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Ogneva, O., Mollenhauer, G., Juhls, B., Sanders, T., Palmtag, J., Fuchs, M., . . . Strauss, J. (2023). Particulate organic matter in the Lena River and its delta: from thepermafrost catchment to the Arctic Ocean. Biogeosciences, 20(7), 1423-1441
Open this publication in new window or tab >>Particulate organic matter in the Lena River and its delta: from thepermafrost catchment to the Arctic Ocean
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2023 (English)In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 20, no 7, p. 1423-1441Article in journal (Refereed) Published
Abstract [en]

Rapid Arctic warming accelerates permafrost thaw, causing an additional release of terrestrial organic matter (OM) into rivers and, ultimately, after transport via deltas and estuaries, to the Arctic Ocean nearshore. The majority of our understanding of nearshore OM dynamics and fate has been developed from freshwater rivers despite the likely impact of highly dynamic estuarine and deltaic environments on the transformation, storage, and age of OM delivered to coastal waters. Here, we studied particulate organic carbon (POC) dynamics in the Lena River delta and compared them with POC dynamics in the Lena River main stem along a similar to 1600 km long transect from Yakutsk, downstream to the delta. We measured POC, total suspended matter (TSM), and carbon isotopes (delta C-13 and Delta C-14) in POC to compare riverine and deltaic OM composition and changes in OM source and fate during transport offshore. We found that TSM and POC concentrations decreased by 70% during transit from the main stem to the delta and Arctic Ocean. We found deltaic POC to be strongly depleted in C-13 relative to fluvial POC. Dual-carbon (Delta C-14 and delta C-13) isotope mixing model analyses indicated a significant phytoplankton contribution to deltaic POC (similar to 68 +/- 6 %) and suggested an additional input of permafrost-derived OM into deltaic waters (similar to 18 +/- 4% of deltaic POC originates from Pleistocene deposits vs. similar to 5 +/- 4% in the river main stem). Despite the lower concentration of POC in the delta than in the main stem (0.41 +/- 0.10 vs. 0.79 +/- 0.30 mg L-1, respectively), the amount of POC derived from Yedoma deposits in deltaic waters was almost twice as large as the amount of POC of Yedoma origin in the main stem (0.07 +/- 0.02 and 0.04 +/- 0.02 mg L-1, respectively). We assert that estuarine and deltaic processes require consideration in order to correctly understand OM dynamics throughout Arctic nearshore coastal zones and how these processes may evolve under future climate-driven change.

National Category
Other Earth Sciences Other Biological Topics
Identifiers
urn:nbn:se:su:diva-230018 (URN)10.5194/bg-20-1423-2023 (DOI)000969256900001 ()2-s2.0-85153956876 (Scopus ID)
Available from: 2024-06-03 Created: 2024-06-03 Last updated: 2025-02-01Bibliographically approved
Palmtag, J., Obu, J., Kuhry, P., Richter, A., Siewert, M. B., Weiss, N., . . . Hugelius, G. (2022). A high spatial resolution soil carbon and nitrogen dataset for the northern permafrost region based on circumpolar land cover upscaling. Earth System Science Data, 14(9), 4095-4110
Open this publication in new window or tab >>A high spatial resolution soil carbon and nitrogen dataset for the northern permafrost region based on circumpolar land cover upscaling
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2022 (English)In: Earth System Science Data, ISSN 1866-3508, E-ISSN 1866-3516, Vol. 14, no 9, p. 4095-4110Article in journal (Refereed) Published
Abstract [en]

