Change search
Refine search result
1 - 19 of 19
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1. Bartsch, Annett
    et al.
    Widhalm, Barbara
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Palmtag, Juri
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Siewert, Matthias Benjamin
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Can C-band synthetic aperture radar be used to estimate soil organic carbon storage in tundra?2016In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 13, no 19, p. 5453-5470Article in journal (Refereed)
    Abstract [en]

    A new approach for the estimation of soil organic carbon (SOC) pools north of the tree line has been developed based on synthetic aperture radar (SAR; ENVISAT Advanced SAR Global Monitoring mode) data. SOC values are directly determined from backscatter values instead of upscaling using land cover or soil classes. The multi-mode capability of SAR allows application across scales. It can be shown that measurements in C band under frozen conditions represent vegetation and surface structure properties which relate to soil properties, specifically SOC. It is estimated that at least 29 Pg C is stored in the upper 30 cm of soils north of the tree line. This is approximately 25% less than stocks derived from the soil-map-based Northern Circumpolar Soil Carbon Database (NCSCD). The total stored carbon is underestimated since the established empirical relationship is not valid for peatlands or strongly cryoturbated soils. The approach does, however, provide the first spatially consistent account of soil organic carbon across the Arctic. Furthermore, it could be shown that values obtained from 1 km resolution SAR correspond to accounts based on a high spatial resolution (2 m) land cover map over a study area of about 7 x 7 km in NE Siberia. The approach can be also potentially transferred to medium-resolution C-band SAR data such as ENVISAT ASAR Wide Swath with similar to 120m resolution but it is in general limited to regions without woody vegetation. Global Monitoring-mode-derived SOC increases with unfrozen period length. This indicates the importance of this parameter for modelling of the spatial distribution of soil organic carbon storage.

  • 2. Capek, P. T.
    et al.
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kastovska, E.
    Wild, B.
    Diakova, K.
    Barta, J.
    Schnecker, J.
    Blasi, C.
    Martikainen, P. J.
    Alves, R. J. E.
    Guggenberger, G.
    Gentsch, N.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Palmtag, Juri
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Mikutta, R.
    Shibistova, O.
    Urich, T.
    Schleper, C.
    Richter, A.
    Santruckova, H.
    A plant-microbe interaction framework explaining nutrient effects on primary production2018In: Nature Ecology & Evolution, E-ISSN 2397-334X, Vol. 2, no 10, p. 1588-1596Article in journal (Refereed)
    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.

  • 3. Capek, Petr
    et al.
    Diakova, Katerina
    Dickopp, Jan-Erik
    Barta, Jiri
    Wild, Birgit
    Schnecker, Jörg
    Alves, Ricardo Jorge Eloy
    Aiglsdorfer, Stefanie
    Guggenberger, Georg
    Gentsch, Norman
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Lashchinsky, Nikolaj
    Gittel, Antje
    Schleper, Christa
    Mikutta, Robert
    Palmtag, Juri
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Shibistova, Olga
    Urich, Tim
    Richter, Andreas
    Santruckova, Hana
    The effect of warming on the vulnerability of subducted organic carbon in arctic soils2015In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 90, p. 19-29Article in journal (Refereed)
    Abstract [en]

