The effect of measured and estimated soil hydraulic properties on simulated water regime in the analysis of grapevine adaptability to future climate

In the last years many research works have been addressed to evaluate the impact of future climate on cropproductivity and plant water use at different spatial scales (global, regional, field) by means of simulationmodels of agricultural crop systems. Most of these approaches use estimated soil hydraulic properties, throughpedotransfer functions (PTF). This choice is related to soil data availability: soil data bases lack measured soilhydraulic properties, but generally they contain information that allow the application of PTF . Although thereliability of the predicted future climate scenarios cannot be immediately validated, we address to evaluatethe effects of a simplification of the soil system by using PTF. Thus we compare simulations performed withmeasured soil hydraulic properties versus simulations carried out with estimated properties. The water regimesresulting from the two procedures are evaluated with respect to crop adaptability to future climate. In particularwe will examine if the two procedures bring about different seasonal and spatial variations in the soil water regimepatterns, and if these patterns influence adaptation options.The present case study uses the agro-hydrological model SWAP (soil-water-atmosphere and plant) and studiesfuture adaptability of grapevine. The study area is a viticultural area of Southern Italy (Valle Telesina, BN) devotedto the production of high quality wines (DOC and DOCG), and characterized by a complex geomorphology andpedology.The future climate scenario (2021-2050) was constructed applying statistical downscaling techniques to GCMsscenarios. The moisture regime for 25 soils of the selected study area was calculated by means of SWAP model,using both measured and estimated soil hydraulic properties. In the simulation, the upper boundary conditionswere derived from the regional climate scenarios. Unit gradient in soil water potential was set as lower boundarycondition. Crop-specific input data and model parameters were estimated on the basis of scientific literature andassumed to be generically representative of the species.From the output of the simulation runs, the relative evapotranspiration deficit (or CropWater Stress Index - CWSI)of the soil units was calculated. Since CWSI is considered an important indicator of the qualitative grapevineresponses, its pattern in both simulation procedures has been evaluated.The work was carried out within the Italian national project AGROSCENARI funded by the Ministry forAgricultural, Food and Forest Policies (MIPAAF, D.M. 8608/7303/2008)