We have measured the bomb-fallout radionuclide 137Cs in soils under various management practices. In bulk soil samples
taken at various depths from forested woodlots, we found a deeper distribution of 137Cs in soils with greater numbers and
biomass of the anecic earthworm species Lumbricus terrestris. In soils of similar texture under no-till management we found
signi®cant increases in earthworm populations relative to conventionally tilled (moldboard plow) soils. Activity of 137Cs was
depleted in the upper 3 cm of the no-till soils which may be a result of (1) dilution due to the addition of fresh organic matter
to the soil surface and/or (2) dilution in surface horizons by sub-soil material containing no 137Cs transported by earthworms
casting it at the soil surface. We have also measured the 137Cs content in coatings of individual L. terrestris earthworm
burrows with depth in a forested and a conventionally tilled soil. Some earthworm burrow coatings were devoid of 137Cs
activity, suggesting that those burrows were likely to be active prior to any bomb fallout (i.e. before the 1940s). Other burrows
showed signi®cantly higher radioactivity suggesting more recent earthworm habitation. Our data suggest that the distribution
of 137Cs is related to the activity of earthworms in the soils. The methodology developed can be used to qualitatively measure
the age of burrows and thus better quantify the rates at which L. terrestris can store soil organic matter below the plow layer.
Although the soils studied were free of Chernobyl-derived 137Cs, this technique holds potential for evaluating the in¯uence of
fauna on soil processes in the areas affected by the Chernobyl fallout.