    Arctic permafrost soils contain large stocks of organic carbon (OC). Extensive cryogenic processes in these soils cause subduction of a significant part of OC-rich topsoil down into mineral soil through the process of cryoturbation. Currently, one-fourth of total permafrost OC is stored in subducted organic horizons. Predicted climate change is believed to reduce the amount of OC in permafrost soils as rising temperatures will increase decomposition of OC by soil microorganisms. To estimate the sensitivity of OC decomposition to soil temperature and oxygen levels we performed a 4-month incubation experiment in which we manipulated temperature (4-20 degrees C) and oxygen level of topsoil organic, subducted organic and mineral soil horizons. Carbon loss (C-LOSS) was monitored and its potential biotic and abiotic drivers, including concentrations of available nutrients, microbial activity, biomass and stoichiometry, and extracellular oxidative and hydrolytic enzyme pools, were measured. We found that independently of the incubation temperature, C-LOSS from subducted organic and mineral soil horizons was one to two orders of magnitude lower than in the organic topsoil horizon, both under aerobic and anaerobic conditions. This corresponds to the microbial biomass being lower by one to two orders of magnitude. We argue that enzymatic degradation of autochthonous subducted OC does not provide sufficient amounts of carbon and nutrients to sustain greater microbial biomass. The resident microbial biomass relies on allochthonous fluxes of nutrients, enzymes and carbon from the OC-rich topsoil. This results in a negative priming effect, which protects autochthonous subducted OC from decomposition at present. The vulnerability of subducted organic carbon in cryoturbated arctic soils under future climate conditions will largely depend on the amount of allochthonous carbon and nutrient fluxes from the topsoil.

  • 4. Gentsch, N.
    et al.
    Mikutta, R.
    Alves, R. J. E.
    Barta, J.
    Capek, P.
    Gittel, A.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Lashchinskiy, N.
    Palmtag, Juri
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Richter, A.
    Santruckova, H.
    Schnecker, J.
    Shibistova, O.
    Urich, T.
    Wild, B.
    Guggenberger, G.
    Storage and transformation of organic matter fractions in cryoturbated permafrost soils across the Siberian Arctic2015In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 12, no 14, p. 4525-4542Article in journal (Refereed)
    Abstract [en]

    In permafrost soils, the temperature regime and the resulting cryogenic processes are important determinants of the storage of organic carbon (OC) and its small-scale spatial variability. For cryoturbated soils, there is a lack of research assessing pedon-scale heterogeneity in OC stocks and the transformation of functionally different organic matter (OM) fractions, such as particulate and mineral-associated OM. Therefore, pedons of 28 Turbels were sampled in 5m wide soil trenches across the Siberian Arctic to calculate OC and total nitrogen (TN) stocks based on digital profile mapping. Density fractionation of soil samples was performed to distinguish between particulate OM (light fraction, LF, < 1.6 g cm(-3)), mineral associated OM (heavy fraction, HF, > 1.6 g cm(-3)), and a mobilizable dissolved pool (mobilizable fraction, MoF). Across all investigated soil profiles, the total OC storage was 20.2 +/- 8.0 kgm(-2) (mean +/- SD) to 100 cm soil depth. Fifty-four percent of this OC was located in the horizons of the active layer (annual summer thawing layer), showing evidence of cryoturbation, and another 35% was present in the upper permafrost. The HF-OC dominated the overall OC stocks (55 %), followed by LF-OC (19% in mineral and 13% in organic horizons). During fractionation, approximately 13% of the OC was released as MoF, which likely represents a readily bioavailable OM pool. Cryogenic activity in combination with cold and wet conditions was the principle mechanism through which large OC stocks were sequestered in the subsoil (16.4 +/- 8.1 kgm(-2); all mineral B, C, and permafrost horizons). Approximately 22% of the subsoil OC stock can be attributed to LF material subducted by cryoturbation, whereas migration of soluble OM along freezing gradients appeared to be the principle source of the dominant HF (63 %) in the subsoil. Despite the unfavourable abiotic conditions, low C/N ratios and high delta C-13 values indicated substantial microbial OM transformation in the subsoil, but this was not reflected in altered LF and HF pool sizes. Partial least-squares regression analyses suggest that OC accumulates in the HF fraction due to co-precipitation with multivalent cations (Al, Fe) and association with poorly crystalline iron oxides and clay minerals. Our data show that, across all permafrost pedons, the mineral-associated OM represents the dominant OM fraction, suggesting that the HF-OC is the OM pool in permafrost soils on which changing soil conditions will have the largest impact.

