Large-scale biogeochemical research with particular reference to forest ecosystems, an overview

•Predictive models require a range of scales.•Linkages across multiple scales are investigated.•A dual-constraint approach is most suitable to verify regional budgets.•The approach was successfully applied for Europe, Siberia and Africa.

The following overview summarizes observational and experimental approaches to study plant and ecosystem processes, starting from physiological mechanisms up to continental carbon balances mainly based on Eurosiberian data. It is shown that different observational scales are needed to interpret and predict phenomena at various resolutions and that observational studies cannot replace controlled experiments. Both sources are essential.