Reflectance modeling of vineyards under water stress based on the coupling between 3D architecture and water balance model

摘要

A vineyard architecture model coupled with a soil water balance model is used to explore the links between vineyard reflectance in different scenarios of plant water stress, taking into account meteorological data, agricultural data and site specificinformation to produce virtual 3D scenes describing vineyard canopies. The ability of the model to predict LAI dynamics was evaluated against destructive measurements in four experimental sites producing reasonable results (RMSE=0.30). The model was runin direct mode to simulate vineyard canopies with three different levels of water stress (no irrigation, intermediate irrigation and full irrigation). Canopy reflectance and NDVI vegetation index were calculated for the simulated scenes using ray-tracingtechniques. The results show that vineyard water stress can be detected in vineyard canopies through LAI estimation from canopy reflectance and NDVI. However, the links between LAI and reflectance are highly influenced by canopy architecture at zenith viewings: the effect of agricultural practices as trellis system or pruning should be taken into account to interpret correctly reflectance data. The sensitivity of reflectance to vineyard architecture depends on the viewing direction: at zenith the contribution of row dimensions and leaf spatial distribution is maxima, while at viewing zenith angles > 60 deg and azimuth perpendicular to rows, sensitivity of reflectance to LAI is enhanced, with a small influence of vineyard architecture.