Soils in the northern high latitudes are a key component in the global carbon cycle; the northern permafrost region covers 22 % of the Northern Hemisphere land surface area and holds almost twice as much carbon as the atmosphere. Permafrost soil organic matter stocks represent an enormous long-term carbon sink which is in risk of switching to a net source in the future. Detailed knowledge about the quantity and the mechanisms controlling organic carbon storage is of utmost importance for our understanding of potential impacts of and feedbacks on climate change. Here we present a geospatial dataset of physical and chemical soil properties calculated from 651 soil pedons encompassing more than 6500 samples from 16 different study areas across the northern permafrost region. The aim of our dataset is to provide a basis to describe spatial patterns in soil properties, including quantifying carbon and nitrogen stocks. There is a particular need for spatially distributed datasets of soil properties, including vertical and horizontal distribution patterns, for modeling at local, regional, or global scales. This paper presents this dataset, describes in detail soil sampling; laboratory analysis, and derived soil geochemical parameters; calculations; and data clustering. Moreover, we use this dataset to estimate soil organic carbon and total nitrogen storage estimates in soils in the northern circumpolar permafrost region (17.9×106 km2) using the European Space Agency's (ESA's) Climate Change Initiative (CCI) global land cover dataset at 300 m pixel resolution. We estimate organic carbon and total nitrogen stocks on a circumpolar scale (excluding Tibet) for the 0–100 and 0–300 cm soil depth to be 380 and 813 Pg for carbon, and 21 and 55 Pg for nitrogen, respectively. Our organic carbon estimates agree with previous studies, with most recent estimates of 1000 Pg (−170 to +186 Pg) to 300 cm depth. Two separate datasets are freely available on the Bolin Centre Database repository (https://doi.org/10.17043/palmtag-2022-pedon-1, Palmtag et al., 2022a; and https://doi.org/10.17043/palmtag-2022-spatial-1, Palmtag et al., 2002b).

National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-209434 (URN)10.5194/essd-14-4095-2022 (DOI)000850455700001 ()
Available from: 2022-09-19 Created: 2022-09-19 Last updated: 2025-02-07Bibliographically approved
Sanders, T., Fiencke, C., Fuchs, M., Haugk, C., Juhls, B., Mollenhauer, G., . . . Dahnke, K. (2022). Seasonal nitrogen fluxes of the Lena River Delta. Ambio, 51(2), 423-438
Open this publication in new window or tab >>Seasonal nitrogen fluxes of the Lena River Delta
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2022 (English)In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 51, no 2, p. 423-438Article in journal (Refereed) Published
Abstract [en]

The Arctic is nutrient limited, particularly by nitrogen, and is impacted by anthropogenic global warming which occurs approximately twice as fast compared to the global average. Arctic warming intensifies thawing of permafrost-affected soils releasing their large organic nitrogen reservoir. This organic nitrogen reaches hydrological systems, is remineralized to reactive inorganic nitrogen, and is transported to the Arctic Ocean via large rivers. We estimate the load of nitrogen supplied from terrestrial sources into the Arctic Ocean by sampling in the Lena River and its Delta. We took water samples along one of the major deltaic channels in winter and summer in 2019 and sampling station in the central delta over a one-year cycle. Additionally, we investigate the potential release of reactive nitrogen, including nitrous oxide from soils in the Delta. We found that the Lena transported nitrogen as dissolved organic nitrogen to the coastal Arctic Ocean and that eroded soils are sources of reactive inorganic nitrogen such as ammonium and nitrate. The Lena and the Deltaic region apparently are considerable sources of nitrogen to nearshore coastal zone. The potential higher availability of inorganic nitrogen might be a source to enhance nitrous oxide emissions from terrestrial and aquatic sources to the atmosphere.

Keywords
Arctic Ocean, Lena Delta, Nitrogen, Nitrous oxide
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-200534 (URN)10.1007/s13280-021-01665-0 (DOI)000730895100001 ()34914031 (PubMedID)
Available from: 2022-01-10 Created: 2022-01-10 Last updated: 2025-02-07Bibliographically approved
Beer, C., Knoblauch, C., Hoyt, A. M., Hugelius, G., Palmtag, J., Mueller, C. W. & Trumbore, S. (2022). Vertical pattern of organic matter decomposability in cryoturbated permafrost-affected soils. Environmental Research Letters, 17(10), Article ID 104023.
Open this publication in new window or tab >>Vertical pattern of organic matter decomposability in cryoturbated permafrost-affected soils
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2022 (English)In: Environmental Research Letters, E-ISSN 1748-9326, Vol. 17, no 10, article id 104023Article in journal (Refereed) Published
Abstract [en]

