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Veronika Dirksen

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Papers by Veronika Dirksen

Research paper thumbnail of Distribution of Diatoms in sediment core PG1857-2

Research paper thumbnail of Scores of principle components of sediment core PG1856-3

Research paper thumbnail of Distribution and assessment of the conservation status of Erioderma pedicellatum in Asia

The Lichenologist, 2019

The first detailed survey is presented of a recently discovered population of Erioderma pedicella... more The first detailed survey is presented of a recently discovered population of Erioderma pedicellatum, a globally rare lichen, in the primeval spruce forests of the Kamchatka Peninsula, Russia. Three subpopulations are described, located in the Levaya Schapina River basin, in the Kimitina River basin, and on the slopes of the extinct volcano, Nikolka. In total, we observed 1894 thalli on 167 Yezo spruce trunks. In Kamchatka, E. pedicellatum occurs exclusively on bark-covered spruce twigs of mainly young and dwarf-stressed older trees. We discovered a high number of juvenile thalli, which suggests that this population is reproducing. However, its habitat is declining because spruce forests in the region are the target of industrial clear-cutting and there is a high incidence of forest fires. Over the next 60 years, which corresponds to three generations of E. pedicellatum, we infer that continued habitat loss will induce a 48% decline in these lichen populations. As a result of our an...

Research paper thumbnail of 100 Holocene vegetation dynamics and climate change in Kamchatka, Russian Far East

Japanese Journal of Palynology

Research paper thumbnail of 099 Holocene pollen record from Lake Sokoch, interior Kamchatka (Russia), and its palaeobotanical and paleoclimatic interpretation

Japanese Journal of Palynology

Research paper thumbnail of Multi-proxy records of Two-Yurts Lake

Within the scope of Russian-German palaeoenvironmental research, Two-Yurts Lake (TYL, Dvuh-Yurtoc... more Within the scope of Russian-German palaeoenvironmental research, Two-Yurts Lake (TYL, Dvuh-Yurtochnoe in Russian) was chosen as the main scientific target area to decipher Holocene climate variability on Kamchatka. The 5x2 km large and 26 m deep lake is of proglacial origin and situated on the eastern flank of Sredinny Ridge at the northwestern end of the Central Kamchatka Valley, outside the direct influence of active volcanism. Here, we present results of a multi-proxy study on sediment cores, spanning about the last 7000 years. The general tenor of the TYL record is an increase in continentality and winter snow cover in conjunction with a decrease in temperature, humidity, and biological productivity after 5000-4500 cal yrs BP, inferred from pollen and diatom data and the isotopic composition of organic carbon. The TYL proxy data also show that the late Holocene was punctuated by two colder spells, roughly between 4500 and 3500 cal yrs BP and between 1000 and 200 cal yrs BP, as local expressions of the Neoglacial and Little Ice Age, respectively. These environmental changes can be regarded as direct and indirect responses to climate change, as also demonstrated by other records in the regional terrestrial and marine realm. Long-term climate deterioration was driven by decreasing insolation, while the short-term climate excursions are best explained by local climatic processes. The latter affect the configuration of atmospheric pressure systems that control the sources as well as the temperature and moisture of air masses reaching Kamchatka.

Research paper thumbnail of Pollen profile of sediment core PG1857-5

Research paper thumbnail of Sedimentology of core PG1857-2

Research paper thumbnail of New Paleoclimate Records from the Russian Far East: Carbon Accumulation Rates and Ecological Change Over the Last 13,000 Years from Western and Central Kamchatka

Research paper thumbnail of Sedimentology of core PG1856-3

Research paper thumbnail of Late Quaternary Lake Records of Northeastern Eurasia

Research paper thumbnail of Pollen profile of sediment core PG1857-2

Research paper thumbnail of Pollen profile of sediment core PG1856-3

Research paper thumbnail of Distribution of diatoms in sediment core PG1856-3

Research paper thumbnail of Sedimentology of core PG1857-5

Research paper thumbnail of Scores of principle components of sediment core PG1857-2

Research paper thumbnail of Scores of principle components of sediment core PG1856-3

Research paper thumbnail of Holocene Environment and Climate Dynamics on Kamchatka: Findings from Two-Yurts Lake

Research paper thumbnail of Distribution of Diatoms in sediment core PG1857-2

Research paper thumbnail of Holocene evolution of a proglacial lake in southern Kamchatka, Russian Far East

Boreas, 2021

The Kamchatka Peninsula (Russian Far East) remains among the least studied regions of eastern Asi... more The Kamchatka Peninsula (Russian Far East) remains among the least studied regions of eastern Asia. Recent studies revealed a high degree of palaeoenvironmental variability between different parts of the peninsula. We investigated semi‐aquatic (chironomids) and terrestrial (leaf wax biomarkers) proxies from a sediment core collected from Lake Sokoch (southern Kamchatka) to provide reconstruction of the mean July air temperature and variations in limnic conditions. The lake formed after 10.0 cal. ka BP as a result of postglacial warming and was fed by glacial meltwaters from neighbouring glaciers. Our data show a later beginning of the Holocene thermal maximum (HTM) relative to more northern sites in Kamchatka, Siberia and Chukotka and support climate model experiments that suggest that the HTM was delayed in southern and central Kamchatka by about 2000 years compared with Alaska and NE Siberia. Warm conditions prevailed between 10.0 and 6.4 cal. ka BP with a short spell of cool and ...

