Reconstructed forest age structure in Europe 1950–2010

Abstract

Forest age structure is an important factor for understanding the history of forests, their current functioning and their future development. It is, for instance, crucial information to be able to assess sustainable harvesting potentials. Furthermore, since the development of growing stock and increment, and thus the patterns of net carbon exchange, are strongly affected by the age of the forest, information about the age structure is needed to understand the temporal variability of the greenhouse gas budgets and potential contributions of forest management (i.e. their additionality) to long-term removal of carbon from the atmosphere. European forests have changed drastically in recent decades, but to date no European level compilation of historical forest age structure data is available. In this study, country level historical age-class data was combined with a backcasting method to reconstruct the age-class structure for 25 European countries from 1950 to 2010 (total forest area in 2010: 118.3million ha). Based on the results, dynamic maps of forest age-class distributions on 0.25°×0.25° grid were generated, and the change in the forest age structure was analysed. Results show that the share of old forests (>100years) has decreased from 26% in 1950 to 17% in 2010, and the mean age over the studied area decreased from 67 to 60years. However, when looking at the change of the mean age from 1950 to 2010 at country level, there is a large variation between the countries. We discuss implications of the results and argue that the development of forest age structure contributed less than previously thought to the carbon sink in European forests from 1950 onwards.