The phylogenetic impact on hydrogen isotopes in sugars and cellulose of woody plant species
Hydrogen isotope ratios in tree ring cellulose (δ2HC) have been recognized as a potential proxy for plant-climate interactions, plant physiology, and carbon metabolism. This goes along with recent studies showing species-specific δ2HC differences that cannot be explained by climatic conditions. However, systematic investigations on the phylogenetic impact on 2H-fractionations in carbohydrates of woody plant species are missing.
Here, we sampled leaves and twigs of 152 trees and shrubs, out of 73 species representing 48 genus, 19 families and 12 orders containing evergreen and deciduous angio- and gymnosperms groups in a common garden. We extracted leaf water and sugars, as well as twig water and the current year twig xylem cellulose for δ2H analysis, using a newly established hot water vapour equilibration method.
We found a clear phylogenetic impact on δ2H for sugars (>150‰) and cellulose (>80‰) across species growing under common conditions. The strongest differences were observed at the group level, with sugar and cellulose of gymnosperms being more 2H depleted than in angiosperm. Yet, we found no δ2H difference between leaf shedding types (evergreen vs. deciduous). Significant differences in δ2H of sugars and cellulose were also observed between different orders and families, but not between genus and species within a family or genus, respectively. The phylogenetic differences are likely explained by 2H-fractionation at the leaf level rather than by those in sink tissues.
Our study thus advances the knowledge for applying δ2HC in dendro and paleo sciences for the reconstruction of physiological and metabolic responses of trees to climate.