  • 5.
    Hugelius, Gustaf
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Strauss, J.
    Zubrzycki, S.
    Harden, J. W.
    Schuur, E. A. G.
    Ping, C. -L
    Schirrmeister, L.
    Grosse, G.
    Michaelson, G. J.
    Koven, C. D.
    O'Donnell, J. A.
    Elberling, B.
    Mishra, U.
    Camill, P.
    Yu, Z.
    Palmtag, Juri
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Estimated stocks of circumpolar permafrost carbon with quantified uncertainty ranges and identified data gaps2014In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 11, no 23, p. 6573-6593Article in journal (Refereed)
    Abstract [en]

    Soils and other unconsolidated deposits in the northern circumpolar permafrost region store large amounts of soil organic carbon (SOC). This SOC is potentially vulnerable to remobilization following soil warming and permafrost thaw, but SOC stock estimates were poorly constrained and quantitative error estimates were lacking. This study presents revised estimates of permafrost SOC stocks, including quantitative uncertainty estimates, in the 0-3m depth range in soils as well as for sediments deeper than 3m in deltaic deposits of major rivers and in the Yedoma region of Siberia and Alaska. Revised estimates are based on significantly larger databases compared to previous studies. Despite this there is evidence of significant remaining regional data gaps. Estimates remain particularly poorly constrained for soils in the High Arctic region and physiographic regions with thin sedimentary overburden (mountains, highlands and plateaus) as well as for deposits below 3mdepth in deltas and the Yedoma region. While some components of the revised SOC stocks are similar in magnitude to those previously reported for this region, there are substantial differences in other components, including the fraction of perennially frozen SOC. Upscaled based on regional soil maps, estimated permafrost region SOC stocks are 217 +/- 12 and 472 +/- 27 Pg for the 0-0.3 and 0-1 m soil depths, respectively (+/- 95% confidence intervals). Storage of SOC in 0-3m of soils is estimated to 1035 +/- 150 Pg. Of this, 34 +/- 16 PgC is stored in poorly developed soils of the High Arctic. Based on generalized calculations, storage of SOC below 3m of surface soils in deltaic alluvium of major Arctic rivers is estimated as 91 +/- 52 Pg. In the Yedoma region, estimated SOC stocks below 3mdepth are 181 +/- 54 Pg, of which 74 +/- 20 Pg is stored in intact Yedoma (late Pleistocene ice-and organic-rich silty sediments) with the remainder in refrozen thermokarst deposits. Total estimated SOC storage for the permafrost region is similar to 1300 Pg with an uncertainty range of similar to 1100 to 1500 Pg. Of this, similar to 500 Pg is in non-permafrost soils, seasonally thawed in the active layer or in deeper taliks, while similar to 800 Pg is perennially frozen. This represents a substantial similar to 300 Pg lowering of the estimated perennially frozen SOC stock compared to previous estimates.

  • 6. Muster, Sina
    et al.
    Roth, Kurt
    Langer, Moritz
    Lange, Stephan
    Aleina, Fabio Cresto
    Bartsch, Annett
    Morgenstern, Anne
    Grosse, Guido
    Jones, Benjamin
    Sannel, A. Britta K.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Sjöberg, Ylva
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Günther, Frank
    Andresen, Christian
    Veremeeva, Alexandra
    Lindgren, Prajna R.
    Bouchard, Frédéric
    Lara, Mark J.
    Fortier, Daniel
    Charbonneau, Simon
    Virtanen, Tarmo A.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Palmtag, Juri
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Siewert, Matthias B.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Riley, William J.
    Koven, Charles D.
    Boike, Julia
    PeRL: a circum-Arctic Permafrost Region Pond and Lake database2017In: Earth System Science Data, ISSN 1866-3508, E-ISSN 1866-3516, Vol. 9, no 1, p. 317-348Article in journal (Refereed)
    Abstract [en]

