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 tpart of soil litters. Gamasidae and Collembola in the top andmiddle part of the slope have been met in the whole mass ofpeaty horizons, while in the wettest bottom part of the slope,they are mostly at the top part of the organic horizons. Thegeneral number of Collembola in tundra permafrost-affectedsoils is low. On the average in the top part of the organichorizon, it is nearby 15,300 sp./m 2 , and in the bottom part– 1,130 sp./m 2 . At the same time the number of Collemboladepends on the part of the slope. The wettest bottom part ofa slope is characterized by a maximum of Collembola whichare concentrated in the top part of a litter, while the maximumquantity of Gamasidae (2,800 sp./m 2 ) and Oribatei (8,400sp./m 2 ) is related to the middle part of the slope.The frontier studies concern the non-stability of thesoil thermic regimes, shrinking of isolated patches andthe northward retreat of permafrost-affected soils, and theassessments of possible soil change related to vegetationtransformation on the base of soil studies (carbon fluxes,humus quality, mineral composition, etc.) in different typesof ecotones (forest-tundra, tundra-bog, meadow-tundra).In the Vorkuta tundra, the constant deepening of thepermafrost table was observed. Leveling of the permafrostsurface revealed that the ground subsidence due to thaw was18 cm per 7 years, thus the subsidence rate is 2.5 cm/year.The average increment (396 measurements per year) of thesoil layer reached 20 cm, and if adjusted to the subsidenceis 38 cm per 7 years. Thus, the average thickness of thepermafrost involved annually into soil formation is 5.5 cm.In the tundra of the Lower Kolyma River, the generaltendency for decrease of the permafrost table was alsorevealed, but the process seems to be more complicated andhas more fluctuations. It is the result of the influence of 2factors: (1) lower permafrost temperature at the EurasianNortheast, and (2) various processes with negative feedbacksresulting in thaw mitigation.At the southern part of the Cryolithozone, in Buryatia, in1907–08 in undisturbed Gelic Chernozems, the permafrosttable was identified at a depth of 1.5–1.6 m; in the 1960s,2.0–2.1 m; at present time, 2.5–2.75 m. In loamy GelicLuvisols, the permafrost at the beginning of the previouscentury was found at a depth of 1.2–1.3 m; in 1960–70s,1.5–1.6 m; at present time, 2.2–2.5 m.The analysis of archives and personal data revealed a shiftof the southern permafrost boundary in the region northwardfrom Arkhangelsk since 1933 to 2000. During 67 years,the southern border of the sporadic permafrost has movednorthward 20–30 km.The monitoring of the “forest-bog” ecotone in the subarcticzone of the Arkhangelsk region has been conducted.Besides the well-known phenomenon of northern soils bogging,it revealed the ecotone sustainability based on negativefeedbacks.The study of soil and geomorphic processes has beenconducted in formerly permafrost-affected Tatra Mountains,which are the highest part of the Central EuropeanCarpathians (2655 m a.s.l.). The Tatra Mountains are notglaciated, and nowadays, the presence of permafrost hasnot been found. However, these mountains are subjected88to intense geomorphic processes (rock falls, rock slides,debris and grain flows, solifluction, gelifluction, and others).The soils studied have been localized in the alpine zone(1800–2200 m a.s.l.), where the most intensive geomorphicprocesses occur (cryo-nivale zone). The soils studied areshallow and contain a considerable amount of clast. Theyare subjected to the podzolization process, and they can becharacterized by thick humus horizons. Slow geomorphicprocesses (solifluction, soil creep) modify the upper part ofthe soil profile, comprised of humus horizons and eluvialhorizons. The influence of these processes depends onthe participation of the phenomena associated with thefreeze-thaw action concerning the ground ice. Along withthe increased importance of frost action in the movementof regolith, the degree of soil modification increases. Themost profound transformation of the soil cover occurs in thecase of gelifluction. Within the forms, which developed as aresult of secular processes (protuberances, bench terraces,lobes), the soils are modified, although without leading toessential changes in their properties. The soil affected bygelifluction have the properties and morphology of Fluvisols.Catastrophic processes (rock slides, debris and grain flows)cause strong transformation of soil cover and uniformityof soil mass. Further development of soil depends on thegeomorphic position; it is different within erosion zonesand different within accumulation zones; so the soils abovethe upper timberline in the Tatra Mountains are youngforms. In relatively stable areas or those subjected to onlymoderate geomorphic processes, they often display thefeatures of polygenesis associated with changing climaticand geomorphic conditions.The other part of the frontier studies is the detailedanalysis of soil process at the interface of the soil andpermafrost tables. It concerns the study of the biochemicaland geochemical barrier on this interface and the study ofthe process of cryogenic lateral transportation at the contactzone of the soil and the permafrost table. This interface isthe zone of high concentration of organic matter and othercompounds, including pollutants. These detailed physicochemicalstudies allow for a determination of the fate ofthese materials as affected by permafrost thawing due toclimate change or anthropogenic impact.The important feature of the cryogenic structure of thetransitional layer is the zone of concentration of labilesubstances which are situated in the zone of the segregativeice. In depressions of the permafrost surface, there are localzones of accumulation of labile substances—cryogenicgeochemical traps. The chemical analysis showed that thegeneral salinity and composition of soluble substancesconcentrated in these traps differ from the composition ofintrasoil ice. The differences observed can be explainedby cryogenic transformation of suprapermafrost water andselective penetrability of the cryogenic geochemical barrier.Local accumulation of labile substances in geochemicalpermafrost traps is the essential part of geochemical balance.If the soil thawing depth increases, then the elementsconcentrated in permafrost geochemical traps could escapeinto the surface-water flow.