From fibrous plant residues to mineral-associated organic carbon – the fate of organic matter in Arctic permafrost soils

Permafrost-affected soils of the Arctic account for 70 % or 727 Pg of the soil organic carbon (C) stored in the northern circumpolar permafrost region and therefore play a major role in the global C cycle. Most studies on the budgeting of C storage and the quality of soil organic matter (OM; SOM) in the northern circumpolar region focus on bulk soils. Thus, although there is a plethora of assumptions regarding differences in terms of C turnover or stability, little knowledge is available on the mechanisms stabilizing organic C in Arctic soils besides impaired decomposition due to low temperatures. To gain such knowledge, we investigated soils from Samoylov Island in the Lena River delta with respect to the composition and distribution of organic C among differently stabilized SOM fractions. The soils were fractionated according to density and particle size to obtain differently stabilized SOM fractions differing in chemical composition and thus bioavailability. To better understand the chemical alterations from plant-derived organic particles in these soils rich in fibrous plant residues to mineral-associated SOM, we analyzed the elemental, isotopic and chemical composition of particulate OM (POM) and clay-sized mineral-associated OM (MAOM). We demonstrate that the SOM fractions that contribute with about 17 kg C m$^{-3}$ for more than 60 % of the C stock are highly bioavailable and that most of this labile C can be assumed to be prone to mineralization under warming conditions. Thus, the amount of relatively stable, small occluded POM and clay-sized MAOM that currently accounts with about 10 kg C m$^{-3}$ for about 40 % of the C stock will most probably be crucial for the quantity of C protected from mineralization in these Arctic soils in a warmer future. Using δ$^{15}$N as a proxy for nitrogen (N) balances indicated an important role of N inputs by biological N fixation, while gaseous N losses appeared less important. However, this could change, as with about 0.4 kg N m$^{-3}$ one third of the N is present in bioavailable SOM fractions, which could lead to increases in mineral N cycling and associated N losses under global warming. Our results highlight the vulnerability of SOM in Arctic permafrost-affected soils under rising temperatures, potentially leading to unparalleled greenhouse gas emissions from these soils

Forms of International Cooperation in Environmental Education: the Experience of Saint Petersburg State University

The authors analyse different forms of environmental education projects and programmes implemented in the Baltic Sea region. The first one is "The Baltic University" programme taught in English. The "Baltic University" is a network of more than 200 universities from 14 counties of the Baltic Sea region. This education programme offers an opportunity for students to enroll on bachelor and master degree programmes related to environmental and social problems of the Baltic Sea region. The Polar and Marine Sciences, POMOR master programme, represents the second form of international environmental education. Russian and German researchers from six universities and four research centres have developed the programme. The target group of the programme are Russian and international students, studying together during the whole duration of the programme. It is the first internationally accredited MA programme taught in English. International accreditation proves the compliance of the programme with international education standards. The same cooperation model is used in a new international master programme - Cold Regions Environmental Landscapes Integrated Science (CORELIS). The programme started in 2016. It is implemented jointly by Hamburg university (the lead partner of the project), and university professors from Helsinki (Finland) and Lisbon (Portugal). Researchers from the Austrian National Institute of Polar Research (Austria, and Lund University (Sweden) will join the programme at a later stage. Such an approach will help achieve the synergy of the European and Russian approaches to environmental education. The Russian-Norwegian master programme "Geoecological monitoring and rational use of natural resources in the Northern oil and gas production regions" is a good example of the third form of international environmental education. The programme similar to POMOR and CORELIS. However, it has one distinctive feature - Russian and foreign students study together from the second term only. The authors describe the ways of achieving the learning objectives of these master programmes depending on the students' language skills and their basic knowledge of ecology and nature management

The nitrogen stock of the ice-rich yedoma domain

Recent studies on permafrost organic matter (OM) suggest that a portion of previously frozen carbon will enter the active carbon cycle as high latitudes warm. Less is known about the fate of other OM components, including nutrients such as nitrogen (N). The abundance and availability of N following permafrost thaw will regulate the ability of plants to offset carbon losses. Additionally, lateral N losses could alter aquatic food webs. There is growing evidence that some N is lost vertically as N2O, a greenhouse gas 300 times stronger than CO2 over 100 years. Despite broad recognition of its role regulating both carbon and non-carbon aspects of the permafrost climate feedback, estimates of permafrost N remain uncertain. To address this knowledge gap, we quantified N content for different stratigraphic units, including yedoma, Holocene cover deposits, refrozen thermokarst deposits, taberal sediments, and active layer soils. The resulting N estimates from this one permafrost region were similar in magnitude to previous estimates for the entire permafrost zone. We conclude that the permafrost N pool is much larger than currently appreciated and a substantial pool of permafrost N could be mobilized after thaw, with continental-scale consequences for biogeochemical budgets and global-scale consequences

