MICROMETEOROLOGICAL AND SAP FLOW MEASUREMENT OF WATER VAPOUR EXCHANGES IN OLIVE: SCALING UP FROM CANOPY TO ORCHARD

A comparison of water consumption evaluated at tree and orchard level was carried out in a commercial olive orchard located in Sicily using up-scaled sap-flow evapotranspiration estimations and eddy covariance measurements. Sap flow probes were installed on olive trees placed in one of the four plots characterizing a heterogeneous orchard. Trees were chosen, from a preliminary footprint analysis, in correspondence to the peak of the “relative normalized contribution” to flux for the prevailing wind conditions measured by an eddy covariance station localized in the central part of the orchard. Tree-age and planting density as well as main tree and orchard characteristics (Leaf Area per tree, within plot distribution of Trunk Cross Sectional Area TCSA, height and canopy diameter), were used to characterize the plot-to-plot differences. Both TCSA and LAI adopted as scaling parameters showed a high performance. A good agreement between ETec (daily integral of EC-estimated evapotranspiration) and ETsf (up-scale sap flow ET estimate) was found in correspondence of limited canopy or soil evaporation conditions (absence of rain, dew, irrigation supply). Eddy covariance can be considered a reliable reference for up-scaled sap flow estimations of ET, and sap flow can be used as a replacement (proxy) of eddy covariance when atmospheric conditions invalidate the application of this technique to assess ET.