Permafrost thaw will release additional carbon dioxide into the atmosphere resulting in a positive feedback to climate change. However, the mineralization dynamics of organic matter (OM) stored in permafrost-affected soils remain unclear. We used physical soil fractionation, radiocarbon measurements, incubation experiments, and a dynamic decomposition model to identify distinct vertical pattern in OM decomposability. The observed differences reflect the type of OM input to the subsoil, either by cryoturbation or otherwise, e.g. by advective water-borne transport of dissolved OM. In non-cryoturbated subsoil horizons, most OM is stabilized at mineral surfaces or by occlusion in aggregates. In contrast, pockets of OM-rich cryoturbated soil contain sufficient free particulate OM for microbial decomposition. After thaw, OM turnover is as fast as in the upper active layer. Since cryoturbated soils store ca. 450 Pg carbon, identifying differences in decomposability according to such translocation processes has large implications for the future global carbon cycle and climate, and directs further process model development.

Keywords
Lena-Delta, transport, fractionation, carbon, residence time, radiocarbon
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-210667 (URN)10.1088/1748-9326/ac9198 (DOI)000861671500001 ()2-s2.0-85139594256 (Scopus ID)
Available from: 2022-11-23 Created: 2022-11-23 Last updated: 2025-02-07Bibliographically approved
Mishra, U., Hugelius, G., Shelef, E., Yang, Y., Strauss, J., Lupachev, A., . . . Orr, A. (2021). Spatial heterogeneity and environmental predictors of permafrost region soil organic carbon stocks. Science Advances, 7(9), Article ID eaaz5236.
Open this publication in new window or tab >>Spatial heterogeneity and environmental predictors of permafrost region soil organic carbon stocks
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2021 (English)In: Science Advances, E-ISSN 2375-2548, Vol. 7, no 9, article id eaaz5236Article in journal (Refereed) Published
Abstract [en]

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 1014+194−175 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.

National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-193291 (URN)10.1126/sciadv.aaz5236 (DOI)000622481300001 ()33627437 (PubMedID)
Available from: 2021-05-21 Created: 2021-05-21 Last updated: 2025-02-07Bibliographically approved
Wojcik, R., Palmtag, J., Hugelius, G., Weiss, N. & Kuhry, P. (2019). Land cover and landform-based upscaling of soil organic carbon stocks on the Brogger Peninsula, Svalbard. Arctic, Antarctic and Alpine research, 51(1), 40-57
Open this publication in new window or tab >>Land cover and landform-based upscaling of soil organic carbon stocks on the Brogger Peninsula, Svalbard
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2019 (English)In: Arctic, Antarctic and Alpine research, ISSN 1523-0430, E-ISSN 1938-4246, Vol. 51, no 1, p. 40-57Article in journal (Refereed) Published
Abstract [en]

In this study we assess the total storage, landscape distribution, and vertical partitioning of soil organic carbon (SOC) stocks on the Brogger Peninsula, Svalbard. This type of high Arctic area is underrepresented in SOC databases for the northern permafrost region. Physico-chemical, elemental, and radiocarbon (C-14) dating analyses were carried out on thirty-two soil profiles. Results were upscaled using both a land cover classification (LCC) and a landform classification (LFC). Both LCC and LFC approaches provide weighted mean SOC 0-100 cm estimates for the study area of 1.0 +/- 0.3 kg C m(-2) (95% confidence interval) and indicate that about 68 percent of the total SOC storage occurs in the upper 30 cm of the soil, and about 10 percent occurs in the surface organic layer. Furthermore, LCC and LFC upscaling approaches provide similar spatial SOC allocation estimates and emphasize the dominant role of vegetated area (4.2 +/- 1.6 kg C m(-2)) and solifluction slopes (6.7 +/- 3.6 kg C m(-2)) in SOC 0-100 cm storage. LCC and LFC approaches report different and complementary information on the dominant processes controlling the spatial and vertical distribution of SOC in the landscape. There is no evidence for any significant SOC storage in the permafrost layer. We hypothesize, therefore, that the Brogger Peninsula and similar areas of the high Arctic will become net carbon sinks, providing negative feedback on global warming in the future. The surface area that will have vegetation cover and incipient soil development will expand, whereas only small amounts of organic matter will experience increased decomposition due to active-layer deepening.

