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Zheleznogorsk, Russia

Boy J.,Leibniz University of Hanover | Godoy R.,Austral University of Chile | Shibistova O.,Leibniz University of Hanover | Shibistova O.,VN Sukachev Institute of Forest | And 6 more authors.
Revista Chilena de Historia Natural | Year: 2016

Background: Maritime Antarctica is severely affected by climate change and accelerating glacier retreat forming temporal gradients of soil development. Successional patterns of soil development and plant succession in the region are largely unknown, as are the feedback mechanisms between both processes. Here we identify three temporal gradients representing horizontal and vertical glacier retreat, as well as formation of raised beaches due to isostatic uplift, and describe soil formation and plant succession along them. Our hypotheses are (i) plants in Antarctica are able to modulate the two base parameters in soil development, organic C content and pH, along the temporal gradients, leading to an increase in organic carbon and soil acidity at relatively short time scales, (ii) the soil development induces succession along these gradients, and (iii) with increasing soil development, bryophytes and Deschampsia antarctica develop mycorrhiza in maritime Antarctica in order to foster interaction with soil. Results: All temporal gradients showed soil development leading to differentiation of soil horizons, carbon accumulation and increasing pH with age. Photoautptroph succession occurred rapidly after glacier retreat, but occurrences of mosses and lichens interacting with soils by rhizoids or rhizines were only observed in the later stages. The community of ground dwelling mosses and lichens is the climax community of soil succession, as the Antarctic hairgrass D. antarctica was restricted to ornithic soils. Neither D. antarctica nor mosses at the best developed soils showed any sign of mycorrhization. Conclusion: Temporal gradients formed by glacier retreat can be identified in maritime Antarctic, where soil development and plant succession of a remarkable pace can be observed, although pseudo-succession occurs by fertilization gradients caused by bird feces. Thus, the majority of ice-free surface in Antarctica is colonized by plant communities which interact with soil by litter input rather than by direct transfer of photoassimilates to soil. © 2016 Boy et al. Source


Hellmann L.,Swiss Federal Institute of forest | Hellmann L.,Oeschger Center for Climate Change Research | Tegel W.,Albert Ludwigs University of Freiburg | Kirdyanov A.V.,VN Sukachev Institute of Forest | And 13 more authors.
Arctic, Antarctic, and Alpine Research | Year: 2015

Recent findings indicated spruce from North America and larch from eastern Siberia to be the dominating tree species of Arctic driftwood throughout the Holocene. However, changes in source region forest and river characteristics, as well as ocean current dynamics and sea ice extent likely influence its spatiotemporal composition. Here, we present 2556 driftwood samples from Greenland, Iceland, Svalbard, and the Faroe Islands. A total of 498 out of 969 Pinus sylvestris ring width series were cross-dated at the catchment level against a network of Eurasian boreal reference chronologies. The central Siberian Yenisei and Angara Rivers account for 91% of all dated pines, with their outermost rings dating between 1804 and 1999. Intensified logging and timber rafting along the Yenisei and Angara in the mid-20th century, together with high discharge rates, explain the vast quantity of material from this region and its temporal peak ca. 1960. Based on the combined application of wood-anatomical and dendrochronological techniques on a well-replicated data set, our results question the assumption that Arctic driftwood mainly consists of millennial-old larch and spruce. Nevertheless, data from other species and regions, together with longer boreal reference chronologies, are needed for generating reliable proxy archives at the interface of marine and terrestrial environments. © 2015 Regents of the University of Colorado. Source


Buntgen U.,Swiss Federal Institute of forest | Buntgen U.,Oeschger Center for Climate Change Research | Buntgen U.,Academy of Sciences of the Czech Republic | Hellmann L.,Swiss Federal Institute of forest | And 8 more authors.
Journal of Ecology | Year: 2015

Summary: The effects of climate change on Arctic ecosystems can range between various spatiotemporal scales and may include shifts in population distribution, community composition, plant phenology, primary productivity and species biodiversity. The growth rates and age structure of tundra vegetation as well as its response to temperature variation, however, remain poorly understood because high-resolution data are limited in space and time. Anatomical and morphological stem characteristics were recorded to assess the growth behaviour and age structure of 871 dwarf shrubs from 10 species at 30 sites in coastal East Greenland at 70°N. Recruitment pulses were linked with changes in mean annual and summer temperature back to the 19th century, and a literature review was conducted to place our findings in a pan-Arctic context. Low cambial activity translates into estimated average/maximum plant ages of 59/204 years, suggesting relatively small turnover rates and stable community composition. Decade-long changes in the recruitment intensity were found to lag temperature variability by 2 and 6 years during warmer and colder periods, respectively (r = 0.851961-2000 and 1881-1920). Synthesis. Our results reveal a strong temperature dependency of Arctic dwarf shrub reproduction, a high vulnerability of circumpolar tundra ecosystems to climatic changes, and the ability of evaluating historical vegetation dynamics well beyond the northern treeline. The combined wood anatomical and plant ecological approach, considering insights from micro-sections to community assemblages, indicates that model predictions of rapid tundra expansion (i.e. shrub growth) following intense warming might underestimate plant longevity and persistence but overestimate the sensitivity and reaction time of Arctic vegetation. Our results reveal a strong temperature dependency of Arctic dwarf shrub reproduction, a high vulnerability of circumpolar tundra ecosystems to climatic changes, and the ability of evaluating historical vegetation dynamics well beyond the northern treeline. The combined wood anatomical and plant ecological approach, considering insights from microsections to community assemblages, indicates that model predictions of rapid tundra expansion (i.e. shrub growth) following intense warming might underestimate plant longevity and persistence but overestimate the sensitivity and reaction time of Arctic vegetation. © 2014 British Ecological Society. Source


