| 1. |
- Hugelius, Gustaf, 1980-, et al.
(författare)
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Characterization of Soil Organic Matter in Permafrost Terrain – landscape scale analyses from the European Russian Arctic
- 2010
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- 1 INTRODUCTIONSoils of high latitude terrestrial ecosystems are considered key components in the global carbon cycle and hold large stores of Soil Organic Carbon (SOC). The absolute and relative sizes of labile and recalcitrant SOC pools in periglacial terrain are mostly unknown (Kuhry et al. in prep.). Such data has important policy relevance because of its impact on climate change.We sampled soils representative of all major land cover and soil types in discontinuous permafrost terrain, European Russian Arctic. We analyzed the bulk soil characteristics including the soil humic fraction to assess the recalcitrance in organic matter quality in down-depth soil profiles.2 METHODSA comprehensive stratified random soil sampling program was carried out in the Seida area during late summer 2008. From these, we selected nine sites considered representative for the landscape. Active layer and permafrost free upland soils were sampled from dug soil pits with fixed volume corers. Peat plateaus were sampled near thermally eroding edges. Permafrost soils were cored using steel pipes hammered into the frozen peat. Permafrost free fens were sampled using fixed volume Russian corers.Radiocarbon dating was used to determine the SOC ages. The soils were analyzed for dry bulk density, elemental content, and stable isotope composition of organic C and N (δ13C, and δ15N). Further, humic acids were extracted, and the degree of humification of SOM assessed based on A600/C and ∆ log K (Ikeya and Watanabe, 2003).3 RESULTSFigure 1 shows soil organic matter (SOM) characteristics in a peat sequence from one of the nine described sites, a raised bog peat plateau.The peatland first developed as a permafrost-free fen during the Holocene Hypsithermal. Permafrost only aggraded in the late Holocene. Anoxic conditions in the fen and permafrost in peat plateau stages reduced decomposition rates and the degree of humification (A600/C) is relatively constant throughout the peat deposit.Botanical origin is a key factor in determining SOM quality, which is clearly reflected in the elemental ratio (C/N) and isotopic composition of C and N. There are sharp shifts in humification, C/N and isotopic composition at the peat/clay interface.REFERENCESIkeya, K. and Watanabe, A., 2003, Direct expression of an index for the degree of humification of humic acids using organic carbon concentration. Soil Science and Plant Nutrition, 49: 47-53.Kuhry, P., Dorrepaal, E., Hugelius G., Schuur, E.A.G. and Tarnocai C., Potential remobilization of permafrost carbon under future global warming. Permafrost and Periglacial Processes, Submitted.
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| 2. |
- Hugelius, Gustaf, 1980-, et al.
(författare)
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Estimating soil organic carbon storage in periglacial terrain at very high resolution; a case study from the European Russian Arctic
- 2010
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- 1 Introduction While recent research advances have significantly increased our understanding of SOC storage in the periglacial landscape, there are still many uncertainties. Local scale studies have shown that the landscape distribution of SOC is highly heterogeneous (e.g. Hugelius and Kuhry, 2009). Some landscape components, such as peat deposits or cryoturbated soil horizons, can dominate local SOC storage. However, there are no clear trends in landscape distribution and regional differences emerge (Kuhry et al., in prep.). We have conducted a very high resolution study of SOC storage in four study sites (Seida and Rogovaya 1-3) in discontinuous permafrost terrain, European Russian Arctic. Point pedon data is upscaled to areal coverage using two different upscaling tools, land cover classifications and soil maps. 2 Methods 2.1 Soil sampling and upscaling Soil sampling was performed (i) along landscape transects and (ii) according to a weighted, stratified random sampling program. Sampling was done in 10 cm increments to 1 