Genetic and Environmental Influences on First Rotation Shrub Willow (Salix spp.) Bark and Wood Elemental Composition

The elemental composition of woody biomass has important consequences for both energy conversion processes and agronomic management of nutrient budgets. In this study, the largest shrub willow yield trial dataset in North America has been leveraged to evaluate the effects of cultivar, growing environment and their interaction on elemental concentrations and content in shrub willow. Stem samples from six commercial cultivars in four trial locations in the Northeastern USA were separated into bark and wood and analyzed for C, N, and H by combustion and for elemental composition by ICP-OES. A second set of samples in the form of whole biomass from the same six cultivars and from six additional trial locations were also analyzed, totaling to 252 total independent observations. A Salix purpurea cultivar had greater N, Mg, and Fe concentrations in bark, whereas S. miyabeana cultivars had high Ca concentrations in both bark and wood. Hybrids between these two species displayed intermediate values. Multivariate analyses of the broader suite of biomass samples showed strong environmental effects on elemental composition, but there were a number of significant cultivar x location interactions. Nutrient export rates at harvest were largely a function of yield. These results showed potential cultivar-specific differences in nutrient uptake, but more broadly the results provide a robust method for nutrient management planning. These findings suggest a capacity to exploit existing genetic resources for improving phytoremediation and excess nutrient management projects.