INFLUENCE OF HERBIVORY ON CESIUM TURNOVER IN A FOREST ECOSYSTEM

The effect of herbivory by bank vole (Clethrinomys glareolus) and moos e (Alces alces) in relation to litterfall in a boreal forest is analys ed. The main purpose is to estimate the relative importance of these p rocesses for the transfer of caesium-137 to soil. Biomasses of litterf all and food consumption were selected from different forest biotopes. The analysis of the input and output of caesium-137 in the vole and m oose populations is based on mass balance calculations for caesium-137 in steady state conditions. From this assessment, herbivory appears t o be within an order of magnitude of litterfall. With due regard to th e lower caesium level in litterfall than in living plant tissue, trans fer of radioactive caesium by herbivory is seen to be even higher in c omparison to that by litterfall, than apparent from the corresponding transfer of organic matter. In addition, the availability of caesium-1 37 from animal excrements is expected to be high and fast, which furth er emphasises the relative importance of herbivory feed-back from vege tation to soil.