Laimdota Kalnina | University of Latvia (original) (raw)

Papers by Laimdota Kalnina

Research paper thumbnail of Changes of peat properties in differently affected parts of the Lauga Bog

G̦eogrāfiski raksti, 2019

At the present time much attention on the identification and investigation of degraded peatland a... more At the present time much attention on the identification and investigation of degraded peatland areas is mainly being undertaken by studies on growing bog plant species, vegetation cover continuity and character. However, it is also understood that to choose the most effective re-cultivation method it is necessary to know the properties of the remaining peat layers and local hydrological conditions. The aim of this study was to discover the characteristics of peat properties and their changes in three differently affected areas of the Lauga Bog. Field work included geological coring and the collecting of deposit samples for further laboratory analysis including loss on ignition (LOI) analysis, determination of the peat density, pH and magnetic susceptibility measurements. The obtained results reveal that peat properties in the Lauga Bog vary in differently affected areas. In the affected areas (Lauga-1 and Lauga-3) the top layer of the peat section has a higher natural density and larger proportion of mineral matter. Whereas a natural bog section is characterised by peat with lower natural density, a higher percentage of organic matter and lower pH is typical for raised bogs.

Research paper thumbnail of Reconstruction of past anthropogenic impact intensity in Lake Engure using sedimentary record analysis

Proceedings of the Latvian Academy of Sciences. Section B, Natural, Exact and Applied Sciences, 2011

Contributed by Mâris Kïaviòð Environmental pollution with trace elements is considered as one of ... more Contributed by Mâris Kïaviòð Environmental pollution with trace elements is considered as one of the most important environmental problems. Analysis of trace element accumulation in sedimentary phases of lakes may reflect the overall regional pollution level, and analysis of trace element accumulation patterns in sediment profiles can help to reconstruct the history of anthropogenic impact. The aim of this study was to analyse trace element concentrations in sediments of Lake Engure in Latvia and to determine factors influencing their availability. The metal concentrations in sediments of Lake Engure are at background levels, especially compared with metal concentrations in West European countries. However, the change in element concentration in sedimentary profiles provides information about trends of recent accumulation (within the last 100 years) and on the balance between natural and human-induced accumulation processes.

Research paper thumbnail of Mires in Latvia

Research paper thumbnail of Introduction for the SI “Understanding the Baltic Sea”

Estuarine Coastal and Shelf Science, Aug 1, 2017

Research paper thumbnail of Holocene relative shore‐level changes and development of the Ģipka lagoon in the western Gulf of Riga

Boreas

Holocene relative shore‐level changes and development of the Ģipka palaeolagoon in the western Gu... more Holocene relative shore‐level changes and development of the Ģipka palaeolagoon in the western Gulf of Riga are reconstructed using multiproxy analyses by combining litho‐, biostratigraphical and chronological data with remote sensing and geophysical data. The results show the development of the Ģipka basin from the Ancylus Lake/Initial Litorina Sea coastal zone (before c. 9.1 cal. ka BP) to coastal fen (c. 9.1 to 8.4 cal. ka BP) and gradual development of the Litorina Sea lagoon (c. 8.4 to 4.8 cal. ka BP) and its transition to a freshwater coastal lake (c. 4.8 to 4.6 cal. ka BP), fen (c. 4.6 to 4.2 cal. ka BP), and river floodplain (since c. 4.2 cal. ka BP). The highest shorelines of the Ancylus Lake and Litorina Sea were mapped at an elevation of 12–11 and 9 m a.s.l., respectively. A new relative shore level (RSL) curve for the western Gulf of Riga was constructed based on RSL data from the Ģipka area and from nearby Ruhnu Island studied earlier. The reconstruction shows that the ...

Research paper thumbnail of Sarnate pollen dataset

Raw data for the Sarnate pollen dataset obtained from the Neotoma Paleoecology Database.

Research paper thumbnail of Climate variability in the Baltic Sea Basin over the last 12,000 calendar years: Lessons from the past for the future

Research paper thumbnail of Supplementary material to "Patterns in recent and Holocene pollen influxes across Europe; the Pollen Monitoring Programme Database as a tool for vegetation reconstruction

Research paper thumbnail of Patterns in recent and Holocene pollen influxes across Europe; the Pollen Monitoring Programme Database as a tool for vegetation reconstruction

