Permafrost

end of April. Seasonal variation of the permafrost active layer suggests that the thaw–frost cycle
may not affect biological processes of the grass, because the thaw depth exceeded 3 m during
the growth period (May to September), even though the study site was underlain by permafrost.
Vegetation was uniformly sparse grass with coverage of 38-60% during the maximum
growth period. Over the pasture, plant type and species did not vary. Artemisia frigita
dominated (~60%) and other species included Arenaria and Leymus chinensis. The maximum
grass height in mid-July was less than 20 cm. Figure 4 shows the vertical distribution of grass
root density (dry biomass) measured in April and June 2003. Grass roots develop mainly in the
surface ground layer (the top 50 cm). Differences in root biomass between April and June also
occurred only in the ground surface layer.
Eco-hydrological observations since July 2002 and June 2004 at a sparse grassland site in
Mongolia suggest that variability of evapotranspiration shows temporal decline processes
response to precipitation events or snow melting. The effect of vegetation cover on
evapotranspiration was insignificant comparing to that of surface soil moisture. Changes in soil
evaporation, related to precipitation, mainly caused the very large inter-annual differences in
evapotranspiration. The transpiration partition was 22%. Evapotranspiration was sensitive to
precipitation (ground surface moisture) and influenced by seasonal heat fluxes. The partition of
transpiration was small during wetter grass-growing periods but large in drier periods. The
growing period is short along the periphery of the cryosphere, but water fluxes during the
growing period contribute significantly to the annual water cycle.
Key words: Mongolia, permafrost, surface condition, evapotranspiration
208
Cryomorphogenesis in the mountains of North-Eastern Russia
Yuri. V. Mudro
(Department of Cryolithology and Glaciology, Faculty of Geography,Moscow State University,
Moscow, Russia, 119992. mudrov@geogr.msu.ru)
Abstract: Permafrost, perennially frozen ground, occupies over 11 million km 2 or 65 per cent
of Russian territory. The permafrost zone (cryolithozone) extends from the Arctic islands and
the Arctic coast at 80-82°N across the continent to the Mongolian border at 49°N in
Transbaikalia. The Arctic shelf is occupied by subsea permafrost. The distribution of permafrost
in the mountains varies with altitude, latitude and longitude. North-eastern Russia, which
includes Eastern Siberia and the northern Pacific, is a predominantly mountainous region which
extends from the river Lena to the Bering Strait and occupies about 1.5 million km 2 .
It is difficult to analyse the climate of the north-eastern mountains in detail, first, because
of the sheer size and diversity of the region: and second, because observations are still sparse.
The most severe weather is associated with locally transformed air masses, while the advection
of the fresh arctic air rises temperature by about 10ºC. Temperature inversion are frequent and
elevated regions often exhibit higher temperatures. Ameliorating effects of the Bering Sea and
the North Pacific are mostly limited to the narrow coastal mountains prevent the advection of
the maritime air landwards. The southern limit of the continuous permafrost coincides