Biomass allocation and photosynthetic capacity of willow (Salix spp.) bio-energy varieties.

Producing woody biomass for energy in short rotation coppice requires physiological understanding of willow growth. We tested growth parameters for a select group of 12 willow varieties grown from cuttings for 90 days in a field experiment with four replicate blocks in cool-humid climate. Varieties differed significantly (p < 0.05) for leaf area, leaf chlorophyll concentration, biomass, and leaf allocation of biomass. Willow growth was functionally balanced as root biomass scaled positively with leaf area and the relationship between leaf chlorophyll concentration and leaf area remained non-significant. Mean plant biomass ranged from 3.8 g to 13.2 g for Salix discolor and the hybrid ‘Fabius’ (Salix miyabeana x S. viminalis), respectively. Plant biomass closely correlated with leaf area (R 2 = 0.83; p < 0.05). Accounting for leaf chlorophyll concentration slightly increased the predictive power of leaf area thus photosynthetic capacity. High photosynthetic capacity at low leaf allocation of biomass rendered ‘Fabius’ morphologically most suitable for producing woody biomass in willow short rotation coppices. The shoot-chlorophyll mass ratio is recommended for future screening of willow bio-energy species and hybrids.