Canopy Management Effects on Temperature and CO2 Dynamics in Garnacha Grapes Under Mediterranean Conditions

Grape (Vitis vinifera L.) production is increasingly challenged by rising temperatures and drought conditions due to climate change, especially in Mediterranean regions. These conditions affect grapevine photosynthesis and berry metabolism, ultimately impacting yield and wine quality. This study aimed to quantify the dynamics of CO2 fluxes from Garnacha grapes in response to temperature, radiation, and ripening stage. An empirical model was developed to estimate the impact of canopy management on fruit carbon balance using data from vineyards in Majorca, where defoliation and grape cluster shading were applied. Our model accurately predicted CO2 release across ripening stages and environmental conditions. CO2 release under darkness increased during early ripening stages but declined as berries matured, while light conditions substantially reduced respiratory losses. Temperature significantly influenced CO2 release, with defoliation raising berry temperatures by over 4 °C and increasing maximum daytime carbon losses by approximately 17% compared to controls. Shading berries from defoliated plants mitigated these effects, lowering temperature and carbon losses to control levels. The study underscores the risks of heatwaves and elevated nighttime temperatures, which most drive respiratory carbon losses that shading cannot offset. These findings highlight the importance of adaptive canopy management, combining defoliation and shading, to sustain grape quality and yield under warming climates.