Estimating root biomass in Salix viminalis x Salix schwerinii cultivar oOlofo using the electrical capacitance method

Non-destructive assessment of root systems is important in order to understand and optimise the potential of resource capture and allocation by the plant. We studied the relationships between electrical capacitance (EC) and the below- and above-ground biomass of willows. Cuttings of Salix viminalis x Salix schwerinii cv. Olof were maintained in pots and root development was followed up using a portable capacitance meter over the course of 2.5 months. Pot observations were compared with excavation of two-year-old established trees. A strong significant linear relationship (R2 = 0.81, p 0.001) was obtained between EC and root biomass (dry weight [DW]) for the pot experiment. EC also showed good correlations with stem and leaf biomass, as well as with stem height. In the excavated willow trees, there was a strong logarithmic relationship between EC and root biomass (R2 = 0.66, p 0.001). These results suggest that EC is a good estimator of below-ground biomass in willow and may become useful in screening varieties for differences in root biomass traits, especially in distinguishing below-ground resource allocation at an early stage.