Ninth International Conference on Permafrost ... - IARC Research

Ni n t h In t e r n at i o n a l Co n f e r e n c e o n Pe r m a f r o s tResultsThe most plausible age-depth model suggests that thedeposit represents ca. 650 calendar years with a rapidlydeclining net carbon accumulation rate due to cumulativedecay of the organic matter with age. There has been a (near)complete turnover of organic material deposited prior to thistime, leaving no evidence of the older history at the site.Chronological control becomes increasingly more accuratetowards the present, allowing a more detailed reconstructionof the timing and duration of successive vegetation phases.Macrobotanical remains reveal significant changes insurface conditions at the site over time. The first recordedphase, characterized as dwarf-birch tundra, lasted until ca.1860 AD. At this time the site paludified, resulting in theformation of an Eriophorum-dominated wetland. Afterabout 40 years, drier surface conditions developed startingwith Sphagnum fuscum and culminating in a Polytrichum/Dicranum phase. Wetter conditions reappeared in the 1930sas indicated by Sphagnum Sect. Cuspidata. In recent decadesthe surface became drier again with a Sphagnum fuscumphase, followed by the present Polytrichum/Dicranum/lichen phase.An assessment will be made whether these recent changesin surface conditions can be linked to monitored long-termclimate variability in the region. Alternatively, the observedtemporal dynamics can be associated with permafrostaggradation following the development of a thick organiclayer in the dwarf-birch phase and subsequent differentialfrost heave/ground subsidence at and in the immediatevicinity of the investigated site.The final objective is to assess net carbon storage andmethane emission characteristics throughout the recenthistory of the site with the aim to reconstruct the variablenet radiative climate forcing originating from this type ofdynamical tundra ecosystems.AcknowledgmentsThe collection of the material was funded through theEU 4 th Framework Environment and Climate Programme(TUNDRA project) and the EU INTAS Programme (PERUSAproject). Current analyses of the material are supported by agrant from the Swedish Research Council.ReferencesHeikkinen, J.E.P., Virtanen, T., Huttunen, J.T., Elsakov, V.& Martikainen, P.J. 2004. Carbon balance of EastEuropean tundra. Global Biogeochemical Cycles 18,doi:10.1029/2003GB002054.Kuhry, P., Mazhitova, G., Forest, P.A., Deneva, S., Virtanen,T. & Kultti, S. 2002. Upscaling soil carbon estimatesfor the Usa Basin (Northeast European Russia) usingGIS-based landcover and soil classification schemes.Danish Journal of Geography 102: 11-25.158