m depth or to full depth of peat deposits in a total of 94 sites. Point pedon data is upscaled to areal coverage using two different upscaling tools: 1. Thematic land cover classifications based on multiresolution segmentation of high-resolution Quickbird imagery (2.44 m raster resolution, 17 separate land cover classes, software Definiens Professional 5.0) and: 2. High resolution thematic soil maps following World Reference Base for Soil Resources terminology (20 distinct soil types, median polygon size 1960 m2). Mean SOC storage for each land cover or soil type is multiplied by the areal coverage within the study areas to calculate total storage and landscape partitioning of SOC. Figure 1 illustrates the spatial resolution of the two upscaling tools. It also shows 4 pixels of Landsat TM resolution, representing the highest resolution of previous land cover based SOC storage studies in permafrost terrain. 3 results Preliminary calculations show that the estimates in the four different areas are between 38-58 kg C m-2 for land cover upscaling and between 37-49 kg C m-2 for soil map upscaling. Both upscaling methods yield higher estimates than what has previously been reported for this area (Hugelius and Kuhry, 2009). A majority of SOC is stored in Cryic Histosols or Folic/Histic Cryosols. Contiguous permafrost peat plateaus are present in all study areas, covering ~20-30 % of the landscape. The mean depth of peat deposits in the four plateaus is between 150-250 cm, but it is highly variable (recorded range 30-420 cm). There is no evidence of any significant deep burial of SOC through cryoturbation processes. References Hugelius G. and Kuhry P. 2009, Landscape partitioning and environmental gradient analyses of soil organic carbon in a permafrost environment. Global Biogeochemical Cycles, 23, GB3006, doi:10.1029/2008GB003419. Kuhry, P., Dorrepaal, E., Hugelius G., Schuur, E.A.G. and Tarnocai C., Potential remobilization of permafrost carbon under future global warming. Permafrost and Periglacial Processes, Submitted.
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| 3. |
- Hugelius, Gustaf, 1980-
(författare)
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Quantity and quality of soil organic matter in permafrost terrain
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- High latitude terrestrial ecosystems are considered key components in the global carbon (C) cycle and hold large reservoirs of soil organic carbon (SOC). Much of this is stored as soil organic matter (SOM) in permafrost soils and peat deposits and is vulnerable to remobilization under future global warming. While the large size and potential vulnerability of arctic SOM reservoirs is recognized, detailed knowledge on its landscape partitioning and quality is poor. This thesis describes total storage, landscape partitioning and lability of SOM stored in permafrost areas of Canada and Russia. Detailed studies of SOC partitioning highlight the importance of especially permafrost peatlands, but also of O-horizons in moist tundra soils and cryoturbated soil horizons. A general characterization of SOM in an area of discontinuous permafrost shows that >70% of the SOC in the landscape is stored in SOM with a low degree of decomposition. Projections of permafrost thaw predict that the amount of SOC stored in the active layer of permafrost soils in this area could double by the end of this century. A lateral expansion of current thermokarst lakes by 30 m would expose comparable amounts of SOC to degradation. The results from this thesis have demonstrated the value of high-resolution studies of SOC storage. It is found that peat plateaus, common in the sporadic and discontinuous permafrost zones, store large quantities of labile SOM and may be highly susceptible to permafrost degradation, especially thermokarst, under future climate warming. Large quantities of labile SOM is also stored in cryoturbated soil horizons which may be affected by active layer warming and deepening. The current upscaling methodology is statistically evaluated and recommendations are given for the design of future studies. To accurately predict responses of periglacial C pools to a warming climate detailed studies of SOC storage and partitioning in different periglacial landscapes are needed.
