognized the interpretive potential of multidisciplinary investigations. During the sixth- eight decades of the last century cooperation in the performing of complex interdisciplinary studies was established among geomorphologists, geologists, palaeobotanists, lithologists, chemists, physicists and etc.

Geographer Prof. V. Gudelis (1923–2007) initiated investigations describing palaeogeographical situation in the present territory of Lithuania, stratigraphi-cal features of the postglacial sediment sequences, glaciogeomorphology, neotectonics, aeolian processes of the coastal region. Investigations of the coastal

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area were of particular interest and numerous publications dealing with history of the Baltic Sea and Kuršių Marios as well as development of Kuršių marios (Curonian lagoon) were published by Professor and his Colleagues (Gudelis, 1953). Under the leadership of Prof. Gudelis first stratigraphical scheme of the lateglacial and Holocene in Lithuania was compiled (Gudelis, 1955).

Associated Professor A. Garunkštis (1928–1992) had emphasized his investigations on the survey of stratigraphical and lithological features of the lake‘s sediments, origin and development of these sedimentary bodies (Garunkštis and Stanaitis, 1969, 1978). Alongside with above mentioned issues the hydrological regime in lakes was vividly described. For a long time, classification of the limnic strata proposed by A. Garunkštis was the main tool describing sedimentary beds of our lakes (Гарункштис, 1975).

A special attention of Lithuanian scientists was paid to reconstruction of vegetation history, climatic fluctuations and interpretation of human impact upon environment based on palaeobotanical investigations of limnic and biogenic strata deposited during the different stages of the postglacial. The most significant results in this field was achieved by M. Kabailienė, Professor of Vilnius University. Based on numerous investigated pollen sequences, composition of the Holocene forest was reconstructed (Kabailienė, 1979, 1998, 2006). Searching for the reliable background discussing postglacial stratigraphical questions and regional correlation of identified features, the lateglacial and Holocene stratigraphical scheme, based on biostratigraphical features, lithological evidences and results of 14C dating was constructed (Kabailienė, 1990). Investigation of diatom composition accomplished by Professor provided our scientific society with new data describing the postglacial history of numerous lakes stretching in the region. Character of human activity, agriculture history and human/nature interaction was discussed in numerous papers published in cooperation with archaeologists and geographies. Peculiarities of the human impact changes have also been discussed in articles published by Dr. N. Savukynienė and Dr. A. Seibutis (Seibutis and Savukynienė, 1998). Mentioned scientists give their special attention to description of agriculture history in the region, changes of agriculture system and etc. In the sixth decade of the XX century Dr. A. Seibutis was the first who has started investigations of the Early Holocene thermokarst phenomenon in Lithuania and prolonged discussion on this issue in the context of the peat bog history (Seibutis, 1963–1964; Seibutis and Sudnikavičienė, 1960). Problems of the human/environmental interaction were discussed in numerous papers published by Dr. R. Kunskas (Kunskas, Butrimas, 1985, Kunskas et al., 1985). Changes of the water level in the investigated lakes, migration of the human habitation sites in context of environmental fluctuations, peculiarities of the land use and other population-related facts were emphasized in these articles.

The information accumulated as a result of all of the aforementioned investigations as well as many others has created a database that has been supplemented during recent decades.

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A significant impulse in the in the investigations of the postglacial environmental occurred when Lithuania regained its independence. After opportunities to collaborate with the global scientific community, actively investigating similar problems, arose, a new stage in the activity of the local scientific community started. Modern equipment and new investigation methods were introduced and already employed methods and methodologies improved. Deglaciation chronology, stratigraphical attribution of the registe red environmental fluctuations, reconstruction of palaeovegetation patter, palaeo-climatic records, human induced environmental changes were of particular interest for the scientific society of our country during the last decades. The palaeobotanists, sedimentologists, lithologists, chemists, physicists and etc., working at the Institute of Geology and Geography or Nature Research Centre nowadays, Vilnius and Klaipėda Universities, Lithuanian Geological Survey have actively collaborated investigating palaeoenvironmental changes recorded in sediment layers deposited in numerous mires and lakes.

Resent investigations provided scientists with the detailed lateglacial environmental history of Lithuania. First of all increasing number of absolute datings i.e. 10Be and 14C based new chronological background for the reconstruction of the territory deglaciation (Rinterknecht et al., 2008). Alongside with the reconstruction of the lateglacial palaeoenvironmental patter, i.e. vegetation changes, history of the sedimentary basins, climatic shifts, regional correlation of identified environmental fluctuations has been discussed (Stančikaitė et al., 2008a, 2009a, Balakauskas et al., 2013). Moreover the main stages of the Late Glacial environmental history were discussed in the context of the North Atlantic climatic events of the Last Termination. On top of all, understanding of the lateglacial vegetation history has improved considerably during the last years. Presence of Pinus sylvestris L. shortly before 13,700 cal, and the occurrence of Picea sp. seeds in the sediments of Allerød age in the south-eastern Lithuania as well as an early Holocene (10,600 cal yr BP) immigration of the latter taxa to the north-eastern Lithuania suggest new pattern of forest development (Stančikaitė et al., 1998, 2009a). Whereas origin of the Alnus incana (L.) Moench, and Alnus glutinosa (L.) Gaertn. macrofossils, identified in the lateglacial layers, western Lithuania, are still debatable though macroremains of Alnus sp. were recently discovered in northern Poland (Latałowa and Borowka, 2006). Traces of the short-lasted environmental fluctuations, like that named Gerzensee oscillation in Western Europe, were recorded in our territory as well suggesting continental scale of mostly lateglacial and early Holocene environmental variations. However some kind of delayed reaction of the local ecosystem to the Pleistocene/Holocene warming infers the particular pattern of the local climate. Rapid formation of a new type of vegetation and changing sedimentation environment confirming increasing humidity and rising temperatures only occurs after 11,100 cal BP (Šeirienė et al., 2006, Stančikaitė et al., 2009a).

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Talking about the Holocene period lack of the well-dated palaeoen-vironmental investigations based of the multi-proxy investigations of lakes and mires sediments should be stressed. Relatively few studies have been lately devoted to this issue (Balakauskas, 2003, Kabailienė et al., 2009, Mažeika et al., 2009, Šeirienė et al., 2009). Recently main stages of the lateglacial and Holocene vegetation history and environmental pattern were established in the eastern Lithuania (Gaidamavičius et al., 2011, Kurila and Balakauskas, in press). Immigration of the tree taxa in the context of the regional and local environmental pattern was of particular interest in above mentioned publications. Application of the plant macrofossil survey provided new data on the Holocene vegetation history and sedimentary environment of the water bodies (Gryguc et al., in press).

During the last twenty years, a great deal of attention has been devoted to reconstructing the natural and human induced environmental changes within and around the Stone and Iron Age archaeological sites. Mostly of them were situated on the shores of lakes and mires where rich set of the remains related with human activity was deposited and could be traced in our days. Indicated Holocene palaeoenvironmental history has allowed the indication of the earliest sings of the human activity, to be brought out (Stančikaitė et al., 2006, 2009b, 2013). Cerealia-type pollen grains of Early Neolithic age were recorded in the lake sediments in the southeastern Lithuania (Stančikaitė et al., 2002). Furthermore presence of Cerealia type and Plantago lanceolata pollen dated back to about 4300 cal BC suggests earlier human interference in the Šventoji area, western Lithuania, with possible contact between the local population and farming communities (Piličiauskas et al., 2012). Pollen analyses show the minor but constant role of cereal cultivation after 3250 cal BC in this region. Palaeobotanical data representing the lakes situated in the southeaster Lithuania attest that agriculture had become a continuous human activity here since about 3600 cal BP. Modernization of the subsistence economy, appearance of new tillage systems, spread of new domesticated plants, and increasing areas of worked fields and pastures were recorded during the Iron Age (Stančikaitė et al., 2009b, 2013). The earliest rye (Secale cerealia) and flax (Linum usitatissimum) pollen finds at the Impiltis archaeological site were dated back to the 10th–11th centuries whereas pollen grains of buckwheat (Fagopyrum) occurred at the mid-13th c. AD. both in the eastern (Stančikaitė et al., 2008b) and western (Stančikaitė et al., 2013) Lithuania.

Present ecological situation of the mires and lakes are an object of detailed investigations also. Hydrological, hydrochemical, morphometric studies, survey of the lake’s eutrophication and sedimentation pattern (Šimanauskienė et al., 2004, Linkevičienė et al., 2005, Mažeika and Taminskas, 2005) as well as the formation and degradation studies of the peat bogs (Taminskas et al., 2012) together with the research of peatland microclimate are of particular interest for scientific society.

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rEfErEncEsBalakauskas, L. 2003. Formation and evolution of the Skrebiškiai karst peat-bog (Northern

Lithuania) according to pollen data. Geologija, 43, 36–42.Balakauskas, L., Taminskas, J., Mažeika, J., Stančikaitė, M. 2013. Lateglacial and early-Holocene

palaeohydrological changes in the upper reaches of the Ūla River: An example from southeastern Lithuania. The Holocene, 23, 117–126.

Brundza, K. 1934. Lietuvos miškų istorijos pradmenys. Mūsų girios. Nr. 1–2, 9–24; Nr. 3, 127–133; Nr. 4, 184–194.

