Expressing leaf water and cellulose oxygen isotope ratios as enrichment above source water reveals evidence of a P clet effect

Abstract

There is an increasing ecological interest in understanding the gradients in H₂ ¹⁸O enrichment in leaf water (i.e. a Péclet effect), because an appreciation of the significance of the Péclet effect is important for improving our understanding of the mechanistic processes affecting the ¹⁸O composition of leaf water and plant organic material. In data sets where both source water and leaf water ¹⁸O data are available, we can evaluate the potential contribution of a Péclet effect. As an example, we recalculate data published earlier by Roden and Ehleringer (1999, Oecologia 121:467–477) as enrichments in leaf water (Δ_L) and cellulose (Δ_cell) above source water. Based on these recalculations, we present support for the relevance of a Péclet effect in leaves. Further, we demonstrate that the subtle variations in Δ_L and Δ_cell caused by a Péclet effect may be masked in experimental systems in which variation in the source water oxygen isotope ratio is considerable.