Tree crown economics

Abstract

Trees respond to global change in myriad ways, many of which may be linked to adaptations relating to tree crown architecture. However, there is a paucity of theory capable of predicting the adaptive importance and dynamics of crown architecture, most likely because of the difficulties involved in measuring the three-dimensional arrangement and orientation of tree leaves within individual crowns. Here, we describe a theory of tree crown economics, and use measurements from new lidar (light detection and ranging) instruments, UAVs (unoccupied aerial vehicles), and time-lapse camera imagery to identify support for two predictions of the theory, that (1) a light competition versus water use economic trade-off drives covariance among three tree crown functional traits (mean leaf angle, crown density, and crown rugosity), and (2) crown traits can drive spatial and temporal variability in near-infrared spectral reflectance and related ecosystem functions. Tree crown economic theory can complement leaf economic theory in helping ecologists map and model forest ecosystem responses to global change.