Brundza, K. 1936. Kamanos. Žemės ūkio akademijos metraštis. T. 10. Sąs. 3–4.Brundza, K. 1940. Šepeta. Žemės ūkio akademijos metraštis. T. 13. Sąs. 4.Gaidamavičius, A., Stančikaitė, M., Kisielienė, D., Mažeika, J., Gryguc, G. 2011. Post-glacial

vegetation and environment of the Labanoras region, East Lithuania: implications for regional history. Geological Quarterlay, 55(3), 269–284.

Garunkštis, A., Stanaitis, A. 1969. Ežerai gimsta, bręsta ir miršta. Vilnius, Mintis, 159.Garunkštis, A., Stanaitis, A. 1978. Kodėl senka Lietuvos ežerai. Vilnius, Mokslas, 92.Gudelis, V. 1953. Baltijos pajūrio geologinė raida vėlyvajame glaciale ir postglaciale Lietuvos

TSR ir Kaliningrado srities RTFSR ribose. Liet. TSR MA Geologijos ir Geografijos instituto fondai. Vilnius.

Gudelis, V. 1955. Lietuvos TSR Baltijos pajūrio geologinės raidos vėlyvajame glaciale ir postglaciale (holocene) pagrindiniai etapai. VVU Mokslo darbai, T.VII. Biologijos, geologijos ir geografijos mokslų serija, T. III. 119–139.

Gryguc, G., Kisielienė, D., Stančikaitė, M., Šeirienė, V., Mažeika, J., Vaitkevičius, V. 2013. Holocene sediment record from Briaunis Lake, Eastern Lithuanian: vegetation and environmental history. Baltica, in press.

Kabailienė, M. 1979. Taikomosios palinologijos pagrindai. Vilnius. 147.Kabailienė, M. 1990. Lietuvos holocenas. Vilnius, 175.Kabailienė, M. 1998. Vegetation history and climate changes in Lithuania during the Late Glacial

and Holocene, according pollen and diatom data. PACT, 54, 13–30.Kabailienė, M. 2006. Gamtinės aplinkos raida Lietuvoje per 14000 metų. Vilniaus universiteto

leidykla. Vilnius. Kabailienė, M., Vaikutienė, G., Damušytė, A., Rudnickaitė, E. 2009. Post-Glacial stratigraphy

and palaeoenvironment of the northern part of the Curonian Spit, Western Lithuania. Quaternary International, 207(1–2), 69–79.

Kunskas, R., Butrimas, A. 1985. Biržulio ežero krantų ir akmens amžiaus gyvenviečių kaita holocene. Lietuvos archeologija, 4, 66–79.

Kunskas, R., Butrimas, A., Česnys, G., Balčiūnienė, I., Jankauskas, R. 1985. Duonkalnis: vėlyvojo neolito gyvenvietė, alkas ir kapinynas. Lietuvos archeologija, 4, 25–66.

Kurila, L., Balakauskas, L. 2012. Aplinka ir žmogus holocene Baliulių-Perūno mikroregione (Švenčionių r.): tarpdisciplininis tyrimas. Lietuvos archeologija, in press.

Latałowa, M., Borowka, R.K. 2006. The Alleröd–Younger Dryas transition in Wolin Island, northwest Poland, as reflected by pollen, macrofossils, and chemical content of an organic layer separating two Aeolian series. Veget. Hist. Archaeobot., 15(4), 321–331.

Linkevičienė, R., Taminskas, J., Šimanauskienė, R. 2005. Synergetic influence of climate change and anthropogenic activity towards the lake’s quality: the case study of Babrukas Lake. Limnological review, 5, 137–144.

Mažeika, J. Taminskas, J. 2005. Evaluation of recent sedimentation rates in the Lake Druksiai (Northeastern Lithuania). Limnological review, 5, 167–174.

Mažeika, J., Guobytė, R., Kibirkštis, G., Petrošius, R., Skuratovič, Ž., Taminskas, J. 2009. The use of carbon-4 and tritium for peat and water dynamics characterizations: case of Čepkeliai peatland, South eastern Lithuania. Geochronometria, 34, 41–48.

Piličiauskas, G., Mažeika, J., Gaidamavičius, A., Vaikutienė, G., Bitinas, A., Skuratovič, Ž.,

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Stančikaitė, M. 2012. New archaeological, paleoenvironmental, and 14C data from Šventoji Neolithic sites, NW Lithuania. Radiocarbon, 54(3–4), 1017–1031.

Rinterknecht, V.R., Bitinas, A., Clark, P.U., Raisbeck, G.M., Yiou, F., Brook, E.J. 2008. Timing of the last deglaciation in Lithuania. Boreas, 37, 426–433.

Seibutis, A. 1963–1964. Borealinio ledo luistų tirpimo pėdsakai pelkių sluoksnyne. Geografinis metraštis. T. VI–VII. Vilnius. 347–371.

Seibutis, A., Savukynienė, N. 1998. A review of major turning points in the agriculture history of the area inhabited by the Baltic peoples, based on palynological, historical and linguistic data. PACT, 54, 51–60.

Seibutis, A., Sudnikavičienė, F. 1960. Apie holoceninių pelkių susidarymo pradžią Lietuvos TSR teritorijoje. Geografinis metraštis. T. III. Vilnius. 299–263.

Stančikaitė, M., Šeirienė, V., Šinkūnas, P. 1998. New results of Pamerkys outcrop investigations, South Lithuania. Geologija, 23, 77–88.

Stančikaitė, M., Kabailienė, M., Ostrauskas, T., Guobytė, R. 2002. Environment and man in the vicinity of Lakes D_uba and Pelesa, SE Lithuania, during the Late Glacial and Holocene. Geological Quarterly, 46(4), 391–409.

Stančikaitė, M., Baltrūnas, V., Šinkūnas, P., Kisielienė, D., Ostrauskas, T. 2006. Human response to the Holocene environmental changes in the Biržulis Lake region, NW Lithuania. Quaternary International, 150(1), 113–129.

Stančikaitė, M., Šinkūnas, P., Šeirienė, V., Kisielienė, D. 2008a. Patterns and chronology of the Lateglacial environmental development at Pamerkiai and Kašučiai, Lithuania. Quaternary science reviews, 27(1–2), 127–147.

Stančikaitė, M., Kisielienė, D., Mažeika, J., Blaževičius, P. 2008b. Environmental conditions and human interference during the 6th and 13th–15th centuries. Vegetation history and archaeobotany, 17(1), 239–250.

Stančikaitė, M., Kisielienė, D., Moe, D., Vaikutienė, G. 2009a. Lateglacial and early Holocene environmental changes in northeastern Lithuania. Quaternary International, 207(1–2), 80–92.

Stančikaitė, M., Šinkūnas, P., Risberg, J., Šeirienė, V., Blažauskas, N., Jarockis, R., Karlsson, S., Miller, U. 2009b. Human activity and the environment during the Late Iron Age and Middle Ages at the Impiltis archaeological site, NW Lithuania. Quaternary International, 203(1–2), 74–90.

Stančikaitė, M., Bliujienė, A., Kisielienė, D., Mažeika, J., Taraškevičius, R., Messal, S., Szwarczewski, P., Kusiak, J., Stakėnienė, R. 2013. Population history and palaeoenvironment in the Skomantai archaeological site, West Lithuania: two thousand years. Quaternary International (http://dx.doi.org/10.1016/j.quaint.2012.08.2108).

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the impact of the teutonic oRdeR on the landscape of the easteRn baltic: pReliminaRy Results

of inVestiGations on miRe and laKe sediments in latVia

a alex brown, aleks pluskowski Department of Archaeology, School of Human and Environmental Sciences,

University of Reading, Whiteknights, PO Box 227, Reading, RG6 6AB, United Kingdom

e-mail: a a.d.brown@reading.ac.uk

AbStrACtPreliminary pollen data are presented from three mires and one lake in the landscape

surrounding Cēsis, Latvia, undertaken as part of the Ecology of Crusading Project. The pollen sequences produced little evidence for sustained agricultural activity during the late Iron Age. Although pollen of cereals and anthropogenic indicators increase during the medieval period, they do not occur in levels that suggest intensive agricultural land-use, with substantial woodland remaining throughout the medieval period. The pollen evidence is interesting since Cēsis was the headquarters of the Livonian Order and a major power centre in the eastern Baltic. The pollen evidence is considered in context of the broader palynological record from Latvia and southern Estonia.

