Corrected heat capacity of wood for sap flow calculations

Values for the temperature-dependent heat capacity of wood were applied to correct the coefficient used to calculate sap velocity from heat pulse velocity, leading to values at 20 degrees C about 5% smaller than values calculated with the widely employed algorithm of Edwards and Warwick. Errors are larger at lower temperatures (7% at 10 degrees C) and so are more problematic at night and during cold periods.