The collection of modern spatially extensive pollen data are important for the interpretation of ... more The collection of modern spatially extensive pollen data are important for the interpretation of fossil pollen diagrams. Such datasets are readily available for percentage data but lacking for pollen accumulation rates (PAR). Filling this gap has been the motivation of the pollen monitoring network, whose contributors monitored pollen deposition in modified Taubertraps for several years or decades across European latitudes. Here we present this monitoring dataset consisting of 351 trap locations with a total of 2742 annual samples covering the period from 1981 to 2017. This dataset shows that climate parameters correlating with latitude determine pollen productivity. A signal of regional forest cover can be detected in the data, while local tree cover seems more important. Pollen traps situated beyond 200 km of the distribution of the parent tree are still collecting occasional pollen grains of the tree in question. PAR's of up to 30 grains cm-2 y-1 in fossil diagram should therefore be interpreted as long distance transport. Comparisons to fossil data from the same areas show comparable values. Comparisons often demonstrate that similar high values for temperate taxa in fossils sites are found further south or downhill. While modern situations comparable to high PAR values of some taxa (e.g. Corylus) may be hard to find, CO 2 fertilization and land use may case high modern PAR's that are not documented in the fossil record. The modern data is now publically available in the Neotoma Paleoecology Database and hopefully serves improving interpretations of fossil PAR data.

Research paper thumbnail of Compositional turnover and variation in Eemian pollen sequences in Europe

Vegetation History and Archaeobotany, 2019

The Eemian interglacial represents a natural experiment on how past vegetation with negligible hu... more The Eemian interglacial represents a natural experiment on how past vegetation with negligible human impact responded to amplified temperature changes compared to the Holocene. Here, we assemble 47 carefully selected Eemian pollen sequences from Europe to explore geographical patterns of (1) total compositional turnover and total variation for each sequence and (2) stratigraphical turnover between samples within each sequence using detrended canonical correspondence analysis, multivariate regression trees, and principal curves. Our synthesis shows that turnover and variation are highest in central Europe (47-55°N), low in southern Europe (south of 45°N), and lowest in the north (above 60°N). These results provide a basis for developing hypotheses about causes of vegetation change during the Eemian and their possible drivers. Keywords Detrended canonical correspondence analysis • Extrinsic and intrinsic processes • Inertia • Last interglacial dataset • Multivariate regression trees • Neutral processes • Principal curves Communicated by F. Bittmann.

Research paper thumbnail of Characteristics of peat properties from extracted peatlands in the context of sustainable management

Folia Geographica, 2019

The degradation level and re-cultivation possibilities of extracted peat fields have usually been... more The degradation level and re-cultivation possibilities of extracted peat fields have usually been evaluated using data from vegetation studies, and partly from hydrological measurements. Very little attention has been paid to the remaining peat layer properties; however, this is important for the planning and choice of scenario for re-cultivation. The aim of this study has been to investigate the properties of the remaining peat section with special attention to the top layer. This research project included the following laboratory methods: losson ignition method, pH, degree of peat decomposition botanical composition and natural peat density analysis. The results of this study point to those peat properties that are changing due to extraction processes. The obtained results suggest that peat properties in the studied affected peatlands vary differently. The top layers of the peat section have a higher natural density and increased amount of mineral matter. The main changes observed were in the peat natural moisture, pH, mineral content, degradation rates, and ash content, which in the extracted peat field were associated with hydrological regime modification.

Research paper thumbnail of Changes of the palaeo-geographical conditions in the Lake Usma depression during the end of the Late Glacial and the Holocene

Folia Geographica, 2019

Lake Usma occupies the lowest part of the Late Glacial glacio-depression at the Kursa Lowland (NW... more Lake Usma occupies the lowest part of the Late Glacial glacio-depression at the Kursa Lowland (NW Latvia), where the Venta-Usma ice-dammed lake and the Baltic Ice Lake sediments have been accumulated. Geological and geo-morphological investigations have been carried out on the largest Lake Usma islands-Moricsala and Viskūži Island as well as at Košķēni Bay. Changes in palaeo-geographic conditions in the Lake Usma depression during the Holocene are evidenced by organogenic sediments from cores in Moricsala and Viskūži Island and in the lake bottom of Košķēni Bay. The loss on ignition analysis of these sediments has been carried out with the aim to determine changes of organic, mineral and carbonate matter proportions and the relative percentage in their composition, which together with macro-remain analysis data allow to gain better understanding about the character of the palaeogeographic conditions during the lake's development,

Research paper thumbnail of Palaeo-geographic changes in the Sārnate former lagoon area

Folia Geographica, 2019

Due to the lowering of the Littorina Sea level before approximately 5000 years, Sārnate lagoon wa... more Due to the lowering of the Littorina Sea level before approximately 5000 years, Sārnate lagoon was separated from the sea and became a shallow lagoon lake, which gradually terrestrialised and filled in with peat. The aim of the research project reported in this paper was to characterise the changing palaeogeographical conditions in the former Sārnate lagoon area, as recorded by changes in sediment properties, pollen and plant macro-remain composition. The plant macro-remain and pollen studies indicate intensive human activity in the area during the latter part of the Holocene climatic optimum and the first part of the Late Holocene, Subboreal, including a record of Water chestnut (Trapa natans) fruits and pollen in the gyttja under the grass peat, indicating that water chestnut grew in the lake adjacent to the settlement. The presence of cereal and weed pollen confirms that agriculture was also being practiced, at least during the final phase of occupation, in the late 6th and the 5th millennium BP.