IntroduCtIonThe large number of lakes, mires and peatlands in Latvia represent a valuable

resource for the study of past vegetation and environmental change and retain important evidence on past human impact histories. Palynological studies from the eastern Baltic region have contributed significantly to our understanding of the vegetation history of Europe during the 11,500 years since the end of the last (Weichselian) Ice Age (e.g. Saarse and Veski 2001; Ralska–Jasiewiczowa et al., 2004; Niinemets and Saarse, 2007; Stančikaite et al., 2004; Heikkilä and Seppä, 2010). The majority of palynological investigations have tended to focus on reconstructing overall patterns of late-glacial and Holocene vegetation history and land-use change by prehistoric agrarian and pre-agrarian hunter-gatherer communities; less attention has been focused on landscape transformations during the medieval and post-medieval periods. However, evidence for important changes in vegetation and land-use are apparent from the upper portions of many pollen diagrams from across the south-eastern and eastern Baltic, often characterised by prolonged declines in woodland (particularly in northern Poland) and an intensification in agricultural activity. This key horizon in pollen sequences is often poorly dated and/or studied at a low temporal resolution, and, in the absence of a precise chronology, may relate to a broad period from the late Iron Age to post-medieval (ca. 10th–18th centuries AD)

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when there was significant economic and demographic expansion accompanied by substantial socio-political upheavals (e.g. Kihno and Valk, 1999). This short paper summarises results of preliminary investigations of mire and lake sediments in Latvia in the context of the Ecology of Crusading Project, focusing on the extent to which local environments were transformed from the 13th century AD as a result of the Crusading movement.

aRchaEoLogIcaL aNd hISToRIcaL backgRoUNd The medieval period, beginning in the 13th century in Latvia, is a time of

significant social, economic and political development, dominated by the Crusading movement of the 13th–15th centuries. The Baltic Crusades involved the conquest, colonisation and Christianisation of present day north-eastern Poland, Kaliningrad Oblast, Latvia and Estonia by the Teutonic and Livonian Order. The Livonian Crusade began with the conquest of the Livs and Latgalians (1209–1227) (eastern Latvia) by the armies of the Bishops and Order of the Livonian Brothers of the Sword, and later, following the conquest of Estonia (1208–1227), by partially successful crusades in western Latvia (1219–1290) resulting in the subjugation of Curonia and northern Semigalia. Samogitia (present-day north-western Lithuania) remained unconquered, forming contested territory between Livonia and the Grand Duchy of Lithuania. Following their defeat by the Samogitians in 1236, the Livonian Brothers of the Sword were merged into the Teutonic Order, known thereafter as the Livonian Order (Fig. 1).

Fig. 1. map showing a) latvia, highlighted in black, b) showing the location of the territories of the bishops and livonian branch of the teutonic order

with the cēsis commandery highlighted in dark grey

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The Teutonic State is unique in being a Theocracy, established through conquest and run exclusively by the military orders and bishops. Conquest and Christianisation was accompanied by colonisation, most intensively in Prussia (present-day north-east Poland and Kaliningrad Oblast) rather than Livonia (present-day Latvia and southern Estonia), marked by the development of networks of towns and settlements, all secured with heavily fortified castles. Conquest, colonisation and religious conversion occurred in tandem with economic expansion and the growth of pan-European trading networks; most notably the development of the Hanse from the 13th century. These interlinked processes had a significant impact on the medieval landscapes of the south-eastern and eastern Baltic that are detectable in the pollen record.

The interim pollen data presented here forms part of the Ecology of Crusading Project, funded by the European Research Council (Directed by Aleks Pluskowski). This research focuses on how the castles and associated settlements constructed by the Teutonic Order acted to re-organise and transform local environments in north-eastern Poland, western Lithuania, Latvia and southern Estonia (medieval Prussia and Livonia) (Pluskowski et al., 2011). Research involves the examination of a diverse range of archaeological, zooarchaeological, palaeobotanical (micro and macro-botanical remains) and geoarchaeological materials along with written and cartographic sources. Previous studies of the environmental impact of Crusading have been almost exclusively informed by the written sources, which date predominantly from the end of the 14th century and lack the longer-term perspective available from the palynological record. Research is sub-divided into on- and off-site sampling within the administrative hinterlands of the castles. The sedimentary sequences from mires and lakes form the primary element of the off-site sampling, and are crucial both in understanding the broader ecological and landscape impact of the Crusades, but also in placing the site-specific evidence from castles and rural settlements in a broader spatial and chronological context.

pollEn SItESA total of 33 cores have so far been sampled from across the south-eastern

and eastern Baltic, ten from Latvia, of which preliminary pollen result from four sequences are presented here. All sequences are located in the landscape surrounding Cēsis (Nineris Lake and mire, Blusu Purvs and Blanku Purvs, Fig. 2–4) which was the headquarters for the Livonian Order and a major power centre in the eastern Baltic. The Castle and wider administrative area of Cēsis forms one of several case-studies for the Ecology of Crusading Project. Coring has focused on retrieving only the top parts of the sedimentary sequences from these sites, i.e., those sediments most likely to date from the late Iron Age onwards. As such, no attempt has been made to determine the overall depth or topography of the lakes or mires investigated.

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Blanku Purvs (N 57° 23’ 12.4”, E 25° 18’ 05.1”): irregular shaped mire 2 x 1.5 km at maximum extent located 8 km north of Cēsis. Coring across the mire indicates a shallow depth of peat to a maximum depth of 2.25 m overlying lacustrine silts. The peat was sampled to a depth of 2 m, ca. 150 m from the western edge of the mire.

Blusu Purvs (N 57° 17’ 28”, E 25° 17’ 20.1”): small afforested mire (1.3 by 0.8 km) located on the present south-eastern edge of Cēsis, ca. 2.2 km from the castle. Coring across the mire indicates a relatively shallow depth of peat to a maximum depth of 1.5 m, but typically no more than 0.75 m. The core was taken from the greatest depth of peat within the central area of the current mire.

Fig. 2. map of the landscape surrounding cēsis showing the location of the pollen cores; 1) blusu purvs, 2) blanku purvs, 3), lake nineris, 4) nineris mire, 5) cēsis castle moat,

6) lake āraiši, 7) āraiši castle outer bailey, 8) āraiši mire. only cores

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Fig. 3. selected taxa pollen percentage diagrams, a) blanku purvs, b) blusu purvs. the black curve represents the percentage of the taxon, the grey curve shows values

exaggerated x10

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Fig. 4. selected taxa pollen percentage diagrams, a) lake nineris, b) nineris mire. the black curve represents the percentage of the taxon, the grey curve shows values

exaggerated x10

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Lake Nineris (N 57° 20’ 17”, E 25° 17.4’ 41.7”): small lake 550 × 270 m in diameter located 2.8 km north of Cēsis castle and currently surrounded by coniferous plantation woodland, largely Picea and Pinus interspersed with Betula. The top 3.5 metres of the sediment sequence was sampled, comprising a generally homogenous sequence of highly organic lake muds.

Nineris mire (N 57° 20’ 10.4”, E 25° 17’ 16.5”): located adjacent to Lake Nineris and extending a further 800 m to the west, the mire comprises a deep sequence of herbaceous peats to a depth greater than 5 m, likewise surrounded by Picea-Pinus plantation woodland, with the surface of the bog currently covered with Picea saplings.

mEthodSSamples for pollen analysis ca. 1 cm3 in volume were taken from each

sequence at intervals from 1–4 cm. One Lycopodium tablet was added to enable calculation of pollen concentrations. Samples were prepared following standard laboratory techniques (Moore et al., 1991) and mounted in glycerol jelly stained with safranin. A minimum of 500 pollen of terrestrial species were counted for each level. Pollen percentages are calculated based on terrestrial plants. Ferns spores, aquatics and Sphagnum are calculated as a percentage of terrestrial pollen plus the sum of the component taxa within the respective category. Identification of cereal pollen followed the criteria of Andersen (1979). Indeterminable grains were recorded according to Cushing (1967). Pollen diagrams were produced using Tilia (v. 1.7.16) with zonation achieved in Psimpoll based upon a comparison of binary splitting by sum of squares, optimal splitting by sum of squares and constrained cluster analysis. Radiocarbon AMS 14C dates were obtained from SUERC (Scottish Universities Environmental Research Centre). The 14C dates were calibrated using the program OxCal and the calibration curve of Reimer et al. (2004).

rESultS And dISCuSSIonThe preliminary results of pollen analysis are discussed here primarily in the

context of the evidence for human activity and land-use within the framework of the Ecology of Crusading Project. All the sequences are awaiting the results of additional radiocarbon dates, in the absence of which only outline chronologies are available, but it is highly likely that the sequences cover different lengths of time extending back into the Iron Age. However, the sequences from Lake Nineris, Nineris mire, Blusu Purvs and Blanku Purvs provide a valuable picture of the vegetation environment in the landscape surrounding Cēsis during the Iron Age to post-medieval period. All four sequences, unsurprisingly, demonstrate that woodland formed an important component of the landscape throughout (Fig. 3 and 4). Pollen of broadleaved trees is more apparent from the base of the analysed sections of the cores from Blusu Purvs (Fig. 3b) and Lake Nineris (Fig. 4a). Whilst this suggests that the base of these sequences likely predate those from Nineris

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mire (Fig. 4b) and Blanku Purvs (Fig. 3a), it demonstrates also that broadleaved trees such as Tilia, Ulmus and Quercus were increasingly rare components of sub-Atlantic woodlands dominated by Pinus, Betula and Picea.

The second characteristic feature of the pollen sequences, though less so of Nineris mire, is the decline in Picea. At Blanku and Blusu Purvs the decline occurs prior to dates of 515±35 BP (GU-27666, cal AD 1320-1448) and 545±35 BP (GU-27667, cal AD 1310-1438), and at Lake Nineris below a date of 745±35 BP (GU-27669, cal AD 1217-1294). Similar late Holocene declines in Picea from central Latvia are apparent from Lake Ķūži, dating to ca. 1000 BP (Kangur et al., 2009), and from Eipurs Bog, prior to a date of 689±50 BP (cal AD 1228-1398; Kušķe et al., 2010). The decline is apparently non-synchronous in date and appears unrelated to increases in evidence for human activity, occurring also in situations where there is little evidence for human activity.

