Poplars (Populus spp.) are widely used in short rotation forestry (SRF) where plantations are characterized by high stool and shoot density. At the end of the first rotation coppice (2010-2012), one native P. nigra provenance from southern Italy (“Ripiti” stream, Campania region) and one selected hybrid P. xgenerosa “Hoogvorst” clone were examined to describe stand structure and determine the dry biomass yield. Living shoots diameter distribution was analyzed with the two- parameter Weibull probability density function (PDF). Aboveground woody volume was estimated according to general formula and equivalent dry biomass was obtained via woody basal density. According to their heights the shoots were classified as dominant, intermediate and suppressed and dry biomass was estimated for each class. Using a two-parameter Weibull PDF it was possible to soundly describe diameter distributions of the two selected Populus species. Moreover, a different biomass partitioning pattern between the two species was observed in our experimental SRFs: black poplar allocated biomass between dominant and intermediate shoots, while in hybrid poplar this occurred mainly on dominant shoots. The observed partitioning pattern, which is most likely due to a contrasting (i.e. natural and man-made) selection history of the two species, might affect the biomass physical characteristics of wood and SRF plantation management.