Keywords
Permafrost-carbon feedback, Soil organic carbon, Land cover upscaling, Landform upscaling, High Arctic
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-174991 (URN)10.1080/15230430.2019.1570784 (DOI)000486105800004 ()
Available from: 2019-10-16 Created: 2019-10-16 Last updated: 2025-02-07Bibliographically approved
Capek, P. T., Manzoni, S., Kastovska, E., Wild, B., Diakova, K., Barta, J., . . . Santruckova, H. (2018). A plant-microbe interaction framework explaining nutrient effects on primary production. Nature Ecology & Evolution, 2(10), 1588-1596
Open this publication in new window or tab >>A plant-microbe interaction framework explaining nutrient effects on primary production
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2018 (English)In: Nature Ecology & Evolution, E-ISSN 2397-334X, Vol. 2, no 10, p. 1588-1596Article in journal (Refereed) Published
Abstract [en]

In most terrestrial ecosystems, plant growth is limited by nitrogen and phosphorus. Adding either nutrient to soil usually affects primary production, but their effects can be positive or negative. Here we provide a general stoichiometric framework for interpreting these contrasting effects. First, we identify nitrogen and phosphorus limitations on plants and soil microorganisms using their respective nitrogen to phosphorus critical ratios. Second, we use these ratios to show how soil microorganisms mediate the response of primary production to limiting and non-limiting nutrient addition along a wide gradient of soil nutrient availability. Using a meta-analysis of 51 factorial nitrogen-phosphorus fertilization experiments conducted across multiple ecosystems, we demonstrate that the response of primary production to nitrogen and phosphorus additions is accurately predicted by our stoichiometric framework. The only pattern that could not be predicted by our original framework suggests that nitrogen has not only a structural function in growing organisms, but also a key role in promoting plant and microbial nutrient acquisition. We conclude that this stoichiometric framework offers the most parsimonious way to interpret contrasting and, until now, unresolved responses of primary production to nutrient addition in terrestrial ecosystems.

Keywords
n-p stoichiometry carbon-use efficiency sub-arctic tundra phosphorus limitation terrestrial ecosystems nitrogen mineralization co-limitation resource limitation vascular plants global analysis
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-161773 (URN)10.1038/s41559-018-0662-8 (DOI)000447947600015 ()
Available from: 2018-11-07 Created: 2018-11-07 Last updated: 2025-02-07Bibliographically approved
Wild, B., Alves, R. J. E., Bárta, J., Čapek, P., Gentsch, N., Guggenberger, G., . . . Richter, A. (2018). Amino acid production exceeds plant nitrogen demand in Siberian tundra. Environmental Research Letters, 13(3), Article ID 034002.
Open this publication in new window or tab >>Amino acid production exceeds plant nitrogen demand in Siberian tundra
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2018 (English)In: Environmental Research Letters, E-ISSN 1748-9326, Vol. 13, no 3, article id 034002Article in journal (Refereed) Published
Abstract [en]

Arctic plant productivity is often limited by low soil N availability. This has been attributed to slow breakdown of N-containing polymers in litter and soil organic matter (SOM) into smaller, available units, and to shallow plant rooting constrained by permafrost and high soil moisture. Using N-15 pool dilution assays, we here quantified gross amino acid and ammonium production rates in 97 active layer samples from four sites across the Siberian Arctic. We found that amino acid production in organic layers alone exceeded literature-based estimates of maximum plant N uptake 17-fold and therefore reject the hypothesis that arctic plant N limitation results from slow SOM breakdown. High microbial N use efficiency in organic layers rather suggests strong competition of microorganisms and plants in the dominant rooting zone. Deeper horizons showed lower amino acid production rates per volume, but also lower microbial N use efficiency. Permafrost thaw together with soil drainage might facilitate deeper plant rooting and uptake of previously inaccessible subsoil N, and thereby promote plant productivity in arctic ecosystems. We conclude that changes in microbial decomposer activity, microbial N utilization and plant root density with soil depth interactively control N availability for plants in the Arctic.

