Ninth International Conference on Permafrost ... - IARC Research

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Comparison of Thermal Regimes in Tundra Virgin and Post-Agricultural Soils ofthe European NortheastDmitry KaverinKomi Science Center, Russian Academy of Sciences, Syktyvkar, RussiaIntroductionIn tundra, agricultural activity transformed the soils andtheir properties including temperature conditions. Soilthermal regimes are considered to change into ones having noanalogues among virgin soils. We studied thermal propertiesof tundra post-agricultural and virgin soils. Revealinginterannual and seasonal temperature dynamics in these soilsis important in view of present climate change.Regional BackgroundThe research was conducted in upland tundra near the townof Vorkuta (67°30′N; 64°02′E) in the east-European RussianArctic. The terrain is a rolling plain covered generally withsilty loams. The area is attributed to the subzone of southerntundra characterized by the distribution of relatively highshrubs: birch and willow. The area under study belongsto the zone of discontinuous permafrost (Oberman &Mazhitova 2003). Massive islands of permafrost occupyslightly dissected hill slopes and hill summits covered withdwarf-shrub/moss vegetation. Permafrost temperatures varyaround -1°C.Mean annual air temperature (MAAT) is -5.8°C, meanannual thawing degree days (DDT) 1005°C-days, and meanannual precipitation 513 mm.Objects and MethodsSoil temperature regimes were studied in 2 post-agriculturaltundra soils. Two undisturbed soils, one permafrost-affectedand another one permafrost-free, served as controls.Grassland soils are located in the landscape position similarto that of the control virgin soils.Soils under study(1) Abandoned overgrowing sown grassland, soil EpigleyicGelisol, grass/dwarf-shrub community, willow covers 7–8%of the site area (2005). Permafrost is at 1.35 m depth.(2) R2 site of the Circumpolar Active Layer Monitoringnetwork, dwarf-shrub/moss tundra, soil Histi-Turbic Cryosol(Reductaquic), permafrost depth is 100 cm;(3) Abandoned overgrowing arable land, soil Endogleyi-Stagnic Cambisol, grass-moss community, willow covers only2% of the site area (2005), no permafrost within 2 m depth.(4) Shrub-moss tundra, soil Dystri-Stagnic Cambisol, nopermafrost within 2 m depth.Post-agricultural sites were abandoned about 10 yearsago, and tall shrubs cover up to 10% of the area. Beforeabandonment, since 1970s the grasslands were annuallyharvested with periodic rototilling and fertilizing.The records were conducted with digital Hobo loggersprogrammed for 8 measurements daily. Loggers were set atdepths of 0, 20, 50, and 80 cm and in the upper layer ofpermafrost in case of its presence. The study was conductedin the period of 2005–2007.Results and DiscussionBy now, there is not much data about the temperatureregime of tundra soils in the European Northeast.Kononenko (1986) studied summer temperatures in virginand agricultural soils but winter thermal regime was quitepoorly characterized. Thermal regimes of the soils were notstudied at landscape level.Continuous soil temperature measurements have beenconducted in the area since 1996 by Galina Mazhitova. Itwas revealed that MAST (mean annual air temperature) in allsoils of the area is strongly correlated with snow thickness inwinter, with permafrost occurring only in the sites with snowthickness less than 50 cm. A progressive increase in shrubcoverage is, therefore, the major MAST-controlling factor.Shrubs effectively intensify snow accumulation, catchingthe snow redistributed by winds (Mazhitova 2001, 2008).As in previous years during our study, MAST at depth0–50 cm was commonly above 0°C in all permafrost-freesoils. Negative mean annual temperatures in permafrostaffectedsoils and positive ones in permafrost-free soilsare quite typical for discontinuous permafrost zone (Burn2004).Studied permafrost-affected soils (No. 1, 2) are locatedat the southern windward hill slopes. Shallow snow cover(30–40 cm) and quite thick peat layer (10–20 cm) preservepermafrost within the soil profile. Soils of northern slopeslocated in the same landscape have no permafrost. Such aninversion is