Research paper thumbnail of Evidence of palaeo-climate changes and their impact on sediment accumulation conditions in the Lubāns Stone-Age settlement areas

Folia Geographica, 2019

The Latvian Geospatial Information Agency Map. https://kartes.lgia.gov.lv/karte/ (11.02.2019). Ve... more The Latvian Geospatial Information Agency Map. https://kartes.lgia.gov.lv/karte/ (11.02.2019). Veinbergs, I. (1999). Baltijas jūras leduslaikmeta beiguposma un pēcleduslaikmeta baseinu Latvijas krasta zonas morfo-un litodinamika (pēc Latvijas piekrastes pētījumu rezultātiem). Latvijas Universitātes Ģeoloģijas institūts, atskaite.

Research paper thumbnail of Palynology and lithostratigraphy of Late Elsterian to Early Saalian aquatic sediments in the Ziemupe–Jūrkalne area, western Latvia

Quaternary International, 2000

This study is based upon lithological and palynological investigation of test-drilling cores alon... more This study is based upon lithological and palynological investigation of test-drilling cores along the Baltic Sea coast. Three intertill units of basin sediments are underlain by a thin layer of Le tiz\ a (Elsterian) till and overlain by glaciotectonically deformed Kurzeme (Saalian Complex) till. The Kurzeme till di!ers from the Le tiz\ a till by higher contents of limestone clasts and rounded hornblende grains. The lowermost intertill unit consists of glaciolacustrine to glaciomarine laminated clay of the Sudrabi member, a late glacial deposit of the Le tiz\ a glaciation. Treeless vegetation covered the adjoining land. Next is the marine to brackish Akmen7 rags formation, deposited during the Pulvernieki (Holstenian) interglaciation. Thermophilous deciduous trees, spruce and alder dominated the forests during its climatic optimum. The youngest, dominantly sandy Ju rkalne formation was deposited in brackish-to freshwater at the beginning of the Kurzeme (Saalian Complex) glaciation, when land was covered by treeless vegetation. It contains a thin interbed of diamicton of Kurzeme till lithology suggesting a brief glacial advance in the Baltic Sea Basin at the beginning of the Kurzeme glaciation.

Research paper thumbnail of Peldošais ezerrrieksts (Trapa natans) dabas un cilvēku vēstures liecinieks Latvijā

G̦eogrāfiski raksti, 2018

Due to the lowering of the Littorina Sea level before approximately 5000 years, Sārnate lagoon wa... more Due to the lowering of the Littorina Sea level before approximately 5000 years, Sārnate lagoon was separated from the sea and became a shallow lagoon lake, which gradually terrestrialised and filled in with peat. The aim of the research project reported in this paper was to characterise the changing palaeogeographical conditions in the former Sārnate lagoon area, as recorded by changes in sediment properties, pollen and plant macro-remain composition. The plant macro-remain and pollen studies indicate intensive human activity in the area during the latter part of the Holocene climatic optimum and the first part of the Late Holocene, Subboreal, including a record of Water chestnut (Trapa natans) fruits and pollen in the gyttja under the grass peat, indicating that water chestnut grew in the lake adjacent to the settlement. The presence of cereal and weed pollen confirms that agriculture was also being practiced, at least during the final phase of occupation, in the late 6th and the 5th millennium BP.

Research paper thumbnail of What happens to peat during bog fires? thermal transformation processes of peat organic matter

Agronomy research, 2020

Bog fires are a serious natural phenomena. Major increase in the number of fires has happened dur... more Bog fires are a serious natural phenomena. Major increase in the number of fires has happened during the last decades due to bog transformation into agricultural lands, accidents and human activities. During bog fires the peat is exposed to high temperatures due to which chemical transformation and even mineralisation of peat can occur. The aim of the study was to analyse the impacts of the bog fires on the bog as an ecosystem, advance the understanding and knowledge of fire impact on peat and humic matter properties and application possibilities. As the material for the study peat samples from burnt sites and thermally treated peat were used. To reveal peat transformation during bog fires, thermogravimetric analysis of peat samples were done, where amounts of bitumens, humic acids and mineral matter were estimated. During bog fires thermal modification of peat properties takes place, resulting in full mineralisation of peat and release of mineral substances. Bog fires lead to development of peat char, bitumens and significant changes in structure and properties of peat humic acids. However, from perspective of application of peat as a substrate and from perspective of impacts on the bog ecosystems, the effects are negligible.

