HR: 17:00h
AN: C24A-05    [Abstracts]
TI: Cryogenic Features Of Tundra Soils Along A Bioclimate Gradient In Arctic Alaska And Canada
AU: * Ping, C
EM: pfclp@uaa.alaska.edu
AF: University of Alaska Fairbanks, Palmer Research Center 533 E. Fireweed Ave., Palmer, AK 99645 United States
AU: Michaelson, G J
EM: pngjm@uaa.alaska.edu
AF: University of Alaska Fairbanks, Palmer Research Center 533 E. Fireweed Ave., Palmer, AK 99645 United States
AU: Tarnocai, C
EM: tarnocaict@agr.gc.ca
AF: Ag.and Agri-Food Canada, K.W. Neatby Bldg, Room 1135 960 Carling Ave., Ottawa, ONT K1A 0C6 Canada
AU: Walker, D A
EM: ffdaw@uaf.edu
AF: University of Alaska Fairbaks, Institute of Arctic Biology 311 Irving, Fairbanks, AK 99775 United States
AB: Previous field research describing Polar Desert soils of High Arctic, Canada, have emphasized the soils as having minimal development. However, based on recent field studies we found that cryogenesis plays a controlling role in soil formation in the High Arctic, just as in the Middle and Low Arctic. Cryoturbation is one kind of cryogenic process in that soil horizons are mixed, warped, broken or mixed due to frost heave, frost churning and frost cracking. However, in most recent sediments or young soils, cryoturbation is none to minimal and soil horizons are relatively flat. As the cryogenic process proceeds with time, cryoturbated features become dominant through most of the profile. The landscape of the High Arctic (Isechsen, Subzone A) is dominated by small contraction-crack polygons, cryogenesis results in strong cryogenic structures but cryoturbated features are more prominent at the surface horizons. Massive ground ice, including ice wedge, is common. In Middle Arctic (Mould Bay, Subzone B; and Green Cabin, Subzone C) the landscape is dominated by nonsorted circles (frost boils), small nonsorted polygons, earth hummocks and turf hummocks. In Subzone C, nonsorted circles, small nonsorted polygons and turf hummocks formed in loamy and sandy soils. Throughout the bioclimate transect, the depth of the active layer does not decrease with increasing latitude but responds primarily to the insulating effects of vegetation cover where present. The depth of active layers ranges from 40 to 60 cm. Due to the presence of permafrost, downward drainage is restricted; reducing condition often appear at the lower active layer and upper permafrost due to a saturated zone on top of the upper permafrost. The most common reduced metals are Fe and Mn. Soils in the center of the nonsorted circle and small polygons are subjected to alternate reduction and oxidation which result in redoximorphic features. Whereas soils between the circles are mostly reduced due to thicker organic horizon and shallow active layer. Freeze-thaw cycles often result in cryogenic soil structures. Cryptogamic crust commonly occur on the surface of frost boils and crumb structures are commonly associated with crusts in soils of Subzone C through D but are less common in Subzone A and B. Hard crusts form in frost boils of Subzone A through C due to the drier climate with salt accumulations on the surface. Granular structures form around the edge of earth hummocks and nonsorted circles. Platy and lenticular structures form in the upper active layers and reticulate and ataxitic structures form on top of the permafrost table. These structures provide for passage of air and water and result in a surface for biogeochemical reactions after thawing. Cryogenic processes, mainly cryoturbation also plays a controlling role in carbon sequestration across the bioclimate transect from Subzone A to D in Arctic Canada and Alaska. The forms of cryogenic features/patterns that are expressed at the soil surface result in differing carbon-distributions throughout the soil profile. The soils of hummock features tend to store more C in the upper permafrost than in the active layer whereas carbon sequestered in nonsorted circles is more evenly divided between the upper permafrost and the surface active-layer. This could result in differing impacts and feedbacks to the carbon balance of these ecosystems under changing climate conditions.
DE: 0475 Permafrost, cryosphere, and high-latitude processes (0702, 0716)
DE: 0486 Soils/pedology (1865)
DE: 0710 Periglacial processes
DE: 0712 Cryosol
DE: 0718 Tundra (9315)
SC: Cryosphere [C]
MN: Fall Meeting 2005