Measurement methodologies: linking sap flow measurements with hydraulics of woody plants at different levels of organization

GUILLERMO GOLDSTEIN, FABIÁN G. SCHOLZ, SANDRA J. BUCCI AND PIEDAD CRISTIANO

Workshop; 7 WORKSHOP OF SAP FLOW; 2013

The analysis of sap flow methodologies will be done in the context of the hydraulic functioning of woody plants but it will go beyond sap flow technical aspects. We will discuss latest applications of classical and broadly disseminated sap flow methodologies and the relationship between internal water movements and plant hydraulics. Water moves not only axially from soil to leaves but also from plant to soil and radially between the active xylem tissues and the cortex in the bark tissues (including the phloem). For axial water movement heat has been used as the main tracer for non invasive and continuous monitoring of long distance water transport (e.g. heat pulse, heat dissipation, heat balance methodologies). The assumptions, practical considerations, limitations and advantages of each method will be briefly discussed. Examples of competing water sinks such as the transpiring leaves during the day and night, reverse flow (from plant to soil), water storages along the roots to leaves pathways and transpiring barks will be provided in the context of the hydraulic architecture of the plant and the sap flow technique used in each case. New approaches to assess the role and magnitude of internal water storages in stems, an important component of the water transport system, will be presented. This discussion will take into account the biophysical differences between water storage capacity and capacitance and its functional significances. A new non invasive technique for monitoring continuously volumetric water content, based on the dielectric permittivity of the tissue will be introduced.  Radial water transport between xylem and phloem tissues, its directions and driving forces and hydraulic connectivity, as well as methods for assessing water fluxes at whole forest ecosystem levels will be discussed.