Despite the dominance of woodland, evidence for human activity is apparent from all four sequences. Intermittent and low frequencies of cereal-type pollen are apparent during the late Iron Age, but it is only during the medieval period that there is a consistent presence of cereals, along with pollen of a range of anthropogenic indicators. At both Blusu Purvs and Blanku Purvs (Fig. 3), located on opposite sides of Cēsis (Fig. 2), there is a broadly synchronous increase in cereal pollen (Secale, Avena-Triticum, Hordeum type) and anthropogenic indicators (including Rumex acetosa-type, Sinapis-type, Plantago lanceolata); the associated radiocarbon dates cover the early 14th – early 15th centuries AD, but a late 14th – early 15th century AD date appears more likely on the basis of the probability distributions (Table 1).

Table 1AMS radiocarbon dates for Nineris mire, Lake Nineris,

Blanku Purvs and Blusu Purvs. * 95.4% probability

Site Lab No Material dated

Depth (cm)

Age (B.P)

δ13C (‰) Age range a (cal AD)

Blanku Purvs

GU-27666 Peat bulk 80–81 515±35 –28.2 1320–1350 (13.1%)1391–1448 (82.3%)

Blusu Purvs

GU-27667 Peat bulk 52–53 545±35 –28.4 1310–1360 (38.2%)1386–1438 (57.2%)

Lake Nineris

GU-27669 Gyttja 1086–1087

745±35 –26.8 1217–1294

Nineris mire

GU-23349 Peat bulk 55–56 205±30 –25.9 1640–1690 (27.4%)1730–1810 (50.4%)1920–1960 (17.6%)

Nineris mire

GU-22883 Peat bulk 151–152 610±30 –27.5 1290–1410

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The increase in human activity at Blusu and Blanku Purvs is significantly later than at Lake Nineris (Fig. 4b). Here a small increase in Poaceae, a range of cultigens (Secale, Avena-Triticum, Hordeum, Linum usitatissimum, Fagopyrum esculentum) and anthropogenic indicators characteristic of cultivated, grazed and disturbed ground (Chenopodiaceae, Rumex acetosa-type, Cannabis-type, Urtica, Chenopodiaceae, Sinapis-type and Plantago lanceolata) is dated just prior to 745±35 BP (GU-27669, cal AD 1217-1294). Pollen of Centaurea cyanus also appears at this time, a weed typically associated with cereal cultivation and which has been argued to reflect the presence of permanent fields (Vuorela, 1986). However, the pollen signal from Lake Nineris differs to the adjacent mire sequence (Fig. 4a), located ca. 700 m to the west. Although the principal arboreal taxa occur in broadly similar value, pollen of cereals, associated weeds and ruderal species are otherwise intermittent and occur in low frequencies throughout the medieval period, only appearing more consistently from the post-medieval period. The disparity between the two Nineris sequences highlight the benefits, where the opportunity arises, of comparing closely related lake and mire sediments, and may largely reflect the different depositional pathways and pollen source areas between lake and mire.

Nevertheless, in all four pollen studies, the frequency of cereal pollen and other anthropogenic indicators is relatively low. This can be explained partly by the sandy soils surrounding Cēsis to the north and west (EC European Soil Portal), where three of the four pollen sequences are located, that are generally less favourable for intensive agriculture. Given the pollen evidence and current distribution of woodland these areas seem likely to have remained significantly wooded through the medieval period. Soils with higher clay content, distributed from the northeast to southwest of Cēsis, have greater agricultural potential, characterised today by a more mosaic agricultural landscape. However, current pollen studies suggest similarly low levels of agricultural activity. Indeed, preliminary pollen and fungal analyses by Normunds Stivriņš from Lake Āraiši, located adjacent to the late Iron Age lake village and Order Castle (Fig. 2), suggest a decline in human activity from ca. 1200 AD (Stivriņš pers. comm., 2012). The pollen and fungal evidence appear counter intuitive in view of the close proximity to Āraiši castle; excavations within the western range of the castle in the 1980s produced an assemblage of 20,000 animal bones (Apals, 1995). However, subsequent excavations in 2012 within both castle and outer bailey produced almost no material cultural evidence for medieval activity, suggesting highly localised, and potentially low-level, activity restricted to the southern range of the castle.

In addition, evidence for human activity can be harder to detect in pollen sequences from mires as opposed to lakes, and may account for the comparatively low frequency and later date for the appearance of anthropogenic indicators from Blusu Purvs, Blanku Purvs and Nineris mire. This can occur where the pollen sequence is located some distance from the dry ground and

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therefore biased against those anthropogenic indicator taxa (particularly self-pollinating cereals and associated insect-pollinated weeds) with poor pollen production and dispersal characteristics. Issues of limited production and dispersal of pollen is further compounded on those mires containing woodland where the canopy and trunk space act to further filter out pollen from plants growing on the surrounding dry ground. Every effort has therefore been made when sampling mires to balance the requirements between sufficient depths of peat to capture the last ca. 1500 years, with proximity to the edge of the mire where signals of human activity is likely to be stronger.

Nonetheless, some initial observations can be made of the pollen sequences presented here within the context of the broader palynological and documentary evidence for medieval landscape transformation from the eastern Baltic. The majority of pollen sequences from Latvia with associated radiocarbon dates ≤1500 14C years BP (i.e. Iron Age – post medieval) suggest that arboreal pollen does not in general decline significantly until perhaps the end of the 15th century, recording only more modest activity prior to this. Pollen analysis from Eipurs and Dzelve–Kronis bogs (Kušķe et al., 2010) show only small increases in pollen indicative of pasture/meadow and arable land during the medieval period, at Eipurs bog from a level dated 689±50 BP (cal. AD 1228–1398) and at Dzelve–Kronis bog after 757±55 BP (cal. AD 1169–1381), in both cases following the start of the Crusades. An earlier, although small increase in pasture and arable land was recorded in the Lake Kūži sequence from a level dated 925±30 BP (cal. AD 1029–1180, Kangur et al., 2009). In eastern Latvia, pollen analysis from Lake Kurjanova produced evidence for an increase and continuous curve in cereal pollen from the Bronze Age, with an increase in rye, albeit intermittent, from the ca. 10th century AD (Heikkilä and Seppä, 2010). In all of these cases, however, one has to take into account the depositional context, surrounding soils, geology, topography and archaeological context. Pollen sequences from extensive mires located large distances from archaeological sites in areas of otherwise low agricultural potential are unlikely to reveal evidence for significant human impact on the environment, providing potentially false negative evidence for human activity. A focus on mires and lakes with smaller pollen catchments is therefore preferable in order to provide a more localised comparative picture of vegetation change.

In addition to the palynological data, written sources suggest that there was little management of Latvian woodlands, with no evidence for coppicing, whilst some sacred forests, mainly of oak and lime, were tolerated by the Teutonic Order until the arrival of Jesuits in the 16th century (Kļaviņš, 2011). However, written sources relating to Riga indicate that there was a lack of timber resources in the surrounding landscape by AD 1255, with a subsequent increase in exploitation along the Daugava River and its tributaries. Oak wainscots (high quality timber boards) are also recorded as an important export from Riga (Zunde, 1998–99), but this timber could have originated from outside Latvia. For example, written

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sources show that Lithuanian timber was being transported to Königsberg and Danzig for export from the early 15th century, although Lithuanian woodlands were most extensively exploited from the mid–16th century (Pukienė and Ožalas, 2007).

As a point of comparison, arable farming does not appear to intensify/re-intensity in the majority of radiocarbon dated pollen sequences from southern Estonia until the 14th century, although there is evidence from many pollen studies across Estonia for the cultivation of a range of crops throughout the Viking Age and late Iron Age (see Brown and Pluskowski 2013 for a review). Within Prussia, however, intensive human impact is apparent in pollen sequences throughout the Vistula Basin associated with extensive Slavic and Germanic colonisation from the ca. 10th and 13th centuries respectively. Towns became the new centres for food consumption and trade, whilst the castles and manors of the Order and Bishops gained revenue in part through taxing local agricultural produce. Livonia did not witness the same intensity of colonisation as Prussia; the population was sparser and the extent of human activity perhaps more localised around the principal urban and rural centres.

The preliminary hypothesis advanced here is that the first decades of the 13th century following the conquest probably saw few changes in the nature of land-use within Livonia; there was limited colonisation beyond the towns and castles and it took most of the 13th century to fully conquer and stabilize the territory. It was only with increased political stability, the growth of urban centres, the growing significance of the Hanseatic League and foreign trading networks, and the establishment of serfdom and the development of the manorial system that created an increased demand for agricultural produce. The growing importance of cereals, particularly rye, is demonstrated not only through the pollen record, but through documentary and archaeobotanical evidence for its significance both as a consumable, tradable and taxable commodity (e.g. Sillasoo and Hiie, 2007). Areas of low agricultural potential seem to have remained significantly wooded throughout the medieval period with only limited land-use.