Pflugmacher D.,Oregon State University | Krankina O.N.,Oregon State University | Cohen W.B.,U.S. Department of Agriculture | Friedl M.A.,Boston University | And 8 more authors.
Remote Sensing of Environment | Year: 2011

Information on land cover at global and continental scales is critical for addressing a range of ecological, socioeconomic and policy questions. Global land cover maps have evolved rapidly in the last decade, but efforts to evaluate map uncertainties have been limited, especially in remote areas like Northern Eurasia. Northern Eurasia comprises a particularly diverse region covering a wide range of climate zones and ecosystems: from arctic deserts, tundra, boreal forest, and wetlands, to semi-arid steppes and the deserts of Central Asia. In this study, we assessed four of the most recent global land cover datasets: GLC-2000, GLOBCOVER, and the MODIS Collection 4 and Collection 5 Land Cover Product using cross-comparison analyses and Landsat-based reference maps distributed throughout the region. A consistent comparison of these maps was challenging because of disparities in class definitions, thematic detail, and spatial resolution. We found that the choice of sampling unit significantly influenced accuracy estimates, which indicates that comparisons of reported global map accuracies might be misleading. To minimize classification ambiguities, we devised a generalized legend based on dominant life form types (LFT) (tree, shrub, and herbaceous vegetation, barren land and water). LFT served as a necessary common denominator in the analyzed map legends, but significantly decreased the thematic detail. We found significant differences in the spatial representation of LFT's between global maps with high spatial agreement (above 0.8) concentrated in the forest belt of Northern Eurasia and low agreement (below 0.5) concentrated in the northern taiga-tundra zone, and the southern dry lands. Total pixel-level agreement between global maps and six test sites was moderate to fair (overall agreement: 0.67-0.74, Kappa: 0.41-0.52) and increased by 0.09-0.45 when only homogenous land cover types were analyzed. Low map accuracies at our tundra test site confirmed regional disagreements and difficulties of current global maps in accurately mapping shrub and herbaceous vegetation types at the biome borders of Northern Eurasia. In comparison, tree dominated vegetation classes in the forest belt of the region were accurately mapped, but were slightly overestimated (10%-20%), in all maps. Low agreement of global maps in the northern and southern vegetation transition zones of Northern Eurasia is likely to have important implications for global change research, as those areas are vulnerable to both climate and socio-economic changes. © 2011 Elsevier Inc. Source


Gentsch N.,Leibniz University of Hanover | Mikutta R.,Leibniz University of Hanover | Shibistova O.,Leibniz University of Hanover | Shibistova O.,VN Sukachev Institute of Forest | And 18 more authors.
European Journal of Soil Science | Year: 2015

Permafrost degradation may cause strong feedbacks of arctic ecosystems to global warming, but this will depend on if, and to what extent, organic matter (OM) is protected against biodegradation by mechanisms other than freezing and anoxia. Here, we report on the amount, chemical composition and bioavailability of particulate (POM) and mineral-associated OM (MOM) in permafrost soils of the East Siberian Arctic. The average total organic carbon (OC) stock across all soils was 24.0 ± 6.7 kg m-2 within 100 cm soil depth. Density fractionation (density cut-off 1.6 g cm-3) revealed that 54 ± 16% of the total soil OC and 64 ± 18% of OC in subsoil horizons was bound to minerals. As well as sorption of OM to clay-sized minerals (R2 = 0.80; P < 0.01), co-precipitation of OM with hydrolyzable metals may also transfer carbon into the mineral-bound fraction. Carbon:nitrogen ratios, stable carbon and nitrogen isotopes, 13C-NMR and X-ray photoelectron spectroscopy showed that OM is transformed in permafrost soils, which is a prerequisite for the formation of mineral-organic associations. Mineral-associated OM in deeper soil was enriched in 13C and 15N, and had narrow C:N and large alkyl C:(O-/N-alkyl C) ratios, indicating an advanced stage of decomposition. Despite being up to several thousands of years old, when incubated under favourable conditions (60% water-holding capacity, 15°C, adequate nutrients, 90 days), only 1.5-5% of the mineral-associated OC was released as CO2. In the topsoils, POM had the largest mineralization but was even less bioavailable than the MOM in subsoil horizons. Our results suggest that the formation of mineral-organic associations acts as an important additional factor in the stabilization of OM in permafrost soils. Although the majority of MOM was not prone to decomposition under favourable conditions, mineral-organic associations host a readily accessible carbon fraction, which may actively participate in ecosystem carbon exchange. © 2015 British Society of Soil Science. Source

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