Understanding the specific vulnerability of forest species to disturbance is essential for predicting the evolution of our forest ecosystems in the context of climate change. Using data from national inventories in France, Spain and Finland, researchers have modelled the probability of mortality of 40 European tree species on the basis of various parameters.
The study shows that the vulnerability of species to disturbance can be fairly well explained by a combination of different characteristics. Resistance to fire, for example, is linked to the size of the tree: small trees are less resistant to fire than large ones. Fire-sensitive species also have thin bark, are not very tolerant of shade and have a high C/N ratio in their leaves.
Storm-sensitive species have a high height to diameter ratio at 1.30 m (H/d), low wood density and high height growth. In softwoods, vulnerability to storms increases with shade tolerance, and vulnerability to fire decreases with wood density.
Whatever the type of disturbance, softwoods are the most vulnerable and hardwoods, mainly of the Quercus genus, the least.
The study identified key relationships between the functional traits of species and their vulnerability to disturbance, enabling more reliable predictions to be made about the evolution of the structure and composition of future forests on a broad spatial scale. It finds a synergy between strategies leading to high resistance to different disturbances and different traits such as high wood density or low growth. For example, high wood density will limit the spread of decay in trees injured by disturbance, increase resistance to cavitation in the xylem, and hence resistance to drought.
Researchers noted that most of the traits associated with high vulnerability to disturbance tend to be characteristics of productive species. Foresters can therefore expect that, in the future, selection will focus on less productive but more resistant species.