Research paper thumbnail of Impact of the physico-chemical properties of fen peat on the metal accumulation patterns in mires of Latvia

Baltica, 2016

The article presents a study of the physico-chemical properties of fen peat and their influence o... more The article presents a study of the physico-chemical properties of fen peat and their influence on the metal accumulation patterns in three Latvian fens: Svētupes Mire, Elku Mire and Vīķu Mire. Full peat profiles were obtained at all study sites and analysed with a multi-proxy approach. The content of metals in fen peat was determined using the atomic absorption spectroscopy (AAS) and normalised to the concentration of Ti in the studied peat profiles. Both the character of deposits and agricultural land use in the mire catchment areas were taken into account and the possible natural and anthropogenic metal supply sources were evaluated. The content of metals in the studied fen peat significantly varied due to the heterogeneity of fen environment; however, noticeable similarities were also traced throughout all study sites. The results indicate an increased amount of transition metals and Pb in the upper peat layer. This can be explained by a direct impact from anthropogenic sources ...

Research paper thumbnail of Recurrent Mesolithic–Neolithic occupation at Sise (western Latvia) and shoreline displacement in the Baltic Sea Basin

The Holocene, 2016

A major assemblage of Mesolithic and Neolithic wooden artefacts has been recovered from the bed o... more A major assemblage of Mesolithic and Neolithic wooden artefacts has been recovered from the bed of the River Užava at Sise, in the coastal belt of western Latvia. New archaeological investigation has also produced wooden remains and other evidence of occupation on the riverbank. On the basis of multi-proxy environmental data and radiocarbon dating, this article offers a first attempt to place the human activity in a palaeolandscape context. The earliest evidence of human presence is provided by wooden artefacts dated to c. 10,500–9700 cal. BP, during the Ancylus Lake transgression. These remains are thought to reflect fishing activities in the shallows of the Ventspils Bay, which existed during the transgression. The regression that followed brought a return to river-valley conditions at the site, and the next recorded period of human activity, evidenced by 14C-dated antler tool finds, is associated with the beginning of the Littorina Sea transgression, culminating c. 7500 cal. BP. ...

Research paper thumbnail of Peat humification character in two ombrotrophic bogs depending on peat properties

Proceedings of the Latvian Academy of Sciences. Section B. Natural, Exact, and Applied Sciences., 2010

Peat humification character in two ombrotrophic bogs depending on peat properties Study of the li... more Peat humification character in two ombrotrophic bogs depending on peat properties Study of the living organic matter humification process is essential for understanding of the carbon biogeochemical cycle. The aim of this study is to determine the relations between peat properties and humification degree in two peat profiles in ombrotrophic bogs in Latvia, to identify the links between peat age, decomposition degree, peat properties, peat botanical composition and peat properties. The peat diagenesis process was described using multiproxy analysis of peat age, botanical composition, elemental composition, elemental ratios of the peat organic matter and peat alkaline extracts. This approach supports a better understanding of the peat properties and their relation both to peat decomposition processes, and also to original living organic matter. Multiproxy study of peat properties supports development of peat humification indicators.

Research paper thumbnail of Changes of peat properties in differently affected parts of the Lauga Bog

G̦eogrāfiski raksti, 2019

At the present time much attention on the identification and investigation of degraded peatland a... more At the present time much attention on the identification and investigation of degraded peatland areas is mainly being undertaken by studies on growing bog plant species, vegetation cover continuity and character. However, it is also understood that to choose the most effective re-cultivation method it is necessary to know the properties of the remaining peat layers and local hydrological conditions. The aim of this study was to discover the characteristics of peat properties and their changes in three differently affected areas of the Lauga Bog. Field work included geological coring and the collecting of deposit samples for further laboratory analysis including loss on ignition (LOI) analysis, determination of the peat density, pH and magnetic susceptibility measurements. The obtained results reveal that peat properties in the Lauga Bog vary in differently affected areas. In the affected areas (Lauga-1 and Lauga-3) the top layer of the peat section has a higher natural density and larger proportion of mineral matter. Whereas a natural bog section is characterised by peat with lower natural density, a higher percentage of organic matter and lower pH is typical for raised bogs.

