Expanding the wood anatomy economics spectrum: the correlates of vessel element lengths and pit apertures sizes in tropical forest trees

Plant functions all have an anatomical basis, but there are still major knowledge gaps in functional wood anatomy, especially of tropical trees. To examine the relationships between the functional anatomy of woody tissue in poorly studied rainforest trees, focussing on anatomical traits including vessel element lengths, pit aperture dimensions, grouping indices and xylem tissue fractions. We examined how these anatomical traits influence drought vulnerability indices, theoretical conductivity and structural traits such as wood density and stem diameter. We measured wood anatomical traits and higher-level structural traits from 25 Atlantic rainforest species and examined the relationships among these traits using univariate and multivariate methods. Regression models were used to explore how anatomical traits were related to drought vulnerability, theoretical conductivity, and wood structural traits. Vulnerability index was positively correlated with parenchyma fraction and both intervessel and vessel-ray pit aperture diameters. Theoretical conductivity was negatively associated with fibre fractions. Wood density was positively associated with fibre fraction and was also related to parenchyma and vessel fractions and vessel element lengths. Anatomical traits constitute an important economics spectrum, which could be positioned against leaf economics spectra to further our understanding of plant ecological and hydraulic strategies.