In the framework of the study of the ecology of breeding and moulting geese and wader birds using the Northwest-European migration routes, expeditions focusing on permafrost have continued in 2008.

In the delta of the Pyasina River investigations focused on permafrost dynamics and the understanding of the permafrost at Cape East on the Pyasina Delta, Taimyr, northern Siberia (74° 06‘ N, 86° 44‘ E). The research is carried out by Alterra Wageningen UR (B.S. Ebbinge, contact person GBM Pedroli) and the Netherlands Institute of Ecological Research (NIOO, B. Nolet) in collaboration with Russian partners (Heritage Institute, Moscow). In 2008 the percentage of tundra covered by snow was surveyed daily on a 2-km line transect, until snow was completely melted. The thaw depth over the permafrost was measured on the same transect at three dates during the second part of the field season. The vegetation on the transect was surveyed by recording the presence-absence of six indicative plant species.

Active layer thawing was observed to be considerably shallower in 2008 than in 2006 when it was especially intensive. This is mainly due to late spring and late snowmelt in 2008. Spatial variation in active layer thawing is correlated with the type of vegetation. Thawing is shallower where Sphagnum, Eriophorum polystachum and Salix reptans are present, and deeper where Salix polaris and Dupontia fisheri are present.

Research on carbon and water exchange of taiga and tundra ecosystems in eastern Siberia was performed in cooperative projects with the Institute for Biological Problems Cryolithozone (IBPC) of the Siberian Division of the Russian Academy of Sciences in Yakutsk and the Vrije Universiteit (VU) in Amsterdam, Department of Hydrology and Geo- Environmental Sciences. Recently, the University of Utrecht (paleoecology) and Wageningen University (vegetation Ecology) have been involved. This project is partly funded by the Dutch Organization of Scientifi c Research (NWO), the Darwin Centre for Biogeology and the NWO Dutch-Russian Scientific Cooperation Fund .

In a larch/birch forest near Yakutsk (Spasskaya Pad Field Station) and on a tundra site near Chokhurdakh in the Indigirka lowlands (Kytalyk Reserve) flux measurements have been made with eddy correlation towers. From 2004 onwards, this research has been 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.

Apart from a methane flux measurement campaign on tundra and floodplain environments and on thermokarst lakes, vegetation ecological experiments were set up and lake bottom sediments were sampled for paleoecological research. Also a site was established for long-term monitoring of active layer thickness. In the summer of 2008, for the first time eddy covariance measurements using a cavity ringdown laser system were successfully set up and operated at the tundra site.

Jef Vandenberghe (jef.vandenberghe@falw.vu.nl)