Worldwide correlations of mechanical properties and green wood density

Abstract

Premise of the study: The density of wood is highly correlated with the ability of stems and roots to resist bending or twisting, which is important for evaluating the mechanical behavior of trees. It also provides a measure of carbon storage, which is an important variable in modeling ecosystem processes and tree construction costs. However, most measurements of the density and mechanical properties of wood have little direct bearing on understanding the biomechanics of living plants because they are based on kiln- or air-dried samples. Methods: Here, we present and analyze the relationships between four important mechanical properties (Young' s modulus, the modulus of rupture, and the maximum strength in shearing and in compression) and the density of green wood (i.e., wood at 50% moisture content) from a worldwide, taxonomically broad spectrum of 161 species. Key results: These data indicate that each of the mechanical properties disproportionately increases across species with increasing green wood density, i.e., stems composed of denser green wood are disproportionately stiffer and stronger than stems with equivalent cross-sections composed of less dense green wood. Conclusions: Although denser wood may have a higher carbon construction cost, the mechanical benefits of denser woods likely outweigh the extra cost. © 2010 Botanical Society of America.