Ninth International Conference on Permafrost ... - IARC Research

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Temporal Variability in Plant Cover and Carbon Balance of Permafrost-AffectedTundra EcosystemsPeter KuhryDepartment of Physical Geography and Quaternary Geology, Stockholm University, SwedenIntroductionThe extant tundra in Northeast European Russia ischaracterized by high spatial variability. Previous studieshighlight the fine mosaic of microsites with differentvegetation, soil, permafrost, carbon storage, and methaneemission characteristics (e.g., Kuhry et al. 2002, Heikkinenet al. 2004). This investigation points in addition to hightemporal landscape dynamics in relation to recent climateand/or permafrost changes, which represents a furtherchallenge for the past reconstruction and future prediction ofthe tundra carbon balance.MethodsThe temporal ecosystem dynamics in a tundra site atLek-Vorkuta (Northeast European Russia) is traced usinghigh resolution (1–2 cm depth intervals), absolute dating,geochemical, and plant macrofossil analyses of a 22 cmthick top organic sequence in permafrost-affected peaty soil.The LVPS3 profile was excavated from a small hummockin wet tundra (67°40′N, 63°35′E). The upper permafrosttable at the time of collection (August 3, 1999) was locatedat 25 cm. This implies that the entire top organic horizon islocated within the active layer. Although the profile at thesite showed considerable deformation of the original layers,no evidence was found for complete stratigraphic inversions(Fig 1).The LVPS3 sequence was dated through a combinationof 210 Pb dating of the upper 16 cm and 14 C AMS wigglematchingof the lower 7 cm of the top organic deposit.The geochemical analyses of the sequence included bulkdensity, loss-on ignition (550°C) and carbon/nitrogen ratiomeasurements. Figure 2 presents the gross stratigraphy ofthe profile and the samples (intervals and materials) utilizedfor the different types of analyses performed.Figure 1. Collection site and material of the LVPS3 profile.Figure 2. LVPS3 gross stratigraphy and samples analyzed for different analytical procedures. Stratigraphy from base to top: horizontaldash (mineral subsoil); uniform grey (organic soil); vertical dash (monocot peat); diagonal dash, two layers (Polytrichum/Dicranum peat);horizontal wave (Sphagnum peat); white (present lichen cover).157
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
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ContentsPreface ...................
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Mapping and Modeling the Distributi
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Satellite Observations of Frozen Gr
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xiiIce Wedge Thermal Regime in Nort
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xivPermafrost Response to Dynamics
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NICOP SponsorsUniversitiesUniversit
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Deep Permafrost Studies at the Lupi
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Effect of Fire on Pond Dynamics in
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Cryological Status of Russian Soils
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Acoustical Surveys of Methane Plume
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Permafrost Delineation Near Fairban
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Preparatory Work for a Permanent Ge
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A Provisional Soil Map of the Trans
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Martian Permafrost Depths from Orbi
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Time Series Analyses of Active Micr
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Impact of Permafrost Degradation on
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DC Resistivity Soundings Across a P
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Modeling Thermal and Moisture Regim
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A Provisional Permafrost Map of the
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Alpine Permafrost Distribution at M
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Cryogenic Formations of the Caucasu
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Modeling Potential Climatic Change
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A Hypothesis: A Condition of Growth
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Modeled Continual Surface Water Sto
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Freeze/Thaw Properties of Tundra So
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Discontinuous Permafrost Distributi
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Thermal Regime Within an Arctic Was
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Seasonal and Interannual Variabilit
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Twelve-Year Thaw Progression Data f
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Continued Permafrost Warming in Nor
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Landsliding Following Forest Fire o
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A Permafrost Model Incorporating Dy
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Seasonal Sources of Soil Respiratio
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Greenland Permafrost Temperature Si
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The Importance of Snow Cover Evolut
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The Account of Long-Term Air Temper
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The Combined Isotopic Analysis of L
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Adaptating and Managing Nunavik’s
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Human Experience of Cryospheric Cha
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HiRISE Observations of Fractured Mo
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A Soil Freeze-Thaw Model Through th
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Mapping and Modeling the Distributi
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First Results of Ground Surface Tem
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Historical Changes in the Seasonall
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Rock Glaciers in the Kåfjord Area,
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Snowpack Evolution on Permafrost, N
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Climate Change in Permafrost Region
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Maximizing Construction Season in a
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Pleistocene Sand-Wedge, Composite-W
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