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- Andrén, Elinor, et al.
(author)
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Holocene climate and environmental change in north-eastern Kamchatka (Russian Far East), inferred from a multi-proxy study of lake sediments
- 2015
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In: Global and Planetary Change. - : Elsevier BV. - 0921-8181 .- 1872-6364. ; 134, s. 41-54
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Journal article (peer-reviewed)abstract
- A sediment record from a small lake in the north-eastern part of the Kamchatka Peninsula has been investigated in a multi-proxy study to gain knowledge of Holocene climatic and environmental change. Pollen, diatoms, chironomids and selected geochemical parameters were analysed and the sediment record was dated with radiocarbon. The study shows Holocene changes in the terrestrial vegetation as well as responses of the lake ecosystem to catchment maturity and multiple stressors, such as climate change and volcanic eruptions. Climate change is the major driving force resulting in the recorded environmental changes in the lake, although recurrent tephra deposition events also contributed. The sediment record has an age at the base of about 10,000 cal yrs BP, and during the first 400 years the climate was cold and the lake exhibited extensive ice-cover during winter and relatively low primary production. Soils in the catchment were poor with shrub alder and birches dominatingthe vegetation surrounding the lake. At about 9600–8900 cal yrs BP the climate was cold and moist, and strong seasonal wind stress resulted in reduced ice-cover and increased primary production. After ca. 8900 cal yrs BP the forest density increased around the lake, runoff decreased in a generally drier climate resulting in decreasedprimary production in the lake until ca. 7000 cal yrs BP. This generally dry climate was interrupted by a brief climatic perturbation, possibly attributed to the 8.2 ka event, indicating increasingly windy conditions with thick snow cover, reduced ice-cover and slightly elevated primary production in the lake. The diatom record shows maximum thermal stratification at ca. 6300–5800 cal yrs BP and indicates together with the geochemical proxies a dry and slightly warmer climate resulting in a high productive lake. The most remarkably change in the catchment vegetation occurred at ca. 4200 cal yrs BP in the form of a conspicuous increase in Siberian dwarf pine (Pinus pumila), indicating a shift to a cooler climate with a thicker and more long-lasting snow cover. Thisvegetational change was accompanied by marked shifts in the diatom and chironomid stratigraphies, which are also indicative of colder climate and more extensive ice-cover.
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| 3. |
- Hammarlund, Dan, et al.
(author)
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Late Holocene expansion of Siberian dwarf pine (Pinus pumila) in Kamchatka in response to increased snow cover as inferred from lacustrine oxygen-isotope records
- 2015
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In: Global and Planetary Change. - : Elsevier BV. - 0921-8181 .- 1872-6364. ; 134:SI, s. 91-100
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Journal article (peer-reviewed)abstract
- Holocene records of cellulose-inferred lake-water δ18O were produced from two lake-sediment sequences obtained in central and northern Kamchatka, Russian Far East. The sediment records share similar fluctuations in δ18O during the interval of ca. 5000-800calyr BP that correspond (inversely) with changes in K+ content of the GISP2 ice-core record from Greenland, a proxy for the relative strength of the Siberian High, suggesting control by climate-related variability in δ18O of regional precipitation. The dramatic expansion of Siberian dwarf pine (Pinus pumila) in northern and central Kamchatka between ca. 5000 and 4000calyr BP, as inferred from pollen records from the same and neighbouring sites, appears to have occurred at a time of progressively declining δ18O of precipitation. This development is interpreted as reflecting a regional cooling trend accompanied by increasing winter snowfall related to gradual intensification of the Siberian High from ca. 5000 to ca. 3000calyr BP. A thicker and more long-lasting snow cover can be assumed to have favoured P. pumila by providing a competitive advantage over other boreal and subalpine tree and shrub species in the region during the later part of the Holocene. These results, which are the first of their kind from Kamchatka, provide novel insight into the Holocene vegetational and climatic development in easternmost Asia, as well as long-term atmospheric circulation dynamics in Beringia.
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- Pircs, Karolina, et al.
(author)
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Distinct subcellular autophagy impairments in induced neurons from patients with Huntington's disease
- 2022
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In: Brain : a journal of neurology. - : Oxford University Press (OUP). - 1460-2156. ; 145:9, s. 3035-3057
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Journal article (peer-reviewed)abstract
- Huntington's disease (HD) is a neurodegenerative disorder caused by CAG expansions in the huntingtin (HTT) gene. Modelling Huntington's disease is challenging, as rodent and cellular models poorly recapitulate the disease as seen in aging humans. To address this, we generated induced neurons (iNs) through direct reprogramming of human skin fibroblasts, which retain age-dependent epigenetic characteristics. HD-iNs displayed profound deficits in autophagy, characterised by reduced transport of late autophagic structures from the neurites to the soma. These neurite-specific alterations in autophagy resulted in shorter, thinner and fewer neurites specifically in HD-iNs. CRISPRi-mediated silencing of HTT did not rescue this phenotype but rather resulted in additional autophagy alterations in ctrl-iNs, highlighting the importance of wild type HTT in normal neuronal autophagy. In summary, our work identifies a distinct subcellular autophagy impairment in adult patient derived Huntington's disease neurons and provides a new rational for future development of autophagy activation therapies.
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