Research paper thumbnail of Reconstruction of past anthropogenic impact intensity in Lake Engure using sedimentary record analysis

Proceedings of the Latvian Academy of Sciences. Section B, Natural, Exact and Applied Sciences, 2011

Contributed by Mâris Kïaviòð Environmental pollution with trace elements is considered as one of ... more Contributed by Mâris Kïaviòð Environmental pollution with trace elements is considered as one of the most important environmental problems. Analysis of trace element accumulation in sedimentary phases of lakes may reflect the overall regional pollution level, and analysis of trace element accumulation patterns in sediment profiles can help to reconstruct the history of anthropogenic impact. The aim of this study was to analyse trace element concentrations in sediments of Lake Engure in Latvia and to determine factors influencing their availability. The metal concentrations in sediments of Lake Engure are at background levels, especially compared with metal concentrations in West European countries. However, the change in element concentration in sedimentary profiles provides information about trends of recent accumulation (within the last 100 years) and on the balance between natural and human-induced accumulation processes.

Research paper thumbnail of Mires in Latvia

Research paper thumbnail of Introduction for the SI “Understanding the Baltic Sea”

Estuarine Coastal and Shelf Science, Aug 1, 2017

Research paper thumbnail of Holocene relative shore‐level changes and development of the Ģipka lagoon in the western Gulf of Riga

Boreas

Holocene relative shore‐level changes and development of the Ģipka palaeolagoon in the western Gu... more Holocene relative shore‐level changes and development of the Ģipka palaeolagoon in the western Gulf of Riga are reconstructed using multiproxy analyses by combining litho‐, biostratigraphical and chronological data with remote sensing and geophysical data. The results show the development of the Ģipka basin from the Ancylus Lake/Initial Litorina Sea coastal zone (before c. 9.1 cal. ka BP) to coastal fen (c. 9.1 to 8.4 cal. ka BP) and gradual development of the Litorina Sea lagoon (c. 8.4 to 4.8 cal. ka BP) and its transition to a freshwater coastal lake (c. 4.8 to 4.6 cal. ka BP), fen (c. 4.6 to 4.2 cal. ka BP), and river floodplain (since c. 4.2 cal. ka BP). The highest shorelines of the Ancylus Lake and Litorina Sea were mapped at an elevation of 12–11 and 9 m a.s.l., respectively. A new relative shore level (RSL) curve for the western Gulf of Riga was constructed based on RSL data from the Ģipka area and from nearby Ruhnu Island studied earlier. The reconstruction shows that the ...

Research paper thumbnail of Sarnate pollen dataset

Raw data for the Sarnate pollen dataset obtained from the Neotoma Paleoecology Database.

Research paper thumbnail of Climate variability in the Baltic Sea Basin over the last 12,000 calendar years: Lessons from the past for the future

Research paper thumbnail of Supplementary material to "Patterns in recent and Holocene pollen influxes across Europe; the Pollen Monitoring Programme Database as a tool for vegetation reconstruction

Research paper thumbnail of Patterns in recent and Holocene pollen influxes across Europe; the Pollen Monitoring Programme Database as a tool for vegetation reconstruction

The collection of modern spatially extensive pollen data are important for the interpretation of ... more The collection of modern spatially extensive pollen data are important for the interpretation of fossil pollen diagrams. Such datasets are readily available for percentage data but lacking for pollen accumulation rates (PAR). Filling this gap has been the motivation of the pollen monitoring network, whose contributors monitored pollen deposition in modified Taubertraps for several years or decades across European latitudes. Here we present this monitoring dataset consisting of 351 trap locations with a total of 2742 annual samples covering the period from 1981 to 2017. This dataset shows that climate parameters correlating with latitude determine pollen productivity. A signal of regional forest cover can be detected in the data, while local tree cover seems more important. Pollen traps situated beyond 200 km of the distribution of the parent tree are still collecting occasional pollen grains of the tree in question. PAR's of up to 30 grains cm-2 y-1 in fossil diagram should therefore be interpreted as long distance transport. Comparisons to fossil data from the same areas show comparable values. Comparisons often demonstrate that similar high values for temperate taxa in fossils sites are found further south or downhill. While modern situations comparable to high PAR values of some taxa (e.g. Corylus) may be hard to find, CO 2 fertilization and land use may case high modern PAR's that are not documented in the fossil record. The modern data is now publically available in the Neotoma Paleoecology Database and hopefully serves improving interpretations of fossil PAR data.

