Effect of rising atmospheric CO₂ levels on grapevine yield and composition by the middle of the 21st century: what can we learn from the VineyardFACE?

Abstract

Atmospheric CO₂ levels have been rising continuously since the industrial revolution, affecting crop physiology, yield and quality of harvest products, and grapevine is no exception ^[1]. Most of previously reported studies used potted plants in controlled environments, and explored grapevine response to relatively high CO₂ levels, 700 ppm or more. The vineyardFACE, established in Geisenheim in 2012, uses a free air carbon dioxide enrichment (FACE) system to simulate a moderate (ambient +20%) increase in atmospheric CO₂ in a vineyard planted with cvs. Cabernet-Sauvignon and Riesling grafted on rootstock 161-49 Couderc and SO4, respectively. Using this experimental setup, we report a 3 years survey of grape yield, and berry composition responses to a moderate increase in ambient CO₂. An increase in net assimilation in leaves was observed for both cultivars, as well as a significant increase in fruit yield per vine. Berry size was not significantly affected, even though a general trend of larger berries was noted under elevated CO₂. Berry ripening dynamics and composition at harvest were largely unaffected by the CO₂ level increase, with the noticeable exception that anthocyanin levels tended to be lower under elevated CO₂, compared to ambient. Profiling of central carbon metabolism intermediates and branching points to secondary metabolism pathways confirmed this result in both cultivars. Must terpene content analysis in Riesling showed little impact of elevated CO₂, suggesting that its aromatic potential was probably unaffected. In conclusion, our results indicate that, although predicted mid-century CO₂ levels do have an impact on grapevine yield, grape composition and oenological potential will probably be largely unaffected. However, it is noteworthy that non significant but consistent trends have been observed throughout the years, suggesting that the continuous rise in CO₂ during the second half of the 21^st century may finally overcome berry metabolic plasticity and acclimation to elevated CO₂.

Acknowledgements: This work was supported by a PhD grant from the German-French University to C. Kahn (grant # DGSEIP/A1-3 N°2019-0203).

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