Tracking past and ongoing lemming cycles on the Eurasian tundra

During the Swedish-Russian Tundra Ecology -94 expedition one of the goals w as to describe the local population fluctuations of Siberian lemmings over the Eurasian tundra. In order to compensate for the lack of repeated sampli ng, we used 4 different estimates to determine the phase position of the le mming populations at the different sites: i) the number of lemmings trapped per unit time; ii) the age structure of the lemming population; iii) the l evel of chemical defences in important food plants; and iv) the age distrib ution of microtine scars on willow stems ("a historical archive" on past le mming fluctuations on the site). We present data from 4 of the 12 sites inv estigated. The 4 different approaches gave, to a large extent, coherent res ults. We suggest that our combined approach may be useful when sampling is possible during 1 year only, but we strongly recommend that the sampling is done at the same phenological stage at all the compared sites. Data report ed here and elsewhere by us, indicate that the local populations of Siberia n lemmings do not show synchronous dynamics over the vast Eurasian tundra.