Research paper thumbnail of Compositional turnover and variation in Eemian pollen sequences in Europe

Vegetation History and Archaeobotany, 2019

The Eemian interglacial represents a natural experiment on how past vegetation with negligible hu... more The Eemian interglacial represents a natural experiment on how past vegetation with negligible human impact responded to amplified temperature changes compared to the Holocene. Here, we assemble 47 carefully selected Eemian pollen sequences from Europe to explore geographical patterns of (1) total compositional turnover and total variation for each sequence and (2) stratigraphical turnover between samples within each sequence using detrended canonical correspondence analysis, multivariate regression trees, and principal curves. Our synthesis shows that turnover and variation are highest in central Europe (47-55°N), low in southern Europe (south of 45°N), and lowest in the north (above 60°N). These results provide a basis for developing hypotheses about causes of vegetation change during the Eemian and their possible drivers. Keywords Detrended canonical correspondence analysis • Extrinsic and intrinsic processes • Inertia • Last interglacial dataset • Multivariate regression trees • Neutral processes • Principal curves Communicated by F. Bittmann.

Research paper thumbnail of Characteristics of peat properties from extracted peatlands in the context of sustainable management

Folia Geographica, 2019

The degradation level and re-cultivation possibilities of extracted peat fields have usually been... more The degradation level and re-cultivation possibilities of extracted peat fields have usually been evaluated using data from vegetation studies, and partly from hydrological measurements. Very little attention has been paid to the remaining peat layer properties; however, this is important for the planning and choice of scenario for re-cultivation. The aim of this study has been to investigate the properties of the remaining peat section with special attention to the top layer. This research project included the following laboratory methods: losson ignition method, pH, degree of peat decomposition botanical composition and natural peat density analysis. The results of this study point to those peat properties that are changing due to extraction processes. The obtained results suggest that peat properties in the studied affected peatlands vary differently. The top layers of the peat section have a higher natural density and increased amount of mineral matter. The main changes observed were in the peat natural moisture, pH, mineral content, degradation rates, and ash content, which in the extracted peat field were associated with hydrological regime modification.

Research paper thumbnail of Changes of the palaeo-geographical conditions in the Lake Usma depression during the end of the Late Glacial and the Holocene

Folia Geographica, 2019

Lake Usma occupies the lowest part of the Late Glacial glacio-depression at the Kursa Lowland (NW... more Lake Usma occupies the lowest part of the Late Glacial glacio-depression at the Kursa Lowland (NW Latvia), where the Venta-Usma ice-dammed lake and the Baltic Ice Lake sediments have been accumulated. Geological and geo-morphological investigations have been carried out on the largest Lake Usma islands-Moricsala and Viskūži Island as well as at Košķēni Bay. Changes in palaeo-geographic conditions in the Lake Usma depression during the Holocene are evidenced by organogenic sediments from cores in Moricsala and Viskūži Island and in the lake bottom of Košķēni Bay. The loss on ignition analysis of these sediments has been carried out with the aim to determine changes of organic, mineral and carbonate matter proportions and the relative percentage in their composition, which together with macro-remain analysis data allow to gain better understanding about the character of the palaeogeographic conditions during the lake's development,

Research paper thumbnail of Palaeo-geographic changes in the Sārnate former lagoon area

Folia Geographica, 2019

Due to the lowering of the Littorina Sea level before approximately 5000 years, Sārnate lagoon wa... more Due to the lowering of the Littorina Sea level before approximately 5000 years, Sārnate lagoon was separated from the sea and became a shallow lagoon lake, which gradually terrestrialised and filled in with peat. The aim of the research project reported in this paper was to characterise the changing palaeogeographical conditions in the former Sārnate lagoon area, as recorded by changes in sediment properties, pollen and plant macro-remain composition. The plant macro-remain and pollen studies indicate intensive human activity in the area during the latter part of the Holocene climatic optimum and the first part of the Late Holocene, Subboreal, including a record of Water chestnut (Trapa natans) fruits and pollen in the gyttja under the grass peat, indicating that water chestnut grew in the lake adjacent to the settlement. The presence of cereal and weed pollen confirms that agriculture was also being practiced, at least during the final phase of occupation, in the late 6th and the 5th millennium BP.

Research paper thumbnail of Evidence of palaeo-climate changes and their impact on sediment accumulation conditions in the Lubāns Stone-Age settlement areas

Folia Geographica, 2019

The Latvian Geospatial Information Agency Map. https://kartes.lgia.gov.lv/karte/ (11.02.2019). Ve... more The Latvian Geospatial Information Agency Map. https://kartes.lgia.gov.lv/karte/ (11.02.2019). Veinbergs, I. (1999). Baltijas jūras leduslaikmeta beiguposma un pēcleduslaikmeta baseinu Latvijas krasta zonas morfo-un litodinamika (pēc Latvijas piekrastes pētījumu rezultātiem). Latvijas Universitātes Ģeoloģijas institūts, atskaite.

