A New Architectural Perspective on Wind Damage in a Natural Forest

Wind damage is a significant driver of forest structure, ecology and carbon cyclingin both temperate and tropical regions, but most of the literature on wind damage focusses on conifer plantations. Previous studies in broadleaf forests have been limited by a lack of data on tree architecture, a problem that is potentially overcome by terrestrial laser scanning. Here we apply novel approaches to estimate the critical wind speedsat which trees will break in a temperate, deciduous forestplot in Wytham Woods, UK, using a combination of field data and finite element analysis. Ash trees ( Fraxinusexcelsior) tend to have lower critical wind speedsthan sycamores ( Acer pseudoplatanus), while English oak ( Quercus robur) are the most mechanically robust. This difference in critical wind speedis driven by tree size and architecture, rather than material properties. We observe a trade-off between critical wind speedand growth rate, both within and across species. Our estimates of critical wind speedsfrom field data are lower in summer than in winter, emphasizing the importance of the spring and autumn transition periods. Of the three species we studied, those with lower critical wind speedsdrop their leaves earlier in autumn, suggesting that the timing of leaf shedding may be under selection pressure to minimize risk of tree damage from winter storms. These results are tentative, but also intriguing and intuitive.