Title: Linear and non-linear functions of volume index to estimate woody biomass in high density young poplar stands
Abstract: Biomass estimations are very important in short rotation high density stands, but usu- ally require some destructive sampling.This paper discusses the potential use of allometric rela- tionships based on volume index (height x diameter squared) for accurate and non-destructive esti- mations of stem biomass.When using this approach, one implicitly assumes a constant conversion factor from stem volume index to real stem volume as well as a constant wood infradensity (stem dry mass versus fresh volume), both assumptions being questionable.Our results on five different poplar clones grown at two different sites (Afsnee, near Gent, Belgium and Orsay, near Paris, France) and under two different cultural management regimes underscore the following points: i) stem diameter measured at 22 cm aboveground and in two perpendicular directions is a relevant parameter to com- pute volume index in high density poplar stands; ii) power function regression equations fit the stem volume index versus stem dry mass relationship better than simple linear regressions; iii) attention should be paid to variation in wood infradensity, which ranged from 0.35 to 0.44 kg dm -3 in our study.short rotation forestry / high density plantations / Populus / volume index / allometric relationships Résumé -Fonctions linéaires et non linéaires de l'indice de volume pour l'estimation de la biomasse sèche de jeunes plantations de peupliers.L'estimation de la biomasse sur pied de parcelles denses cultivées en courtes rotations est généralement indispensable mais requiert le plus souvent des techniques destructives lourdes.Cet article discute de l'utilisation potentielle des relations allométriques utilisant l'indice de volume (hauteur du brin x carré de son diamètre à la base) pour l'estimation précise de la biomasse sèche de jeunes tiges de peuplier.Par ce type d'approche, on suppose impli-