Modeling grapevine performance with 'VitiSim', a weather-based carbon balance model: Water status and climate change scenarios

A carbon balance model (VitiSim) was used for assessing the effects of vine water status and different climate scenarios on the dry matter production and partitioning of 'Tempranillo' grapevines (Vitis vinifera L.) grown in two different Spanish regions. Inputs included weather daily variables, stem water potential measurements and vineyard system data. Partitioning is based on the supply and demand balance using relative sink strength coefficients when carbon supply is lower than organ demands. A new routine to consider the effect of vine water status on photosynthesis rate was implemented in the model. Experimental data from two Spanish locations, several seasons (2007-2011) and well-watered and water-stressed vines were used for validating the model. A sensitivity analysis showed that model outputs are greatly influenced by those inputs linked to light interception. Simulated dry matter productions were realistic even though in general the amounts were underestimated. VitiSim was able to reproduce the effect of water stress on dry matter production observed in the field. Then, the model was used to estimate vine dry mass in different locations within Spain and worldwide under the standard current meteorological condition and under two climate change scenarios. Results were in accordance with those commonly found in field studies. Hence, this model appears useful to estimate vine dry matter potential from few easily available inputs and to simulate the effects of deficit irrigation strategies on grape yield. Further routines must be implemented to enhance VitiSim predictive capabilities and reliability.