Simulating berry sunburn in virtual vineyards

Abstract

Context and purpose of the study. Berry sunburn in vineyards is a recurring disorder that can cause severe yield loss. As sunburn observations are often associated with heat waves, a link to climate change is likely. Sunburn depends on local heat exposure on the berry surface and its susceptibility to sunburn. Since sunburn only occurs when berries are exposed to direct sunlight, the canopy architecture itself may already protect berries from sunburn. Therefore, this study aimed to provide a model-based analysis of berry sunburn that captures temporal and spatial dynamics in vineyard systems. 

Materials and methods. We advanced the functional-structural grapevine model Virtual Riesling for conducting in silico studies on berry sunburn. This temperature-sensitive dynamic architecture model was used to create natural, realistic environments covering a variety of typical light conditions within a virtual canopy. Our simulation study involved several possible future temperature scenarios on differently oriented vineyards. Virtual plant management included vertical shoot positioning, cutting, and leaf removal.

Results. Simulation results confirmed the pivotal role of ambient temperatures in the occurrence of sunburn, but also highlighted the particular importance of the timing of the environmental conditions. When virtual berries were shaded by surrounding leaves during times of high temperatures, they likely did not get sunburned. Azimuthal crossing, i.e., the alignment of sun azimuth and row orientation, takes place at different times in differently orientated vineyards. In the virtual vineyards, this significantly affected the progression of the sunburn over the day. As anticipated, the simulations conducted with increased temperatures led to higher sunburn damages, but only when critical temperatures coincided with low self-protective shading. Consequently, e.g., a vineyard with a northeast-southwest orientation may have greater resistance to sunburn after leaf removal than a vineyard with a north-south orientation.

Our study provided first insights into favorable canopy configurations and a valuable expandable data set for in-depth analysis. The approach allowed us to identify critical periods of sunburn occurrence related to environment and vineyard set-up. This makes it a suitable tool for developing mitigation strategies that focus on the interaction between plant architecture and environmental conditions.