    Ponds and lakes are abundant in Arctic permafrost lowlands. They play an important role in Arctic wetland ecosystems by regulating carbon, water, and energy fluxes and providing freshwater habitats. However, ponds, i. e., waterbodies with surface areas smaller than 1.0 x 10(4) m(2), have not been inventoried on global and regional scales. The Permafrost Region Pond and Lake (PeRL) database presents the results of a circum-Arctic effort to map ponds and lakes from modern (2002-2013) high-resolution aerial and satellite imagery with a resolution of 5m or better. The database also includes historical imagery from 1948 to 1965 with a resolution of 6m or better. PeRL includes 69 maps covering a wide range of environmental conditions from tundra to boreal regions and from continuous to discontinuous permafrost zones. Waterbody maps are linked to regional permafrost landscape maps which provide information on permafrost extent, ground ice volume, geology, and lithology. This paper describes waterbody classification and accuracy, and presents statistics of waterbody distribution for each site. Maps of permafrost landscapes in Alaska, Canada, and Russia are used to extrapolate waterbody statistics from the site level to regional landscape units. PeRL presents pond and lake estimates for a total area of 1.4 x 10(6) km(2) across the Arctic, about 17% of the Arctic lowland (<300ma. s.l.) land surface area. PeRL waterbodies with sizes of 1.0 x 10(6) m(2) down to 1.0 x 10(2) m(2) contributed up to 21% to the total water fraction. Waterbody density ranged from 1.0 x 10 to 9.4 x 10(1) km(-2). Ponds are the dominant waterbody type by number in all landscapes representing 45-99% of the total waterbody number. The implementation of PeRL size distributions in land surface models will greatly improve the investigation and projection of surface inundation and carbon fluxes in permafrost lowlands. Waterbody maps, study area boundaries, and maps of regional permafrost landscapes including detailed metadata are available at https://doi.pangaea.de/10.1594/PANGAEA.868349.

  • 7.
    Palmtag, Juri
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Grain size controls on cryoturbation and soil organic carbon density in permafrost-affected soilsManuscript (preprint) (Other academic)
    Abstract [en]

    This meta-analysis aims to describe the relationship between grain size distributions and soil organic carbon (SOC) storage in mineral subsoil and carbon (C)-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 fine-grained (colloid to medium silt) fractions and SOC storage. Finer textured soils had a significantly higher SOC storage in mineral subsoil samples (not C-enriched through cryoturbation) than coarser textured soils. However, the process of C-enrichment through cryoturbation was most pronounced in soils with coarser grain sizes in the range of coarse silt and very fine sand. Even though fine-grained textures provide a 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 % coarse silt to % clay ratio in samples was a good predictor of C-enrichment through cryoturbation across soil samples, soil profiles and study areas.

  • 8.
    Palmtag, Juri
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Improved landscape partitioning and estimates of deep storage of soil organic carbon in the Zackenberg area (NE Greenland) using geomorphological landformsManuscript (preprint) (Other academic)
    Abstract [en]

    This study aims to improve the previous soil organic carbon (SOC) 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 SOC estimates for deeper deposits (to 300 cm depth) are presented. We hypothesize that landforms 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 C m−2, which is 42% lower than the previous estimate of 8.3 kg C m−2 based on land cover upscaling. We ascribe the difference to a previous areal overestimate of SOC-rich vegetated land cover classes. The landform-based approach more correctly constrains the depositional areas in alluvial fans and deltas with high SOC storage. These are also areas of deep carbon storage with an additional 2.4 kg C m−2 in the 100–300 cm depth interval. This research emphasizes the need to consider geomorphology when assessing SOC pools in mountain permafrost landscapes.

  • 9.
    Palmtag, Juri
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Landscape partitioning and burial processes of soil organic carbon in contrasting areas of continuous permafrost2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Recent studies have shown that permafrost soils in the northern circumpolar region store almost twice as much carbon as the atmosphere. Since soil organic carbon (SOC) pools have large regional and landscape-level variability, detailed SOC inventories from across the northern permafrost region are needed to assess potential remobilization of SOC with permafrost degradation and to quantify the permafrost carbon-climate feedback on global warming.

