Christopher Bahr:
Virtual Riesling – a functional-structural grapevine model for climate impact research


Christopher Bahr is employed at Hochschule Geisenheim University at the Department of Modeling and Systems Analysis. He is specialized in functional-structural plant modeling and currently working on his PhD project “Modelling virtual Riesling canopies for reducing sunburn risks in grapevine (Vitis vinifera L.) berries”. This project is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) –Projektnummer 449374897.

Presentation Abstract

Virtual Riesling isa functional-structural grapevine model used at Hochschule Geisenheim University for climate impact research. The model is based on data of the experimental site of the Geisenheim VineyardFACE experiment (Schmidt et al. 2019). In this free air carbon dioxide enrichment facility Vitis vinifera cv. Riesling and Cabernet Sauvignon are grown either under ambient or elevated carbon dioxide (CO2) conditions (the latter with 480 ppm, estimated conditions of 2050, see Wohlfahrt et al. 2018). Our team digitizes Riesling vines in this facility and analyzes the data to gain information on plant growth and organ topology.
With this information we have developed Virtual Riesling, a model for simulating daily growth of Riesling vines in a virtual vineyard based on grapevine and trellis set-up of the Geisenheim VineyardFACE facility. In the model plant development is temperature-sensitive, vertical shoot positioning is implemented and leaf removal can be applied. A light model for direct and diffuse sun light allows to analyze light absorption data of the canopies (Bahr et al. 2021a; Schmidt et al. 2019).

With Virtual Riesling we have conducted several simulation studies: first, using historical weather data to analyze the effects of different temperature courses on canopy growth and leaf area distribution (Schmidt et al. 2019); then, we analyzed light absorption in the context of the dynamic growth of grapevine canopies in a vineyard including shoot positioning (Bahr et al. 2020); next, we compared virtual grapevine growth based on elevated CO2 with growth based on ambient CO2 conditions and the effect on architectural differences and phenology (Schmidt et al. 2020); and most recently, we compared leaf removal at two different heights and the effects on light absorption throughout the simulation period (Bahr et al. 2021a).

These studies have shown that plant architecture and light distribution in canopies of Virtual Riesling simulations are sensitive to abiotic environments and plant management. Next, a berry sunburn model will be implemented into Virtual Riesling to study effects of changing environmental conditions and plant management on berry sunburn occurrence in future climates. Virtual Riesling could then be a useful tool for identifying promising strategies to reduce berry sunburn occurrence in future vineyards (Bahr et al 2021b). 

Bahr Christopher1 (, Schmidt Dominik1, Friedel Matthias2, Kahlen Katrin1
1Dpt. of Modeling and Systems Analysis, Hochschule Geisenheim University, Geisenheim, Germany;
2 Dpt. of General and Organic Viticulture, Hochschule Geisenheim University, Geisenheim, Germany;

Bahr C., Schmidt D., Friedel M., Kahlen K. (2020). Shedding light on virtual Riesling canopies (Vitis vinifera L.). [abstract]. in iCROPM2020- Crop Modelling for the Future (Montpellier). 54-55.

Bahr C., Schmidt D., Friedel M., Kahlen K. (2021a). Leaf removal effects on light absorption in virtual riesling canopies (Vitis vinifera). in silico Plants 3 (2).

Bahr C., Schmidt D., Friedel M., Kahlen K. (2021b). Missing Links in Predicting Berry Sunburn in Future Vineyards. Frontiers in Plant Science, 12.

Schmidt D., Bahr C., Friedel M., Kahlen K. (2019). Modelling approach for predicting the impact of changing temperature conditions on grapevine canopy architectures. Agronomy 9, 426.

Schmidt D., Bahr C., Friedel M., Kahlen K. (2020). In silico analysis of grapevine architectural response to elevated CO2. [abstract] FSPM2020: Towards Computable Plants (Hannover). 76–77.

Wohlfahrt Y., Smith J. P., Tittmann S., Honermeier B., Stoll M. (2018). Primary productivity and physiological responses of Vitis vinifera L. cvs. under Free Air Carbon dioxide Enrichment (FACE). Eur. J. Agron. 101, 149–162.