ConCluSIonSThe four pollen sequences presented here provide preliminary indications

of the potential impact of the Crusades on parts of the eastern Baltic landscape, in this case surrounding the headquarters of the Livonian Order at Cēsis. The pollen sequences demonstrate that woodland was, and remained, a significant component of the Cēsis landscape throughout the medieval period and thereafter. There is little evidence for sustained agricultural activity during the preceding late Iron Age, and although pollen of cereals and associated anthropogenic indicators increase and appear consistently during the medieval period, they do not occur at a level that suggests intensive agricultural land-use. This may in part reflect the low potential of the surrounding sandy soils for intensive agriculture, but also the sparser populations and the absence of

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intensive colonisation of the level that accompanied the Crusades in Prussia. Little may have changed in the nature or intensity of land-use in those more isolated rural area following the Crusades until perhaps the growth in urban centres, trade and the development of the manorial system during the 14th century. It is interesting therefore that the immediate landscape surrounding the headquarters of the Livonian Order, a major power centre in the eastern Baltic, should record such limited intensity of human impact. The hypotheses advanced here will be tested and refined through further palaeoenvironmental research (including additional sequences from the Cēsis landscape) but critically through integration and comparison with the full range of data (zooarchaeological, geoarchaeological, archaeobotanical and historical) currently under analysis as part of the Ecology of Crusading Project from sites across Latvia, Estonia and north-east Poland.

ACknowlEdGEmEntSThe Ecology of Crusading Project is funded by a grant from the European

Union’s Seventh Framework Programme (FP7/2007-2013) under Grant Agreement no. 263735. The authors would like to thank Laimdota Kalniņa, Ilze Ozola (University of Latvia), Normunds Stivriņš and Siim Veski (Tallinn University of Technology) for access to unpublished materials and discussions related to on-going palynological research. We are also grateful to Kevin Williams, Rob Batchelor (University of Reading) Siim Veski and Normunds Stivriņš (Tallinn University of Technology) for help in sampling the pollen sequences, and to Gundars Kalniņš (Castle museum, Cēsis) for his continued support and hospitality.

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chanGes in the leVel of laKe sāRnate and the conditions foR settlement alonG its shoRe

duRinG the holocene

1 a aija ceRiŅa, 1 b laimdota KalniŅa, 2 c Valdis bēRziŅš

1 University of Latvia, Faculty of Geography and Earth Sciences2 Institute of Latvian History at the University of Latvia

e-mails: a Aija.Cerina@lu.lv; b Laimdota.Kalnina@lu.lv; c valdis-b@latnet.lv

IntroduCtIonThe former Lake Sārnate developed within the southern part of the area

known as the Ventspils Lagoon, where evidence has been found of the Ancylus Lake and Littorina Sea transgressions (Grinbergs, 1957; Grinbergs and Guzlena, 1972). Palynological analysis has previously been undertaken on the deposits of the former lakes (Dreimanis, 1947; Murniece et al., 1999; Kalnina et al., 2011). In this study, plant macrofossils (seeds) in the upper part of the sedimentary sequence of the former Lake Sārnate have been analysed for the first time.

mAtErIAlS And mEthodSThe samples were collected in 1956 during archaeological excavation of the

Sārnate Stone Age settlement, under the direction of Lūcija Vankina. The samples, from the NW edge of Dwelling O, had been preserved in the collections of the National History Museum of Latvia. At the time of collection, each sample had an approximate volume of 150–200 ml. The samples had been preserved in dry condition. Seed analysis was undertaken in accordance with the methodology of Nikitin (1969). The analysed sediment sequence has been compared with the Sārnate IX section, located 400 m south of Dwelling O. The results of the plant macrofossil study are compared with the pollen analysis data from Sārnate IX.

Pollen analysis was carried out with a sampling interval of 5 cm. A total of 82 samples from Core Sārnate IX were prepared following standard techniques (Berglund and Ralska-Jasiewiczowa, 1986; Bennett and Willis, 2001). Quantitative and qualitative pollen analyses were done using light microscopes Axiostar and Primostar with 400–1000 times magnification. Glycerine was used as an embedding medium to prepare slides. At least 700 pollen grains, except for aquatic herb pollen, were counted in each subsample. The identification of pollen and spores was carried out by comparison with the available pollen and spore reference materials, and pictures and descriptions in P.D. Moore and J.A. Webb (1978). Pollen diagrams were constructed and the data plotted using the computer program TILIA 1.5.12. (Grimm, 2011). Percentage of pollen was calculated on the basic sum – composed of all terrestrial pollen. Aquatic plant pollen and spores are calculated as a percentage of this sum.

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rESultSThe section has been compiled using the results of plant macrofossil analysis.

From the bottom upwards, the following layers were distinguished (Fig. 1):2.5–2.3 m – clay, light grey, carbonaceous, with fine freshwater mollusc and

ostracod shells, and fine detritus of aquatic plant leaves, rare wood fragments and rare fish scales. Very sharp contact with overlying layer.

2.3–1.95 m – peaty coarse detritus gyttja, dark brown, with a minor admixture of fine sand; inclusions of carbonaceous clay fragments in lower part of layer; wood and reed stem fragments, rare Hypnum stem fragments; thin strata of Hypnum in middle part of layer. Sharp contact with the overlying layer.

1.95–1.65 m – peat, weakly decomposed, consisting of Hypnum stems with leaves, along with fragmentary aquatic plant leaves; thin strata of peaty gyttja in upper part of layer. Gradual contact with overlying layer.

1.65–1.15 m – peaty coarse detritus gyttja, with Hypnum strata in lower part. Gyttja strata with abundant plant detritus alternate with gyttja strata containing less detritus. This consists mainly of wood and bark fragments, along with wood charcoal and aquatic plant leaf remains; Hypnum remains are occasional, decreasing in quantity upwards. Gradual contact with overlying layer.

1.15–0 m – dominated by peaty fine detritus gyttja, alternating with separate strata of coarse peaty gyttja; minor admixture of fine sand in lower part of layer; wood fragments predominate in the detritus, some of those in the lower part of the layer being rolled. Fish vertebrae or scale fragments in some intervals.

The upper 0.40 m of this layer contained frequent wood charcoal fragments, as well as grains of coarse quartz sand, bird bone fragments, occasional fish scales and some amber fragments.

In the plant macrofossil diagram (Fig. 1), five macrofossil assemblage zones (MAZ) are distinguished: I – Characeae – Najas marina MAZ (int. 2.5–2.3 m), Characeae oogonia with lime-encrusted cases; II – Lemna trisulca-Menyanthes trifoliata-Nuphar luteum MAZ (int. 2.3–1.9 m); III – Menyanthes-Carex MAZ (int. 1.9–1.6 m); IV – Menyanthes-Nuphar lutea-Cladium mariscus-Carex MAZ (int. 1.6–0.75 m). Regularly occurring from 1.1 m upwards are bulrush (Schoenoplectus lacustris) nutlets, along with remains of water chestnut (Trapa natans) fruit. V – Schoenoplectus lacustris-Nuphar lutea-Trapa natans MAZ (int. 0.75–0.35 m); VI? – (int. 0.35–0 m): no plant seeds recovered (poorly expressed cultural layer).

The plant macrofossil (seed) study indicates that the carbonaceous lacustrine clay was laid down in an oligotrophic lake. It has been concluded in earlier research (Dreimanis, 1947; Murniece et al., 1999) that the upper part of the carbonaceous lake deposits was laid down during the Ancylus Lake stage.

The coarse detritus gyttja was deposited in the shallow littoral belt of the lake. Hypnum moss gradually increases in abundance upwards, with a decrease in the range of aquatic species, indicating terrestrialisation of the lake.

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The Hypnum layer, containing only Carex and Menyanthes seeds, formed after a rapid fall in the water level, as indicated by the sharp contact with the underlying gyttja.

The transition to the overlying course detritus gyttja layer is a gradual one, as is the transition from the course detritus gyttja to the layer above it, with alternating strata of course and fine detritus gyttja. This indicates a gradual rise in the water level. The plant assemblage indicates that the deposits at a depth of 1.65–0.75 m formed in an fill-in part of the lake, with a fluctuating water level.

In the depth interval 0.75–0.35 m aquatic plant remains dominate in the gyttja. Bulrush (Schoenoplectus lacustris) is frequent; yellow water lily (Nuphar lutea) seeds and remains of water chestnut (Trapa natans) fruit occur regularly. The plant society is characteristic of the belt of rushes close to the open water of a lake. It is thought that the lake level was higher at this time than previously. Vankina (1970) likewise reports that during the archaeological excavation whole water chestnuts were found in the peat directly under the cultural layer – an indication that area of Dwelling O had been flooded by the waters of the lake. In the section from Sārnate Core IX, SE of the excavated Stone Age

Fig. 1. plant macrofossil diagram for the section from the area of sārnate dwelling o

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settlement, the contact between the gyttja layer and the overlying grass peat has been dated to 5100–4910 cal. BP (Kalnina et al., 2011). The uppermost interval of the gyttja layer (0.40–0 m) consists of gyttja with fine plant detritus, along with wood charcoal, bone fragments and fish vertebrae – indications of the cultural layer of the Stone Age site. Evidently, Dwelling O was established on the lacustrine deposits soon after a lowering of the lake level. Many of the paddles, spears and other wooden artefacts that were found close to the structural remains of Dwellings A, K, N, O, T, X and Y, belonging to the latest occupation phase (c. 5600–4900 cal. BP), and likewise objects in the vicinity of Dwelling I, from an earlier occupation phase, were discovered in a slanting or near-vertical position, one end projecting into the natural deposits below the cultural layer (Vankina, 1970). Also, some of the stone net sinkers were found in the underlying natural stratum. During the excavation of the approximately contemporaneous settlement site of Šventoji 1 in Lithuania, located in a similar environmental setting, analogous observations were made: wooden paddles were discovered in a vertical position in gyttja, while stone sinkers had sunk deep down into it (Rimantienė 2005, 251). At least in the case of Sārnate it is clear that the Stone Age houses were erected not on piles out in the lake, but directly on the boggy ground, as proven by the occurrence of pits and tree stumps at the base of the hearth structures (Bērziņš 2008, 281–284, Fig. 81). Nevertheless, the presence of artefacts in a sloping position in the immediate vicinity of the dwelling structures demonstrates that the surrounding area was wet, with very soft ground, at the time of occupation.