Research paper thumbnail of Palynology and lithostratigraphy of Late Elsterian to Early Saalian aquatic sediments in the Ziemupe–Jūrkalne area, western Latvia

Quaternary International, 2000

This study is based upon lithological and palynological investigation of test-drilling cores alon... more This study is based upon lithological and palynological investigation of test-drilling cores along the Baltic Sea coast. Three intertill units of basin sediments are underlain by a thin layer of Le tiz\ a (Elsterian) till and overlain by glaciotectonically deformed Kurzeme (Saalian Complex) till. The Kurzeme till di!ers from the Le tiz\ a till by higher contents of limestone clasts and rounded hornblende grains. The lowermost intertill unit consists of glaciolacustrine to glaciomarine laminated clay of the Sudrabi member, a late glacial deposit of the Le tiz\ a glaciation. Treeless vegetation covered the adjoining land. Next is the marine to brackish Akmen7 rags formation, deposited during the Pulvernieki (Holstenian) interglaciation. Thermophilous deciduous trees, spruce and alder dominated the forests during its climatic optimum. The youngest, dominantly sandy Ju rkalne formation was deposited in brackish-to freshwater at the beginning of the Kurzeme (Saalian Complex) glaciation, when land was covered by treeless vegetation. It contains a thin interbed of diamicton of Kurzeme till lithology suggesting a brief glacial advance in the Baltic Sea Basin at the beginning of the Kurzeme glaciation.

Research paper thumbnail of Peldošais ezerrrieksts (Trapa natans) dabas un cilvēku vēstures liecinieks Latvijā

G̦eogrāfiski raksti, 2018

Due to the lowering of the Littorina Sea level before approximately 5000 years, Sārnate lagoon wa... more Due to the lowering of the Littorina Sea level before approximately 5000 years, Sārnate lagoon was separated from the sea and became a shallow lagoon lake, which gradually terrestrialised and filled in with peat. The aim of the research project reported in this paper was to characterise the changing palaeogeographical conditions in the former Sārnate lagoon area, as recorded by changes in sediment properties, pollen and plant macro-remain composition. The plant macro-remain and pollen studies indicate intensive human activity in the area during the latter part of the Holocene climatic optimum and the first part of the Late Holocene, Subboreal, including a record of Water chestnut (Trapa natans) fruits and pollen in the gyttja under the grass peat, indicating that water chestnut grew in the lake adjacent to the settlement. The presence of cereal and weed pollen confirms that agriculture was also being practiced, at least during the final phase of occupation, in the late 6th and the 5th millennium BP.

Research paper thumbnail of What happens to peat during bog fires? thermal transformation processes of peat organic matter

Agronomy research, 2020

Bog fires are a serious natural phenomena. Major increase in the number of fires has happened dur... more Bog fires are a serious natural phenomena. Major increase in the number of fires has happened during the last decades due to bog transformation into agricultural lands, accidents and human activities. During bog fires the peat is exposed to high temperatures due to which chemical transformation and even mineralisation of peat can occur. The aim of the study was to analyse the impacts of the bog fires on the bog as an ecosystem, advance the understanding and knowledge of fire impact on peat and humic matter properties and application possibilities. As the material for the study peat samples from burnt sites and thermally treated peat were used. To reveal peat transformation during bog fires, thermogravimetric analysis of peat samples were done, where amounts of bitumens, humic acids and mineral matter were estimated. During bog fires thermal modification of peat properties takes place, resulting in full mineralisation of peat and release of mineral substances. Bog fires lead to development of peat char, bitumens and significant changes in structure and properties of peat humic acids. However, from perspective of application of peat as a substrate and from perspective of impacts on the bog ecosystems, the effects are negligible.

Research paper thumbnail of Impact of the physico-chemical properties of fen peat on the metal accumulation patterns in mires of Latvia

Baltica, 2016

The article presents a study of the physico-chemical properties of fen peat and their influence o... more The article presents a study of the physico-chemical properties of fen peat and their influence on the metal accumulation patterns in three Latvian fens: Svētupes Mire, Elku Mire and Vīķu Mire. Full peat profiles were obtained at all study sites and analysed with a multi-proxy approach. The content of metals in fen peat was determined using the atomic absorption spectroscopy (AAS) and normalised to the concentration of Ti in the studied peat profiles. Both the character of deposits and agricultural land use in the mire catchment areas were taken into account and the possible natural and anthropogenic metal supply sources were evaluated. The content of metals in the studied fen peat significantly varied due to the heterogeneity of fen environment; however, noticeable similarities were also traced throughout all study sites. The results indicate an increased amount of transition metals and Pb in the upper peat layer. This can be explained by a direct impact from anthropogenic sources ...

