Decomposition in two pine forests: The mobilisation of 137Cs and K from forest litter

Decomposition rates of pine litter and cotton were measured in the litter (AoL) and fermentation (AoF) horizons of two forests in Ireland (Pinus contorta) and the Ukraine (Pinus sylvestris). The extent of decomposition was similar in spite of seasonal climatic differences between the two sites. The amounts of 137Cs and K in litter bags were determined at different stages of decomposition. During the first 2–4 months of decomposition, the K content of litter bags decreased by up to 80%; maximum weight loss in this time was 18%. At both sites decomposition of the litter was accompanied by an increase in 137Cs content of the litter bags. It is suggested that the increase in 137Cs content is due to importation of 137Cs by invading decomposer fungi. Fungus-mediated translocation of 137Cs to fresh litter is proposed to explain the persistence of Chernobyl radiocaesium in the upper horizons of forest soils.