Growing of willow (Salix sp.) plantations for energy production is an opportunity to get additional biomass-for-energy without increasing forest felling. This study objective was to create a non-destructive method for the estimation of aboveground yield of willows, which could be suitable for practical use in commercial short rotation willow plantations in Lithuania. Willow plantations of different 1–6-year old were chosen for the study. For the detailed measurements, the model stems and representative plant samples were taken.

    A strong dependency between the dry aboveground biomass of willow stems and stem diameter (R² = 0.95) was determined and the model M = 0.0003 × D^2.4311 (where M is the dry biomass; D is the diameter at 55 cm above the ground; a and b are constants of regression parameters) was worked out for the estimation of dry above-ground biomass of willow plantations. The study results showed that the annual dry aboveground biomass of willows varied in a wide range, from 2 to 10 t ha^-1 per year. The annual increment higher than 6 t ha^-1 was found for the older than 4 years plantations grown in more fertile soil (sandy loam), which was additionally fertilized and weeded; also, these plantations had lower initial plant density. The obtained tendencies suggest that it would be reasonable to prolong the rotation period of willow plantations in order to increase annual yield. The study results also supported the idea that more fertile sites should be preferred for cultivation of the commercial willow plantations.

   Keywords: Salix sp., short rotation, yield, non-destructive method