What factors influence the stem taper of Eucalyptus: growth, environmental conditions, or genetics?

Introduction Stem taper equations have been widely used for volume estimation to varied top diameter limits or for biomass calculations. However, their main drawback is that specific calibration is often necessary for each species or clone, and accounting for genetic and environmental effects is often a challenge. Methods In order to investigate this point, we decided to study the stem shape of several clones growing in Congo and to build an equation which should (1) be simple and have a good predictive quality, (2) have explicit parameters, and (3) be generic enough so as to be transposable to other species or to other eucalyptus clones. A sample of 1,623 trees, representing 16 genetically different clones selected for their contrasting growth patterns, was used. Results Even though these clones had different stem shapes, we successfully developed a single equation using the triplet (height/diameter at breast height/age) for all the clones. Conclusions The study also indicates that both growth environmental conditions and genetics have an impact on the stem shape, but that the genetic effect was fully realized through tree growth. The root mean square error for the over-bark diameter was 7 mm, allowing its use over the whole plantation area