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| 4. |
- Hugelius, Gustaf, 1980-
(författare)
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Uncertainty analysis for estimates of soil organic carbon storage in permafrost terrain, a regionalstudy from the western Russian Arctic
- 2011
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Studies of periglacial regions confirm their importance in the global carbon (C) cycle,but estimates of e.g. soil organic carbon (SOC) storage are poorly constrained and lack quantitativeestimates of errors following upscaling. In this study, a comprehensive regional SOC database from thenorthern Usa River Basin (European Russian Arctic, 55 000 km2) is used to evaluate the currentmethodology of SOC upscaling in periglacial terrain. The selection of classes for upscaling and the need forreplication in soil sampling are statistically evaluated. Upscaling using a land cover classification and a soilmap estimates SOC storage at 48.5 and 47.0 kg C m-2, respectively with 95% confidence intervals (CI)within ±8%. When corrected for spatial errors in the upscaling proxy, SOC is estimated to 46.5 kg C m-2with a 95% CI reflecting propagated variance from both natural variability and spatial errors of ±11%.Artificially decreasing the size of the database used for upscaling shows that relatively stable results can beachieved with lower replication in some upscaling classes. For future upscaling studies at large geographicscales, a priori determination of sample sizes and tests to insure unimodal and statistically independentsamples are recommended. If these prerequisites are not fulfilled, classes may be merged or subdividedprior to upscaling. Decreased spatial resolution for upscaling from 30 m to 1 km has little impact on SOCestimates in this region, but classification accuracy is dramatically reduced and land cover classes show different, sometimes non-linear, responses to scale.
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| 5. |
- Palmtag, Juri, et al.
(författare)
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Soil organic carbon storage in continuous permafrost terrain; two case studies from NE Greenlandand NE Siberia
- 2011
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 6. |
- Pastukhov, Alexander, et al.
(författare)
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Soil organic carbon storage in the forest-tundra ecotone zone in the North-Eastern Europe
- 2011
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Ingår i: Geophysical Research Abstracts Vol. 13, EGU2011-53, 2011.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- High latitude terrestrial ecosystems are considered key components in the global carbon (C) cycle [McGuire et al.,2009, Hugelius et al., 2010, in press]. Large stocks of soil organic carbon (SOC) have accumulated in Cryosolsand Histosols, where permafrost affects to reduce decomposition rates. In a recent study based on the NorthernCircumpolar Soil Carbon Database (3530 pedons, soil map mean polygon size 259 km2), Tarnocai et al. [2009]estimated soil organic carbon (SOC) stocks in the northern permafrost region to be 1024 Pg (Pg = g x 1015) forthe upper three meters (with Histosols contributing 278 Pg and Cryosols 634 Pg).This study describes detailed partitioning of soil organic carbon (SOC) for the forest-tundra ecotone zone in theborder of the discontinuous and massive island permafrost terrain with MAGT -0.5 to -2.0 C, North-EasternEuropean Russia.Soil cover of the study area is diverse and mosaic and form complexes of soils owing to a variety of microrelief,cryoturbation processes, snow cover distribution, etc. In peat plateau/thermokarst complexes, Cryic Folic Histosolswith shallow permafrost tables are interspersed with Fibric Histosols (permafrost free fens) and Fibric FloaticHistosols (thermokarst lakes in-filling with vegetation). Permafrost-affected mineral soils (Cryosols) are usuallyformed on loamy wind-exposed surfaces under tundra dwarf-shrub vegetation where shallow snow cover preservespermafrost within the soil profile. In these sites, quite thick peaty layers (10-40 cm) also favours shallow permafrostoccurrence (Histic Cryosols). Non-permafrost soils (Gleysols, Cambisols and Albeluvisols) are usually formed insites under tall shrub vegetation where thicker snow cover in winter results in a warmer soil regime. Non-permafrostsoils are developed under forest vegetation (Cambisols and Albeluvisols) and in floodplains (Fluvisols).Georeferenced soil data from field observations were overlaid on Landsat images and a supervised classificationprocedure was carried out. As a result satellite images were coded to raster maps containing soil type informationin pixel classes. The images were then homogenized prior to conversion to vector polygons. Resulting vector mapswere processed as shape files in the software ArcGIS 9.1, where adjacent uniform polygons were merged andcorrected and soil maps were compiled.Mean SOC storage (kg C m-2) for each soil type (SOC only) was calculated as the arithmetic mean of C storagein the sites belonging to that class and was upscale to soil groups in the map.Mean SOC storage for all four study areas combined is estimated to be 39.5 kg C m-2 (soil map and LCC upscalingrespectively). Detailed GIS map of SOC storage can be used to model the potential effect of permafrost thaw onSOC stores.
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