UC Davis

Atmospheric CO2 has increased over the past several decades at a rate faster than all previous natural increases and is likely to increase by another 15% by 2050. Currently, impacts of elevated atmospheric CO2 on growth, performance, and production in viticulture are not well understood and difficult to decouple from other climatic variations (e.g. water availability and warming). This study was conducted in 2019 at the Free-Air Carbon dioxide Enrichment (FACE) at the University of Geisenheim established in 2012 to assess effects of elevated CO2 (eCO2) (+20%) on physiological, structural, and morphological responses of Vitis vinifera cv. Cabernet Sauvignon and Riesling. The baseline ambient CO2 (aCO2) was 411 ppm in 2019 while the eCO2 treatment was 480 ppm. To evaluate the physiological effects, CO2 response curves, leaf gas exchange measurements, and isotopic data were collected from elevated and ambient blocks. To assess the morphological effects, the same leaves used for gas exchange from ambient and elevated blocks were collected and scanned using X-ray microcomputed tomography (micro-CT) at Swiss Light Source. There were few significant differences between treatments on the parameters tested suggesting that, over time, there may be an acclimation effect of some Vitis vinifera species to moderate eCO2.