Studies on wood basic density (BD) vertical variations become essential to predict more accurately the within-stem distributions of biomass and wood quality in the forest resource. The vertical variation of wood BD in the stem has been little studied until now, most BD studies being based on measurements taken at breast height. The main objective of this work was to observe and to understand the patterns of vertical BD variation within stems in relation to classical dendrometric variables and to propose relevant equation forms for future modelling. Two softwood species were studied: Abies alba and Pseudotsuga menziesii. Contrasted thinning intensities were studied including strongly thinned plots versus control plots without thinning. BD was most of the time highest at the base of the tree for both species. Then, after a strong decrease from the base of the tree, an increase in BD was often observed towards the top of the tree especially for A. alba. The variation in BD with height was stronger for the unthinned plots than for the heavily thinned ones of A. alba. The opposite was observed for Ps. menziesii. The modulation of growth rate and tree size through thinning intensities modifies the observed vertical variations in BD. Two types of biexponential models were proposed to describe BD variations. The first model used the height in the stem and classical easily-measurable tree variables as inputs, the other one additionally used BD at breast height (BD130). The relative RMSE of BD for A. alba and Ps. menziesii were 9.9% and 8.1%, respectively, with the model without BD130 and 7.6% and 5.9%, respectively, with the model including BD130.

对木材基本密度 (BD) 垂直变化的研究对于更准确地预测森林资源中生物量和木材质量的茎内分布至关重要。到目前为止，对茎中木材 BD 的垂直变化的研究很少，大多数 BD 研究是基于在胸高处进行的测量。这项工作的主要目的是观察和理解与经典树状变量相关的茎内垂直 BD 变化的模式，并为未来的建模提出相关的方程形式。研究了两种软木树种：Abies alba和Pseudotsuga menziesii。研究了对比变薄强度，包括强烈变薄的图与没有细化的控制图。对于这两个物种，BD 大部分时间在树的基部最高。然后，在从树的基部强烈减少之后，经常观察到树顶的 BD 增加，尤其是A. alba。与高度变薄的A. alba相比，未变薄的地块的 BD 随高度的变化更大。对Ps观察到相反的情况。门泽西. 通过间伐强度对生长速度和树木大小的调节改变了观察到的 BD 垂直变化。提出了两种类型的双指数模型来描述 BD 变化。第一个模型使用茎中的高度和经典的易于测量的树变量作为输入，另一个模型额外使用胸高的 BD (BD130)。A. alba和Ps的 BD 的相对 RMSE 。menziesii在不含 BD130 的模型中分别为 9.9% 和 8.1%，在包含 BD130 的模型中分别为 7.6% 和 5.9%。