Keywords
permafrost, tundra, protein depolymerization, nitrogen mineralization, nitrogen limitation, plant productivity
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-154836 (URN)10.1088/1748-9326/aaa4fa (DOI)000425435300002 ()
Available from: 2018-04-10 Created: 2018-04-10 Last updated: 2025-02-07Bibliographically approved
Palmtag, J. & Kuhry, P. (2018). Grain size controls on cryoturbation and soil organic carbon density in permafrost-affected soils. Permafrost and Periglacial Processes, 29(2), 112-120
Open this publication in new window or tab >>Grain size controls on cryoturbation and soil organic carbon density in permafrost-affected soils
2018 (English)In: Permafrost and Periglacial Processes, ISSN 1045-6740, E-ISSN 1099-1530, Vol. 29, no 2, p. 112-120Article in journal (Refereed) Published
Abstract [en]

This meta-analysis aims to describe the relationship between grain size distributions and soil organic carbon (SOC) storage in mineral subsoil and SOC-enriched cryoturbated pockets in five areas of continuous permafrost that differ in glaciation history and soil parent materials. Our results show a positive relationship between the proportion of soil particles in fine-grained fractions (colloid to medium silt) and SOC storage. Finer textured soils had significantly higher SOC storage in mineral subsoil samples (not SOC-enriched through cryoturbation) than coarser textured soils. However, the process of SOC enrichment through cryoturbation was most pronounced in soils with coarser grain sizes in the range of coarse silt and very fine sand. Although fine-grained textures provide better physical and biochemical protection for soil organic matter, their strong cohesion reduces the mixing of soil horizons and the effectiveness of cryoturbation. A higher ratio of coarse silt to clay in samples was a good predictor of SOC enrichment through cryoturbation across soil samples, soil profiles and study areas.

Keywords
cryoturbation, grain size distributions, permafrost soils, SOC storage, soil parent materials, soil texture
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-156677 (URN)10.1002/ppp.1975 (DOI)000430304700004 ()
Available from: 2018-05-31 Created: 2018-05-31 Last updated: 2025-02-07Bibliographically approved
Palmtag, J., Cable, S., Christiansen, H. H., Hugelius, G. & Kuhry, P. (2018). Landform partitioning and estimates of deep storage of soil organic matter in Zackenberg, Greenland. The Cryosphere, 12(5), 1735-1744
Open this publication in new window or tab >>Landform partitioning and estimates of deep storage of soil organic matter in Zackenberg, Greenland
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2018 (English)In: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 12, no 5, p. 1735-1744Article in journal (Refereed) Published
Abstract [en]

Soils in the northern high latitudes are a key component in the global carbon cycle, with potential feedback on climate. This study aims to improve the previous soil organic carbon (SOC) and total nitrogen (TN) storage estimates for the Zackenberg area (NE Greenland) that were based on a land cover classification (LCC) approach, by using geomorphological upscaling. In addition, novel organic carbon (OC) estimates for deeper alluvial and deltaic deposits (down to 300 cm depth) are presented. We hypothesise that land-forms will better represent the long-term slope and depositional processes that result in deep SOC burial in this type of mountain permafrost environments. The updated mean SOC storage for the 0-100 cm soil depth is 4.8 kg Cm-2, which is 42% lower than the previous estimate of 8.3 kg Cm-2 based on land cover upscaling. Similarly, the mean soil TN storage in the 0-100 cm depth decreased with 44% from 0.50 kg (+/- 0.1 CI) to 0.28 (+/- 0.1 CI) kg TN m(-2). We ascribe the differences to a previous areal overestimate of SOC- and TN-rich vegetated land cover classes. The landform-based approach more correctly constrains the depositional areas in alluvial fans and deltas with high SOC and TN storage. These are also areas of deep carbon storage with an additional 2.4 kg Cm-2 in the 100-300 cm depth interval. This research emphasises the need to consider geomorphology when assessing SOC pools in mountain permafrost landscapes.

National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-157729 (URN)10.5194/tc-12-1735-2018 (DOI)000433005400001 ()
Available from: 2018-08-02 Created: 2018-08-02 Last updated: 2025-02-07Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-6921-5697

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