Hydrogen isotope fractionation in carbohydrates of leaves and xylem tissues follows distinct phylogenetic patterns: a common garden experiment with 73 tree and shrub species

Abstract

Summary Recent methodological advancements in determining the nonexchangeable hydrogen isotopic composition (δ2Hne) of plant carbohydrates make it possible to disentangle the drivers of hydrogen isotope (2H) fractionation processes in plants. Here, we investigated the influence of phylogeny on the δ2Hne of twig xylem cellulose and xylem water, as well as leaf sugars and leaf water, across 73 Northern Hemisphere tree and shrub species growing in a common garden. 2H fractionation in plant carbohydrates followed distinct phylogenetic patterns, with phylogeny reflected more in the δ2Hne of leaf sugars than in that of twig xylem cellulose. Phylogeny had no detectable influence on the δ2Hne of twig or leaf water, showing that biochemistry, not isotopic differences in plant water, caused the observed phylogenetic pattern in carbohydrates. Angiosperms were more 2H‐enriched than gymnosperms, but substantial δ2Hne variations also occurred at the order, family, and species levels within both clades. Differences in the strength of the phylogenetic signals in δ2Hne of leaf sugars and twig xylem cellulose suggest that the original phylogenetic signal of autotrophic processes was altered by subsequent species‐specific metabolism. Our results will help improve 2H fractionation models for plant carbohydrates and have important consequences for dendrochronological and ecophysiological studies.