The Nitrogen Inventory of the Yedoma Permafrost Domain

Fossil organic matter (OM) stored in permafrost is an important subject in climate research. Such OM represents a huge reservoir of carbon (C). Multiple studies suggest its source potential for C release into the active C cycle through permafrost thaw and subsequent microbial turnover in a warming Arctic. However, net ecosystem OM balance in the permafrost region depends on more than just carbon. The abundance and availability of nitrogen (N) following permafrost thaw will influence plant growth, nutrient delivery to aquatic and estuarine ecosystems, and N oxide (N2O) emissions. Despite its central importance to predicting permafrost impacts and feedbacks to climate change, relatively little is known about permafrost N stocks and composition. In this study, we present the most extensive dataset to date of permafrost N in the Siberian and Alaskan Yedoma domain. The Yedoma domain comprises decameter thick ice-rich silts intersected by syngenetic ice wedges, which formed in late Pleistocene tundra-steppe environments, as well as other deposits resulting from permafrost degradation during the Holocene. Together, the deposits in this region constitute a large C inventory storing several hundred Gt C, but are also known to be nutrient-rich due to rapid burial and freezing of plant remains. Hitherto, the total organic C pool of the Yedoma region was quantified, while the total N inventory is lacking so far. Based on the most comprehensive data set of N content in permafrost to date, our study aims to estimate the present pool of N stored in the different stratigraphic units of the Yedoma domain: 1) late Pleistocene Yedoma deposits, 2) in-situ thawed and diagenetically altered Yedoma deposits (taberite), 3) Holocene thermokarst deposits, 4) Holocene cover deposits on top of Yedoma, and 5) the modern active layer of soils. To quantify measurement uncertainty, we estimated nitrogen stocks with bootstrapping techniques. We show that the deposits of the Yedoma region store a substantial pool of N that is expected to get mobilized after thaw and, at least partially, affecting biogeochemical budgets of thawing warming permafrost ecosystems

A globally relevant stock of soil nitrogen in the Yedoma permafrost domain

Nitrogen regulates multiple aspects of the permafrost climate feedback, including plant growth, organic matter decomposition, and the production of the potent greenhouse gas nitrous oxide. Despite its importance, current estimates of permafrost nitrogen are highly uncertain. Here, we compiled a dataset of >2000 samples to quantify nitrogen stocks in the Yedoma domain, a region with organic-rich permafrost that contains ~25% of all permafrost carbon. We estimate that the Yedoma domain contains 41.2 gigatons of nitrogen down to ~20 metre for the deepest unit, which increases the previous estimate for the entire permafrost zone by ~46%. Approximately 90% of this nitrogen (37 gigatons) is stored in permafrost and therefore currently immobile and frozen. Here, we show that of this amount, ¾ is stored >3 metre depth, but if partially mobilised by thaw, this large nitrogen pool could have continental-scale consequences for soil and aquatic biogeochemistry and global-scale consequences for the permafrost feedback

Organic Matter Matters – Quantifying the Amount of Carbon in Northern Siberia

The Lena River Delta is underlain by permafrost. Thus, it is highly vulnerable to climate warming and may degrade in different ways, by shoreline erosion, land surface subsidence, deepening of the seasonal thawing front, and development of rapid thaw features such as lakes, gullies and landslides

Kohlenstoff in Permafrost – Quantifizierung der Menge an organischem Material in Sibirien

Permafrost in Sibirien taut, und das auf verschiedene Weise. Besonders gut sichtbar sind Küstenerosion und Bodenabsenkungen, oder wenn vorhandene Straßen, Häuser und andere Infrastruktur dadurch beschädigt wird. Doch auch eine Vertiefung der sommerlichen Auftauschicht und Entstehung von Seen, was zu schnellen Auftauprozessen (Thermokarst) führt, machen die Permafrostregion zu einer Region, in der der Klimawandel heute deutlich sichtbar wird

Spatial heterogeneity and environmental predictors of permafrost region soil organic carbon stocks

Large stocks of soil organic carbon (SOC) have accumulated in the Northern Hemisphere permafrost region, but their current amounts and future fate remain uncertain. By analyzing dataset combining >2700 soil profiles with environmental variables in a geospatial framework, we generated spatially explicit estimates of permafrost-region SOC stocks, quantified spatial heterogeneity, and identified key environmental predictors. We estimated that Pg C are stored in the top 3 m of permafrost region soils. The greatest uncertainties occurred in circumpolar toe-slope positions and in flat areas of the Tibetan region. We found that soil wetness index and elevation are the dominant topographic controllers and surface air temperature (circumpolar region) and precipitation (Tibetan region) are significant climatic controllers of SOC stocks. Our results provide first high-resolution geospatial assessment of permafrost region SOC stocks and their relationships with environmental factors, which are crucial for modeling the response of permafrost affected soils to changing climate