    This thesis provides high-resolution data on SOC storage in five study areas located in undersampled regions of the continuous permafrost zone (Zackenberg in NE Greenland; Shalaurovo and Cherskiy in NE Siberia; Ary-Mas and Logata in Taymyr Peninsula). The emphasis throughout the five different study areas is put on SOC partitioning within the landscape and soil horizon levels as well as on soil forming processes under periglacial conditions. Our results indicate large differences in mean SOC 0–100 cm storage among study areas, ranging from 4.8 to 30.0 kg C m-2, highlighting the need to consider numerous factors as topography, geomorphology, land cover, soil texture, soil moisture, etc. in the assessment of landscape-level and regional SOC stock estimates.

    In the high arctic mountainous area of Zackenberg, the mean SOC storage is low due to the high proportion of bare grounds. The geomorphology based upscaling resulted in a c. 40% lower estimate compared to a land cover based upscaling (4.8 vs 8.3 kg C m-2, respectively). A landform approach provides a better tool for identifying hotspots of SOC burial in the landscape, which in this area corresponds to alluvial fan deposits in the foothills of the mountains. SOC burial by cryoturbation was much more limited and largely restricted to soils in the lower central valley. In the lowland permafrost study areas of Russia the mean SOC 0–100 cm storage ranged from 14.8 to 30.0 kg C m-2. Cryoturbation is the main burial process of SOC, storing on average c. 30% of the total landscape SOC 0–100 cm in deeper C-enriched pockets in all study areas. In Taymyr Peninsula, the mean SOC storage between the Ary-Mas and Logata study areas differed by c. 40% (14.8 vs 20.8 kg C m-2, respectively). We ascribe this mainly to the finer soil texture in the latter study area. Grain size analyses show that cryoturbation is most prominent in silt loam soils with high coarse silt to very fine sand fractions. However, in profiles and samples not affected by C-enrichment, C concentrations and densities were higher in silt loam soils with higher clay to medium silt fractions.

  • 10.
    Palmtag, Juri
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Storage, landscape partitioning and lability of soil organic matter in permafrost terrain2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Recent estimates indicate that soils in the northern circumpolar permafrost region store substantial amounts of soil organic carbon (SOC). This reservoir has accumulated over 10-100.000 years and is often preserved in a relatively undecomposed state because frozen and often water-logged conditions prevented microbial degradation. Under a projected future climate change caused by rising greenhouse gases, permafrost thaw and rapid decomposition of vulnerable soil organic matter (SOM) could provide a positive feedback on global warming by releasing large amounts of carbon dioxide and/or methane into the atmosphere.

    SOC pools have large regional and landscape-level variability depending on topographic, ecoclimatic and edaphic factors. As a consequence, large scale maps and even regional data sets describing SOC storage should be taken with caution since they are highly simplified. The purpose of this thesis is to improve our knowledge on quantity and quality of SOM in different areas of continuous permafrost and provide regional high quality data from hitherto under-sampled regions for future assessment of the potential remobilization of SOC under global warming. A special focus is put on SOC partitioning within the landscape and soil horizon levels as well as on soil forming processes under periglacial conditions. Throughout the five different study areas presented in this thesis the landscape mean SOC storage ranges between 8 and 30 kg C m-2, while site differences are in the order of 0 to 80 kg C m-2. Paper I presents new SOC data from contrasting areas in continuous permafrost: a mountainous High Arctic site in Zackenberg (NE Greenland) and lowland sites in Shalaurovo and Cherskiy lower Kolyma (NE Siberia). The main difference is that about 60% of the Zackenberg area is higher elevation terrain with mostly barren ground and very low SOC content, resulting in a much lower landscape-level mean SOC storage compared to the Siberian sites. In addition, Paper II shows that even when comparing two lowland sites located only 150 km apart in Taymyr Peninsula (N Siberia) the mean SOC storage differs with 40% between the areas. This emphasizes that even in lowlands on a regional scale not only different landforms and land cover but also microrelief, soil moisture and especially parent material play a very important role for obtaining more accurate SOC storage estimates.

