A combined simulation model of Scots pine, Norway spruce and Silver birch ecosystems in the European boreal zone

A combined (hybrid) spatially distributed individual-based model of a forest ecosystem (EFIMOD) has been elaborated for a Scots pine, Norway spruce and Silver birch stand of the European boreal tone. This model represents a realization of the concept of a 'single plant ecosystem' (Chertov, 1983a). EFIMOD simulates the biological cycle of every tree with an expedient soil pot in a stand. The tree models calculate the total leaf, fine root and litter mass using a set of the characteristic ecological tree parameters. The soil sub-model simultaneously allows for a calculation of the rate of tree litter and soil organic matter mineralization with the corresponding carbon dioxide and nitrogen release for plant growth. The validation of the model, with various initial stand densities on different soils, shows a relatively realistic picture of tree growth, stand self-thinning and soil changes. Convergence of leaf/needle mass has been observed at various initial stand densities. An application of EFIMOD for a qualitative evaluation of climate change effects shows fairly different reactions of the mentioned ecosystems in relation to productivity, leaf mass and soil organic matter pool. There is a shift in the timing of the first intensive self-thinning in young stands. A strong oscillation of leaf/needle mass has also been observed. (C) 1999 Elsevier Science B.V. All rights reserved.