An architectural understanding of natural sway frequencies in trees

The relationship between form and function in treesis the subject of a longstanding debate in forest ecologyand provides the basis for theories concerning forest ecosystem structure and metabolism. Treesinteract with the wind in a dynamic manner and exhibit natural sway frequencies and damping processes that are important in understanding wind damage. Tree-wind dynamics are related to treearchitecture, but this relationship is not well understood. We present a comprehensive view of natural sway frequencies in treesby compiling a dataset of field measurement spanning conifers and broadleaves, tropical and temperate forests. The field data show that a cantilever beam approximation adequately predicts the fundamental frequency of conifers, but not that of broadleaf trees. We also use structurally detailed treedynamics simulations to test fundamental assumptions underpinning models of natural frequencies in trees. We model the dynamic properties of greater than 1000 treesusing a finite-element approach...