EGU22-5772
https://doi.org/10.5194/egusphere-egu22-5772
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

The phylogenetic impact on photosynthetic and post-photosynthetic hydrogen isotope fractionation in 73 tree species

Philipp Schuler1, Valentina Vitali1, Matthias Saurer1, Arthur Gessler1,3, Nina Buchmann2, and Marco Lehmann1
Philipp Schuler et al.
  • 1Swiss Federal Institute for Forest, Snow, and Landscape Research WSL, Birmensdorf, Switzerland
  • 2Department of Environmental Systems Science, Group of Grassland Sciences, ETH Zurich, Zürich, Switzerland
  • 3Department of Environmental Systems Science, Institute of Terrestrial Ecosystems, ETH Zurich, Zürich, Switzerland

While carbon (δ13C) and oxygen (δ18O) isotopes in tree-ring cellulose are widely used as climatic and physiological proxy in dendro sciences, the processes that are affecting the fractionation of non-exchangeable hydrogen (δ2H) isotopes and shaping the tree-ring δ2H profile are barely understood and thus not widely applied yet.

To establish a first comprehensive comparison of the photosynthetic and post-photosynthetic 2H-fractionation of northern-hemisphere trees, we sampled leaves and twigs of 152 trees representing 73 species, 48 genus, 19 families and 12 orders containing both evergreen and deciduous angio- and gymnosperms in a common garden, as well as diurnal cycles (6 species from 6 families) of leaf sugar. We extracted leaf water and sugar, as well as twig water and the current year twig xylem cellulose for δ2H analysis. Leaf sugar and twig cellulose were measured with a newly established hot water vapour equilibration method.

Our findings show a wide variation in 2H-fractionation between species growing at a common site. The measured δ2H values ranged from -63.5 to –33.4‰ for xylem water, between -22.3 and +28.5‰ for leaf water, between -160.9 and +12.6‰ for leaf sugar and between -79.1 and +6.9‰ for twig cellulose. The biological fractionation between leaf water and leaf sugar ranged between -169.6 and +24.2‰ and between leaf sugar and current year twig cellulose from -34.6 to +116.8‰. In general, sugar and cellulose of gymnosperms were significantly more 2H depleted than those of angiosperm species, with no impact of the leaf shedding behaviour to the measured δ2H values. We observed significant differences in the δ2H values between different orders and families, but not between genus and species within a family or genus, respectively. This pattern indicates that the photosynthetic and post-photosynthetic 2H-fractionation are based on conservative metabolic reactions with a generally low mutation rate.

Additionally, the results from our diurnal sampling of leaf sugar are showing first evidence for a dynamic and species-specific nature of the photosynthetic 2H-fractionation, which is in contrast to current models, which are assuming the same constant 2H-fractionation processes for all plant species.

We conclude that the here presented results will help to improve our understanding of the mechanisms influencing the δ2H values of leaf sugar and tree-ring cellulose and thus enabling the scientific community to use δ2H in tree-ring cellulose as the third isotope-proxy for dendrochronological studies.

How to cite: Schuler, P., Vitali, V., Saurer, M., Gessler, A., Buchmann, N., and Lehmann, M.: The phylogenetic impact on photosynthetic and post-photosynthetic hydrogen isotope fractionation in 73 tree species, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5772, https://doi.org/10.5194/egusphere-egu22-5772, 2022.

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