Research paper thumbnail of Distribution of Diatoms in sediment core PG1857-2

Research paper thumbnail of Scores of principle components of sediment core PG1856-3

Research paper thumbnail of Distribution and assessment of the conservation status of Erioderma pedicellatum in Asia

The Lichenologist, 2019

The first detailed survey is presented of a recently discovered population of Erioderma pedicella... more The first detailed survey is presented of a recently discovered population of Erioderma pedicellatum, a globally rare lichen, in the primeval spruce forests of the Kamchatka Peninsula, Russia. Three subpopulations are described, located in the Levaya Schapina River basin, in the Kimitina River basin, and on the slopes of the extinct volcano, Nikolka. In total, we observed 1894 thalli on 167 Yezo spruce trunks. In Kamchatka, E. pedicellatum occurs exclusively on bark-covered spruce twigs of mainly young and dwarf-stressed older trees. We discovered a high number of juvenile thalli, which suggests that this population is reproducing. However, its habitat is declining because spruce forests in the region are the target of industrial clear-cutting and there is a high incidence of forest fires. Over the next 60 years, which corresponds to three generations of E. pedicellatum, we infer that continued habitat loss will induce a 48% decline in these lichen populations. As a result of our an...

Research paper thumbnail of 100 Holocene vegetation dynamics and climate change in Kamchatka, Russian Far East

Japanese Journal of Palynology

Research paper thumbnail of 099 Holocene pollen record from Lake Sokoch, interior Kamchatka (Russia), and its palaeobotanical and paleoclimatic interpretation

Japanese Journal of Palynology

Research paper thumbnail of Multi-proxy records of Two-Yurts Lake

Within the scope of Russian-German palaeoenvironmental research, Two-Yurts Lake (TYL, Dvuh-Yurtoc... more Within the scope of Russian-German palaeoenvironmental research, Two-Yurts Lake (TYL, Dvuh-Yurtochnoe in Russian) was chosen as the main scientific target area to decipher Holocene climate variability on Kamchatka. The 5x2 km large and 26 m deep lake is of proglacial origin and situated on the eastern flank of Sredinny Ridge at the northwestern end of the Central Kamchatka Valley, outside the direct influence of active volcanism. Here, we present results of a multi-proxy study on sediment cores, spanning about the last 7000 years. The general tenor of the TYL record is an increase in continentality and winter snow cover in conjunction with a decrease in temperature, humidity, and biological productivity after 5000-4500 cal yrs BP, inferred from pollen and diatom data and the isotopic composition of organic carbon. The TYL proxy data also show that the late Holocene was punctuated by two colder spells, roughly between 4500 and 3500 cal yrs BP and between 1000 and 200 cal yrs BP, as local expressions of the Neoglacial and Little Ice Age, respectively. These environmental changes can be regarded as direct and indirect responses to climate change, as also demonstrated by other records in the regional terrestrial and marine realm. Long-term climate deterioration was driven by decreasing insolation, while the short-term climate excursions are best explained by local climatic processes. The latter affect the configuration of atmospheric pressure systems that control the sources as well as the temperature and moisture of air masses reaching Kamchatka.

Research paper thumbnail of Pollen profile of sediment core PG1857-5

Research paper thumbnail of Sedimentology of core PG1857-2

Research paper thumbnail of New Paleoclimate Records from the Russian Far East: Carbon Accumulation Rates and Ecological Change Over the Last 13,000 Years from Western and Central Kamchatka

Research paper thumbnail of Sedimentology of core PG1856-3

Research paper thumbnail of Late Quaternary Lake Records of Northeastern Eurasia

Research paper thumbnail of Pollen profile of sediment core PG1857-2

Research paper thumbnail of Pollen profile of sediment core PG1856-3

Research paper thumbnail of Distribution of diatoms in sediment core PG1856-3

Research paper thumbnail of Sedimentology of core PG1857-5

Research paper thumbnail of Scores of principle components of sediment core PG1857-2

Research paper thumbnail of Scores of principle components of sediment core PG1856-3

Research paper thumbnail of Holocene Environment and Climate Dynamics on Kamchatka: Findings from Two-Yurts Lake

Research paper thumbnail of Distribution of Diatoms in sediment core PG1857-2

Research paper thumbnail of Holocene evolution of a proglacial lake in southern Kamchatka, Russian Far East

Boreas, 2021

The Kamchatka Peninsula (Russian Far East) remains among the least studied regions of eastern Asi... more The Kamchatka Peninsula (Russian Far East) remains among the least studied regions of eastern Asia. Recent studies revealed a high degree of palaeoenvironmental variability between different parts of the peninsula. We investigated semi‐aquatic (chironomids) and terrestrial (leaf wax biomarkers) proxies from a sediment core collected from Lake Sokoch (southern Kamchatka) to provide reconstruction of the mean July air temperature and variations in limnic conditions. The lake formed after 10.0 cal. ka BP as a result of postglacial warming and was fed by glacial meltwaters from neighbouring glaciers. Our data show a later beginning of the Holocene thermal maximum (HTM) relative to more northern sites in Kamchatka, Siberia and Chukotka and support climate model experiments that suggest that the HTM was delayed in southern and central Kamchatka by about 2000 years compared with Alaska and NE Siberia. Warm conditions prevailed between 10.0 and 6.4 cal. ka BP with a short spell of cool and ...

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