Assessment of plant water status variability by thermography: comparing ground measurements with remote imaging

Abstract

Remote sensing provides a fast alternative for traditional in situ water status measurement in vineyards. Canopy temperature measurements derived from aerial thermography were compared to thermal and plant physiological ground-truthing data of single vines in a low and high vigour zone. The experimental trial was carried out in a vineyard of Colli Piacentini, located in the province of Piacenza (Italy). Statistical methods were used to evaluate the correlation between acquired temperatures and plant physiological parameters. Results by simple regression showed significant correlation, with coefficient of determination (R2) higher than 0.6 for the indices studied; R2 higher than 0.7 for correlations of thermal data with vine water status' and R2 higher than 0.9 for correlations deriving from data of vines of the high vigour zone. These results propose that thermography is a good estimator for vine water status and photosynthetic activity. However, records of aerial and proximal thermal imaging are not congruent but have a similar behaviour and correlation when comparing to ground measurements. Therefore, when only using thermography, vine water stress is not only indicated by a higher canopy temperature in absolute values but is an implication of temperature variation within the field over time. Comparative measurements can improve assessing vine water status by observing changes in canopy temperature