    Throughout this thesis a special emphasis is put on understanding the role of cryoturbation for SOC storage. Signs of cryoturbation were observed at all sites and 14C dates show that this process is occurring since at least the early Holocene. On average, 30% of all SOC in the top meter of soil is located in buried C-enriched pockets. The only exception is Zackenberg, with only 12%, where slope processes were the dominant mechanism for burying C-enriched material into deeper layers.

    We use the weight ratio of Carbon/Nitrogen (C/N) to gain information about SOM decomposability. Generally, all sites show the same trend that the C/N ratio decreases with soil depth. Top organic soil and peat samples have always the highest C/N ratios, suggesting little decomposed SOM. Except for the Zackenberg site, the buried C-enriched pockets have significantly higher C/N ratios than the adjacent mineral subsoil samples. We assume that this C-enriched material was exposed over longer time periods to aerobic decomposition and was therefore relatively well decomposed before it was buried by reactivated slope processes.

  • 11.
    Palmtag, Juri
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Cable, Stefanie
    Christiansen, Hanne H.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Landform partitioning and estimates of deep storage of soil organic matter in Zackenberg, Greenland2018In: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 12, no 5, p. 1735-1744Article in journal (Refereed)
    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.

  • 12.
    Palmtag, Juri
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Soil organic carbon storage in continuous permafrost terrain; two case studies from NE Greenlandand NE Siberia2011Conference paper (Other academic)
    Abstract [en]

    The northern circumpolar permafrost region occupies about 16% of the global soil areaand holds approximately 50% of the global belowground soil organic carbon (SOC). We describe thequantity and quality of soil organic matter (SOM) in two areas of continuous permafrost in NE Greenland andNE Siberia. The main emphasis lies on the role of cryoturbation and Pleistocene loess-like deposits(yedoma) for SOC storage. This study is based on field work in three different study sites: Zackenberg(Greenland) and Shalaurovo and Chersky (Siberia), as well as laboratory analysis and radiocarbon dating.The estimated mean SOC storage in the upper meter of soil for Zackenberg is 10.5 kg C m-2 with 16% incryoturbated soil pockets. In Shalaurovo, the mean SOC storage is 29.0 kg C m-2 and in Chersky 21.7 kg Cm-2 with more than 30% stored in cryoturbated soil pockets. The study also presents new analyses for deepyedoma deposits(down to 5 m depth). Data from these sites show that the dry bulk densities are muchlower (due to excess ground ice) than those previously reported in the literature, leading to lower estimatesof SOC storage in these deposits.

  • 13.
    Palmtag, Juri
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Lashchinskiy, Nikolay
    Tamstorf, Mikkel P.
    Richter, Andreas
    Elberling, Bo
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Storage, Landscape Distribution, and Burial History of Soil Organic Matter in Contrasting Areas of Continuous Permafrost2015In: Arctic, Antarctic and Alpine research, ISSN 1523-0430, E-ISSN 1938-4246, Vol. 47, no 1, p. 71-88Article in journal (Refereed)
    Abstract [en]

    This study describes and compares soil organic matter (SOM) quantity and characteristics in two areas of continuous permafrost, a mountainous region in NE Greenland (Zackenberg study site) and a lowland region in NE Siberia (Cherskiy and Shalaurovo study sites). Our assessments are based on stratified-random landscape-level inventories of soil profiles down to 1 m depth, with physico-chemical, elemental, and radiocarbon-dating analyses. The estimated mean soil organic carbon (SOC) storage in the upper meter of soils in the NE Greenland site is 8.3 ± 1.8 kg C m-2 compared to 20.3 ± 2.2 kg C m-2 and 30.0 ± 2.0 kg C m-2 in the NE Siberian sites (95% confidence intervals). The lower SOC storage in the High Arctic site in NE Greenland can be largely explained by the fact that 59% of the study area is located at higher elevation with mostly barren ground and thus very low SOC contents. In addition, SOC-rich fens and bogs occupy a much smaller proportion of the landscape in NE Greenland (∼3%) than in NE Siberia (∼20%). The contribution of deeper buried C-enriched material in the mineral soil horizons to the total SOC storage is lower in the NE Greenland site (∼13%) compared to the NE Siberian sites (∼24%–30%). Buried SOM seems generally more decomposed in NE Greenland than in NE Siberia, which we relate to different burial mechanisms prevailing in these regions.