The pollen diagram of core Sārnate IX can be divided into 11 local pollen zones (LPZ), which reflect vegetation changes in the environs of the Sārnate site since the Early Holocene.

The appearance and significant increase of broadleaved tree pollen starts in calcareous clay at a depth of 2.45 m. Further up, with the accumulation of peaty gyttja, the section becomes richer in plant remains. The pollen composition in the sediment, reflecting the Holocene Thermal Maximum, starting with LPZ Ulmus-Tilia-Quercus-Corylus and corresponding to calcareous clay with organic remains and peaty gyttja (8050–7810 cal. BP), reflects the widest distribution broad-leaved trees (Ulmus, Tilia and Quercus), along with Alnus and Corylus.

Peaty gyttja at 1.9–1.25 m, dated 4900 cal. BP, shows an increase in Pinus, Picea and Quercus, as well as in aquatic plant pollen (Nymphaceae, Stratoides aloides, Menyanthes, Typhaceae), which mark the start of the Late Holocene. Trapa natans pollen has been found in this interval, and is also recorded in the upper part of the peaty gyttja layer.

The uppermost layer of Core IX (LPZ Pinus-Betula; (Picea-Alnus) and LPZ Pinus-Alnus) contains pollen of cultivated plants (Hordeum, Triticum, Avena) and anthropogenic indicators Plantago major/media, Chenopodium album, Polygonum aviculare, Urtica and Rumex acetosella, dated to 4890–4670 BP and

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3950–2770 BP. The sediment in this interval is rich in charcoal dust particles. It can be correlated to the upper part of the sediment sequence at Sārnate Dwelling O.

ConCluSIonSThe changes in plant macrofossil associations and sediment composition

indicate fluctuations in the level of the former Lake Sārnate. No remains of brackish-water plant species were found, and diatom study would be required in order to assess the impact of the Littorina Sea transgressions on the fluctuations in the level of the former lake. The gyttja containing Trapa natans was laid down in a freshwater lake, a rise in the level of which could also have come about as a result of local factors, such as meandering of the River Užava. Detailed reconstruction of the specific environmental conditions pertaining at the time when the cultural layer of the Sārnate settlement was formed would require additional palaeobotanical studies of the corresponding intervals in the depositional sequence.

ACknowlEdGmEntSThis study was supported by the Wenner-Gren Foundation in the frame of

the Post-PhD Research Grant Long-term dynamics of resource use in the changing Baltic coastal environment (Latvia).

rEfErEncEsBennett, K.D., Willis, K.J. 2001. Pollen. In: Smol, J.P., Birks, H.J.B., Last, W.M. (eds.) Tracking

Environmental Change using Lake Sediments. Vol. 3. Terestrial, Algal and Siliceous Indicators. London, Kluwer Academic Publishers, 5–33.

Berglund, B.E., Ralska-Jasiewiczowa, M. 1986. Pollen analysis and pollen diagrams. In: Berglund, B.E. (ed.) Handbook of Holocene Palaeoecology and Palaeohydrology. Brisbane Inc., John Wiley & Sons, 455–484.

Bērziņš, V. 2008. Sārnate: Living by a Coastal Lake During the East Baltic Neolithic. Acta Universitatis Ouluensis B Humaniora 86. Oulu, Oulu University Press. Available at: http://herkules.oulu.fi/isbn9789514289415/

Dreimanis, A. 1947. Pollenanalytische Datierung archaeologischer Funde von Sarnate, Lettland, und die Entwicklungsgeschichte des Sarnate-Moores. Contributions of Baltic University Pinneberg, 28, 1–15.

Grimm, E.C. 2011. Tilia v.1.5.12. Illinois state museum, research and collections center.Grinbergs, E. 1957. Pozdnelednikovaja i poslelednikovaja istorija poberezja Latviiskoi SSR, Riga

(in Russian).Grinbergs, E., Guzlena, A. 1972. K voprosu ob absolutnom vozraste litorinovoi transgressii

v nizoviah r. Venti. In: Voprosi fiziceskoi geografii Latviiskoi SSR. Ucenie zapiski Latviiskogo gosudarstvennogo universiteta imeni Petra Stucki, tom 162, 5–15.

Kalnina, L., Cerina, A., Berzins, V. 2011. Environment and Vegetation Changes During the Neolithic Settlement at Sarnate Site, Western Latvia. XVIII INQUA-Congress: ID: 3387, Session: 95 Climate, Environment, and Economy in the North and Central European Neolithic. http://www.inqua2011.ch/?a=programme&subnavi=abstract&id=3387&sessionid=95

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Murniece, S., Kalnina, L., Bērziņš, V., Grasis, N. 1999. Environmental Change and Prehistoric Human Activity in Western Kurzeme, Latvia. In: Miller, U. et al. (eds.) Environmental and cultural history of the Baltic Region. Belgium, PACT 57, 35–70.

Moore, P.D., Webb, J.A. 1978. An Illustrated Guide to Pollen Analysis. Oxford, Blackwell.Nikitin, V.P. 1969. Palaeocarpological Method. Tomsk, Publishing House of Tomsk University

(in Russian). Rimantienė, R. 2005. Die Steinzeitfischer an der Ostseelagune in Litauen. Forschungen in Šventoji

und Būtingė. Vilnius, Litauisches Nationalmuseum, 525.Vankina, L. 1970. Torfjanikovaja stojanka Sarnate. Rīga, Zinatne, 268 (in Russian).

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palaeoenViRonmental chanGes and GeoloGical deVelopment of the puiKule miRe

a ilze ozola, b Vita Ratniece

University of Latvia, Faculty of Geography and Earth Sciences e-mails: a ilze07@gmail.com, b vita.ratniece@inbox.lv

IntroduCtIon The Holocene is the latest epoch of the Quaternary period, and it covers

roughly the last 11,700 years (Lowe et al., 2008; Walker et al., 2009; Cohen et al., 2012; Walker et al., 2012). The evidence of environmental and vegetation changes has been well preserved in organogenic sediments, expecially in gyttja and peat.

The aim of the study was to reconstruct palaeovegetation changes and events that have influenced these changes during the organogenic sediment accumulation time in Puikule Mire.

Study SItE Investigations has been carried out in Puikule Mire, Northern Vidzeme,

(coordinates 57°40’55.51”Z, 24°45’20.59, size 2200 ha, depth 8.2 m).Puikule Mire is located in Limbaži Undulated Plain. On the south and

southeast sides it borders with Idumeja highland’s Augstroze interlobate hilly ridge, which is one of the Salaca River basin watersheds, while on the west side the mire borders with Puikule-Aloja ridge, behind which Metsepole Plain of Middle Latvia lowland begins. To the east from mire Burtnieks drumlin field lies, crossed by the Briede River on the southwest side. The total area of Puikule-Tēvgārša Bog is 2200 ha, of which 1591 ha is low mire and 609 ha – raised bog. The relief of the study area is comparative flat as it is located in the morainic plain. Puikule Mire surface nowadays is characterised by typical raised bog cupola with elevation from 74.4–82.1 m a.s.l. The largest depth of the mire depression is at area of Lake Purezers. Some hillocks appear in the northern part of bog and reach 1.5 m. Banks of mire depression are steep in the northern and western part, but flat at southern and eastern part. The depression of Puikule Mire has been former due to activities of the last glacier and it meltwaters. Depression surface is covered by glacigenic and glaciolimnic deposits.

mEthodSField and laboratory methods were carried out, as well as, previous

investigations materials were studied. Field works were carried out in raised bog, where coring and sampling were performed. In the central part of mire where the largest thickness of peat was found and 8 m long sediment core were obtained.

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Sediments were studied at the laboratory using peat botanical composition, decomposition degree, spore-pollen, loss on ignition, and fossil microorganism analysis. Pollen analysis was performed according to Birks and Birks (1980). At least 400–600 pollen grains were counted per sample for 52 samples. For pollen identification – Erdtman et al., 1963; Galenieks, 1960; Moore and Webb, 1978; Nilsson et al., 1977 were used. Non-pollen palynomorphs were identified. Loss on ignition analysis was done according to Heiri et al., 2001.

Radiocarbon dating was performed for 5 bulk samples (Table 1) at the Institute of Geology of the Tallinn University of Technology. For radioactive carbon dating calibration CLAM software was used (Blaauw, 2010). Results of spore-pollen, plant macro-remain, botanical composition and loss on ignition analysis have been visualised as diagrams using Tilia 1.5.12.

