Quantitative comparison of models of 137Cs cycling in forest ecosystems

The predictions of nine mathematical models of radiocesium (137Cs) cycling in forest ecosystems were evaluated through a model– data comparison on the basis of a scenario consisting of an acute dry deposition of 137Cs over a pine forest located in the Ukrainian territory affected by the Chernobyl accident (Zhitomir region). The forest compartments included in the comparisons were: organic and mineral soil layers, bilberries, fungi, roe deer, and different parts of the tree: bark, needles, shoots, and wood. The model predictions and the data agreed within a factor of 1.1 to 65 depending on the model and forest compartment. Statistically significant differences in the degree of agreement between model predictions and experimental data could be demonstrated for some models and forest compartments. The observed differences suggest that efforts for improving model predictions of radiocesium transfer to tree wood, needles, and shoots should be directed to a better simulation of the processes of root uptake and translocation of the radionuclide within the tree.