Plants in changing climate: Linking isotope effects, manipulation experiments, plant archives and modelling to derive long-term ecophysiogical signals

Abstract

Conventional isotope applications in plant ecophysiology measure isotope ratios (e.g. δ2H, δ13C) of whole molecules. However, it is well established that isotope abundance varies AMONG the CH groups of metabolites (isotopomers), because they are biochemically distinct. This variation reflects enzyme isotope fractionations and encodes metabolic information, but it is unclear how these fractionations get transferred into signals that can be recovered from archives of plant material.Here, we will describe physical and biochemical mechanisms of hydrogen isotope fractionation in plants and compare their magnitudes. Based on observations for hydrogen isotope transfer in plants, we present a model for the extraction of H isotope signals from plant archives.Plant responses to increasing CO2 are critical for plant productivity and as climate feedbacks. As CO2 is the substrate for photosynthesis, plants should benefit from increasing CO2, but the magnitude of this “CO2 fertilization” disagrees with biomass estimates. Photorespiration is a side reaction of photosynthesis that reduces C assimilation in most vegetation, therefore its response under climate change is critical for the future C cycle. Photorespiration should be reduced by increasing CO2 yet exacerbated by rising T, but its response is not well captured in models, adding large uncertainty to C cycle predictions.To retrieve ecophysiological signals from plant archives, we use manipulation experiments to develop proxies for plant C fluxes, based on intramolecular abundance variation of 2H and 13C, detected by NMR. We then retrieve these proxies from archives such as tree-ring series, to derive metabolic responses over long time scales, and to improve global vegetation models.Here we will describe progress in tracking isotopomer signals from controlled experiments to plant archives, and results on long-term trends of photorespiration in response to increasing atmospheric CO2 for two globally important ecosystems. In Sphagnum species, we link trends in photorespiration to the C sink of boreal peatlands. In the tropical tree species Toona ciliata, we describe long-term trends in photosynthetic efficiency.As intrinsic quantities, isotope data are well suited to report on metabolic shifts, but not about fluxes in absolute numbers. Therefore we use isotopomer data as input for the LPJ-GUESS Ecosystem Model, to translate isotopomer-derived changes in photorespiration into trends in ecosystem C fluxes.References:Augusti A. et al (2008) Chem. Geol. 252, 1-8, doi 10.1016/j.chemgeo.2008.01.011Ehlers I. et al (2015) PNAS 112, 15585-15590 doi 10.1073/pnas.1504493112Walker AP. et al (2021) New Phytol 229, 2413-2445 doi 10.1111/nph.16866Serk H. et al (2021) Scientific Reports 11, 24517 doi 10.1038/s41598-021-02953-1Zwartsenberg SA. et al (2025) New Phytol in press.

Plant phenotyping relevance

植物アーカイブから光合成・光呼吸などの生理状態を推定する同位体・NMRプロキシとモデルを開発・適用しており、植物表現型の取得・抽出が中心である。

Code and data availability

The supplied blocks contain only an EGU abstract describing isotopomer-based phenotyping and LPJ-GUESS modelling. No public dataset, image, code, model, or supplement with availability language or URL is provided; cited references are prior work.

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