Table 1 Radiocarbon dating results

Depth, m Lab. code Material Age, 14C Cal.yr. BP (approx.)0.90–1.00 Tln3243 peat 1142 + –70 BP 9663.00–3.10 Tln3244 peat 2357 + –70 BP 23935.40–5.50 Tln3245 peat 3658 + –65 BP 41437.70–7.80 Tln3247 peat 7483 + –75 BP 8205

rESultS And IntErprEtAtIonPoLLEN SPEcTRa of PUIkULE mIRE SEdImENTS

PKU-1 LPAZ ~8450 to 8200 cal. yr BP; 7.87 m to 7.75 m when gyttja, accumulated in the lake. The lower part of the section of the pollen diagram (Fig.1 and Fig. 2) (8.00 to 7.75 m) is characterized by a birch peak (65%), there is also a lot of pine pollen (30%), however the amount has a tendency to decrease, grasses are found in a small amount (5%), pointing to a sudden temperature drop and hence probably a 8.2 event. After the 8.2 event (7.75 to 7.64 m) a grass – sphagnum peat, dark brown, medium to well-decomposed started to accumulate.

PKU-2 LPAZ ~ 7980–7800 cal. yr BP; 7.64 m to 7.55 m. Grass-sedge and wood-cotton grass peat accumulated. The fast-growing amount of hazel-tree (20%) indicates the increase in temperatures and a relatively open landscape, because hazel-tree is a light-demanding tree species. The open landscape is also indicated by significant increase in the amount of grass (up 25%).

The rest of the interval up to the present time is formed by sphagnum peat, during the accumulation of which several other birch peaks have been found, which possibly point to a number of cold periods: before 200 to 600, 1400 to 1600, 2600 to 2800, 3600 to 3400, 6100 to 6200, 8200 to 8300 cal. yr BP.

PKU-3 LPAZ ~6610 to 5914 cal. yr BP; 6.95 m to 6.58 m. Interval consists of wood-cotton grass and sphagnum-cotton grass peat in which in the pollen

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composition significant increase in birch pollen quantity (from 24% to 42%) has been found, whereas the curves of Ulmus and Corylus are decreasing. A slight increase starts in the percentage of Tilia, whereas the Alnus curve remains little affected, steadily retaining more than 20%.

PKU-4 LPAZ ~ 6000 to 4700 cal. yr BP; 6.58 m to 6.25 m. Cotton grass-sphagnum and cotton grass peat has accumulated. Their peak at this time is reached by Alnus and Corylus pollen curves, respectively, 32% and 29%. A significant increase in broad-leaved pollen can be observed with peaks also of Ulmus (10%) and Tilia (10%).The percentage of Picea gradually increases. At the end of the period the presence of Cannabis appears as well. There is a slight increase also in ruderal plant percentage, mainly Urtica, Chenopodiaceae, are encountered, with a small proportion of Artemisia and Plantago. Of caulescent plants, Poaceae remains at a constant level (in the 2–5% range) while the other caulescent plants are encountered very scarcely (less than 1%). There is a significant increase in the percentage of spore-bearing plants, as regards Sphagnum even up to 85%, Polypodiaceae is encountered at a steady level (approximately 1%) as well. Of aquatic plants in turn, there is a slight presence of Potamogetonaceae and Typhaceae.

PKU-5 LPAZ ~4700 to 2500 cal. yr BP; 6.25–3.20 m. Cotton grass-sphagnum, sphagnum-cotton grass, sphagnum peat has accumulated. During this period the proportion of spruce (Picea) has considerably increased. Throughout the period birch (Betula) pollen is encountered in significant amounts; however the curve is quite volatile, as it ranges from 8% at the beginning of the period to 33% in the middle of the second half, but drops again to 15%, whereas in the final stage a peak of 40% is reached. The amount of alder (Alnus) pollen is also significant and sometimes slightly above 20%, whereas the average curve stays within the limits of 17%. The amount of Ulmus and Tilia decreases, a rather smooth interval is maintained by broad-leaved Quercus (2–5%), Corylus (5% on average) and Tilia (1.5% on average). As regards shrubs its maximum (in the depth of 5.60 m) for a short time is reached by Ericales (26%), with also a small amount of Salix. Ruderal plant representatives are present, however there are very few: of them there are a little more Urtica and Chenopodiaceae, during the second half of the period also Artemisia. Of the caulescent plants the proportion of Poaceae has drastically decreased, which constitutes only just over 1%. Of the other caulescent plants a small amount of Cyperaceae, Rumex, Filipendula, Fabaceae are found as well as Linaceae pollen emerges. Dominance in pollen spore-bearing area is represented by Sphagnum, which witnesses an intense bog development in this area. Ferns (Polypodiaceae) are encountered as well, while of the aquatic plants there is a slight presence of Potamogetonaceae, Callitrithe also emerges in this interval.

PKU-6 LPAZ ~2470 to 1360 years ago; 3.20 m to 1.40 m. Sphagnum peat has accumulated, with medium, sometimes with weak decomposition, sometimes with tree residues, of brown colour. Pollen composition is dominated by

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birch pollen and reaches even up to 39%, whereas spruce pollen curve (13%) decreases rapidly, but still retains a significant role in the total pollen spectrum. At the same time the proportion of Pinus slightly increases (up 22%), thus pine becomes subdominant in the interval. With minor ups and downs Alnus pollen curve (18%) still remains relatively high. In respect to the broad-leaved plants Tilia and Ulmus pollen curves are becoming more and more unstable, however with some ups and downs hazel (Corylus) pollen (on average 2% to 6%) as well as oak (Quercus) pollen (up 3%) are still steadily present. Common hemp (Cannabis) pollen present in the upper segment of the interval provides evidence of cereal plant cultivation in the region.

PKU-7 LPAZ ~1360 to 820 cal. yr BP; depth 1.40 to 0.80 m, when cotton grass-sphagnum and then again poorly decomposed sphagnum peat continues to accumulate, spruce (48%) begins to dominate in the surrounding bog vegetation, the proportion of heather is rising (up to 14%).

PKU-8 LPAZ after approx. 820 cal. yr BP to this day peat with poorly decomposed tree remains continues to accumulate. During this time, a sharp increase in the proportion of birch (up to 52%) takes place, but at the end of the period, namely, the present day, the percentage of pine (45%) is rapidly growing. Compared to the previous zones, there is a slight increase in the number of ruderal plants (Plantago, Chenopodiaceae), which may possibly indicate human activities in the territory, whereas of caulescent plants Poaceae is still encountered; there is also a slight increase in Cyperaceae percentage. Spore-bearing plants are represented by Sphagnum and Lycopodium, whereas of the aquatic plants there is a small amount of Typhaceae and Nymphaceae.

Sporadic moisture and drought indicator amoeba incidence starting from 5.50 m depth (4,200 years ago) in the sediments tells of periodic groundwater level fluctuations during the development of the bog.

Bog type peat accumulation was fastest in the period starting from 4500–2500 cal. yr BP, when during 2000 years thick peat layer with a lower degree of decomposition in cool and wet conditions accumulated even up to the thickness of 2.20 m, because under cool and wet conditions the decomposition of plants occurred more slowly, resulting in relatively quick accumulation of poorly decomposed bog peat.

NoN-PoLLEN PaLYNomoRPhSAt the beginning of fen formation before 8700 to 8450 cal. yr BP (8.00 to

7.87 m) dense, rich greenish grey colour loam has accumulated. In the lake in the mentioned depth interval cladocerans (Cladocera, Daphnia sp.) or water fleas have been found (Fig. 3). They are 0.2 to 6.0 mm long micro-organisms that live in freshwater environment, in the littoral area of the lake. Their presence indicates the climate warming that is taking place simultaneously with the increase of nutrients in the lake (Birks, H.J.B. and Birks, H.H., 1980) and indicates an open, nutrient-rich water environment. In the depth of 7.88 m

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(grass-sphagnum peat layer), the most abundant are the algae of Pediastrum boryanum species. In the depth under consideration both whole P. boryanum colonies and their fragments have been found. P. boryanum adjusts to different atrophic conditions, although it is more associated with eutrophic waters and average temperatures ( Jakubovska, 1996). In the same depth (7.88 m) in the sediments algae Pediastrum integrum of a morphology very similar to the above species have been found and identified. Algae of this species love stagnant water conditions and finding them in the sediments indicates overgrowing of the water body. In the depth of 7.88 m to 7.80 m another species of Pediastrum

Fig. 3. non-pollen remain diagram

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P. kawraiskyi was also identified. This species of green algae has been found in the sediments in very small numbers and rapid decline of their numbers may be observed. P. kawraiskyi is widespread in oligotrophic waters with low temperature and alkaline environment ( Jakubovska, 1996). As in the depth of 7.80 m (8300 years ago), the prevalence of the species discontinues, it may be concluded that the climate during that period has become warmer compared to the previous period.

From 8450 cal. yr BP to 8200 cal. yr BP (7.87 m to 7.75 m) dense, dark brown gyttja, accumulated in the lake, in which three species of green algae (Pediastrum) and one kelp (Botryococcus) species have been found, indicating alterations of the hydrologic situation and ecological conditions in the water body.

