Optimizing the sample size to estimate growth in I-214 poplar plantations at definitive tree density for bioenergetic production

In Europe, over the last decades, the arboriculture for the biomass production for energetic purposes has significantly expanded and one of the species most used is the poplar. In order to maximize production, the flexibility of the cultivation algorithms becomes necessary. For this reason, it is necessary to apply monitoring tools for the evaluation and estimate of the wood productions, without significantly affect the production costs. In particular, for the estimate of the productions, the choice of the sample size is of particular importance. The aim of this study was to verify a simplified sampling approaches in poplar plantations characterized by constant tree density. The research was conducted in a poplar plantation on the Tuscan hills (Italy). The surveys was carried out each year for 13 years, from 4 to 16 years old. Through different statistical techniques, the change in the social position of each tree over time was evaluated. The results showed that the social position of each tree has been characterized by the first years after the plantation. Consequently, the estimate of the productions can be carried out by analyzing the current annual increment of 10% of the trees, included in the diameter classes around the medium-sized tree at the time of the survey. This study provided a valid method for forest managers characterized by a simplified approach useful to estimate the growth and yield of hybrid poplars. This method will permit reliable biomass estimates, but also a reduction of the costs in the sampling activities in the field.