  • 14.
    Palmtag, Juri
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Grain size controls on cryoturbation and soil organic carbon density in permafrost-affected soils2018In: Permafrost and Periglacial Processes, ISSN 1045-6740, E-ISSN 1099-1530, Vol. 29, no 2, p. 112-120Article in journal (Refereed)
    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.

  • 15.
    Palmtag, Juri
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Ramage, Justine
    Stockholm University, Faculty of Science, Department of Physical Geography. Helmholtz Centre for Polar and Marine Research, Germany.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Gentsch, Norman
    Lashchinskiy, Nikolay
    Richter, Andreas
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Controls on the storage of organic carbon in permafrost soil in northern Siberia2016In: European Journal of Soil Science, ISSN 1351-0754, E-ISSN 1365-2389, Vol. 67, no 4, p. 478-491Article in journal (Refereed)
    Abstract [en]

    This research examined soil organic carbon (SOC), total nitrogen (TN) and aboveground phytomass carbon(PhC) stocks in two areas of the Taymyr Peninsula, northern Siberia.We combined field sampling, chemical and14C radiocarbon dating analyses with land cover classifications for landscape-level assessments. The estimatedmean for the 0–100-cm depth SOC stocks was 14.8 and 20.8 kgCm−2 in Ary-Mas and Logata, respectively. Thecorresponding values for TN were 1.0 and 1.3 kgNm−2. On average, about 2% only (range 0–12%) of the totalecosystem C is stored in PhC. In both study areas about 34% of the SOC at 0–100 cm is stored in cryoturbatedpockets, which have formed since at least the early Holocene. The larger carbon/nitrogen (C/N) ratio of thiscryoturbated material indicates that it consists of relatively undecomposed soil organic matter (SOM). Thereare substantial differences in SOC stocks and SOM properties within and between the two study areas, whichemphasizes the need to consider both geomorphology and soil texture in the assessment of landscape-level andregional SOC stocks.

    Highlights

    • This research addresses landscape-scale and regional variation in SOC stocks.

    • Landform and soil texture are taken into account in the analysis.

    • The contribution of phytomass to total ecosystem C stored is limited.

    • Large SOC stocks are susceptible to decomposition following permafrost thaw.

  • 16. Santruckova, Hana
    et al.
    Kotas, Petr
    Barta, Jiri
    Urich, Tim
    Capek, Petr
    Palmtag, Juri
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Alves, Ricardo J. Eloy
    Biasi, Christina
    Diakova, Katerina
    Gentsch, Norman
    Gittel, Antje
    Guggenberger, Georg
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Lashchinsky, Nikolaj
    Martikainen, Pertti J.
    Mikutta, Robert
    Schleper, Christa
    Schnecker, Jörg
    Schwab, Clarissa
    Shibistova, Olga
    Wild, Birgit
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. University of Vienna, Austria.
    Richter, Andreas
    Significance of dark CO2 fixation in arctic soils2018In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 119, p. 11-21Article in journal (Refereed)
    Abstract [en]

