Symbols, SI units and physical quantities within the scope of sap flow studies

Abstract

Some confusion was observed during the 7th International Workshop on Sap Flow (Seville, Spain, 21-24 October 2008) with respect to the use of symbols, units and physical quantities in presentations and during discussions. It was therefore decided at the end of the workshop that a technical note would be very useful with the aim to summarize the basics of the >Système International des Unités (SI)> and to focus on particular aspects that are relevant for sap flow studies. Starting from a number of standard papers that have been published in the past, an extra effort was made to put sap flow nomenclature against the physical background of plant-water relationships, of water flow in the soil-plant-atmosphere continuum and of transport equations for mass, heat and hydraulic flow. Information is given on the application of SI units and the main SI conventions. Tables are included for practical use of basic and derived SI units and for common abbreviations encountered in sap flow studies. An overview of a coherent nomenclature for sap flow studies, together with definitions of sap flow quantities, symbols and units is given as well.