Résumé
In clonal plantations of Eucalyptus trees, inter-tree variations are limited. However due to the very fast growing, wood properties in young trees exhibit very important variations depending on the specimen location inside the log.; most of these variations are "time" dependant: 9 primary juvenility is related to tree age at the time of the creation by the apical bud of the new log portion at height Hsecondary juvenility is related to cambium age at the time of generation of a new xylem ring located at a distance R from corresponding pith of the log portion heartwood formation (duraminisation) is related to wood age after cambial cell division.The study of tree architecture as well as wood anatomy shows that primary and secondary growth are continuous in the case of Eucalyptus hybrids in Congo, so that no growth limits can be found. Only height and radial position (distance from pith) can be used as time indicators inside the trunk. Results from experimental and industrial clonal plantations in Congo can be used to built height/age, D13H/age andsapwood thickness at breast height/age standard relationships for a clone x site situation. Moreover stem analysis on the1 cl ame plots can bring informations on stem diameter, sapwood and bark thicknesses at different height in the stem for a clone x age x site situations. It is then possible to built two dimensional diagrams describing discrete growth units after choosing a realistic time step for these very fast growing trees. hese growth units are defined by two time dependant parameters describing primary and secondary growth. Assuming local homogeneity inside one growth unit, wood properties can be measured for this one.Some results about specific gravity. longitudinal modulus of elasticity, (.7cl growth stains and stresses are discussed for one hybrid Eucalyptus uroph);lla x alba clone. (Résumé d'auteur)