resulted from strong winds blowing in winter.Until 2006, the site with coldest permafrost-affected soil(No. 2) was characterized with negative MAST down allthe profile (Mazhitova 2001, 2008). MAST at a depth of20 cm was -1.9…0.4°C, 50 cm -0.5…-1.9°C. MAST in theupper permafrost layer was -1.2°C with minimum (-4.4°C)in April.According to MAST and freezing degree days at depthsof 0–50 cm the permafrost-affected soil of the abandonedgrassland No. 1 was warmer than the virgin soil No. 2. ThusMAST at a depth of 50 cm was -0.35°C versus -0.5°C in thecontrol soil (2006).The post-agricultural soil (No. 3) was developed in theformer shrubby site similar to that of the soil No. 4. It hadlower temperatures in comparison with profile No. 4. Despitethe absence of thick shrub vegetation, this grassland soilstill had no permafrost and was characterized with positiveMASTs at depths of 20 cm and 50 cm (+1 +2°C).123
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 tThe warmest profile was No. 4. Tall shrub vegetationcatching thick snow cover causes relatively highertemperatures in winter. It results in higher MASTs.In 1996–2005, an increasing trend in MAST was observedin the virgin permafrost-affected soil of R2 CALM site(Mazhitova 2008). It was correlated with an increase inboth MAAT and active layer depth during the same period(Mazhitova & Kaverin 2007).In 2006–2007, negative MAST was changed to positive onein the upper soil layer (0–20 cm). This was quite unusual forpermafrost-affected soils, but was correlated with extremelyhot summer and mild winter that year. MAAT was -2.8°C in2006–2007. In the soil of arable land, freezing even did notreach a depth of 50 cm during winter 2006–2007.Zero curtains which are typical for the research area(Mazhitova 2001) observed both in virgin and postagriculturalsoils. Zero curtains could be observed fromOctober till January–February. The longest ones are recordedat a depth of 50 cm and more expressed in the permafrostaffectedvirgin soil.Mazhitova, G.G. & Kaverin, D.A. 2007. Dynamics ofseasonal thaw depth and surface subsidence at aCircumpolar Active Layer Monitoring (CALM) sitein the European Russia. Earth Cryosphere 9(4): 20-30 (in Russian).Mazhitova, G.G. 2001. Structure-functional organization ofsoils and soil cover in the European North-East. In:F.R. Zaidelman & I.V. Zaboeva (eds.), Monitoring ofHydrothermal Regime in Tundra Soils. S-Petersburg:Nauka, 153-162.Oberman, N.G. & Mazhitova, G.G. 2003. Permafrostmapping of Northeast European Russia based onperiod of the climatic warming of 1970–1995.Norsk Geografisk Tidskrift–Norwegian Journal ofGeography 57(2): 111-120.ConclusionsRemoval of virgin vegetation in permafrost-affected sitesdoes not differentiate thermal properties of soils significantly.Post-agricultural permafrost-affected soils were warmer, butpermafrost did not disappear just sinking deeper.In case of removal, tall-shrub vegetation serving as a heatinsulation cover in winter soil thermal regime is gettingcooler. And still we do not observe permafrost in the postagriculturalsoil of the arable land.Positive mean annual soil temperatures in the permafrostaffectedsoil were caused by high air temperatures andconsidered to be an interannual dynamic.AcknowledgmentsThe study was supported by NSF (OPP-9732051 andOPP-0225603) and RASHER project of <strong>International</strong> PolarYear.ReferencesArchegova, I., Kotelina, N. & Mazhitova, G. AgriculturalUse of Tundra Soils in the Vorkuta Area, NortheastEuropean Russia. In: J. Kimble (ed.), Cryosols(Permafrost-Affected Soils). Berlin-Heidelberg-NewYork: Springer-Verlag, 673-687.Burn, C.R. 2004. The Thermal Regime of Cryosols. In: J.Kimble (ed.), Cryosols (Permafrost-Affected Soils).Berlin-Heidelberg-New York: Springer-Verlag, 391-414.Kononenko, A.V. 1986. Hydrothermal Regime in Taiga andTundra Soils in the European North-East. L: Nauka.Mazhitova, G.G. 2008. Soil Temperature Regimes in theDiscontinuous Permafrost Zone in the East EuropeanRussian Arctic. Eurasian Soil Science 1: 48-62.124
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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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