Linear and non-linear functions of volume index to estimate woody biomass in high density young poplar stands

Biomass estimations are very important in short rotation high density stands, but usually require some destructive sampling. This paper discusses the potential use of allometric relationships based on volume index (height x diameter squared) for accurate and non-destructive estimations 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 compute 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.