Research paper thumbnail of Recurrent Mesolithic–Neolithic occupation at Sise (western Latvia) and shoreline displacement in the Baltic Sea Basin

The Holocene, 2016

A major assemblage of Mesolithic and Neolithic wooden artefacts has been recovered from the bed o... more A major assemblage of Mesolithic and Neolithic wooden artefacts has been recovered from the bed of the River Užava at Sise, in the coastal belt of western Latvia. New archaeological investigation has also produced wooden remains and other evidence of occupation on the riverbank. On the basis of multi-proxy environmental data and radiocarbon dating, this article offers a first attempt to place the human activity in a palaeolandscape context. The earliest evidence of human presence is provided by wooden artefacts dated to c. 10,500–9700 cal. BP, during the Ancylus Lake transgression. These remains are thought to reflect fishing activities in the shallows of the Ventspils Bay, which existed during the transgression. The regression that followed brought a return to river-valley conditions at the site, and the next recorded period of human activity, evidenced by 14C-dated antler tool finds, is associated with the beginning of the Littorina Sea transgression, culminating c. 7500 cal. BP. ...

Research paper thumbnail of Peat humification character in two ombrotrophic bogs depending on peat properties

Proceedings of the Latvian Academy of Sciences. Section B. Natural, Exact, and Applied Sciences., 2010

Peat humification character in two ombrotrophic bogs depending on peat properties Study of the li... more Peat humification character in two ombrotrophic bogs depending on peat properties Study of the living organic matter humification process is essential for understanding of the carbon biogeochemical cycle. The aim of this study is to determine the relations between peat properties and humification degree in two peat profiles in ombrotrophic bogs in Latvia, to identify the links between peat age, decomposition degree, peat properties, peat botanical composition and peat properties. The peat diagenesis process was described using multiproxy analysis of peat age, botanical composition, elemental composition, elemental ratios of the peat organic matter and peat alkaline extracts. This approach supports a better understanding of the peat properties and their relation both to peat decomposition processes, and also to original living organic matter. Multiproxy study of peat properties supports development of peat humification indicators.

Research paper thumbnail of Pollen-based quantitative reconstructions of Holocene regional vegetation cover (plant-functional types and land-cover types) in Europe suitable for climate modelling

We present quantitative reconstructions of regional vegetation cover in north-western Europe, wes... more We present quantitative reconstructions of regional vegetation cover in north-western Europe, western Europe north of the Alps, and eastern Europe for five time windows in the Holocene [around 6k, 3k, 0.5k, 0.2k, and 0.05k calendar years before present (BP)] at a 1° 9 1° spatial scale with the objective of producing vegetation descriptions suitable for climate modelling. The REVEALS model was applied on 636 pollen records from lakes and bogs to reconstruct the past cover of 25 plant taxa grouped into 10 plant-functional types and three land-cover types [evergreen trees,summer-green (deciduous) trees, and open land]. The model corrects for some of the biases in pollen percentages by using pollen productivity estimates and fall speeds of pollen, and by applying simple but robust models of pollen dispersal and deposition. The emerging patterns of tree migration and deforestation between 6k BP and modern time in the REVEALS estimates agree with our general understanding of the vegetation history of Europe based on pollen percentages. However, the degree of anthropogenic deforestation (i.e. cover of cultivated and grazing land) at 3k,
0.5k, and 0.2k BP is significantly higher than deduced from pollen percentages. This is also the case at 6k in some parts of Europe, in particular Britain and Ireland. Furthermore, the relationship between summer-green and evergreen trees, and between individual tree taxa, differs significantly when expressed as pollen percentages or as REVEALS estimates of tree cover. For instance, when Pinus is dominant over Picea as pollen percentages, Picea is dominant over Pinus as REVEALS estimates. These differences play a major role in the reconstruction of European landscapes and for the study of land cover–climate interactions, biodiversity and human resources.

Research paper thumbnail of Regional climate model simulations for Europe at 6 k and 0.2 k yr BP: sensitivity to changes in anthropogenic deforestation

Climate of the Past Discussions, 2013

This study aims to evaluate the direct effects of anthropogenic deforestation on simulated climat... more This study aims to evaluate the direct effects of anthropogenic deforestation on simulated climate at two contrasting periods in the Holocene, ∼ 6 and ∼ 0.2 k BP in Europe. We apply We apply the Rossby Centre regional climate model RCA3, a regional climate model with 50 km spatial resolution, for both time periods, considering three alternative descriptions of the past vegetation: (i) potential natural vegetation (V) simulated by the dynamic vegetation model LPJ-GUESS, (ii) potential vegetation with anthropogenic land use (deforestation) from the HYDE3.