On the leaf inclination angle distribution as a plant trait for the most abundant broadleaf tree species in Europe

Leaf angle distribution influences forest canopy processes like radiation balance, photosynthesis, and evapotranspiration. Indeed, a strong sensitivity to variability in the leaf angle distribution is reported for many models. Difficulties in conducting leaf angle distribution measurements limit data availability and explanations of its species-specific phenology and variation across environmental gradients. This leads to the situation that leaf angle distribution is often the most poorly constrained model parameter. Here, we report a spatial survey of leaf angle distributions and their seasonal and vertical changes for five most abundant forest broadleaf tree species in Europe according to the spatially representative Level I ICP Forests monitoring network. Although we found evidence that leaf angle distribution might be considered a species-specific trait for all studied species except Betula pendula, we advocate the use of leaf angle distributions obtained from actual leaf inclination measurements whenever possible. Data on leaf angle distributions for 50 widespread forest broadleaf tree species in Europe is also reported.