Evaluating different techniques for estimating biomass in short-rotation willow plantations

Abstract

The hallmark of any successful purpose-grown willow production system involves regular monitoring of willow growth to apply timely management techniques for supporting increased productivity, but also timing harvest for maximizing profit. The objective of this study was to compare a conventional allometric technique (i.e., defined by a simple empirical relationship between stem size and mass) with a novel alternative method measuring light attenuation through the willow crop canopy (i.e., Stem Area Index; using a LAI-2000 Plant Canopy Analyzer) and relate these data to harvested willow biomass. Two different hybrid willow clones with contrasting growth form, either single stem (Charlie) or multi-stem (SV1), were studied. The observed allometric models were stronger for multi-stemmed SV1 (R2 = 0.81) compared to the single-stemmed Charlie (R2 = 0.67); however, the allometric relationships in this study were not as robust as those typically reported in the literature for willow and is probably due to the uncoppiced management of the study plantation. Given the strong correlations (R2 > 0.98) between Stem Area Index and harvested willow biomass, regardless of growth form, it appears that this novel mensurative technique is a promising alternative to conventional allometry. It is prudent to develop a rapid, cost-effective, and non-destructive mensurative technique yielding reliable biomass estimates, for supporting effective management decisions in a timely manner.