Projecting future winegrape yields using a combination of V itis vinifera L . growth rings and soil moisture simulations, northern C alifornia, USA

Background and Aim We examined the feasibility of projecting future winegrape productivity by using V itis vinifera L. growth rings as a proxy to winegrape yields. Methods and Results We compared the climate response of V . vinifera radial growth rings and winegrape yields using DENDROCLIM 2002. We used the soil moisture model HYDRUS to determine if V . vinifera radial growth rings and winegrape yield can be modelled by soil moisture. Changes in V . vinifera radial growth were projected for 2020/99 C ommon E ra using downscaled general climate models. Climate influences V . vinifera radial growth and winegrape yield similarly (r = 0.53, P  = 0.001), indicating that V . vinifera can be used as a proxy for winegrape yield. Additionally, HYDRUS provided a robust model for vine growth and winegrape yield. Projected yields are forecasted to decrease significantly through time. Conclusions Based on future climate, winegrape yield showed a consistent and significant decreasing trend resulting in a 12.4% decrease by 2099. Significance of the Study Future climate conditions could create a decreasing trend in future winegrape yields, indicating that developing new irrigation systems or increasing irrigation volume will possibly be required for continued winegrape production in C alifornia.