His main research interests are in the long-term dynamics of forest ecosystems under environmental change, particularly successional dynamics in mountain forests and changes in the disturbance regimes (e.g. wildfires).

From 1997 to 2007, he was involved in various parts of the International Geosphere-Biosphere Programme (IGBP), including the project Global Change and Terrestrial Ecosystems (GCTE), the Mountain Research Initiative (MRI) and Human Impacts on Terrestrial Ecosystems (HITE). He was a Contributing Author or a Reviewer for the second, third und fourth Assessment Reports of the Intergovernmental Panel on Climate Change (IPCC) in Working Group II.