    The occurrence of dark fixation of CO2 by heterotrophic microorganisms in soil is generally accepted, but its importance for microbial metabolism and soil organic carbon (C) sequestration is unknown, especially under C limiting conditions. To fill this knowledge gap, we measured dark (CO2)-C-13 incorporation into soil organic matter and conducted a C-13-labelling experiment to follow the C-13 incorporation into phospholipid fatty acids as microbial biomass markers across soil profiles of four tundra ecosystems in the northern circumpolar region, where net primary productivity and thus soil C inputs are low. We further determined the abundance of various carboxylase genes and identified their microbial origin with metagenomics. The microbial capacity for heterotrophic CO2 fixation was determined by measuring the abundance of carboxylase genes and the incorporation of C-13 into soil C following the augmentation of bioavailable C sources. We demonstrate that dark CO2 fixation occurred ubiquitously in arctic tundra soils, with increasing importance in deeper soil horizons, presumably due to increasing C limitation with soil depth. Dark CO2 fixation accounted on average for 0.4, 1.0, 1.1, and 16% of net respiration in the organic, cryoturbated organic, mineral and permafrost horizons, respectively. Genes encoding anaplerotic enzymes of heterotrophic microorganisms comprised the majority of identified carboxylase genes. The genetic potential for dark CO2 fixation was spread over a broad taxonomic range. The results suggest important regulatory function of CO2 fixation in C limited conditions. The measurements were corroborated by modeling the long-term impact of dark CO2 fixation on soil organic matter. Our results suggest that increasing relative CO2 fixation rates in deeper soil horizons play an important role for soil internal C cycling and can, at least in part, explain the isotopic enrichment with soil depth.

  • 17.
    Wild, Birgit
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. University of Vienna, Austria; Austrian Polar Research Institute, Austria; University of Gothenburg, Sweden; .
    Alves, Ricardo J. Eloy
    Bárta, Jiři
    Čapek, Petr
    Gentsch, Norman
    Guggenberger, Georg
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography. Stanford University, United States of America.
    Knoltsch, Anna
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Lashchinskiy, Nikolay
    Mikutta, Robert
    Palmtag, Juri
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Prommer, Judith
    Schnecker, Jörg
    Shibistova, Olga
    Takriti, Mounir
    Urich, Tim
    Richter, Andreas
    Amino acid production exceeds plant nitrogen demand in Siberian tundra2018In: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 13, no 3, article id 034002Article in journal (Refereed)
    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.

  • 18. Wild, Birgit
    et al.
    Gentsch, Norman
    Capek, Petr
    Diakova, Katerina
    Alves, Ricardo J. Eloy
    Barta, Jiri
    Gittel, Antje
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Knoltsch, Anna
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Lashchinskiy, Nikolay
    Mikutta, Robert
    Palmtag, Juri
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Schleper, Christa
    Schnecker, Jörg
    Shibistova, Olga
    Takriti, Mounir
    Torsvik, Vigdis L.
    Urich, Tim
    Watzka, Margarete
    Santruckova, Hana
    Guggenberger, Georg
    Richter, Andreas
    Plant-derived compounds stimulate the decomposition of organic matter in arctic permafrost soils2016In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, article id 25607Article in journal (Refereed)
    Abstract [en]

    Arctic ecosystems are warming rapidly, which is expected to promote soil organic matter (SOM) decomposition. In addition to the direct warming effect, decomposition can also be indirectly stimulated via increased plant productivity and plant-soil C allocation, and this so called priming effect might significantly alter the ecosystem C balance. In this study, we provide first mechanistic insights into the susceptibility of SOM decomposition in arctic permafrost soils to priming. By comparing 119 soils from four locations across the Siberian Arctic that cover all horizons of active layer and upper permafrost, we found that an increased availability of plant-derived organic C particularly stimulated decomposition in subsoil horizons where most of the arctic soil carbon is located. Considering the 1,035 Pg of arctic soil carbon, such an additional stimulation of decomposition beyond the direct temperature effect can accelerate net ecosystem C losses, and amplify the positive feedback to global warming.

  • 19.
    Wojcik, Robin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Palmtag, Juri
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Weiss, Niels
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Land cover and landform-based upscaling of soil organic carbon stocks on the Brogger Peninsula, Svalbard2019In: Arctic, Antarctic and Alpine research, ISSN 1523-0430, E-ISSN 1938-4246, Vol. 51, no 1, p. 40-57Article in journal (Refereed)
    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.

1 - 19 of 19
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf