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Sökning: WFRF:(Kuhry Peter) > Konferensbidrag

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1.
  • Hugelius, Gustaf, 1980-, et al. (författare)
  • Characterization of Soil Organic Matter in Permafrost Terrain – landscape scale analyses from the European Russian Arctic
  • 2010
  • 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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  • Hugelius, Gustaf, 1980-, et al. (författare)
  • Estimating soil organic carbon storage in periglacial terrain at very high resolution; a case study from the European Russian Arctic
  • 2010
  • 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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  • Palmtag, Juri, et al. (författare)
  • Soil organic carbon storage in continuous permafrost terrain; two case studies from NE Greenlandand NE Siberia
  • 2011
  • 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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