Another species of algae, which was found in the sediments of the lower part of the section is kelp (Botriococcus brauni).The best temperature for their development is +23 °C, whereas the intensity of light is from 30 to 60 W/m2 (Botriococcus brauni, 2011). All algae found dwell in stagnant water conditions, with a relatively high temperature (except P. kawraiskyi) as indicated by the increase in numbers, while their disappearance in the higher layers of the section (at 7.70 m) indicates rapid overgrowth of the lake, loss of open water conditions and beginning of peat accumulation in the Boreal period approximately 8100 years ago.

Various rizopods: Arcella artocrea, Amphitrema flavum and Assulina muscorum were found in a significant number in the entire depth of the borehole. Arcella artocrea is a single-celled amoeba, moss epiphyte dwelling on the moss in order to get closer to light. The species is very sensitive to seasonal humidity alterations, because it mostly dwells in moist environment. In some cases it can survive short periods of drought, but only provided it develops a hood around it. In a small number it is occasionally found starting from the depth of 3.20 m (about 2500 years ago). The largest number of these representatives was found in the depth of 1.20 m (nearly 1200 years ago), indicating that the climate had become cooler and wetter and thus more favourable to the development of the species and perhaps a rise in the groundwater level could also be observed.

Amphitrema flavum amoeba has been found in the sediments in much larger numbers together with the above mentioned species. This species is the most common in the borehole cross-section and start to appear already at the depth of 5.50 m (4,200 years ago). Interconnection in their prevalence with Arcella artocrea can be found, as both species are indicators of wet conditions. The largest spread same as for Arcella artocrea is reached in the depth of 1.20 m 1200 years ago.

Assulina muscorum amoebic distribution also presents itself in an interesting way, which is characterized by dry conditions, thus it can be explained by periodic decrease of the groundwater levels in the bog. Compared to the indicators of wet conditions, the representatives of the species are found in a fairly small number; however they are found also in the depths simultaneously

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with the species loving damp conditions Amphitrema flavum and Arcella artocrea. Most likely it could be explained by short-term fluctuations in the groundwater level of the bog.

dISCuSSIonDuring the middle period of Holocene broad-leaved plants dominate, while

pine forests, on average, constitute 20%, which has been detected in Kurjanova Lake area (Heikkilä and Seppä, 2010) and is more similar to the situation in the vicinity of Verijarve Lake in southern Estonia (Niinemets and Saarse, 2009).

The lower parts of the HTM in the pollen diagrams of Puikule Mire sediments approximately 6700 to 7000 cal. yr. BP ago are characterized by strong hazel pollen curves and peaks (20–30%), which rapidly increase already since the 8.2 event. The peak is discontinued by temporary sharp rise in birch pollen curves (45%) 6200 cal. yr BP ago. Similar changes in the pollen spectra have been also found in Malmuta cross-section in Lubana Lake area (Segliņš et al., 1999) as well as in a number of Riga Gulf sediment research diagrams (Kalniņa et al., 1999)

The curves of broadleaf trees reach their peaks at the final part of the HTM. Linden peaks are reached in the diagrams approximately 5500 cal. yr BP ago, whereas in Verijarv and Kurjanova lake pollen diagrams linden pollen curve is constantly high and the culmination of the HTM is not expressed, however one of the peaks also emerges during this time.

Both in the Puikule cross-sections and Verijarve and Kurjanova Lake sediment and pollen diagrams in the time interval corresponding to late Holocene, although in a small number, broad-leaved tree pollen is still present, forming almost continuous curves.

Approximately 2700 years ago there is an increase in birch and spruce proportion as well as cereal plant pollen appears and the ratio of cereal plants increases, which in toto indicates anthropogenic effects. In Lake Kurjanova area this effect has been established 2500 cal. yr BP ago (Heikkilä, Seppä, 2010).

ConCluSIonSAt the site an open, shallow body of water may have existed previously,

accumulating the surrounding waters, from hypsometrically higher areas. The fact that the lake at the time of 8.2 event was oligotrophic (nutrient-poor) is witnessed by the presence of algae Pediastrum kawraiskyi found at the bottom of the sediment layer. The lake existed in such condition for a very short time, because a sharp increase in other algae (Pediastrum boryanum, Pediastrum integrum), which propagate under improved climatic conditions and with lake water becoming richer in nutrients is observed simultaneously. Climate warming and increase in lake eutrophication approximately 8,500 years ago is indicated also by the findings of microscopic traces of zooplankton Cladocera Daphnia Sp.

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High birch and grass pollen growth curves together with Pediastrum kawraisky algae approximately before 8300 – 8200 cal.yr BP point on the cold 8.2 event.

Pollen curve fluctuation in diagram indicates that during the Holocene thermal maximum there have been climate fluctuations, because the first half (approximately 8100 to 6700 cal. yr BP ago) is characterized by pronounced and sharp hazel pollen curve rise and peaking, accompanied by a gradual increase in the amount of broad-leaved tree pollen.

Holocene thermal maximum (HTM) is characterized by broad-leaved tree and hazel pollen composition is replaced before the interval of 6200 to 6400 cal. yr BP by rapid and short-lived peaks in birch and herb pollen and ascent of their curves, indicating a short-term temperature drop. Lack of wet condition indicators – algae and rizopods indicates that clime during the Holocene was rather dry.

In the pollen diagrams broad-leaved curves reach their peaks at the end of HTM, characterized by lime-tree pollen curve culmination, which is identified approximately 5500 cal. yr BP ago, whereas the first oak culmination is identified 4800 to 5100 cal. yr BP ago. Another oak peak may be observed either just prior the spruce peak 2800 to 3100 cal. yr BP ago.

The development of vegetation during late Holocene in Puikule bog vicinity indicates a number of warmer and colder periods. In the sediments that accumulated 2600 to 2800 cal. yr BP ago a higher birch and herbaceous pollen amount has been found, while there is a decrease in broad-leaf tree pollen amount, which allows to recognize a cold episode during that period. Also paleobiological data obtained from the analysis of sediments accumulated in the period 290 to 600 cal. yr BP ago indicate similar changes in vegetation composition and environmental conditions, which can be compared and ascribed to Little Ice Age events.

High number of rizopods that were found in the sediments together with pollen spectra indicates that climate during the late Holocene was cold and wet.

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Quaternary Geochronology, 5, 512–518.Cohen, J.L., Furtado, J.C., Barlow, M., Alexeev, V.A., Cgerry, J.E. 2012. Symmetric seasonal

temperature trends. Geophysical Research Letters, 39(4). Erdtman, G. 1954. An introduction to pollen analysis. USA, Waltham, Mass.Galenieks, P. 1960. Augu sistemātika. Rīga, Latvijas Valsts izdevniecība.Heikkilä, M., Seppä, H. 2010. Holocene climate dynamics in Latvia, eastern Baltic region: a

pollen-based summer temperature reconstruction and regional comparison. Boreas, 39(4), 705–719.

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Kalnina, L., Juskevics, V., Stiebrin,s O. 1999. Palynostratigraphyl and composition of Late Glacial and Holocene sediments from the Gulf of Riga, Eastern Baltic Sea. In: Andren, Th. (ed.) Proceedings og the Conference The Baltic – past, present and future. Stockholm on March 14–16th, 1994. Quaternaria, SerA., No. 7. Stockholm, 55–62.

Lowe, J.J., Rasmussen, S.O., Björck, S., Hoek, W.Z., Steffensen, J.P., Walker, M.J.C., Yu, Z.C., the INTIMATE group. 2008. Synhronisation of paleoenvironmental events in the North Atlantic region during the last Termination: a revised protocol recommended by the INTIMATE group. Quaternary Science Rewiews, 27, 6–17.

Moore, P.D., Webb, J.A. 1978. An Illustrated Guide to Pollen Analysis. Oxford, Blackwell.Niinemets, E., Saarse, L. 2006. Holocene forest Dynamics and human impact in southeastern

Estonia. Vegetation History and Archaeobotany, 16, 1–13.Segliņš, V., Kalniņa, L., Lācis, L. 1999. The Lubans Plain, Latvia as Reference Area for Long

Term Studies of Human Impact on the Environment. In: Miller, U., Hackens, T., Lang, V., Raukas, A., Hicks, Sh. (eds.) Environmental and cultural history of the Baltic Region, Belgium, Rixensart, 105–130.

Walker, M., Johnsen, S., Rasmussen, S.O., Popp, T., Steffensen, J.P., Gibbard, P., Hoek, W., Lowe, J., Andrews, J., Björck, S., Cwynar, L.C., Hughen, K., Kershaw, P., Kromer, B., Litt, T., Lowe, D.J., Nakagawa, T., Newnham, R., Schwander, J. 2009. Formal definition and dating of the GSSP (Global Stratotype Section and Point) for the base of the Holocene using the Greenland NGRIP ice core, and selected auxiliary records. Journal of Quaternary Science, 24, 3–17.

Walker, M.J.C., Berkelhammer, M., Bjork, S., Cwynar, L.C., Fisher, D.A., Long, A.J., Lowe, J.J., Newham, R.M., Rasmussen, S.O., Weiss, H. 2012. Formal subdivision of the Holocene Series/Epoch: a Discussion Paper by a Working Group of INTIMATE (Integration of ice-core, marine and terrestrial records) and the Subcommission on Quaternary Stratigraphy (International Commission on Stratigraphy). Discussion Paper. Journal of Quaternary Science, 27(7), 649–659.

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