During the Alterra (Wageningen) expedition to Taimyr (northern Siberia) by Bart Ebbinge, the depth of active layer was investigated. On August 13 to 15, 200 depth measurements were made with a simple steel probe at 10- m intervals over a straight 2-km long N-S transect on nearly level tundra at Cape East (Wostochny), Taimyr, northern Siberia (74° 06' N, 86° 44' E). Due to stoniness in the soil at some places, the frozen soil was not always reached.

The following preliminary conclusions can be drawn:

  • Different vegetation revealed different depth of the frozen soil but on average the thawing front was at 45 cm under the level surface
  • In micropolygons with bare clay surface the soil was thawed deeper (up to 55 cm) than around those with Dryas and Cassiopea
  • In wet places thawing was deeper (45 cm) under the grassy vegetation than under the moss hummocks (Sphagnum) spread over these places (less than 40 cm).

This project is carried out by Roeland Bom & Bas Pedroli.

The Vrije Universiteit in Amsterdam (Department of Hydrology and Geo-Environmental Sciences) investigates carbon and water exchange of taiga and tundra ecosystems in eastern Siberia, in collaboration with the Institute for Biological Problems of the Cryolithozone, Siberian Division of the Russian Academy of Sciences in Yakutsk. Measurements are using eddy correlation systems and soil flux chambers in a larch / birch forest near Yakutsk (Spasskaya Pad Field Station) and on a tundra site near Chokhurdakh in the Indigyrka lowlands (Kytalyk reserve). In 2004 and 2005, this research was extended with flux chamber measurements of methane fluxes and a survey of active layer thickness and temperature. The aim is to estimate the annual exchange rates and their interannual variability, and to determine the sensitivity to environmental factors of the fluxes. The present flux data show considerable inter-annual variability. In the tundra site, summer 2005 was a relatively dry year with lower methane fluxes than in 2004.

The 2005 campaign has been funded by the Vrije Universiteit and NWO (Dutch Organisation of Scientific Research) and is a continuation of research in the EU TCOS (Terrestrial Carbon Observation System) project. The methane flux measurements will also be used in a modelling study on last glacial climate and permafrost changes at rapid climate transitions, also funded by NWO. The later project is scheduled to start at the end of 2005. Direct enquiries to: J. van Huissteden (ko.van.huissteden @geo.falw.vu.nl)

Jef Vandenberghe (vanj@falw.vu.nl)